WO2007020442A2

WO2007020442A2 - Organic dyestuffs, organic photovoltaic device, semiconductor crystal film and method of prodicing thereof

Info

Publication number: WO2007020442A2
Application number: PCT/GB2006/003069
Authority: WO
Inventors: Pavel Ivan Lazarev; Elena N. Sidorenko; Alexey Nokel
Original assignee: Cryscade Solar Limited
Priority date: 2005-08-16
Filing date: 2006-08-16
Publication date: 2007-02-22
Also published as: GB0616259D0; WO2007020442A3; GB2430440A; GB0516800D0

Abstract

The present invention relates generally to the field of organic chemistry and particularly to the organic semiconductor materials for organic photovoltaic devices. More specifically, the present invention is related to the synthesis of organic compounds and the manufacture of organic photovoltaic devices and semiconductor films based on these compounds. In one embodiment, these semiconductor films possess a high conductivity in the direction perpendicular to the organic semiconductor layer and are intended for the application in solar cells and in other organic optoelectronic devices. The organic compound has the general structural formula (I), where Het is a predominantly planar heterocyclic molecular system; B is a binding group; and p is the number in the range from 3 to 8.

Description

ORGANIC COMPOUND, ORGANIC PHOTOVOLTAIC DEVICE, SEMICONDUCTOR CRYSTAL FILM AND METHOD OF PRODUCING THEREOF

The present invention relates generally to the field of organic chemistry and particularly to the organic semiconductor materials for organic photovoltaic devices. More specifically, the present invention is related to the synthesis of organic compounds and the manufacture of organic photovoltaic devices and semiconductor films based on these compounds.

Experimental data has shown that the efficiency of solar cell and other organic-based photovoltaic devices increases when the molecular planes in molecular crystals forming organic semiconductor films in such devices are oriented predominantly parallel to the substrate surface and electrodes (see P. Fenter ef. a/., Layer-by-Layer Quasi-Epitaxial Growth of a Crystalline Organic Thin Film", J. Crystal Growth, 152, 65-72 (1995); S. R. Forrest and P. E. Burrows, Growth Modes of Organic Semiconductor Thin Film Using Organic Molecular Beam Deposition: Epitaxy, van der Waals Epitaxy, and Quasi-Epitaxy", Supramol. ScL, 4, 127-139 (1997)). This fact implies the existence of channels for the transfer of electrons and holes along the axis of the τr-π interaction in rodlike stacks inside crystal particles, which provides high mobility of charges (facilitating the transport of electrons and holes). The short vertical distance between electrodes also reduces the probability of undesired recombination of charge carriers.

Materials with molecular stacks oriented perpendicularly to the substrate surface are obtained by epitaxy of planar polycyclic molecules.

There is a known organic quasi-epitaxial method intended for the formation of photovoltaic devices (see US Patent No. 5,315,129, Forrest ef a/., Organic Optoelectronic Devices and Methods). According to this method, the planes of organic molecules are oriented parallel to the substrate surface. A quasi-epitaxial photovoltaic device structure comprises a substrate, the first layer deposited on said substrate, and the second layer deposited above the first layer. Said first layer represents a planar crystalline film of an organic aromatic semiconductor compound and is selected from a group of organic compounds including polyacenes, porphyrins, and their derivatives. Said second layer also represents a planar crystalline film of an organic aromatic semiconductor, whose chemical composition (generally, different from that of the first layer) is also selected from a group of organic compounds including polyacenes, prophyrins, and their derivatives. The first and second layers have crystalline structures, which are in a certain relationship with each other. In particular, the first and second layers can be independently selected from a group including 3,4,9,10- perylenetetracarboxylic dianhydride (PTCDA), 3,4,7,8-naphthalenetetracarboxylic dianhydride (NTCDA), copper phthalocyanine, 3,4,9, 10-perylenetetracarboxylic acid bis-benzimidazole, and -oxadiazole derivatives. Organic photovoltaic devices have been grown by organic molecular beam deposition. The organic substances have been deposited as ultrathin layers

2402764-1 only 10 Angstrom (A) thick using organic molecular beam deposition methods. PTCDA and NTCDA have been identified as excellent materials for the manufacture of organic optoelectronic IC devices, but any planar organic aromatic semiconductor capable of readily forming a crystalline structure may be used. The preferred method of the prior art employs a chamber, comprising an inorganic substrate made of an appropriate material for making electrical contact to the organic structures, and sources of PTCDA and NTCDA. The chamber is maintained at a pressure generally below 10^"6 Torr. The substrate is spaced from the source of film materials by a minimum distance of 10 cm. During deposition, the substrate is kept at a temperature below 150K, while the PTCDA and NTCDA sources are alternatively heated.

Despite all the advantages of said quasi-epitaxial growth method (see US Patent Nos. 6,451 ,415 and 5,315,129), it is not free of drawbacks. According to said known method, a constant temperature regime and vacuum level have to be maintained in the chamber throughout the epitaxial growth process. Any breakdowns in the temperature and vacuum regime lead to the appearance of defects in the growing layer, whereby both crystallographic parameters and the orientation of molecular layer exhibit changes. This sensitivity of the process with respect to instability of the technological parameters can be also considered as a disadvantage of said known method, which is especially significant in the case of deposition of relatively thick (1 to 10 μm) epitaxial layers.

Another disadvantage of said method is the need in sophisticated technological equipment. The reactor chamber must hold an ultrahigh vacuum (down to 10^"6 - 10^"10 Torr) and must withstand considerable temperature gradients between closely spaced zones. The equipment must include the means of heating sources and cooling substrates, a complicated pumping stage, and facilities for gas admission, temperature and pressure monitoring, and technological process control. The high vacuum requirements make the process expensive and limit the substrate dimensions.

One more disadvantage of said known technology is limitation on the substrate materials: only substances retaining their physical, mechanical, optical, and other properties under the conditions of large pressure differences, high vacuum, and considerable temperature gradients can be employed.

The production of a two-dimensional bimolecular surface structure using weak noncovalent interactions has been demonstrated and characterized by scanning tunneling microscopy (see L. Scudiero et al., "A Self-Organized Two-Dimensional Bimolecular Structure", J. Phys. Chem. B, 107, 2903-2909 (2003)). This work follows closely the ideas of three-dimensional crystal engineering and applies the concepts of supramolecular reactants (synthons) to molecular systems constrained to two dimensions by physical adsorption (physisorption) on a conducting surface. A well-ordered planar structure that self-assembles through the influence of fluorine- phenyl interactions has been demonstrated. This study provides an example of the systematic design of self-organized layers. Fully fluorinated cobalt phthalocyanine (F16CoPc) films thermally deposited onto gold were characterized by reflection-absorption infrared spectroscopy (RAIRS), X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), and scanning tunnelling microscopy (STM). The UPS spectra of thin films of CoPc, F16CoPc, and nickel tetraphenylporphyrin (NiTPP) on gold were measured and their relative surface charges were compared. STM images of single molecular layers of F16CoPc, NiTPP, and NiTPP- F16CoPc and NiTPP-CoPc mixtures were obtained. It was found that, while NiTPP-FI 6CoPc spontaneously formed a well-ordered 1 :1 structure, NiTPP-CoPc formed a two-dimensional solid solution.

Ultrathin films prepared from inorganic and organic materials are of increasing interest as hybrid nanocomposite materials. The formation of nanostructured ultrathin films of montmorillonite clay (MONT) and a bicationic sexithiophene derivative (6TN) was investigated using the layer-by-layer self-assembly approach (see X. Fan, J. Locklin, J. Ho Youk, et a/., Nanostructured Sexithiophene/Clay Hybrid Mutilayers: A Comparative Structural and Morphological Characterization, Chem. Mater., 14, 2184-2191 (2002)). The main goal was to investigate the structure and layer ordering in these films suitable for future applications in organic photovoltaic devices. The structure and morphology of 6TN/MONT multilayer films prepared from pure water and 0.1 M NaCI systems have been compared. The 6TN amphiphile showed unique aggregation behaviour both in solution and on the surface, which changed in the presence of salts and THF as a cosolvent. On clay surfaces, the 6TN aggregates deposited from saline solutions exhibited more uniform size distribution and surface coverage as compared to those obtained from a pure water system. This was verified by UV-VIS spectra, X-ray diffraction (XRD), and atomic force microscopy (AFM). The idea of incorporating more 6TN species adsorbed on the surface so as to obtain a smoother surface morphology can be of great significance in photovoltaic device fabrication.

The available literature presents no examples of the films with the vertical orientation of stacks prepared by a low-cost and effective way of solution application on the substrate. The films with the horizontal orientation of stacks are usually obtained using the lyotropic liquid crystal (LLC) solutions of sulfoderivatives (see: U.S. Patent Nos. 5,739,296 and 6,049,428 and the following publications: P. Lazarev et a/., X-ray Diffraction by Large Area Organic Crystalline Nanofilms, Molecular Materials, 14(4), 303-311 (2001), and Y. Bobrov, Spectral Properties of Thin Crystal Film Polarizers, Molecular Materials, 14(3), 191-203 (2001)).

On the other hand, it is known from the literature that some molecules are capable of forming regularly arranged planar fragments (supramolecules) on a substrate surface, being deposited from solutions in water and various organic solvents, and that hydrogen bonding (H-bonding) is the driving force for the formation of such planar supramolecules. This phenomenon was observed for heterocyclic amines, amides, and carboxylic acids. The type of the obtained monolayer structure depends on the molecular structure, the solvent, and the surface activity. The layer structures of various types - stable and unstable, dense and loose - can be obtained using different molecular structures and conditions.

There are many novel adsorbate-substrate systems that are known to exhibit a high degree of large-scale ordering. The method of scanning tunnelling microscopy (STM) has proved to be capable of studying the electronic properties of such systems and their structures on a submolecular resolution level. It was established that, in some systems, H-bonding is the predominant interaction between molecules and governs the molecular self-assembly process.

Selective noncovalent interactions have been widely used in solution chemistry to direct the assembly of molecules into nanometer-sized functional structures such as capsules, switches and prototype nanomachines. The concepts of supramolecular organization have also been applied to two-dimensional (2D) assemblies on surfaces stabilized by means of H-bonding, dipolar coupling, or metal coordination. Another approach to controlling surface structures uses adsorbed molecular monolayers to create preferential binding sites that accommodate individual target molecules. James A. Theobald et a/. (Controlling Molecular Deposition and Layer Structure with Supramolecuiar Surface Assemblies, Nature, 424, 1029-1031 (2003)) combined these approaches by using H-bonding to guide the assembly of two. types of molecules into a 2D open honeycomb network. This network controls and templates new surface phases formed by subsequently deposited fullerene molecules. It was found that the open network acts as a 2D array of large pores of sufficient capacity to accommodate several large guest molecules and serves as a template for the formation of an ordered fullerene layer.

Self-assembly of a 2D loosely packed H-bonded network of trimesic acid (TMA) at the liquid- solid interface has been observed using STM (see Lackinger et a/., Langmuir, 21, 4984-4988 (2005)). Two crystallographically different 2D phases of TMA were identified and selected by varying the solvent. In this paper, some models of various crystallographic structures with the corresponding H-bonding modes were introduced: (a) chickenwire structure, a = b = 1.7 nm, angle A = 60°, area = 2.5 nm², 2 molecules per unit cell; (b) flower structure, a = b ~ 2.5 nm, angle A = 60°, area = 5.4 nm², 6 molecules per unit cell; (c) "super flower" structure, representing more densely packed 2D TMA polymorph based entirely on 3-fold H-bonding. It was suggested that the denser "flower" structure (b) is likely to be the most thermodynamically stable of the two observed monolayer polymorphs. Studies of these adsorbed polymorph structures for TMA dissolved in a series of acid solvents [CH₃(CH₂)_nCOOH with n = 2-7] showed that the flower structure was favored for the shorter-chain solvents, which also corresponded to those in which TMA had the maximum solubility. It should be noted that an even more densely packed TMA structure could presumably be formed with a purely 3-fold H- bonded structure ("super flower" structure), but this TMA form was not observed. A possible explanation for this behaviour is the stabilization, in short-chain solvents, of a TMA trimer [(TMA)₃] solution phase nucleation species, which is a likely precursor to the flower form of TMA; however, an explanation based on differential solvent stabilization of the surface monolayer of flower and chickenwire structures cannot be ruled out.

The crystal packing of some fluorinated azobenzenecarboxylic acids was studied by R. Centore and A. Tuzi (Crystal Eng., 6, 87-97 (2003)). The X-ray crystal structures of C₆H₅COOH₁C₆F₅COOH (1), C₆H₅CONH₂₁C₆F₅CONH₂ (2), and C₆H₅CONH₂₁C₆F₅COOH (3) were analyzed in order to elucidate the role of Ph-PhF synthon in directing self-assembly and H-bonding in these cocrystals (see Reddy et a/., Crystal Growth & Design, 4, 89-94 (2004)). The strong H-bond donor acidity of C₆F₅COOH and C₆F₅CONH₂ together with mixed stacks of phenyl and perfluorophenyl rings steer acid-acid and amide-amide H-bonding in cocrystals 1 and 2. The acid-amide H-bonding is sufficiently strengthened by donor acidity and acceptor basicity in 3, so that the role of the Ph-PhF synthon is weaker because the aromatic rings stack with lateral offset. The complex C₆H₅COOH₁C₆F₅CONH₂ (4) could not be obtained under similar crystallization conditions. The crystal structure of C₆F₅CONH₂ was also determined to compare the molecular conformation and H-bonding with motifs in the cocrystals.

