WO2004030029A2

WO2004030029A2 - Conducting polymer devices for inter-converting light and electricity

Info

Publication number: WO2004030029A2
Application number: PCT/EP2003/010258
Authority: WO
Inventors: Frederik C. Krebs; Mikkel JØRGENSEN; Kristoffer Almdal
Original assignee: Risø National Laboratory
Priority date: 2002-09-27
Filing date: 2003-09-16
Publication date: 2004-04-08
Also published as: AU2003282015A1; AU2003282015A8; GB0222510D0; WO2004030029A3

Abstract

A photovoltaic electroluminescent cell comprises a first electrode and a second electrode separated by dye linked block polymer molecule containing an n-type semiconductor polymer block linked via a light absorbing monomeric dye moiety to a p-type semiconductor polymer block the two polymer blocks being phase separated into distinct layers. The n-type semiconductor polymer block and the p-type semiconductor polymer block are each independently formed from selected polymers formed from terphenylenevinylene, polyaniline, polythiopene, poly (2-vinyl-pyridine), poly(Nvinylcarbazole), poly-acetylene, poly (p-phenylenevinylene), polym-phenylene, poly-p-phenylene, poly-2,6-pyridine, or polypyrrole monomer, said polymers being substituted with electron withdrawing substituents in the case of the n-type polymer block and with electron donating substituents in the case of the p-type polymer block.

Description

Conducting Polymer Devices For Inter-Converting Light And

Electricity

The present invention relates to devices for inter- converting light and electricity, including both photovoltaic cells and electroluminescent cells, based on conducting polymers .

It has been recognised for some time that potentially such devices have advantages over the conventional, similar devices based on inorganic semiconductors. These potential advantages include cheapness of the materials and versatility of processing methods, flexibility (lack of rigidity) and toughness . However, to date, the efficiency of the conversion between light and electricity offered by such materials has been poor.

The article ^Conjugated polymers: New materials for photovoltaics' , Wallace et al, Chemical Innovation, April 2000, Vol. 30, No. 1, 14-22, reviews the field.

Yoshino et al, IEEE Trans. Electron Devices 1997, 44, 1315-1324 describes devices based on the effect of light on conjugated polymers such as poly (p-phenylene vinylene) (PPV) and its derivatives. Devices of this kind operate generally as follows. In an electroluminescent device, electrons and holes injected at opposed electrodes reach one another by conduction through conductive organic molecules and recombine to produce light. In photovoltaic devices, photons are absorbed and the energy of the photon forms an exiton consisting of an electron and a hole which initially are bound together. These can be separated and caused to migrate towards electrodes by an electric field, suitably produced by electrodes of differing work functions.

Yoshino et al proposed the use of a donor polymer D (a p-type semiconducting polymer in which conduction of holes occurs) and an acceptor material A, specifically C₆o fullerene molecules. These are good electron acceptors. They further proposed the use of a middle layer M of a material which is a light absorbing material such as octaethylporphine (OEP) . Thin films of OEP and C₆o were deposited onto a D polymer film by organic molecular beam deposition. The photocurrent intensity of the D-M-A photocell is enhanced by over 100 times with respect to a cell with only the M layer and about twice that of a similar D-A cell. The M layer produces both photocurrent enhancement and broader spectral sensitivity. In an alternative idea, the M material is present in the middle of the device and the D and A materials are both polymers that form an interpenetrating network extending to either side so that there is a large D-A junction area throughout the device. A separate dopant is incorporated from each side of the device.

Wallace et al state that the light harvesting (M) material could be covalently attached to either the donor or that acceptor material in the device.

Crossley MJ et al, Tetrahedron Lett. 1997,38, 6751-6754 and Burrel AK, Officer DL and Wild KY et al, Che Commun disclose the attachment of known dyes such as porphyrins and bi pyridyl metal complexes to conjugated polymer precursors.

Wallace et al indicates that Roncali J Chem Rev 1992, 92, 711-738 describes methods of forming stereoregular polymers applicable to polythiophenes . Stress is laid on the desirability of preparing the polymers so that they form interpenetrating networks and hence the avoidance of materials that phase segregate is taught.

US-A-5670791 describes a photovoltaic cell in which first and second semi-conductive polymers are arranged between ITO and Al electrode^'s. The two polymers form distinct phases in a phase separated blend.

De Boer et al, Polymer, 2001, 42, 9097-9109 describes cells made from a diblock copolymer of PPV (electron donor) and styrene functionalised Cδo_r the blocks of the polymer molecules forming interpenetrating networks following spin casting of the polymer from a solution onto an ITO (indium tin oxide) electrode.

US-A-6007928 describes an electroluminescent cell comprising ITO and aluminium electrodes separated by a block copolymer having a first block of poly-N-carbazole (hole conducting) and a second block of poly-2-β-naphthyl-5- (4- vinylphenyl) -oxadiazole (electron conductor). How the polymer blocks arrange themselves in the layer of block copolymer is not disclosed. 0' Regan, B et al, Letters to Nature, Nature, vol 353, 24

Oct 1991, 737-739, describes a photovoltaic device in which a dye is used to sensitise a Ti0₂ film to separate the functions of light absorption from charge carrier transport. US-A-6084176 discloses a photovoltaic cell having a layer of dye sensitised nanoparticulate semiconductor (Ti0₂) and a layer of hole conducting polymer.

US-A-5665857 discloses electroluminescent devices having a conductive polymer layer sandwiched between a hole conducting layer and an electron conducting layer, each of unspecified nature. The polymer layer conducts both electrons and holes and has dye molecules incorporated into its structure.

US-A-4360703 proposes a photovoltaic cell having ^λa molecular p-n junction' formed by an organic compound having a monomeric electron donor portion and a monomeric electron acceptor portion linked via a linkage portion. The compound forms a self-ordered mono-molecular film in which the donor and acceptor portions of the molecules self aggregate as upper and lower layers. US-A-5201961 describes photovoltaic cells having between electrodes three organic layers, where a first layer is a monomeric electron acceptor compound, a middle layer is a monomeric dye compound (such as chloroaluminumphthalocyanine) and the last layer is a conductive polymer (polyaniline or poly-3-hexylthiophene) . A similar disclosure is found in US- A-5350459.

W094/15368 discloses a tuneable light emitting diode comprising a three block copolymer having two non-π- conjugated polymer blocks, one being hole conducting and the other being electron conducting together with a π-conjugated block, the length of which mainly determines the frequency of the emitted light. Alternatively, all three blocks may be π conjugated, but there is a large difference in band gaps between the outer and middle blocks resulting in no π conjugation between the blocks. The ability of the polymers to self assemble into microphase separated ordered structures is mentioned.

A large number of conductive polymers for use in photovoltaic devices are described in US-A-5814833. Bi-layer films of electron acceptor and electron donor polymers are described for use in photovoltaic or electroluminescent devices .

US-A-5454880 discloses photovoltaic devices in which a p-n junction is formed between an electron donor conductive polymer and an electron accepting polymer comprising fullerenes mixed into or bound in the electron accepting polymer.

The present invention now provides a photovoltaic cell or electroluminescent cell comprising a first electrode and a second electrode separated by a dye linked block polymer material, the molecules of which comprise in electrical connection with said first electrode an n-type semiconductor polymer block linked via a light absorbing monomeric dye moiety to a p-type semiconductor polymer block in electrical connection with said second electrode, the two polymer blocks being phase separated into distinct layers.

Preferably, the n-type semiconductor polymer block and the p-type semiconductor polymer block are each independently formed from selected polymers formed from terphenylene- vinylene, polyaniline, polythiopene, poly (2-vinylpyridine) , poly (N-vinylcarbazole) , poly-acetylene, poly (p-phenyl- enevinylene) , poly-m-phenylene, poly-p-phenylene, poly-2,6- pyridine, or polypyrrole monomer, said polymers being substituted with electron withdrawing substituents in the case of the n-type polymer block and with electron donating substituents in the case of the p-type polymer block. The backbone polymer of the n- and p-type blocks may be the same or different.

Preferably, the dye moiety is a phenanthroimidazole, trioxatriangulene, azadioxatriangulene, diazaoxatriangulene, triazatriangulene, perylene, porphyrin, or phthalocyanine. The dye moiety may be linked to one or both of the polymer blocks by covalent bonding, by ionic interaction, or by hydrogen bonding: The dye moiety is a monomeric compound rather than a conjugated polymer. It should strongly absorb light in the wavelength range 300-1000 nm.

Optionally, the anode and/or the cathode are covalently bonded to the n-type or p-type polymer blocks respectively.

The n-type polymer blocks and the p-type polymer blocks of the diblock polymer material preferably each self assemble into mono-layers separated by said dye moiety.