It has been found that 4-hydroxybenzoic acid (1) crystallizes into three crystalline forms: (i) monoclinic from a DMSO solution (1A)₁ (ii) triclinic from a solution in 1:1 DMSO/hot ethyl acetate (1 B) and (iii) triclinic from a pyridine solution (1C) (see Jayaraman et a/., Crystal Growth & Design, 4, 1403-1409 (2004)). The formation of these pseudopolymorphs and the' structural similarity of their packing motifs can be rationalized in terms of few-multipoint solute-solvent interactions. In all three structures, the crystallographic aspects pertaining to the influence of solvent molecules towards the formation of H-bonded network structures are described. In addition to the strong H-bonds, intermolecular C-H- O, C-H-π, and π-π interactions were found to stabilize the crystal structures.

A series of 4,4-dipyridyl (4,4-DP) derivatives have been prepared and studied using single- crystal X-ray diffraction techniques (see D. E. Lynch et al., Crystal Eng., 2, 137-144 (1999)). The structures had increasing degree of complexity in the overall H-bonded network. The structure of 1 comprises polymeric H-bonded chains of associated 4,4-DP and ICA molecules that propagate through complementary sites on the ICA molecules. The structure of 2 consisted of two parallel polymeric H-bonded chains, each involving associated 4,4-DP and 3- ABA molecules cross-linked through complementary 3-ABA sites. The structure of 3 was an extensive 3-dimensional H-bonded network involving all H-bonded donor and acceptor sites on the constituent molecules. In each case, the positions and directions of the N-H groups were important in determining the final lattice network.

In one embodiment the present invention combines the two types of interactions: the in-plane H-bonding and the vertical π-π interactions. The in-plane H-bonding is applied to large polycyclic molecules and forms a well-ordered planar structure. In turn the vertical π-π interactions stimulate vertical stacking of planar molecular core over the substrate surface. The experiments have affirmed a possibility of obtaining of the films with desirable vertical stacks.

In a first aspect of the present invention there is provided an organic compound of the general structural formula

where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a group providing a solubility of the organic compound; m is the number in the range from 0 to 8; D is a substituent from a list comprising - CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, -CF₃, -CN, -OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range from O to 4. The organic compound may be characterized by the absorption of electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm. Using a solution of the organic compound or its salt, a photovoltaic layer on a substrate may be obtained.

In a second aspect of the present invention there is provided a semiconductor crystal film comprising a substrate and at least one photovoltaic layer on the substrate, wherein the photovoltaic layer comprises at least one organic compound of general structural formula Il

where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a molecular group providing a solubility of the organic compound; m is the number in the range from 0 to 8; X is a counterion from a list comprising H⁺, NH₄ ⁺, Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, and any combination thereof; t is the number of counterions necessary to provide for the electric neutrality of the organic compound (II); D is a substituent from a list comprising -CH₃, -C₂H₅, -NO₂, -CI, -Br, -F, -CF₃, -CN, -OH, -OCH₃, - OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range from O to 4. The counterions are used for providing an electrical neutrality of the organic compounds and some of them may be used for stabilization of the organic compounds and provide their insolubility. The photovoltaic layer may absorb electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm.

In a third aspect of the present invention there is provided a method for producing a semiconductor crystal film, the method comprising an application on the substrate of a solution of one organic compound, or a combination of such organic compounds, of the general structural formula

and a drying with the formation of a photovoltaic layer, where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8;

S is a group providing a solubility of the organic compound; m is the number in the range from

0 to 8; D is a substituent from a list comprising -CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, -CF₃, -CN, -OH,

-OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range from O to 4. The solution exhibits absorption of electromagnetic radiation in one or more predetermined spectral subranges within a wavelength range from

400 to 3000 nm.

In the fourth aspect of the present invention there is provided an organic photovoltaic device comprising the first and second electrodes and at least one photovoltaic layer having the front surface and the rear surface, wherein said photovoltaic layer is produced using an organic compound having the general structural formula II:

where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a molecular group providing a solubility of the organic compound; m is the number in the range from 0 to 8; X is a counterion from a list comprising H⁺, NH₄ ⁺ _, Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, and any combination thereof; t is the number of counterions necessary to provide for the electric neutrality of the organic compound; D is a substituent from a list comprising -CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, -CF₃, -CN, -OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range from O to 4. The counterions are used for providing an electrical neutrality of the organic compounds and some of them may be used for stabilization of the organic compounds and provide their insolubility.

The general description of the present invention having been made, a further understanding can be obtained by reference to the specific preferred embodiments, which are given herein only for the purpose of illustration and are not intended to limit the scope of the appended claims. A more complete assessment of the present invention and its advantages will be readily achieved as the same becomes better understood by reference to the following detailed description, considered in connection with the accompanying drawings and detailed specification, all of which forms a part of the disclosure.

In one preferred embodiment the present invention relates to the creation of organic compounds suitable for producing semiconductor films, wherein the conjugated heterocyclic molecular planes are oriented predominantly parallel to the substrate surface. In one embodiment of the present invention, the π-π interaction between layers may lead to the formation of vertical stacks. In other words, these semiconductor films are characterized by the vertical orientation of π-π conjugated supramolecules (π-π stacks). Anisotropically conducting films, with the vertical conductivity measured across the organic semiconductor layer being higher than the lateral conductivity measured along the substrate surface, have advantages for the applications in organic-based optoelectronics, in particular, in organic photovoltaic devices. In other preferred embodiment the present invention relates to the creation of organic compounds suitable for producing semiconductor films, wherein the conjugated heterocyclic molecular planes are oriented predominantly perpendicularly to the substrate surface.

In one embodiment the structure of the disclosed organic compounds may be characterized by a combination of two specific features: (i) a large heterocyclic system that enables π-π interaction with the tendency to the formation of π-π rodlike supramolecules, and (ii) the presence of one or more binding groups that enables H-bonding with the tendency to the formation of planar H-bonded supramolecules. The interaction of the hydrophilic substrate surface with the system of H-bonds formed by binding groups in planar supramolecules may induce the in-plane orientation of the supramolecules and the formation of vertical π-π stacks. The hydrophilic surface and planar H-bonded supramolecules form layers on the substrate surface. In one embodiment of the present invention, the π-π interaction between layers may lead to the formation of vertical stacks.

A more complete assessment of the present invention and its advantages will be readily achieved as the same becomes better understood by reference to the following detailed description, considered in connection with the accompanying drawings and detailed specification, all of which forms a part of the disclosure. Embodiments of the invention are illustrated, by way of example only, in the following Figures, of which:

Figure 1 shows the absorption spectrum of semiconductor crystal film produced according to present invention.

Figure 2 shows the planar supramolecule comprising phthalocyanine fragments.

Figure 3 shows the planar supramolecule comprising pyrazine fragments.

Figure 4 shows the fragment of H-bonded supramolecule formed of planar heterocyclic molecular systems comprising pyrazine fragments.

Figure 5 shows heterocyclic molecular systems enable π-π interaction with the tendency to the formation of π-π rodlike supramolecules.

Figure 6 is a schematic diagram of an organic photovoltaic device based on a structure with a single photovoltaic layer (single-layer structure) with a Schottky junction and an Ohmic contact, which are located on the opposite surfaces of the photovoltaic layer.

Figure 7a presents an energy band diagram of the typical Schottky junction involving a photovoltaic layer of the n-type.

Figure 7b presents an energy band diagram of the typical Schottky junction involving a photovoltaic layer of p-type.

Figure 8a schematically depicts the layer structure of an organic photovoltaic device with a Schottky junction, an /?-type photovoltaic layer, an electron transport layer, and an Ohmic contact.

Figure 8b schematically depicts a layer structure of organic photovoltaic device with a Schottky junction, a p-type photovoltaic layer, a hole transport layer, and an Ohmic contact.

Figure 9 is a schematic diagram of an organic photovoltaic device based on a single- layer structure with a Schottky junction and an Ohmic contact, which are located on the same surface of the photovoltaic layer.

Figure 10 schematically shows an organic photovoltaic device based on a single-layer structure with a Schottky junction and an Ohmic contact, which are located on the same surface of the photovoltaic layer and form an interdigitated system of barrier and Ohmic contacts.

Figure 11a schematically depicts the structure of an organic photovoltaic device based on a single photovoltaic layer with a Schottky junction and an Ohmic contact located on the same surface, which also contains a reflective depolarizing layer.

Figure 11 b schematically depicts the structure of an organic photovoltaic device based on a single photovoltaic layer with a Schottky junction and an Ohmic contact located on the same surface, which also contains a phase-shifting layer (retarder) and a reflective layer.

Figure 12a schematically depicts the structure of an organic photovoltaic device based on a single photovoltaic layer with a Schottky junction, which also contains an exciton-blocking layer and a reflective depolarizing electrode (Ohmic contact).

Figure 12b schematically depicts the structure of an organic photovoltaic device based on a single photovoltaic layer with a Schottky junction, which also contains an exciton-blocking layer, a phase-shifting layer (retarder), and a reflective layer.

Figure 13a is a schematic diagram of a double-layer organic photovoltaic device based on contacting electron donor and electron acceptor layers forming a photovoltaic heterojunction.

Figure 13b is an energy band diagram of a double-layer organic photovoltaic device depicted in Figure 8a.

Figure 14a is a schematic diagram of an organic photovoltaic device structure comprising a photovoltaic heterojunction, exciton-blocking layers, a hole transport layer, an electron transport layer, and Ohmic contacts.

Figure 14b is an energy band diagram of the organic photovoltaic device shown in Figure 9a.

Figure 15a schematically depicts an organic photovoltaic device structure comprising a conducting layer in Ohmic contact with one photovoltaic layer, a photovoltaic heterojunction, and a reflective depolarizing electrode (Ohmic contact).

Figure 15b schematically depicts an organic photovoltaic device structure comprising a conducting layer in Ohmic contact with one photovoltaic layer, a photovoltaic heterojunction, a phase-shifting layer (retarder) and a reflective layer.

Figure 16 shows the load curve of the organic photovoltaic device with ITO/carboxy- CuPc/Carboxy-DBI PTCA-structure.

Figure 1 shows the absorption spectrum of semiconductor crystal film produced according to present invention by spray-coating method. The semiconductor crystal film comprises a substrate and photovoltaic layer. The photovoltaic layer is made of an organic compound having a mixture of heterocyclic molecular systems (see Table 2, ## 5 and 6) with two carboxylic binding groups.

The arrangement of binding groups influences the structure of planar H-bonded supramolecules and may produce various structural motifs with different spatial structures. The spatial structure influences the electronic properties of the semiconductor film. Several embodiments of the structure of planar H-bonded supramolecules are presented in Figures 2 - 4, of which:

Figure 2 shows the planar supramolecule comprising phthalocyanine fragments bound via H- bonds. The planes of heterocyclic molecular systems are oriented predominantly parallel to the substrate plane.

Figure 3 shows the fragment of planar supramolecule formed of planar heterocyclic molecular systems comprising pyrazine fragments (see Table 4, # 34) and four carboxylic binding groups bound via H-bonds. The planes of heterocyclic molecular systems are oriented predominantly parallel to the substrate plane.

Figure 4 shows the fragment of planar supramolecule formed of planar heterocyclic molecular systems comprising pyrazine fragments (see Table 4, # 32) and two carboxylic binding groups bound via H-bonds. The planes of heterocyclic molecular systems are oriented predominantly parallel to the substrate plane.

Figure 5 shows organic compound comprising heterocyclic molecular system (see Table 2, ## 5 and 6) and two carboxylic binding groups. Said heterocyclic molecular systems enable π-π interaction with the tendency to the formation of π-π rodlike supramolecules. The longitudinal axes of supramolecules are directed predominantly parallel to the substrate plane therefore the planes of heterocyclic molecular systems are oriented predominantly perpendicularly to the substrate plan. The binding groups of adjacent molecules form hydrogen bonds.

Thus, the proposed compounds may be capable of forming films with π-π stacks for the transport of electrons or holes and the ionic components placed between these π-π stacks.

The ammonium ion is a preferable component of the solution that provides the formation of vertical stacks of planar H-bonded supramolecules. The ammonium ion may be removed at the drying stage which also makes it a preferable ion. Additional treatment of the H-bonded semiconductor crystal films with solutions of Ca, Ba, Sr, Mg, Ni, or Mn water-soluble salts renders the films water-insoluble and imparts them a high environmental stability.

In one embodiment of present invention, carboxylic acid may be used as organic compound comprising a planar heterocyclic molecular system and binding groups. In this case carboxylic groups serve as binding groups. Carboxylic acids can be prepared using any conventional method known in the field. Some heterocyclic compounds can be synthesized via the cyclization of fragments containing carboxylic groups. Carboxylic acids can be also produced by introducing substituents into commercially available heterocyclic systems, with their subsequent modification.

Semiconductor crystal films formed by planar H-bonded heterocyclic molecules whose planes are oriented parallel to the substrate offer a number of advantages for use in organic photovoltaic devices.

First, usual organic photovoltaic devices absorb radiation incident on the working surface at various angles. Parallel orientation of the absorbing molecules relative to the substrate significantly decreases the dependence of absorption on the angle of incidence and increases the efficiency of organic photovoltaic devices under the conditions of angular exposure.