The work function of each electrode is preferably matched to the work function of the polymer in contact with that electrode so that carrier transfer between each polymer and its respective electrode is obtained with substantially no barrier energy. In this context, the barrier energy is preferably below 0.5 eV more preferably below 0.2 eV.

Preferably, the first electrode has a relatively low work function as compared to the second electrode and suitably the work function of the first electrode is from 2.5 to 3.8 eV and the work function of the second electrode is from 4.0 to 5.7 eV.

The first electrode may be of calcium, aluminium, scandium, neodynium, yttrium, samarium, europium, magnesium or magnesium-indium, alloy and the second electrode may be of gold, silver, nickel, platinium, tungsten, chromium, or indum-tin-oxide (ITO) .

Said molecules of the dye linked block polymer material may comprise multiple units of n-type semiconductor polymer block - dye moiety - p-type semiconductor polymer block joined head to tail and extending between said electrodes. Preferably, the p-type block, the monomeric dye and the n-type block all form a covalently bonded system.

The invention will be further described and illustrated by the description of illustrative examples and preferred embodiments with reference to the accompanying drawings in which:

Figure 1 shows a schematic drawing of a dye-linked block polymer photovoltaic cell (left) with a more detailed illustration of the molecular structure of the dye-linked block polymer (right) ;

Figure 2 shows two alternative structures for dye-linked block polymers for use in the invention;

Figure 3 shows a scheme for assembling photovoltaic cells according to the invention; and Figure 4 shows a second scheme for assembling photovoltaic cells according to the invention.

In this invention two general types of macromolecules have been employed to harvest light and convert it into electrical energy. The polymers may be disperse or mono- disperse and they may be of small or large molecular weight.

Figure 2 shows at (a) a dye-linked diblock copolymer, where one block is mainly electron conducting and the other block is mainly hole conducting. A schematic representation of the diblock copolymer is shown in which the zig-zag line represents a block of the type of polymer conducting preferentially one type of carriers i.e. holes. This polymer region is linked covalently to a dye molecule represented by the square block which in turn is covalently linked to the other type of polymer (straight solid black line) which conducts with preference the other type of carrier i.e. electrons. Either the dye molecule harvests all the energy with the electron and hole conducting polymer regions being transparent in the wavelength region of interest or one or both of the polymer blocks are also light absorbing, so that all the three regions may absorb light, i.e. the dye, n-type and p-type regions. The absorption coefficient of the dye region or molecule is very high and serves the purpose of absorbing the light and generating charge carriers (holes and electrons) . The absorption coefficient of the polymer blocks may both be high, one may be high and the other low or both may be low. The absorption or transmission of light may be in the same span of wavelengths or in different spans for all three regions, n-block, p-block and dye.

A schematic representation of a second type of dye- linked block polymer material is shown at (b) . The zig-zag line represents one type of polymer conducting preferentially one type of carrier i.e. holes. This polymer region is linked covalently linked to a dye molecule (dark grey square) . The dye molecule is functionalised by being covalently linked to a complex forming molecule (donor, acceptor, receptor or ligand) which may or may not absorb light (illustrated as a rightward facing cup) . The other polymer block (straight solid black line) conducts with preference the other type of carrier i.e. electrons and is linked covalently to the complementary complex forming molecule (donor, acceptor, receptor or ligand) which may or may not absorb light (shown as a light grey extension to the solid black line) . The absorption coefficient of the dye region or molecule is very high and serves the purpose of absorbing the light and generating charge carriers (holes and electrons) . The absorption coefficient of the polymer blocks may both be high, one may be high and the other low or both may be low. The absorption or transmission of light may be in the same span of wavelengths or in different spans for all three regions, n-block, p-block and dye.

In this complexing/aggregating dye block copolymer where one end of each of the conducting polymer regions is functionalized with complementary parts of a receptor system, the absorption of light is either in the dye-complex region alone (by charge transfer or simple bandgap) , or in the polymer regions and the complex region. The complex can be of at least three types: donor-acceptor, metal-ligand, receptor-analyte type. The bonding between the two parts of the complex forming moiety may be by hydrogen bonding or other Van der Waals bonding or by ionic interaction.

In all the cases above one or both ends of the molecules maybe end functionalised for the purpose of assembly of the cell and this process of end functionalisation may take place before, during or after the synthesis of the polymer systems or subsystems themselves.

Alternative synthesis and construction schemes for building a photovoltaic or other cell according to the invention are shown in Figures 3 and 4.

The synthetic procedures leading to these polymers may be condensation type polymerisations, block build up polymerisations and controlled termination polymerisations. The assembly process may be one of the overall types described below. The illustrated processes always start at one electrode. The types of process described are simple self assembly directly onto to the surface of one electrode, multiple steps of assembly onto the electrode, assembly in solution followed by assembly onto the surface, surface activation followed by assembly or polymerisation or assembly by chemical linkage to the surface. The application of the polymers may be performed by, spin-coating, dip-coating, casting, in-situ pyrolysis, in-situ polymerisation, or complexation. In Figure 3, self-assembly directly onto the electrode surface is obtained by treating the cleaned electrode surface with a solution of the polymer system.

The illustration shows how the polymer systems have been end functionalised so that the molecules adsorb onto the surface. Both examples of the polymer types described with reference to Figure 2 are shown. The surface electrode is shown as a thick black horizontal line. In the case of complex assembly of Figure 2 (b) several isolated processes are possible, i.e. first adsorption of one block followed by a separated process with complex formation or in-situ adsorption and complex formation. The horse-shoe shaped objects illustrate a suitable end-functionalisation with a large specificity for the surface.

Preparation of the electrode surface may be carried out in which a polymerisation initiator or complexer is first chemically bound to the surface of interest as shown in step (a) . In some cases this step may be omitted and the affinity of the polymer may be for the electrode surface as such.

The illustration shows in step (a) how a suitable linker is connected to the cleaned electrode surface. The reaction is performed from solution or gas phase and modifies the surface chemically so that adsorption of polymer systems can be made by covalent-, ionic- or complex bond formation.

The polymer systems are attached to the surface in step (b) following on from surface preparation. The bond between the surface groups and the polymer may be of the covalent-, ionic- or complex formation type.

In the scheme shown in Figure 4, the chemically prepared surface is used as an initiator for a sequential polymerisa- tion process which can be in solution or by heating a pre- polymer which has been coated on to the surface. Once the polymerisation of the first polymer region has been completed the process can be continued by attaching a dye molecule that then serves as an initiator for polymerisation of a new type of polymer. Finally the polymer can be terminated with a complex molecule so that assembly can be achieved with another polymer system.

The first electrode on which the polymer assembly takes place as described above may be transparent (metal oxide, polymer type, metallic) or it may be non-transparent

(metallic) . The second electrode is applied by an evaporation, sputtering, coating or ablation technique.

The invention is further illustrated by the following examples .

Example 1

The iodo-porphyrin-aldehyde compound 1, prepared according to Rao et al. J. Org. Chem. 2000, 65, 7327-7244) .

Compound 1, Ig was reduced with sodium borohydride in a mixture of tetrahydrofuran and ethanol. The solvents were removed in vacuum and the remaining solid was partitioned between water and chloroform. The organic phase was treated with cone. HBr and finally evaporated to give the iodo- bromomethyl-porphyrin compound 2 in quantitative yield.

Compound 2 was used as a macro-initiator in an atom transfer radical polymerisation (ATRP) polymerisation with N- vinyl-carbazole. In a typical procedure the macroinitiator (2) was mixed with equimolar amounts of copper (I) chloride, 2, 2 ' -bipyridine N-vinyl-carbazole (10 molar equivalents) in toluene. The reaction mixture was degassed and heated to reflux. After the polymerisation reaction the mixture was cooled and diluted with tetrahydrofuran and filtered through a layer of alumina to remove the copper salts. The solvents were removed in vacuum and the product was repeatedly precipitated from a chloroform solution with a large excess of methanol. The dried product: Iodo-porphyrin- polyvinylcarbazole was obtained in 73% yield. (For a related reaction using a chlorinated C60 as a macroinitiator to prepare C60-polyvinylcarbazole see H. Jing et al. Polymer Bulletin 2002, 48, 135-141) .

Iodo-porphyrin-polyvinylcarbazole 3 (5.3 g) was mixed with 4-carboxy-phenylboronic acid (1 g, excess) in a mixture of toluene (100 mL) and 2 M sodium carbonate. The reaction mixture was degassed with argon and the catalyst PdCl₂(PPh₃)₂ (100 mg) was added. The reaction was heated to reflux overnight to complete the coupling. The cooled reaction mixture was separated and the organic phase was evaporated to dryness. The product was precipitated repeatedly from a chloroform solution by addition of a large excess of methanol.