Second, organic photovoltaic devices employing the semiconductor crystal films with planar H- bonded heterocyclic molecules oriented parallel to the substrate absorb light independently of its polarization. Taking into account that a 60-70% fraction of the natural solar radiation is polarized, the organic photovoltaic devices based on said films must be advantageous to the usual solar cells.

Third, the interelectrode conductivity of organic photovoltaic devices employing said semiconductor crystal films with vertical conducting channels should be higher than their lateral conductivity. This decreases the intrinsic serial resistance of the cell and, hence, increases the efficiency of photoconversion.

In order to obtain a semiconductor crystal film containing planar H-bonded heterocyclic molecules oriented parallel to the substrate, it is preferable to provide for the interactions of ^• three types in this system.

The first condition is the interaction (adsorption) of planar heterocyclic molecules (adsorbate) with the substrate (adsorbent) that results in the desired orientation of molecules or their aggregates at the substrate surface. The adsorption of molecules can be either physical

(physisorption) of chemical (chemisorption). The physical adsorption is mediated by intermolecular forces and is not accompanied by significant changes in the electron structure of adsorbed molecules. In this case, the adsorbed molecules (admolecules) usually retain surface (lateral) mobility. The chemical adsorption involves the formation of chemical bonds between molecules of the adsorbate and adsorbent. Thus, chemisorption can be considered as a kind of chemical reaction in a region confined to the surface layer of the adsorbate.

Obviously, the chemical bonds limit the surface mobility of admolecules. The disclosed invention employs the combinations of organic compounds (adsorbates) and substrates featuring predominantly the physical adsorption. Therefore, the adsorbed molecules and their aggregates can move over the substrate surface.

Second, the physically adsorbed planar heterocyclic molecular systems should interact with each other by means of weak lateral forces acting in the substrate plane. These intermolecular forces play an important role in the formation of a long-range order in the adlayer and in the final photovoltaic layer. The lateral interaction can be provided by H-bonds formed between binding groups of the organic compound comprising predominantly planar heterocyclic molecular systems.

Third, the predominantly planar heterocyclic molecular systems of said organic compounds should be involved into π-π interactions in process of removal of solvent during drying, which makes possible the organization of multilayer crystal film structures with the predominantly planar heterocyclic molecular systems of one layer arranged above the predominantly planar heterocyclic molecular system in the adjacent layer. The stacked predominantly planar heterocyclic molecular systems linked by the π-π bonds form the vertical conducting channels in the disclosed semiconductor crystal films.

The binding groups provide for the physical adsorption of selected heterocyclic compounds on various substrates, including those made of carbon, diamond, gold, silver, glass, and many other materials. These binding groups also provide for the lateral H-bonding of predominantly planar heterocyclic molecular systems and their aggregates with each other. Due to this H- bonding, said predominantly planar heterocyclic molecular systems and their aggregates may form ordered single crystal layers. As indicated above, carboxylic acids may be used as organic compounds comprising predominantly planar heterocyclic molecular systems, binding groups and molecular groups providing a solubility of the organic compound. Carboxylic groups serve as binding groups and molecular groups providing solubility in this case. An important advantage of carboxylic acids is the possibility of obtaining their water-soluble salts, . which provides for the possibility of forming the semiconductor crystal films from aqueous solutions. The planar heterocyclic molecular system (Het) is selected so as to have a developed system of π-π bonds sufficient to provide for the organization of a multilayer crystal film structures with the planar heterocyclic molecular systems of each layer arranged in stacks above the planar heterocyclic molecular systems of the adjacent layer.

In a preferred embodiment, the present invention provides an organic compound of the general structural formula I:

where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a group providing a solubility of the organic compound; m is the number in the range from 0 to 8; D is a substituent from a list comprising - CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, -CF₃, -CN, -OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range from O to 4.

Said organic compound is characterized by the absorption of electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm. The organic compound may absorb electromagnetic radiation only in a part of a wavelength range from 400 to 3000 nm. This part of spectral range will be called as subrange. This subrange may be determined experimentally for each particular (specific) organic compound. A solution of the organic compound or its salt is capable of forming a on a substrate.

In one embodiment of the disclosed invention, said solution is based on water and/or water- miscible solvents. In another embodiment of the disclosed invention, at least one of the groups providing a solubility of the organic compound in water and/or water-miscible solvents is selected from the list comprising the COO , SO₃ ^", HPO₃-, and PO₃ ^2- and any combination thereof. In yet another embodiment of the disclosed invention, the photovoltaic layer produced from water solutions has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the substrate plane.

In one embodiment of the disclosed invention, said solution is based on organic solvent. In this embodiment of the disclosed invention, the organic solvent is selected from the list comprising the benzol, toluene, xylenes, acetone, acetic acid, methylethylketone, hydrocarbons, chloroform, methylenechloride, chlorbenzol, alcohols, nitrometan, acetonitrile, dimethylforamide, 1,4-dioxane or any combination thereof. In another embodiment of the disclosed invention, at least one of the groups providing a solubility of the organic compound in organic solvent is amide of acid residue independently selected from the list comprising the CONRiR₂, CONHCONH₂, SO₂NRiR₂, and any combination thereof, were Ri₁R₂ independently selected from H, alkyl or aryl. The alkyls are selected from the list comprising the methyl, ethyl, propyl, butyl, i-butyl, t-butyl and aryls are selected from the list comprising the phenyl, benzyl, naphthyl. The examples of alkyls and aryls serve to illustrate the invention without limiting it. In yet another embodiment of the disclosed invention, at least one of the groups providing a solubility of the organic compound in organic solvent is alkyl. In still another embodiment of the disclosed invention, the photovoltaic layer produced from organic solutions has heterocyclic molecular systems with planes oriented predominantly parallel to the substrate plane.

In one embodiment of the disclosed invention, said organic compound absorbs electromagnetic radiation within a wavelength range from 400 to 700 nm. In another embodiment of the disclosed invention, the predominantly planar heterocyclic molecular system is a partially or completely conjugated. In still another embodiment of the disclosed invention, said heterocyclic molecular system comprises the hetero-atoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof. In yet another embodiment of the disclosed invention, at least one of the binding group is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂, and any combination thereof, where radical R is alkyl or aryl.

The examples of heterocyclic molecular systems with a general structural formula corresponding to structures 1-39 shown below in Tables 1 - 5 serve to illustrate the invention without limiting it. In one embodiment of the disclosed invention, the planar heterocyclic molecular system comprises phthalocyanine fragments. Table 1 shows some examples of planar heterocyclic molecular systems comprising phthalocyanine fragments with a general structural formula corresponding to structures 1-4, where Latin letter M denotes an atom of metal.

Table 1. Examples of planar heterocyclic molecular systems comprising phthalocyanine fragments

In still another embodiment of the disclosed invention, the planar heterocyclic molecular system comprises rylene fragments. Table 2 shows some examples of heterocyclic molecular systems comprising rylene fragments with a general structural formula corresponding to structures 5-25.

Table 2. Examples of heterocyclic molecular systems comprising rylene fragments ;

In another embodiment of the disclosed invention, the planar heterocyclic molecular system may comprise anthanthrone fragments. Table 3 shows some examples of planar heterocyclic molecular systems comprising such anthanthrone fragments with a general structural formula corresponding to structures 26 and 27.

Table 3. Examples of planar heterocyclic molecular systems comprising anthanthrone fragments

In another embodiment of the present invention, the planar heterocyclic molecular system may comprise pyrazine fragments. Table 4 shows some examples of planar heterocyclic molecular systems comprising such pyrazine fragments with a general structural formula corresponding to structures 28-37.

Table 4. Examples of planar heterocyclic molecular systems comprising planar conjugated pyrazine fragments

In another embodiment of the disclosed invention, the planar heterocyclic molecular system may comprise naphthalene fragments. Table 5 shows some examples of planar heterocyclic molecular systems comprising such naphthalene fragments with a general structural formula corresponding to structures 38-39.

Table 5. Examples of planar heterocyclic molecular systems comprising naphthalene fragments

In another preferred embodiment, the present invention provides a semiconductor crystal film comprising a substrate and at least one photovoltaic layer disposed on the substrate, wherein the photovoltaic layer comprises at least one organic compound of general structural formula

where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a molecular group providing a solubility of the organic compound; m is the number in the range from 0 to 8; X is a counterion from a list comprising H⁺, NH₄ ⁺ _, Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, and any combination thereof; t is the number of counterions necessary to provide for the electric neutrality of the molecule of the given carboxylic acid salt; D is a substituent from a list comprising -CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, - CF₃, -CN, -OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range from O to 4. The counterions are used for providing an electrical neutrality of the organic compounds and some of them may be used for stabilization of the organic compounds and provide their insolubility. The photovoltaic layer absorbs electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm.

In one embodiment of the disclosed semiconductor crystal film, the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the substrate plane. In another embodiment of the disclosed semiconductor crystal film, the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly parallel to the substrate plane.

The disclosed semiconductor crystal film may absorb electromagnetic radiation only in a part of wavelength range from 400 to 3000 nm. This part of spectral range will be called as subrange. This subrange may be determined experimentally for each particular (specific) water-based solution of organic compound which is used for forming the semiconductor crystal film. Similarly, the subrange of absorption may be determined experimentally for a mixture of organic compounds which are used for forming said film. Thus, such experimentally determined subrange of absorption of the electromagnetic radiation can be considered as the predetermined subrange.

Additional treatment of H-bonded crystalline films with water solutions of Ca, Ba, Sr, Mg, Ni, or Mn renders the films water insoluble imparts them a high environmental stability.

In one embodiment of the disclosed semiconductor crystal film, said photovoltaic layer absorbs electromagnetic radiation within a wavelength range from 400 to 700 nm. In another embodiment of the disclosed semiconductor crystal film, said predominantly planar heterocyclic molecular system is a partially or completely conjugated. In still another embodiment of the disclosed semiconductor crystal film, said heterocyclic molecular system comprises the hetero-atoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof. In yet another embodiment of the disclosed semiconductor crystal film, at least one of the binding group is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂, and any combination thereof, where radical R is alkyl or aryl. The alkyls may be selected from the list comprising the methyl, ethyl, .propyl, butyl, i-butyl, t-butyl and aryls may be selected from the list comprising the phenyl, benzyl, naphthyl. The examples of alkyls and aryls serve to illustrate the invention without limiting it.

The examples of heterocyclic molecular systems with a general structural formula corresponding to structures 1-39 shown below in Tables 1 - 5 serve to illustrate the invention without limiting it. In one embodiment of the disclosed semiconductor crystal film, the planar heterocyclic molecular system comprises phthalocyanine fragments. Some examples of such planar heterocyclic molecular systems comprising phthalocyanine fragments having a general structural formula from the group comprising structures 1-4 are given in Table 1. In another embodiment of the disclosed semiconductor crystal film, the planar heterocyclic molecular system comprises rylene fragments. Some examples of such planar heterocyclic molecular systems comprising rylene fragments having a general structural formula from the group comprising structures 5-25 are given in Table 2. In another embodiment of the disclosed semiconductor crystal film, the planar heterocyclic molecular system comprises anthanthrone fragments. Examples of the heterocyclic molecular systems comprising anthanthrone fragments having a general structural formula from the group comprising structures 26 and 27 are given in Table 3. In still another embodiment of the disclosed semiconductor crystal film, the planar heterocyclic molecular system comprises pyrazine fragments. Some examples of such pyrazine fragments having a general structural formula from the group comprising structures 28-37 are given in Table 4. In another embodiment of the disclosed semiconductor crystal film, the planar heterocyclic molecular system comprises naphthalene fragments. Some examples of such heterocyclic molecular systems having a general structural formula from the group comprising structures 38-39 are given in Table 5.

In yet another embodiment of the disclosed semiconductor crystal film, said photovoltaic layer is substantially insoluble in water and/or in water-miscible solvents. In a one embodiment of the disclosed semiconductor crystal film, said heterocyclic molecular system planes form stacks that are oriented predominantly perpendicularly to the substrate surface. In another embodiment of the disclosed invention, said semiconductor crystal film is isotropic. In still another embodiment of the semiconductor crystal film, said organic layer comprises two or more organic compound of the general structural formula II, which absorb electromagnetic radiation in different spectral subranges. In one embodiment of the disclosed invention, said semiconductor crystal film comprises two or more photovoltaic layers, wherein each of these layers comprises an organic compound of the general structural formula Il and absorbs electromagnetic radiation in a predefined spectral subrange.

In the third aspect of the present invention there is provided a method for producing a semiconductor crystal film, which involves application on a substrate of a solution of one organic compound, or a combination of such organic compounds, with the general structural formula

and drying with the formation of a photovoltaic layer. Here, Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a group providing a solubility of the organic compound; m is the number in the range from 0 to 8; D is a substituent from a list comprising -CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, -CF₃, -CN, -OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range of O to 4. The solution exhibits absorption of electromagnetic radiation in one or more predetermined spectral subranges within a wavelength range from 400 to 3000 nm.

The solution may absorb electromagnetic radiation only in a part of wavelength range from 400 to 3000 nm. This part of spectral range will be called as subrange. This subrange may be determined experimentally for each particular (specific) water-based solution of ammonium salt. Similarly, the subrange of absorption may be determined experimentally for a mixture of ammonium salts. Thus, such subrange of absorption of the electromagnetic radiation can be considered as the predetermined subrange.