4-Carboxyphenyl-porphyrin-polyvinylcarbazole 4 (0.4 g) and 4' ' -cyanomethyl-2' , 5' -dioctyl-4-formyl-terphenyl (10 equivalents) was dissolved in tetrahydrofuran (100 mL) . The reaction mixture was degassed with argon and potassium-tert- butoxide (10 mg) was added and stirred for 10 minutes before a concentrated solution of tetrabutyl ammonium hydroxide (0.1 mL) was added. Stirring was continued for 1 hr. to complete the reaction. Dilute hydrochloric acid 200 L was added and the precipitated polymer was recovered by filtration. Small amounts (ca. 1 g) of the pure polyterphenylvinylene- porphyrin-polyvinylcarbazole were purified by gel permeation chromatography (GPC) .

Application in a solar cell

The photovoltaic molecule was dissolved in chloroform at a concentration of 7 mg mL^-1. Careful addition of this onto a water surface using standard LB-techniques and compressing to a surface pressure of 20 N πf¹ allowed for a good film to be obtained that could be transferred onto a ITO substrate or ITO with a thin semitransparent chromium linked gold film. Evaporation of Ca, Al, Mg, Y, Nd, S , Eu, Sc, Ag, V, Nb, Cr, Fe or Cu on top (using an optional LiF tunnel barrier for the very low work function metals, deposited by sputtering or evaporation) . Subsequent measurement of the photovoltaic response in vacuum gave efficiencies in the range 1-100% at current densities of 1-10⁹ pA cm².

Example 2

Compound A

Compound A and compound B (or compound B-polymeric) forms a charge transfer complex upon mixing.

The assembly A was prepared as described below

3- (1-Methyl-phenanthro [9, 10-d] imidazol-2-yl) -phenyl- boronic according to F. C. Krebs, M. Jørgensen J. Org. Chem. (2001), 66, 6169-6173.

2, 6-Dibromo-4-nitro-pyridine-l-oxide according to U. Neumann, F. Voegtle Chem Ber. (1989), 122, 589-592.

4, 4' -Disulfanediyl-bis-butyrylchloride according to Luettringhaus et al. Angew. Chem. (1964), 76, 51. 4-Nitro-2, 6-bis (3- (1-methyl-phenanthro [9, 10-d] imidazol-2- yl) phenyl) pyridine-N-oxide

C₅H₂Br₂ 2θ3 C22H18BCIN2O2

Exact Mass: 295,84 Exact Mass: 388,11

Mol. Wt.: 297,89 Mol. Wt.: 388,65

C. 20,16; H. 0,68; Br. 53,65; N. 9,40; O. C. 67,99; H. 4,67; B. 2,78; Cl. 9,12; N. 7,21; O. 8,23

16,11

0.6,38

Compound 1 (9g), Compound 2 (24g) , Na₂C0₃ (36g) , water (300mL), toluene (450mL) was mixed in a 1L conical flask and degassed with argon. Catalyst (Ph3P)2PdC12 (0.75g) was added and the mixture heated to reflux. Yellow slurry initially. The next morning a thick creamy orange emulsion had formed with an orange colour. The mixture was cooled and filtered and the product washed with water (lOOmL) , ethanol (lOOmL) , ether (lOOmL) , petrol (lOOmL) and finally dried. Yield: 23.45g as a yellow powder. 4-Nitro-2 , 6-bis ( 3- ( 1-methyl-phenanthro [ 9, 10-d] imidazol-2- yl) phenyl ) -N-acetyloxypyridinium bromid

C₄₉H_{32 6}O₃ C₅₁H₃₅BrN₆0₄ ^"

Exact Mass: 752,25 EΞxact Mass: 874,19

Mol. Wt: 752,82 Mol. Wt.: 875,77

C.78,18; H.4,28; N. 11,16; O.6,38 C.69,94; H.4,03; Br. 9,12; N.9,60; 0.7,3

Compound 3 (7g) was suspended in acetone (400mL) and acetyl bromide (15mL) was added. The mixture was refluxed for 12h. During the reaction the suspension changes colour from bright yellow to light yellow. The product was filtered, washed with acetone, ether and dried. Yield quantitative.

4- (N-Benzylamino) benzenethiol

C₆H₇NS

Exact Mass: 125,03 C₁₃H₁₄CINS

Mol. Wt.: 125,19 Exact Mass: 251 ,05

C. 57,56; H. 5,64; N. 11 ,19; S. 25,61 Mol. Wt.: 251 ,78

C. 62,02; H. 5,60; Cl. 14,08; N. 5,56; S. 12,7

Commercially available 4-Mercaptoaniline (25g, 90%) was dissolved in EtOH (99%) (400mL) under argon and stirred while benzaldehyde (21.6g) was added. Acetic acid (lmL) was added. After 1 min a light yellow precipitate formed. This was filtered and dissolved in THF (400mL) . Acetic acid (50mL) was added and NaBH (lOg) was added carefully with cooling. After 30 min. water was added carefully and the mixture evaporated to give an oil which stirred with HCL(aq) 35% (lOOmL) . A yellow precipitate formed that was filtered and washed with water, ethanol, petroleum and finally dried. The product is soluble in DMSO-dβ but the NMR experiment revealed that the product reacts with atmospheric oxygen (or DMSO) to give the disulphide under the conditions of the NMR experiment. Yield 45g.

4- (4-Benzylaminophenylthio) -2, 6-bis (3- (1-methyl- phenanthro [9, 10-d] imidazol-2-yl) phenyl) pyridine

C_s1H3₅BrN₆0₄ ^" C₁₃H₁₄CINS

Exact Mass: 874, 9 Exact Mass: 251 ,05

Mol. Wt: 875,77 Mol. Wt: 251,78

C. 69,94; H. 4,03; Br. 9,12; N. 9,60; 0.7,31 C. 62,02; H. 5,60; Cl. 14,08; N. 5,56; S. 12,74

Compound 4 (9.6g), compound 5 (3.5g), and K₂C0₃ (lOg) was mixed in NMP (lOOmL) . The mixture was refluxed for lh under Ar. It was poured into ice/water and filtered (timeconsuming) Yield 5.6g. The product was chromatographed again using CHCl₃:EtOAc/2 : 1. The product runs in the front whereas the impurity is near stationary. This gave 1.9g of a pale yellow solid that is very soluble in chloroform.

10

C₇₆H₆oCI₂N₆0₄

C₇₄Hg_{2 6}θ₂ Exact Mass: 1190,41

Exact Mass: 1066,49 Mol. Wt: 1192,23

Mol. Wt: 1067,32 C. 76,56; H. 5,07; Cl. 5,95; N. 7,05; O. 5,37

C. 83,27; H. 5,86; N. 7,87; O. 3,00 N,N' -Dibenzyl-naphthalene-1, 5-diamine (7). Naphthalene- 1,5-diamine (100 g) and benzaldehyde (74 g) were mixed neat with a little acetic acid to prepare the imide. THF (1L) was added together with acetic acid (180 mL) . The mixture was cooled on an ice-bath and stirred vigorously while NaBH₄ (56g) was added in small portions (Caution! the reaction is exothermic and hydrogen is evolved) . After 1 hr water was added (2L) slowly to avoid excessive foaming. Separation of the raw product by filtration followed by recrystalization from toluene (5 L) gave the product 3 as a white powder. Yield: -375g.

N,N' -Dibenzyl-1, 5-Bis-chlorocarbonylamino-naphthalene (8). 1, 5-Dibenzylaminonaphthalene (7) (34g) was placed in a flask containing chloroform / toluene (1:1) (200mL) and triethyl amine (40mL) . Phosgene (150mL, 20% in toluene) was added. The mixture becomes warm and the colour changes to a deeper yellow. A precipitate of the triethyl ammonium hydrochloride forms. After lh the mixture was washed with water and dried (MgS0₄) . The phase was evaporated to dryness and the product recrystallised from toluene (400mL) . It was left in the freezer overnight. After filtering and washing with light petroleum the product was dried in the vacuum oven at 80 °C for 4h. Yield: 46g.

^NapK(3) (compound 9). Caesium carbonate (50 g) was dried in an oven at 150 °C for 4 hrs to remove water. In a dried flask caesium carbonate and collidine (500 mL, freshly distilled) was mixed together with compound 7 (75g) and compound 8 (50 g) . The reaction mixture was heated to reflux under argon for 18h and then left to cool overnight. Water (0.5 L) was added with stirring and the slurry was filtered. The product was triturated with more water, filtered and washed with petroleum ether. Finally the product was recrystallised from toluene (2L) . Yield 57.5 g. ^NapK(9) (compound 11) .