In one embodiment of the disclosed method, said solution is based on water and/or water- miscible solvents. In another embodiment of the disclosed method, at least one of the groups providing a solubility of the organic compound in water and/or water-miscible solvents is selected from the list comprising the COO , SO₃ ^", HPO₃-, and PO₃ ^2"" and any combination thereof. In yet another embodiment of the disclosed method, the photovoltaic layer produced from water solutions has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the substrate plane.

In one embodiment of the disclosed method, said solution is based on organic solvent. In this embodiment of the disclosed method, the organic solvent is selected from the list comprising the benzol, toluene, xylenes, acetone, acetic acid, methylethylketone, hydrocarbons, chloroform, methylenechloride, chlorbenzol, alcohols, nitrometan, acetonitrile, dimethylforamide, 1 ,4-dioxane or any combination thereof. In another embodiment of the disclosed method, at least one of the groups providing a solubility of the organic compound in organic solvent is amide of acid residue independently selected from the list comprising the CONR₁R₂, CONHCONH₂, SO₂NR₁R₂, and any combination thereof, were R₁₁R₂ independently selected from H, alkyl or aryl! The alkyls may be selected from the list comprising the methyl, ethyl, propyl, butyl, i-butyl, t-butyl and aryls may be selected from the list comprising the phenyl, benzyl, naphthyl. The examples of alkyls and aryls serve to illustrate the invention without limiting it. In yet another embodiment of the disclosed method, at least one of the groups providing a solubility of the organic compound in organic solvent is alkyl. In still another embodiment of the disclosed method, the photovoltaic layer produced from organic solutions has heterocyclic molecular systems with planes oriented predominantly parallel to the substrate plane.

In one embodiment of this preferred embodiment, said solution absorbs electromagnetic radiation within a wavelength range from 400 to 700 nm. In one embodiment of the disclosed method, said predominantly planar heterocyclic molecular system is a partially or completely conjugated. In still another embodiment of the disclosed method, said heterocyclic molecular system comprises the hetero-atoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof. In yet another embodiment of the disclosed method, at least one of the binding group is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂, and any combination thereof, where radical R is alkyl or aryl.

The examples of heterocyclic molecular systems with a general structural formula corresponding to structures 1-39 shown below in Tables 1 - 5 serve to illustrate the disclosed method without limiting it. In still another embodiment of the disclosed method for obtaining semiconductor crystal films, the planar heterocyclic molecular system comprises phthalocyanine fragments. Some examples of such planar heterocyclic molecular systems comprising phthalocyanine fragments having a general structural formula from the group comprising structures 1-4 are given in Table 1. In another embodiment of the disclosed method, the planar heterocyclic molecular system comprises rylene fragments. Some examples of such planar heterocyclic molecular systems comprising rylene fragments having a general structural formula from the group comprising structures 5-25 are given in Table 2. In another embodiment of the disclosed method, the planar heterocyclic molecular system comprises anthanthrone fragments. Examples of the heterocyclic molecular systems comprising anthanthrone fragments having a general structural formula from the group comprising structures 26 and 27 are given in Table 3. In still another embodiment of the disclosed method, the planar heterocyclic molecular system comprises pyrazine fragments. Some examples of such pyrazine fragments having a general structural formula from the group comprising structures 28-37 are given in Table 4. In another embodiment of the disclosed method, the planar heterocyclic molecular system comprises naphthalene fragments. Some examples of such heterocyclic molecular systems having a general structural formula from the group comprising structures 38-39 are given in Table 5.

In one another embodiment of the disclosed method, the applied solution layer is dried in airflow. In another embodiment of the disclosed method, the substrate is pretreated to provide surface hydrophilization before application of said solution layer. In yet another embodiment of the present invention, the disclosed method further comprises the stage of treatment of the photovoltaic layer with a solution of any water-soluble inorganic salt with a cation selected from the group including Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, and any combination thereof. The polyvalent counterions (Ba⁺⁺, Ca^+4", Mg⁺⁺, Sr⁺⁺, Zn⁺⁺) are used for stabilization of the organic compounds and provide their insolubility. In one embodiment of the disclosed method, said photovoltaic layer is formed by planar heterocyclic molecular systems of two or more types ensuring the absorption of electromagnetic radiation in different subranges within a wavelength range from 400 to 3000 nm.

In one embodiment of the disclosed method, said applied solution is isotropic. In another embodiment of the disclosed method, said solution is a lyotropic liquid crystal solution. In one embodiment of the method, the application of said lyotropic liquid crystal solution on the substrate is accompanied or followed by an orienting action upon this solution. In another embodiment of the method, the application stage is carried out using a spray-coating. In yet another embodiment of the disclosed method, the cycle of the technological operations of solution application and drying is repeated two or more times, and sequential photovoltaic layers are formed using solutions absorbing electromagnetic radiation in predefined spectral subranges, which can be either the same or different for various photovoltaic layers.

In the fourth aspect of the present invention there is provided an organic photovoltaic device comprising the first and second electrodes and at least one photovoltaic layer having the front surface and the rear surface, wherein said photovoltaic layer comprises at least one organic compound having the general structural formula II:

where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a molecular group providing a solubility of the organic compound; m is the number in the range from 0 to 8; X is a counterion from a list comprising H⁺, NH₄ ⁺ _, Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, and any combination thereof; t is the number of counterions necessary to provide for the electric neutrality of the organic compound; D is a substituent from a list comprising -CH₃, -C₂Hs, -NO₂, -Cl, -Br, -F, -CF₃, -CN, -OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and -CONH₂; and z is the number of substituents in the range from O to 4. The counterions are used for providing an electrical neutrality of the organic compounds and some of them may be used for stabilization of the organic compounds and provide their insolubility. The photovoltaic layer exhibits absorption of electromagnetic radiation in one or more predetermined spectral subranges within a wavelength range from 400 to 3000 nm. The photovoltaic layer may absorb electromagnetic radiation only in a part of wavelength range from 400 to 3000 nm. This part of spectral range will be called as subrange. This subrange may be determined experimentally for each particular (specific) organic layer of carboxylic acid salt. Similarly, the subrange of absorption may be determined experimentally for a mixture of carboxylic acid salt. Thus, such subrange of absorption of the electromagnetic radiation can be considered as the predetermined subrange.

In one embodiment of the disclosed organic photovoltaic device, the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the layer plane. In another embodiment of the disclosed organic photovoltaic device, the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly parallel to the layer plane.

In one preferred embodiment, said organic layer absorbs electromagnetic radiation within a wavelength range from 400 to 700 nm. In one embodiment of the disclosed organic photovoltaic device, said predominantly planar heterocyclic molecular system is a partially or completely conjugated. In still another embodiment of the disclosed organic photovoltaic device, said heterocyclic molecular system comprises the hetero-atoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof. In yet another embodiment of the disclosed organic photovoltaic device, at least one of the binding group is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂, and any combination thereof, where radical R is alkyl or aryl. The alkyls may be selected from the list comprising the methyl, ethyl, propyl, butyl, i-butyl, t-butyl and aryls may be selected from the list comprising the phenyl, benzyl, naphthyl. The examples of alkyls and aryls serve to illustrate the invention without limiting it.

The examples of heterocyclic molecular systems with a general structural formula corresponding to structures 1-39 shown below in Tables 1 - 5 serve to illustrate the disclosed organic photovoltaic device without limiting it. In still another embodiment of the disclosed organic photovoltaic device, the planar heterocyclic molecular system comprises phthalocyanine fragments. Some examples of such planar heterocyclic molecular systems comprising phthalocyanine fragments having a general structural formula from the group comprising structures 1-4 are given in Table 1. In another embodiment of the disclosed organic photovoltaic device, the planar heterocyclic molecular system comprises rylene fragments. Some examples of such planar heterocyclic molecular systems comprising rylene fragments having a general structural formula from the group comprising structures 5-25 are given in Table 2. In another embodiment of the disclosed organic photovoltaic device, the planar heterocyclic molecular system comprises anthanthrone fragments. Examples of the heterocyclic molecular systems comprising anthanthrone fragments having a general structural formula from the group comprising structures 26 and 27 are given in Table 3. In still another embodiment of the disclosed organic photovoltaic device, the planar heterocyclic molecular system comprises pyrazine fragments. Some examples of such' pyrazine fragments having a general structural formula from the group comprising structures 28-37 are given in Table 4. In another embodiment of the disclosed organic photovoltaic device, the planar heterocyclic molecular system comprises naphthalene fragments. Some examples of such heterocyclic molecular systems having a general structural formula from the group comprising structures 38-39 are given in Table 5.

The cathode materials (Al, Ca, In, Ag) usually employed in organic photovoltaic devices are characterized by low values of the electron work function, while the anode materials (e.g., Au) are characterized by high values of this parameter. In solar cells and photodiodes, one contact (electrode) has to be at least partially transparent to the incident solar radiation. Semitransparent metal electrodes can be obtained when the metal (e.g., Au) film thickness does not exceed 15 to 20 nm, while nontransparent metal contacts are typically 50 to 100 nm thick. The surface resistance of a thin semitransparent layer is higher than that of a thick (50 to 100 nm) film, which increases the serial resistance of a photovoltaic device and decreases the conversion efficiency. The optical properties of such contacts vary with thickness in the narrow interval from 10 to 20 nm, so that photovoltaic devices with only slightly different metal contact thicknesses may possess incomparable characteristics.

For the above reasons, transparent electrodes in photovoltaic devices are usually made of the so-called conducting glasses. Most widely used is a tin-doped indium oxide (indium tin oxide, ITO) representing a degenerate semiconductor comprising a mixture of ln2O3 (90 %) and SnO2 (10 %) with a bandgap width of 3.7 eV and a Fermi level between 4.5 and 4.9 eV. Because of the large bandgap, ITO does not absorb radiation with a wavelength exceeding 350 nm. This material possesses a high electric conductivity, whereby tin acts as a donor impurity rendering the resistivity very low even for ITO layers with thicknesses on the order of 100 nm. Quartz substrates covered with ITO layers are commercially available because such substrates are widely used as conducting screens in liquid crystal displays. The greater the ITO layer thickness, the lower the resistivity of this film. Then typical ITO layer thickness in organic photovoltaic devices is about 100 nm. Substrates with low resistivity are commercially available. The ability to transmit radiation does not vary significantly with the ITO layer thickness, since the material virtually does not absorb light in the visible spectral range. However, interference effects may considerably influence the spectral dependence of the optical transmission coefficient. The use. of very thick ITO layers (more than several hundred nanometers thick) is problematic, because increasing surface roughness of such thick films may lead to electric shorts in thin Organic films. It should be noted that ITO films can be also used as antireflection coatings. Plasma etching can modify the surface of ITO layers. Transparent electrodes can be also made of some other conducting glasses based on tin and indium oxides.

A comparison of the physical principles of operation of the organic photovoltaic devices based on inorganic and organic semiconductors leads to a conclusion that the photovoltaic conversion efficiency is generally much higher for the inorganic semiconductors. The main reason is that the mobile charge carriers (electrons and holes) in inorganic semiconductors are generated directly under the action of absorbed electromagnetic radiation. In contrast, the generation of free charge carriers in the organic semiconductors, as considered above, proceeds in several stages. The bound electron — hole pairs (excitons) produced in the first stage diffuse toward a photovoltaic heterojunction and dissociate with the formation of mobile electrons and holes. Presence of high dielectric spacing between organic core stacks makes dissociation more probable and re-combination of the electro-hole pair less effective. Thus, given the inherently low carrier generation efficiency in the non-ionic organic semiconductors, an important factor in the organic photovoltaic devices is the possibility to optimize the semiconductor material and device structure so as to provide for the maximum possible efficiency.

In particular, the effective operation of an organic photovoltaic device can be achieved only provided when all photovoltaic layers possess optimum thicknesses. On the one hand, it is desired that the photovoltaic layer thickness would be comparable with or smaller than the diffusion length of photogenerated excitons. In this case, excitons would dissociate predominantly near the photovoltaic heterojunction. On the other hand, such a small thickness of the photovoltaic layer decreases the fraction of absorbed electromagnetic radiation incident upon the organic photovoltaic device and, hence, reduces the external quantum efficiency of the device. In order to increase the fraction of absorbed electromagnetic radiation, it is desired that the photovoltaic layer thickness would be on the order of the effective radiation absorption length Ma, where a is the absorption coefficient. In this case, almost all radiation incident on the device will be absorbed within the photovoltaic layer and will therefore contribute to the exciton production. However, as soon as the photovoltaic layer thickness will exceed that of the active region, excitons will form with increased probability in the electrically neutral region far from the photovoltaic heteroj unction. As a result, because of a small diffusion length of excitons, the electron — hole pairs will recombine before such excitons will diffuse to enter the active region. Thus, the conversion efficiency drops with increase in the photovoltaic layer thickness. Another adverse effect of increase in the photovoltaic layer thickness consists in the related growth of a serial resistance of the organic photovoltaic device, which leads to an increase in the Ohmic losses and a decrease in the conversion efficiency. Taking into account all the aforementioned competitive factors related to the characteristic radiation absorption length, the exciton diffusion length, and the resistivity of the photovoltaic material, one may conclude that there is an optimum photovoltaic layer thickness ensuring the maximum possible conversion efficiency of each particular organic photovoltaic device. An important factor in reaching the maximum efficiency is the possibility of exactly reproducing the optimum thicknesses of the photovoltaic layer. An important advantage of the use of the disclosed photovoltaic layer is 1) control over thickness of the layer during deposition from aqueous solution of one ammonium salt, or a combination of such salts, 2) control over crystal structure and its growth by control of drying process with formation of a solid layer.

The disclosed organic photovoltaic device comprises at least one photovoltaic layer having the front surface, which is facing a light source, and the rear surface facing the opposite direction, and two electrodes. In the general case, the two electrodes will be referred to as the first and second electrodes. In some particular cases, the first electrode, which is located between a light source and the front surface of the photovoltaic layer and is made transparent to the electromagnetic radiation in the spectral range to which the given photovoltaic layer is sensitive, is called front electrode. By the same token, in some particular cases, wherein the second electrode is located next to the rear surface of a photovoltaic layer or a structure containing photovoltaic layers, this electrode is called rear electrode.

One of the embodiments of the disclosed photovoltaic organic device comprises a single photovoltaic layer.

In one preferred embodiment, the disclosed organic photovoltaic device comprises the front transparent electrode and the rear electrode located next to the rear surface of said photovoltaic layer.

The efficiency of an organic photovoltaic device can be increased by allowing the incident electromagnetic radiation to pass two times through the active photovoltaic layers of the device structure. For this purpose, in one embodiment of the invention, the front electrode is made transparent while the rear electrode represents a depolarizing mirror with a reflection coefficient of not less than 95% for the electromagnetic radiation penetrating through the device structure.

In addition, since at least one photovoltaic layer of said organic photovoltaic device is locally anisotropically absorbing, the electromagnetic radiation transmitted through this layer in one direction will be locally polarized. Being reflected from the reflective electrode, this locally polarized radiation will not be repeatedly absorbed in the anisotropic layer on the second passage. In order to avoid this, it is necessary to rotate the polarization vector by 90^°.

Therefore, an additional retarder layer has to be introduced into the organic photovoltaic device according to this embodiment, the thickness and optical anisotropy of which are selected so as to ensure a 45° rotation of the polarization vector of the transmitted radiation.

In a further embodiment, the rear electrode is a reflective electrode for the electromagnetic radiation incident upon the device, and the device further comprises an additional retarder layer located between said rear reflective electrode and the rear surface of said photovoltaic layer, wherein the thickness and optical anisotropy of said retarder layer are selected so as to ensure a 45° rotation of the polarization vector of transmitted electromagnetic radiation. There is another embodiment of the disclosed device, wherein a reflection coefficient of the reflective electrode is not less than 95% for the electromagnetic radiation incident upon the device.

In one embodiment, the front electrode serves as the cathode and the rear electrode serves as the anode. In another embodiment the front electrode serves as the anode and the rear electrode serves the cathode. In a further embodiment of the invention, the organic photovoltaic device further comprises at least one electron transport layer situated between said photovoltaic layer and the cathode. According to the disclosed invention, the organic photovoltaic device further comprises at least one exciton-blocking layer situated between said photovoltaic layer and the electron transport layer.

Another embodiment is possible, whereby the organic photovoltaic device further comprises at least one hole transport layer situated between said photovoltaic layer and the anode. Another embodiment of the organic photovoltaic device further comprises at least one exciton-blocking layer situated between said photovoltaic layer and the hole transport layer.

In another preferred embodiment, the disclosed invention comprises the first electrode, formed on a part of the front surface of the photovoltaic layer, and the second electrode formed on another part of the same front surface of said photovoltaic layer, wherein the first electrode serves as the cathode and the second electrode serves as the anode. In one embodiment, an organic photovoltaic device further comprises an additional retarder layer which is formed on the rear surface of said photovoltaic layer, and an additional reflective layer which is formed on said retarder layer, wherein the thickness and optical anisotropy of said retarder layer are selected so as to ensure a 45° rotation of the polarization vector of the electromagnetic radiation incident upon the device. The reflection coefficient of the reflective layer is not less than 95% for the electromagnetic radiation incident upon the device.

Further embodiment of said organic photovoltaic device is possible, wherein a rectifying Schottky barrier to the front electrode is formed at least on a part of the front surface of the 5 photovoltaic layer and an Ohmic contact to the rear electrode is formed at least on a part of the rear surface of the photovoltaic layer.

The present invention also provides a organic photovoltaic device comprising two photovoltaic layers, which form a double layer structure having the front surface, which is facing a light source, and the rear surface facing the opposite direction, wherein the first layer is an electron

10 donor layer, the second layer is an electron acceptor layer, and these layers are in contact so as to form a photovoltaic heterojunction. The double layer structure is confined between two electrodes. One electrode is situated between a light source and the front surface of the double layer structure. This electrode is made transparent and is named a front transparent electrode. The other electrode is located next'to the rear surface of the double layer structure

15. and is named a rear electrode. In one embodiment, the rear electrode is a reflective depolarizing electrode for electromagnetic radiation incident upon the device. In another embodiment, the rear electrode is a reflective electrode for electromagnetic radiation incident upon the device, and the device further comprises an additional retarder layer which is located between said reflective electrode and said double layer structure, wherein the thickness and

20 optical anisotropy of said retarder layer are selected so as to ensure a 45° rotation of the polarization vector of the incident electromagnetic radiation. The reflection coefficient of the reflective electrode is not less than 95% for the electromagnetic radiation incident upon the device structure. In one embodiment, the front electrode serves as the cathode and the rear electrode serves as the anode. In another embodiment, the front electrode serves as the

25 anode and the rear electrode serves as the cathode. According to the disclosed invention, the organic photovoltaic device may further comprise at least one electron transport layer situated between said double layer structure and the cathode.

In another preferred embodiment, the disclosed invention provides an organic photovoltaic device further comprising at least one exciton-blocking layer situated between said double 30 layer structure and the electron transport layer. In one embodiment, the organic photovoltaic device further comprises at least one hole transport layer situated between said double layer structure and the anode. In another preferred embodiment, the organic photovoltaic device further comprises at least one exciton-blocking layer situated between said double layer structure and the hole transport layer.

35 In one embodiment the organic photovoltaic device further comprises a protective transparent layer formed on at least one surface of said device. In another embodiment, the device further comprises an additional antireflection coating formed on at least one surface of said device. The general description of the present invention having been made, a further understanding can be obtained by reference to the specific preferred embodiments, which are given herein only for the purpose of illustration and are not intended to limit the scope of the appended claims.

Figure 6 presents a schematic diagram of the disclosed organic photovoltaic device, based on photovoltaic layer (1) making a Schottky barrier with the front electrode (2) and an Ohmic contact with the rear electrode (3). The entire structure is formed on a substrate (5) and the electrodes are connected to a resistive load (4).

Figure 7a presents a schematic energy band diagram of the typical Schottky junction involving an n-type photovoltaic layer in contact with the electrode (metal or conducting glass). As can be seen, there is an active space charge region of thickness d with a built-in field of strength EIN inside. This internal electric field, directed from Ohmic contact to rectifying junction, produces bending of the LUMO and HOMO energy levels as depicted in this figure. Figure 7a also indicates the directions of motion of electrons (•) and holes (o) under the action of the built-in electric field in the case when the device is exposed to eiectromagnetic radiation and connected to a resistive load. In the device under consideration, based on an n-type photovoltaic layer, the Ohmic contact is at the cathode and the rectifying junction (Schottky barrier) is at the anode. One of these electrodes is transparent for the electromagnetic radiation in the spectral range to which the given organic photovoltaic device is sensitive. In the case under consideration, either cathode or anode can be transparent: a transparent anode can represent a thin (10- to 20-nm thick) gold film, while a transparent cathode can be made of various metal-like materials such as ITO, gallium indium tin oxide (GITO), zinc indium tin oxide (ZITO), or a polymeric material such as poly(aniline) (PANI).

Figure 7b presents a schematic energy band diagram of the typical Schottky junction involving a p-type photovoltaic layer in contact with the electrode (metal or conducting glass). In this case, the internal electric field is directed from rectifying junction to Ohmic contact, so that the rectifying junction (Schottky barrier) is at the cathode and the Ohmic contact is at the anode.

It can be ascertained that, for a photovoltaic layer of the n-type, a metal with high value of the work function (e.g., Au) should be used for formation of a contact with the Schottky barrier, while for a p-type photoconductor, the electrodes should be made of a metal (e.g., Al, Mg, or In) with a low electron work function. In this embodiment, the separation of charges (necessary in any organic photovoltaic device) is due to the dissociation of excitons in the space charge region at the metal/photoconductor interface. The first electrode must form a barrier contact and the second electrode, an Ohmic contact. If the two electrodes are made of the same metal (or metal-like material), both contacts will be Ohmic or barrier. In case when both contacts are Ohmic, no charge regions featuring a built-in electric field are formed in the organic semiconductor. Such structures do not feature the dissociation of excitons and the separation of bound charges. If both contacts are of the barrier type and no external bias voltage is applied, the organic semiconductor contains two identical space charge regions

(one at each electrode) in which the built-in electric fields are equal in magnitude and opposite in direction. In this case, said organic photovoltaic device generates equal opposite photocurrents compensating one another. In other words, no photocurrent is developed in the absence of external bias voltage. Therefore, in the general case, the electrodes of said organic photovoltaic device should be made of different materials. It is recommended that the charge separation would take place at one electrode, while the other would readily transfer the

^' charge carriers. This can be achieved provided that the latter electrode forms no (or very small) potential barrier for the charge carrier transfer (such contact is characterized by very small resistance and is referred to as Ohmic).

In one embodiment, the organic photovoltaic device further comprises a protective transparent layer formed on at least one external surface of said device. In another embodiment, the device further comprises an antireflection coating formed on the external surface of said device.

Figure 8a schematically depicts the layer structure of an organic photovoltaic device ^' implementing an n-type photovoltaic layer (1) forming a Schottky junction with electrode (2).

This electrode serves as the anode, while electrode (3) on the opposite surface of the

^■ .photovoltaic layer forms an Ohmic contact and serves as the cathode. The electron transport layer (6) situated between the photovoltaic layer (1) and the cathode (3) is made of a material possessing high electron mobility and can also play the role of a planarization layer on an ITO electrode. The multilayer structure of the device is based on substrate (5). The cathode representing a thick ITO film has rather a rough surface and sharp protrusions on this surface can damage (perforate) the photovoltaic layer. This will lead to the formation of numerous microscopic conducting channels and a non-uniform current distribution in the junction, which may result in premature failure of the device. Another negative consequence is a decrease in the shunting resistance and, hence, in the conversion efficiency of the organic photovoltaic device. Thus, use of an electron transport layer favours an increase in the photovoltaic conversion efficiency and in the useful yield of device production.

Figure 8b shows another embodiment of the present invention, which is analogous to that shown in Figure 8a but differs from it in implementing a photovoltaic layer of the p-type. This structure contains a hole transport layer (7) between the photovoltaic layer (1) and the anode

(3). The hole transport layer, made of a material possessing a high hole mobility, favours the hole transfer from the photovoltaic layer to the anode and prevents the organic layer from being damaged by a thick electrode. The multilayer structure of the device is located on substrate (5).

Thus, an organic photovoltaic device according to the disclosed invention may contain layers effectively transferring electric charges (electrons and holes), which can be also active photoconducting layers. The terms electron transport layer and hole transport layer refer to the layers which are analogous to electrodes but differ from them in being intended for transferring mobile charge carriers from one to another layer of the given organic photovoltaic device.

Another embodiment of the present invention, illustrated in Figure 9, is based on a single photovoltaic layer (1). At least a part of the first surface of said photovoltaic layer contacts with the first electrode (2) to form a rectifying Schottky barrier and at least a part of the same surface is in Ohmic contact with the second electrode (3); the photovoltaic layer (1) is formed on substrate (5) and the electrodes are connected to a resistive load (4).

Figure 10 shows an exemplary embodiment of the organic photovoltaic device with an interdigitated system of electrodes. This device comprises a photovoltaic layer (1) bearing a barrier (2) and Ohmic (3) contacts on the first surface. The photovoltaic layer is formed on a substrate (5) and the electrodes are connected to a resistive load (4).

Figure 11a shows another organic photovoltaic device, wherein the first electrode (2) on a part of the first surface of a single photovoltaic layer forms a Schottky junction, the second electrode (3) on the same surface forms an Ohmic contact, while an additional reflective depolarizing layer (8) with a reflection coefficient of not less than 95% for the incident radiation is formed on the second surface of said photovoltaic layer. The reflective depolarizing layer (8) is a diffuse reflector that depolarizes electromagnetic radiation reflected from this layer. The entire multilayer structure is formed on substrate (5) and the electrodes are connected to a resistive load (4). In this structure, the incident electromagnetic radiation passes two times ' through the active photovoltaic layer of the device structure, thus increasing the efficiency of conversion. Since each crystalline particle (grain) of a photovoltaic layer acts as a polarizer of light, then the electromagnetic radiation transmitted through this layer will be locally polarized.

According to the present invention, Figure 11b shows the organic photovoltaic device similar to the device depicted in Figure 6a, except for an additional phase-shifting layer (retarder) (9) situated between a photovoltaic layer (1) and the reflective layer (80). This device operates as follows. Unpolarized electromagnetic radiation is incident onto photovoltaic layer (1). Being transmitted through this layer, the radiation becomes locally polarized owing to dichroism of the crystallites of the photovoltaic layer (1). Thus, each surface region of a photovoltaic layer containing at least one crystallite operates similarly to a local polarizer in such a way that a fraction of electromagnetic radiation incident upon this part of the layer will be absorbed by said local polarizers, and the other fraction of radiation, whose polarization is parallel to the transmission axis of said local dichroic polarizers, will pass through this layer without absorption. For increasing the conversion efficiency of the disclosed organic photovoltaic device, it is necessary to pass the transmitted radiation through the photovoltaic layer once again in the reverse direction. In order to provide that locally polarized radiation reflected from reflective layer (80) would be absorbed by the photovoltaic layer (1), it is necessary to rotate its polarization vector by 90° in each region of the photovoltaic layer. To this end, an additional retarder layer (9) is introduced between the photovoltaic layer (1) and the reflective layer (80). The thickness and optical anisotropy of this retarder are selected so as to ensure a 45°rotation of the polarization vector of the transmitted radiation. Since the electromagnetic radiation doubly passes through this layer, the resulting polarization rotation amounts to 90°. Thus, the combination of retarder and reflective layer provides for a more complete use of the incident electromagnetic radiation and ensures an increase in the photovoltaic conversion efficiency of the photovoltaic device according to this embodiment.

Figure 12a shows one more embodiment of the organic photovoltaic device. This organic photovoltaic device comprises a photovoltaic layer (1) possessing n-type conductivity, forming a rectifying Schottky barrier with a conducting layer (2) situated on the first side of said photovoltaic layer. An exciton-blocking layer (10) formed on the second side of said photovoltaic layer keeps the photogenerated excitons inside the active region of the device. Here, it is necessary to elucidate the term "exciton-blocking layer". The efficiency of a photovoltaic device can be increased by introducing one or several layers restricting the domain of existence of photogenerated excitons to a region in the vicinity of the photovoltaic heterojunction. Such layers hinder the motion of photogenerated excitons toward electrodes where such bound electron — hole pairs can recombine at the interface between the organic semiconductor and electrode material. Thus, the exciton-blocking layer limits the device volume where exciton diffusion is possible. Therefore, this layer (or layers) acts as a diffusion barrier. It should be noted that the exciton-blocking layer should be sufficiently thick to fill small holes in the adjacent photovoltaic layer and exclude the appearance of microscopic conducting channels (microchannels) that might form in the stage of electrode application. Thus, the exciton-blocking layer provides for an additional protection of a brittle photovoltaic layer from being damaged in the course of electrode formation. The ability of blocking excitons is related to the fact that the LUMO— HOMO energy difference in the material of this layer is greater than the bandgap width in the adjacent organic semiconductor layers. This implies an energetic prohibition for excitons to enter the blocking layer. While blocking excitons, this layer must allow the motion of electric charges to electrodes. For these reasons, the blocking layer material has to be selected so as to provide for the passage of charge carriers of the corresponding sign. In particular, the exciton-blocking layer on the cathode side must possess a LUMO level close to (or matched with) that of the adjacent electron transport layer, so that the energy barrier for electrons would be minimum. It must be taken into account that the ability of a material to block excitons is not related to the intrinsic properties such as the LUMO — HOMO energy difference. Apparently, the material will block excitons depending on the relative values of LUMO and HOMO energies in the adjacent layers of the organic photovoltaic materials. Therefore, it is impossible to indicate a priori the class of optimum materials for exciton-blocking layers irrespective of the particular function of such materials in a given photovoltaic device. However, once the organic photovoltaic material for the given device is selected, it is always possible to choose an appropriate exciton-blocking layer material as well. In the preferred embodiment of the disclosed invention, an exciton-blocking layer is situated between an electron acceptor layer and the cathode. A recommended material for this layer is 2,0-dimethyl-4,7-diphenyl-1 ,10-phenanthroline. This exciton-blocking layer simultaneously performs the function of an electron transport layer facilitating the motion of electrons toward a reflective depolarizing electrode (cathode) (85). The reflective depolarizing electrode is a diffuse reflector that depolarizes electromagnetic radiation reflected from this electrode. This electrode acts as Ohmic contact. The reflective depolarizing electrode (85) is necessary to provide that the incident radiation would be doubly transmitted through the device structure, thus increasing the conversion efficiency of the device. A resistive load (4) is connected between the barrier contact (2) and the Ohmic contact (85). The whole multilayer structure is based on substrate (5). Since each crystalline particle (grain) of a photovoltaic layer is a polarizer of a light, then the electromagnetic radiation transmitted through this layer will be locally polarized.

Figure 12b shows an organic photovoltaic device similar to the device depicted in Figure 12a except for an additional phase-shifting layer (retarder) (9) situated between the exciton- biocking layer (10) and the reflective electrode (80). This device operates as follows. The unpolarized electromagnetic is incident onto a photovoltaic layer (1). Being transmitted through this layer, the radiation becomes locally polarized owing to dichroism of the crystallites of the photovoltaic layer (1). Thus, each surface region of a photovoltaic layer containing at least one crystallite operates similarly to a local polarizer in such a way that a fraction of electromagnetic radiation incident upon this part of the layer will be absorbed by said local polarizers, and the other fraction of radiation, whose polarization is parallel to the transmission axis of said local dichroic polarizers, will pass through this layer without absorption. For increasing the conversion efficiency of the disclosed organic device, it is necessary to pass the transmitted radiation through the photovoltaic layer once again in the reverse direction. In order to provide that locally polarized radiation reflected from reflective layer (80) would be absorbed by the photovoltaic layer (1), it is necessary to rotate its polarization vector by 90° in each region of the photovoltaic layer. To this end, an additional retarder layer (9) is introduced between the photovoltaic layer (1) and the reflective layer (8). The thickness and optical anisotropy of this retarder are selected so as to ensure a 45^°rotation of the polarization vector of the transmitted radiation. Since the electromagnetic radiation doubly passes through this layer, the resulting polarization rotation amounts to 90°. Thus, the combination of retarder and reflective layer provides for a more complete use of the incident electromagnetic radiation and ensures an increase in the photovoltaic conversion efficiency of the photovoltaic device according to this embodiment.

Another embodiment of the disclosed organic photovoltaic device schematically depicted in Figure 13a represents a two-layer (bilayer) organic photovoltaic cell in which the dissociation of excitons and the separation of bound charges proceed predominantly at the photovoltaic heterojunction. The built-in electric field is determined by the LUMO — HOMO energy difference between two materials forming the heterojunction. This embodiment comprises two contacting photovoltaic layers — an electron donor layer (11) and an electron acceptor layer (12) — forming Ohmic contacts (3) with the adjacent electrodes. The entire multilayer structure is formed on substrate (5). The energy band diagram of this double-layer organic photovoltaic device is presented in Figure 8b. In this structure, bound electron — hole pairs (excitons 13) are generated by the incident electromagnetic radiation in both the electron donor (D) and acceptor (A) layers, with a photovoltaic heterojunction (14) formed at the interface of these layers. This region features dissociation of excitons with the formation of mobile charge carriers, electrons and holes, moving toward the cathode and anode, respectively, under the action of the built-in electric field. These separated electrons and holes move to the corresponding electrodes in different layers, namely electrons drift from the heterojunction to the cathode via the electron acceptor layer, while holes drift from the heterojunction to the anode via the electron donor layer. This property of a double-layer organic photovoltaic structure reduces probability of the electron — hole recombination, thus increasing the photovoltaic conversion efficiency. Another advantage of the double-layer organic photovoltaic device over the single layer counterpart is the basic possibility of using a wider wavelength range of the incident radiation. To this end, the electron donor and acceptor layers have to be made of materials possessing different absorption bands.

An exemplary embodiment of the organic photovoltaic device schematically shown in Fig. 14a represents a modified embodiment of the device depicted in Fig. 13a. This modified embodiment comprises an electron donor layer (11) in contact with an electron acceptor layer (12), this contact representing a photovoltaic heterojunction. Excitons (13) (see Fig. 14b) can be generated by electromagnetic radiation within both electron and donor layers. Said heterojunction (14) serves as the site where excitons exhibit dissociation to yield electrons and holes moving toward the cathode (17) and the anode (18), respectively, under the action of a built-in electric field. An exciton-blocking layer (16) formed between said electron acceptor layer (12) and the cathode (17) limits the region where photogenerated excitons can occur prior to dissociation, while not hindering the drift of electrons toward the cathode. An additional electron transport layer (6) can be formed between the exciton-blocking layer (16) and the cathode (17). In the same way, another exciton-blocking layer (15) formed on the other side of said heterojunction between an electron donor layer (11) and the anode (18) also restricts the region where excitons occur in the vicinity of the heterojunction, while not hindering the drift of holes toward the anode. An additional hole transport layer (7) can be formed between the exciton-blocking layer (15) and the anode (18). The cathode (17) occurs in Ohmic contact with the adjacent electron transport layer, while the anode (18) is in Ohmic contact with the adjacent hole transport layer. A resistive load (4) is connected between the cathode (17) and the anode (18). The whole multilayer structure is based on substrate (5).

Figure 14b shows an energy band diagram of the device depicted in Fig. 14a. According to this, bound electron — hole pairs (excitons) can be generated under the action of incident electromagnetic radiation in both electron donor and acceptor layer. The boundary between the electron donor and acceptor layers represents a photovoltaic heterojunction (14). The HOMO and LUMO energy levels of the exciton-blocking layer (16) and the adjacent electron acceptor layer (11) are mutually arranged so as to provide for (i) exciton-blocking and (ii) electron passage to the cathode. The photogenerated excitons are blocked because the HOMO — LUMO energy difference in the exciton-blocking layer (16) is greater than the corresponding energy difference in the electron acceptor layer (12). Thus, for energetic reasons, excitons generated in the electron acceptor layer (12) cannot enter the exciton- blocking layer (16) possessing a greater HOMO — LUMO energy difference. As can be seen from Fig. 14b, the LUMO of the exciton-blocking layer (16) lies below the LUMO level of the electron acceptor layer (12) and, hence, electrons can freely move toward the cathode. Analogous considerations are valid for the electron donor layer (11) and the exciton-blocking layer (15); thereby excitons are also blocked while holes can freely drift toward the anode.

Another exemplary embodiment of the organic photovoltaic device is schematically depicted in Fig. 15a. This device also comprises an electron donor layer (11) in contact with an electron acceptor layer (12), this contact representing a photovoltaic heterojunction. In order to increase the efficiency of conversion, the device is additionally provided with a reflective depolarizing electrode (85) in Ohmic contact with the electron acceptor layer (12). The reflective depolarizing electrode is a diffuse reflector that depolarizes electromagnetic radiation reflected from this electrode. A resistive load (4) is connected between the Ohmic contacts (3) and the reflective depolarizing electrode (85). The whole multilayer structure is based on substrate (5). Since each crystalline particle (grain) of a photovoltaic layer is a polarizer of a light, then the electromagnetic radiation elapsing (passing, walking) through this layer will be locally polarized.

There is another embodiment of the disclosed organic photovoltaic device, wherein a protective transparent layer is formed on at least one surface of said device.

In still another embodiment of the disclosed organic photovoltaic device, an additional antireflection coating is formed on at least one surface of said device.

Figure 15b shows an organic photovoltaic device similar to the device depicted in Figure 15a, except for an additional phase-shifting layer (retarder) (9) situated between electron acceptor layer (12) and the reflective layer (80) located on substrate. This device operates as follows. The unpolarized electromagnetic radiation is incident onto the electron donor layer (11) and then onto the electron acceptor layer (12). Being transmitted through these layers, the radiation becomes locally polarized owing to the dichroism of crystallites in photovoltaic layers (11) and (12). Thus, each surface region of these photovoltaic layers containing at least one crystallite operates similarly to a local polarizer in such a way that a fraction of electromagnetic radiation incident upon this part of layer (11) or (12) will be absorbed by said local polarizers, and the other fraction of radiation, whose polarization is parallel to the transmission axis of said local dichroic polarizers, will pass through this layer without absorption. For increasing the conversion efficiency of the disclosed organic device, it is necessary to pass the transmitted radiation through the photovoltaic layers (11) and (12) once again in the reverse direction. In order to provide that locally polarized radiation reflected from reflective layer (80) would be absorbed by the photovoltaic layers (11) and (12), it is necessary to rotate its polarization vector by 90° in each region of the photovoltaic layers. To this end, an additional retarder layer (9) is introduced between the photovoltaic layers and the reflective layer. The thickness and optical anisotropy of this retarder are selected so as to ensure a 45^°rotation of the polarization vector of the transmitted radiation. Since the electromagnetic radiation doubly passes through this layer, the resulting polarization rotation amounts to 90°. Thus, the combination of retarder and reflective layer provides for a more complete use of the incident electromagnetic radiation and ensures an increase in the photovoltaic conversion efficiency of the photovoltaic device according to this embodiment

In order that the invention may be more readily understood, reference is made to the following examples, which are intended to be illustrative of the invention, but are not intended to be limiting in scope.

Example 1

This example describes the synthesis of Copper - tetracarboxyphthalocyanine comprising planar heterocyclic molecular system # 1 from Table 1

via condensation of trimellitic anhydride Urea and Copper Chloride.

Mixture of trimellitic anhydride (10 g), urea (30 g), copper (II) chloride (3 g) and ammonium molybdate (1 g) was agitated in nitrobenzene (100 ml) for 5 hours at 160-165⁰C. After self cooling precipitate was filtered and rinsed with water and acetone.

Filter cake was agitated in the boiling 30% potassium hydroxide solution (200 ml) for 6 hours. After self cooling reaction mass was diluted with water and filtered. Filter cake was dissolved in water (~700 ml) and filtered. After that solution was acidified with concentrated hydrochloric acid (50 ml). Precipitate was filtered and rinsed with water.

Yield 8.08 g.

Dried filter cake was dissolved in concentrated sulfuric acid. Obtained solution was diluted with water (50 ml). Final sulfuric acid concentration became 70%. Precipitate was filtered, rinsed with water and dissolved in the mixture of water (2 I) and concentrated ammonia solution (70 ml). Obtained solution was acidified with concentrated hydrochloric acid (70 ml). Precipitate was filtered and rinsed with water.

Yield 6.6 g.

Example 2

This example describes the synthesis of 5,12-dihydroquinoxalino[2,3-b]phenazine dicarboxylic acids (carboxylic acid of base structure 32 in the Table 4)

via condensation of 2,5-dihydroxy-p-benzochinon with 3,4-diaminobenzoic acid.

Solution of Mixture of 3,4-Diaminobenzoic acid (1.2 g) and 2,5-Dihydroxy-1,4-benzoquinone (0.5 g) in N-Methylpyrrolidone-.(30 ml) was boiled for 13 hours. Self cooled reaction mass was diluted with water (30 ml). Precipitate was filtered and rinsed with 50% N-Methylpyrrolidone and water. Filter cake was dissolved in the mixture of water (150 ml) and concentrated ammonia solution (10 ml). Acetic acid (10 ml) was added into the solution. Precipitate was filtered and rinsed with water. Filter cake was suspended in water (200 ml). Precipitate was filtered.

Yield 0.82 g.

Example 3

This example describes the preparation of a semiconductor crystal layer from an isotropic solution of compound prepared according to the example 2. A solution of 1.0 g of 5,12- dihydroquinoxalino[2,3-b]phenazine dicarboxylic acids in 35.0 g of deionized water is stirred for 5 min at a temperature of 20 °C. Then, 1.3 ml of a 10% aqueous ammonia solution is added and the mixture is stirred until complete dissolution. An ITO-coated glass substrate is sequentially washed with surfactants and with deionized water and then dried with airflow from a compressor. The pretreated glass substrate is coated with the above solution using the Mayer rod #2.5 moved at a linear rate of 15 mm/s, a temperature of 20 ⁰C, and a relative humidity of 65%. Finally, the film is dried at the same humidity and temperature. The obtained film is characterized by measuring the conductivity in the direction perpendicular to the substrate surface. Example 4

This example describes the preparation of a semiconductor layer from a lyotropic liquid crystal solution of compound prepared according to the example 2. A solution of 4 g of 5,12- dihydroquinoxalino[2,3-b]phenazine dicarboxylic acids in 35.0 g of deionized water is stirred for 5 min at a temperature of 20 ⁰C. Then, 1.3 ml of a 10% aqueous ammonia solution is added and the mixture was stirred for 1 h under ambient conditions until a lyotropic liquid crystal solution is formed. An ITO-coated glass is sequentially washed with surfactants and with deionized water and then dried with airflow from a compressor. The pretreated glass substrate is coated with the above solution using the Mayer rod #2.5 moved at a linear rate of 15 mm/s, a temperature of 20 °C, and a relative humidity of 65%. The film is dried in airflow of a fan. The obtained film is characterized by measuring the conductivity in the direction perpendicular to the substrate surface.

Example 5

This example describes the synthesis of Dicarboxymetylimide of perylentetracarboxylic acid (carboxylic acid of base structure 11 in the Table 2)

Mixture of 3,4,9, 10-Perylenetetracarboxylic-3,4:9,10-dianhydride (2 g) and Glycine (3.8 g) was agitated in the boiling N-Methylpyrrolidone (50 ml) for 6 hours. Self cooled reaction mass was filtered. Filter cake was rinsed with N-Methylpyrrolidone, hydrochloric acid and water. Obtained filter cake was suspended in ~300 ml of water, filtered and rinsed with water.

Yield 0.73 g.

Example 6

This example describes the synthesis of bis(carboxybenzimidazoles) of naphthalene tetracarboxylic acid (carboxylic acid of base structures 38 and 39 in the Table 5)

Mixture of 1,4,5,8-Naphthalenetetracarboxylic dianhydride (2 g) and 3,4-Diaminobenzoic acid (9.08 g) was agitated in the boiling Dimethylformamide (50 ml) for 11 hours. Self cooled reaction mass was filtered. Filter cake was rinsed with Dimethylformamide and water.

Yield 1.6 g

Example 7

The sixth example describes the organic photovoltaic device based on the ITO/carboxy- CuPc/Carboxy-DBI PTCA/Ag structure with Ag top contacts. Samples were coated on ITO/glass substrate. Top contact Ag was deposed by thermal evaporation. The copper- 4,4\4^",4'"-tetracarboxyphthalocyanine (carboxy-CuPc) is described by the following structural formula:

The violet dye with carboxylic groups (Carboxy-DBI PTCA) is described by the following structural formula:

At manufacturing of organic photovoltaic device, it is necessary to obtain structure with lowest thickness of the layers and no shorts. Efficiency 0.01% was achieved on structure, wherein the first layer thickness is equal to 70 nm and second layer thickness is equal to120 nm. But such organic photovoltaic device degrades in scale of days. Load curve and I-V curve of this structure is shown in Figure 16. Following layers thickness decreasing is complicated by layer quality lowering with thickness decreasing and possibility of shorts.

Although the present invention has been described in detail with reference to a particular preferred embodiment, persons possessing ordinary skill in the art to which this invention pertains will appreciate that various modifications and enhancements may be made without departing from the spirit and scope of the claims that follow.

Claims

CLAIMSWhat is claimed is

1. An organic compound of the general structural formula I:

where Het is a predominantly planar heterocyclic molecular system;

B is a binding group; p is the number in the range from 3 to 8;

S is a group providing a solubility of the organic compound; m is the number in the range from 0 to 8;

D is a substituent from a list comprising -CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, -CF₃, - CN,

-OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and - CONH₂; and z is the number of substituents in the range from O to 4, wherein said organic compound absorbs electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm, and a solution of the organic compound or its salt is capable of forming a photovoltaic layer on a substrate.

2. An organic compound according to Claim 1 , wherein said solution is based on water and/or water-miscible solvents.

3. An organic compound according to Claim 2, wherein at least one of the groups providing a solubility of the organic compound is selected from the list comprising the COO , SO₃ ^", HPO₃ ^", and PO₃ ^2" and any combination thereof.

4. An organic compound according to any of Claims 2 to 3, wherein the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the substrate plane.

5. An organic compound according to Claim 1 , wherein said solution is based on organic solvent.

6. An organic compound according to Claim 5, wherein the organic solvent is selected from the list comprising the benzol, toluene, xylenes, acetone, acetic acid, methylethylketone, hydrocarbons, chloroform, methylenechloride, chlorbenzol, alcohols, nitrometan, acetonitrile, dimethylforamide, 1 ,4-dioxane or any combination thereof.

7. An organic compound according to any of Claims 5 to 6, wherein at least one of the groups providing a solubility of the organic compound is amide of acid residue independently selected from the list comprising the CONRiR₂, CONHCONH₂, SO₂NRiR₂, and any combination thereof, were R₁₁R₂ independently selected from H, alkyl or aryl.

8. An organic compound according to any of Claims 5 to 6, wherein at least one of the groups providing a solubility of the organic compound is alkyl.

9. An organic compound according to any of Claims 5 to 8, wherein the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly parallel to the substrate plane.

10. An organic compound according to any of Claims 1 to 9, which exhibits absorption of electromagnetic radiation within a wavelength range from 400 to 700 nm.

11. An organic compound according to any of Claims.1 to 10, wherein said predominantly planar heterocyclic molecular system is a partially or completely conjugated.

12. An organic compound according to any of Claims 1 to 11 , wherein said heterocyclic molecular system comprises the hetero-atoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof.

13. An organic compound according to any of the above claims, wherein at least one of the binding groups is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂, and any combination thereof, where radical R is alkyl or aryl.

14. An organic compound according to any of Claims 1 to 13, wherein said planar heterocyclic molecular system comprises phthalocyanine fragments.

15. An organic compound according to Claim 14, wherein said planar heterocyclic molecular system comprising phthalocyanine fragments has a general structural formula from the group comprising structures 1-4, where Latin letter M denotes an atom of metal:

16. An organic compound according to any of Claims 1 to 13, wherein said planar heterocyclic molecular system comprises rylene fragments.

17. An organic compound according to Claim 16, wherein said planar heterocyclic molecular systems comprising rylene fragments has a general structural formula from the group comprising structures 5-25:

18. An organic compound according to any of Claims 1 to 13, wherein said planar heterocyclic molecular system comprises anthanthrone fragments.

19. An organic compound according to Claim 18, wherein said planar heterocyclic molecular systems comprising anthanthrone fragments has a general structural formula from the group comprising structures 26-27:

20. An organic compound according to any of Claims 1 to 13, wherein said planar heterocyclic molecular system comprises pyrazine fragments.

21. An organic compound according to Claim 20, wherein said heterocyclic molecular system comprising pyrazine fragments has a general structural formula from the group comprising structures 28 - 37:

22. An organic compound according to any of Claims 1 to 13, wherein said planar heterocyclic molecular system comprises naphthalene fragments.

23. An organic compound according to Claim 22, wherein said planar heterocyclic molecular system comprising naphthalene fragments has a general structural formula from the group comprising structures 38-39:

24. A semiconductor crystal film comprising a substrate and at least one photovoltaic layer on the substrate, wherein the photovoltaic layer comprises at least one organic compound of general structural formula II:

[⁽Het

where Het is a predominantly planar heterocyclic molecular system;

B is a binding group; p is the number in the range from 3 to 8;

S is a molecular group providing a solubility of the organic compound; m is the number in the range from 0 to 8;

X is a counterion from a list comprising H⁺, NH₄ ⁺, Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, and any combination thereof; t is the number of counterions necessary to provide for the electric neutrality of the organic compound (II);

-OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and - CONH₂; and z is the number of substituents in the range from O to 4,

¹ wherein said photovoltaic layer absorbs electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm. -

25. A semiconductor crystal film according to Claim 24, wherein the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the substrate plane.

26. A semiconductor crystal film according to Claim 24, wherein the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly parallel to the substrate plane.

27. A semiconductor crystal film according to any of Claims 24 to 26, wherein said photovoltaic layer absorbs electromagnetic radiation within a wavelength range from 400 to 700 nm.

28. A semiconductor crystal film according to Claims 24 to 27, wherein said predominantly planar heterocyclic molecular system is a partially conjugated.

29. A semiconductor crystal film according to Claims 24 to 27, wherein said predominantly planar heterocyclic molecular system is a completely conjugated.

30. A semiconductor crystal film according to Claims 24 to 29, wherein said heterocyclic molecular system comprises the heteroatoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof.

31. A semiconductor crystal film according to Claims 24 to 30, wherein the binding group is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂,and any combination thereof, where radical R is alkyl or aryl.

32. A semiconductor crystal film according to any of Claims 24 to 31, wherein said heterocyclic molecular system comprises phthalocyanine fragments.

33. A semiconductor crystal film according to Claim 32, wherein said planar heterocyclic molecular system comprising phthalocyanine fragments has a general structural formula from the group comprising structures 1-4, where Latin letter M denotes an atom of metal:

34. A semiconductor crystal film according to any of Claims 24 to 31, wherein said heterocyclic molecular system comprises rylene fragments.

35. A semiconductor crystal film according to Claim 34, wherein said heterocyclic molecular system comprising rylene fragments has a general structural formula from the group comprising structures 5-25:

36. A semiconductor crystal film according to any of Claims 24 to 31, wherein said planar heterocyclic molecular system comprises anthanthrone fragments.

37. A semiconductor crystal film according to Claim 36, wherein said planar heterocyclic molecular system comprising anthanthrone fragments has a general structural formula from the group comprising structures 26-27:

38. A semiconductor crystal film according to any of Claims 24 to 31, wherein said heterocyclic molecular system comprises pyrazine fragments.

39. A semiconductor crystal film according to Claim 38, wherein said heterocyclic molecular system comprising anthanthrone fragments has a general structural formula from the group comprising structures 28 - 37:

40. A semiconductor crystal film according to any of Claims 24 to 31 , wherein said planar heterocyclic molecular system comprises naphthalene fragments.

41. A semiconductor crystal film according to Claim 40, wherein said planar heterocyclic molecular system comprising naphthalene fragments has a general structural formula from the group comprising structures 38-39:

42. A semiconductor crystal film according to any of Claims 24 to 41 , wherein said photovoltaic layer is substantially insoluble in water and/or in water-miscible solvents.

43. A semiconductor crystal film according to any of Claims 24 to 42, wherein said heterocyclic molecular systems are arranged in stacks, which are oriented predominantly perpendicularly to the substrate surface.

44. A semiconductor crystal film according to any of Claims 24 to 42, wherein said photovoltaic layer is isotropic.

45. A semiconductor crystal film according to any of Claims 24 to 44, wherein said photovoltaic layer comprises two or more organic compound of the general structural formula II, which ensure the absorption of electromagnetic radiation in different spectral subranges.

46. A semiconductor crystal film according to Claim 24 comprising two or more photovoltaic layers, wherein each of these layers comprises an organic compound of the general structural formula Il and absorbs electromagnetic radiation in a predefined spectral subrange.

47. A method of producing a semiconductor crystal film, which involves

(a) application on a substrate of a solution of one organic compound, or a combination of such organic compounds, with the general structural formula I:

where Het is a predominantly planar heterocyclic molecular system; B is a binding group; p is the number in the range from 3 to 8; S is a group providing a solubility of the organic compound; m is the number in the range from 0 to 8; D is a substituent from a list comprising -CH₃, -C₂H₅, -NO₂, -Cl, -Br, -F, -CF₃, -

CN,

-OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and - CONH₂; and z is the number of substituents in the range of 0 to 4, wherein the solution has absorption of electromagnetic radiation in one or more predetermined spectral subranges within a wavelength range from 400 to 3000 nm, (b) drying with formation of a photovoltaic layer.

48. A method according to Claim 47, wherein said solution is based on water and/or water-miscible solvents.

49. A method according to Claim 48, wherein at least one of the groups providing a solubility of the organic compound is selected from the list comprising the COO , SO₃ ^", HPO₃-, and PO₃ ^2- and any combination thereof.

50. A method according to any of Claims 47 or 48, wherein the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the substrate plane. ■ .

51. A method compound according to Claim 47, wherein said solution is based on organic solvent.

52. A method according to Claim 51 , wherein the organic solvent is selected from the list comprising the benzol, toluene, xylenes, acetone, acetic acid, methylethylketone, hydrocarbons, chloroform, methylenechloride, chlorbenzol, alcohols, nitrometan, acetonitrile, dimethylforamide, 1 ,4-dioxane or any combination thereof.

53. An organic compound according to any of Claims 51 or 52, wherein at least one of the groups providing a solubility of the organic compound is amide of acid residue independently selected from the list comprising the CONRiR₂, CONHCONH₂, SO₂NR₁R₂, and any combination thereof, were R₁₁R₂ independently selected from H, alkyl or aryl.

54. An organic compound according to any of Claims 51 or 52, wherein at least one of the groups providing a solubility of the organic compound is alkyl.

55. An organic compound according to any of Claims 51 to 54, wherein the photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly parallel to the substrate plane.

56. A method according to any of Claims 47 or 55, wherein said solution absorbs electromagnetic radiation within a wavelength range from 400 to 700 nm.

57. A method according to Claims 47 to 56, wherein said predominantly planar heterocyclic molecular system is a partially or completely conjugated.

58. A method according to Claims 47 to 57, wherein said heterocyclic molecular system comprises the hetero-atoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof.

59. A method according to Claims 47 to 58, wherein at least one of the binding groups is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂, and any combination thereof, where radical R is alkyl or aryl.

60. A method according to any of Claims 47 to 59, wherein said planar heterocyclic molecular system comprises phthalocyanine fragments.

61. A method according to Claim 60, wherein said planar heterocyclic molecular system comprising phthalocyanine fragments has a general structural formula from the group comprising structures 1-4, where Latin letter M denotes an atom of metal:

62. A method according to any of Claims 47 to 59, wherein said planar heterocyclic molecular system comprises rylene fragments. >

63. A method according to Claim 62, wherein said planar heterocyclic molecular systems comprising rylene fragments has a general structural formula from the group comprising structures 5-25:

64. A method according to any of Claims 47 to 59, wherein said planar heterocyclic molecular system comprises anthanthrone fragments.

65. A method according to Claim 64, wherein said planar heterocyclic molecular systems comprising anthanthrone fragments has a general structural formula from the group ■ comprising structures 26-27:

66. A method according to any of Claim 47 or 59, wherein said planar heterocyclic molecular system comprises pyrazine fragments.

67. A method according to Claim 66, wherein said heterocyclic molecular system comprising pyrazine fragments has a general structural formula from the group comprising structures 28 - 37:

68. A method according to any of Claims 47 or 59, wherein said planar heterocyclic molecular system comprises naphthalene fragments.

69. A method according to Claim 68, wherein said planar heterocyclic molecular system comprising naphthalene fragments has a general structural formula from the group comprising structures 38-39:

70. A method according to any of Claims 47 to 69, wherein said drying stage is carried out using airflow.

71. A method according to any of Claims 47 to 70, wherein the substrate prior to the application of said solution is pretreated so as to render its surface hydrophilic.

72. A method according to any of Claims 47 to 71 , further comprising treatment of the photovoltaic layer with a solution of any water-soluble inorganic salt comprising a cation from the group including Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, or any combination thereof.

73. A method according to any of Claims 47 to 72, wherein said photovoltaic layer is formed by planar heterocyclic molecular systems of two or more types ensuring the absorption of electromagnetic radiation in different subranges within a wavelength range from 400 to 3000 nm.

74. A method according to any of Claims 47 to 73, wherein said solution is isotropic.

75. A method according to any of Claims 47 to 73, wherein said solution is a lyotropic liquid crystal solution.

76. A method according to Claim 75, wherein the application of said solution on the substrate is accompanied or followed by an orienting action upon this solution.

77. A method according to any of Claims 47 to 76, wherein said application stage is carried out using a spray-coating.

78. A method according to any of Claims 47 or 77, wherein the cycle of the technological operations of solution application and drying is repeated two or more times, and sequential photovoltaic layers are formed using solutions absorbing electromagnetic radiation in predefined spectral subranges, which can be either the same or different for various photovoltaic layers.

79. An organic photovoltaic device comprising the first and second electrodes and at least one photovoltaic layer having the front surface and the rear surface, wherein said photovoltaic layer comprises at least one organic compound having the general structural formula II:

where Het is a predominantly planar heterocyclic molecular system;

B is a binding group; p is the number in the range from 3 to 8;

X is a counterion from a list comprising H⁺, NH₄ ⁺, Ba⁺⁺, Zn⁺⁺, Sr⁺⁺, Ca⁺⁺, Mg⁺⁺, and any combination thereof; t is the number of counterions necessary to provide for the electric neutrality of the organic compound;

-OH, -OCH₃, -OC₂H₅, -OCOCH₃, -OCN, -SCN -NH₂, -NHCOCH₃, and - CONH₂; and z is the number of substituents in the range from O to 4, wherein the photovoltaic layer has absorption of electromagnetic radiation in one or more predetermined spectral subranges within a wavelength range from 400 to 3000 nm.

80. An organic photovoltaic device according to Claim 79, wherein said photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly perpendicularly to the layer plane.

81. An organic photovoltaic device according to Claim 79, wherein said photovoltaic layer has heterocyclic molecular systems with planes oriented predominantly parallel to the layer plane.

82. An organic photovoltaic device according to any of Claims 79 to 81 , wherein said organic layer absorbs electromagnetic radiation within a wavelength range from 400 to 700 nm.

83. An organic photovoltaic device according to Claims 79 to 82, wherein said planar heterocyclic molecular system is a partially or completely conjugated.

84. An organic photovoltaic device according to Claims 79 to 83, wherein said heterocyclic molecular system comprises the heteroatoms selected from the list comprising nitrogen, oxygen, sulfur, and any combination thereof.

85. An organic photovoltaic device according to Claims 79 to 84, wherein the binding group is selected from the list comprising the hetero-atoms, COOH, SO₃H, H₂PO₃, NH, NH₂, NHR, NR₂,and any combination thereof, where radical R is alkyl or aryl.

86. An organic photovoltaic device according to any of Claims 79 to 85, wherein said planar heterocyclic molecular system comprises phthalocyanine fragments.

87. An organic photovoltaic device according to Claim 86, wherein said planar heterocyclic molecular system comprising phthalocyanine fragments has a general structural formula from the group comprising structures 1-4, where Latin letter M denotes an atom of metal:

88. An organic photovoltaic device according to any of Claims 79 to 85, wherein said planar heterocyclic molecular system comprises rylene fragments.

89. An organic photovoltaic device according to Claim 88, wherein said planar heterocyclic molecular systems comprising rylene fragments has a general structural formula from the group comprising structures 5-25:

90. An organic photovoltaic device according to any of Claims 79 to 85, wherein said planar heterocyclic molecular system comprises anthanthrone fragments.

91. An organic photovoltaic device according to Claim 90, wherein said planar heterocyclic molecular systems comprising anthanthrone fragments has a general structural formula from the group comprising structures 26-27:

92. An organic photovoltaic device according to any of Claims 79 to 85, wherein said planar heterocyclic molecular system comprises pyrazine fragments.

93. An organic photovoltaic device according to Claim 92, wherein said heterocyclic molecular system comprising pyrazine fragments has a general structural formula from the group comprising structures 28 - 37:

94. An organic photovoltaic device according to any of Claims 79 to 85, wherein said planar heterocyclic molecular system comprises naphthalene fragments.

95. An organic photovoltaic device according to Claim 94, wherein said planar heterocyclic molecular system comprising naphthalene fragments has a general structural formula from the group comprising structures 38-39:

96. An organic photovoltaic device according to any of Claims 79 to 95, wherein at least one of said electrodes is transparent for the incident electromagnetic radiation to which said organic photovoltaic device is sensitive.

97. An organic photovoltaic device according to any of Claims 79 to 96, further comprising a substrate bearing said electrodes and said photovoltaic layer.

98. An organic photovoltaic device according to any of Claims 79 to 97, further comprising at least one electron transport layer situated between said photovoltaic layer and the first electrode that serves as a cathode.

99. An organic photovoltaic device according to Claim 98, further comprising at least one exciton-blocking layer situated between said photovoltaic layer and said electron transport layer.

100. An organic photovoltaic device according to any of Claims 79 to 99, further comprising at least one hole transport layer situated between said photovoltaic layer and the second electrode that serves as an anode.

101. An organic photovoltaic device according to Claim 100, further comprising at least one exciton-blocking layer situated between said photovoltaic layer and said hole transport layer.

102. An organic photovoltaic device according to any of Claims 79 to 101, wherein the first electrode is transparent, and the second electrode is a depolarizing mirror having a reflection coefficient of not less than 95% for the electromagnetic radiation transmitted through the device.

103. An organic photovoltaic device according to any of Claims 79 to 101 , wherein the second electrode is transparent, and the first electrode is a depolarizing mirror having a reflection coefficient of not less than 95% for the electromagnetic radiation transmitted through the device.

104. An organic photovoltaic device according to any of Claims 79 to 97, which contains one said photovoltaic layer, having a rectifying Schottky barrier with the first electrode formed at least on a part of the front surface of said layer and an Ohmic contact with the second electrode formed at least on a part of the rear surface of said layer.

105. An organic photovoltaic device according to any of Claims 79 to 97, which comprises one photovoltaic layer having a rectifying Schottky barrier with the first electrode formed on a part of the front surface of said layer and an Ohmic contact with the second electrode formed on another part of the front surface of said layer.

106. An organic photovoltaic device according to Claim 105, further comprising a reflective depolarizing layer situated on the rear surface of said photovoltaic layer and having a reflection coefficient not less than 95 % for the incident electromagnetic radiation to which the photovoltaic layer is sensitive.

107. An organic photovoltaic device according to Claim 105, further comprising a retarder layer and a reflective layer situated in series on the rear surface of said photovoltaic layer, wherein the reflective layer has a reflection coefficient not less than 95 % for the incident electromagnetic radiation to which the photovoltaic layer is sensitive and the thickness and optical anisotropy of said retarder layer are selected so as to ensure a 45° rotation of the polarization vector of the electromagnetic radiation transmitted through said retarder layer in one direction.

108. An organic photovoltaic device according to any of Claims 79 to 97, comprising the first and second photovoltaic layers forming a double layer structure with front and rear surfaces, wherein said first photovoltaic layer is an electron donor layer, and said second photovoltaic layer is an electron acceptor layer and is in contact with the first photovoltaic layer so as to form a photovoltaic heterojunction.

109. An organic photovoltaic device according to Claim 108, comprising at least one electrode transparent for the incident electromagnetic radiation to which said photovoltaic layers are sensitive, and another reflective depolarizing electrode intended for reflection of this radiation.

110. An organic photovoltaic device according to Claim 108, further comprising a retarder layer and a reflective layer which are situated in series on the rear surface of said double layer structure, wherein the reflective layer has a reflection coefficient not less than 95 % for the incident electromagnetic radiation to which the photovoltaic layer is sensitive and the thickness and optical anisotropy of said retarder layer are selected so as to ensure a 45° rotation of the polarization vector of the electromagnetic radiation transmitted through said retarder layer in one direction.

111. An organic photovoltaic device according to any of Claims 109 or 110, wherein said electrodes form Ohmic contacts with the adjacent organic layers.

112. An organic photovoltaic device according to any of Claims 79 to 111 , further comprising a protective transparent layer formed on at least one surface of said device.

113. An organic photovoltaic device according to any of Claims 79 to 112, further comprising an antireflection coating formed on at least one surface of said device.

114. An organic photovoltaic device photovoltaic device substantially as hereinbefore described with reference to and as shown in Figures 6, 8a, 8b, 9, 10, 11a, 11b, 12a, 12b, 13a, 14a, 15a, 15b of the accompanying drawings.

115. The organic photovoltaic device substantially as hereinbefore described with reference to Example 6.