11

Compound 9 (6g) was placed in a dried flask containing Cs₂C0₃ (lOg) and commercial collidine (lOOmL) . Phosgene (6.0 mL, 20% in toluene) was added and the mixture stirred at 100 °C for 15 min. In this manner compound 10 is formed in situ. Compound 9 (12g) was added and the first sample for SEC drawn. The mixture was the heated to reflux. After 24h the reaction has stopped and the major component was starting material compound 11. The mixture was left to cool. Acetone (lOOmL) was added and the mixture stirred and then poured into water (1L) and the crystalline compound filtered, washed with water (2 x 250mL) , ether (3 x 200mL) and light petroleum (lOOmL) . The product was the boiled in toluene (1L) for 30 min. and filtered. Yield 14 g.

Compound A

Compound 6 (0.5 g) was dissolved in CHC1₃ (20mL) containing Cs₂C0₃ (0.5g). Phosgene (1.5mL, 20% in toluene, excess) was added and the mixture stirred with initial heating to reflux. A precipitate forms shortly after addition of the phosgene. After Ih the mixture was evaporated to dryness and dry collidine (lOmL) was added along with compound 11 (2g) . The reaction was followed by GPC and was stopped after 24h. The mixture was cooled and water and ether was added with stirring for lh followed by filtering, washing with ether and drying. Yield 2.3g of a tan solid. The product was purified by preparative GPC using THF as eluent. Yield 2. Ig.

Compound A terminated with 4-mercaptobuyricacid

Compound A

Compound A (418mg) was dissolved in dry DMF (25mL) containing dry pyridine (5mL) and 4, 4' -Disulfanediyl-bis- butyrylchloride (28mg) was added under argon. The mixture was heated at 100 °C for 12h and evaporated to dryness. The product was purified by preparative GPC. Yield 200 mg.

The assembly B was prepared as described below

Materials:

4-iodo-2, 5, 7-trinitroflouren-9-one was prepared according to M. S. Newman, J. Blum Isr. J. Chem . (1964), 2, 301. 4' ' -Cyanomethyl-2' ,5' -dioctyl-4-formylterphenyl was prepared according to F. C. Krebs, M. Jørgensen Macromolecules (2002), 35, 7200-7206.

4-(4-Formylphenyl) - 2, 5, 7-trinitroflouren-9-one (13)

C₁₃H₄IN₃0₇

Exact Mass: 440,91 CzoHgNaOβ

Mol. Wt: 441,09 Exact Mass: 419,04

C. 35,40; H. 0,91; I. 28,77; N. 9,53; 0. 25,39 Mol. Wt: 419,30

C. 57,29; H. 2,16; N. 10,02; O. 30,53

Compound 12 (4.4g), 4-formylphenylboronic acid (2g) , Na2C03 (lOg) , water (lOOmL) and toluene (250mL) were mixed and degassed with argon. Catalyst (PPh₃)₂PdCl₂ (0.5g) was added and the mixture refluxed under argon for 12h. The mixture was evaporated to dryness. The solids were extracted in a Soxleth apparatus with chloroform for 24h and the chloroform phase evaporated. The crude product was subsequently purified by preparative HPLC. Yield (3g) .

4 ' ' -Cyanomethyl-2 ' , 5' -dioctyl-4- ( 1 , 3-dioxolan-2-yl) terphenyl (14 )

C₃₇H₄₇NO C₃₉H₅₁N0₂

Exact Mass: 521,37 EΞxact Mass: 565,39

Mol. Wt: 521 ,78 Mol. Wt: 565,83

C. 85,17; H. 9,08; N. 2,68; O. 3,07 C. 82,78; H. 9,08; N.2,48; O. 5,66

4' ' -Cyanomethyl-2' , 5' -dioctyl-4-formylterphenyl (lOg) were mixed with ethylene glycol (5g) in toluene (500mL) containing para-toluenesulphonicacid (0.5g) and refluxed for 12h with a water separator. The toluene phase was separated and washed with NaHC0₃(aq) (2M, 500mL) dried with MgS0₄ and evaporated to give an oil. Yield quantitative.

Compound B with n = 0-2

13,8

Compound 13 (4.2g) and compound 14 (5.7g) were mixed in THF (200mL) . tBuOK (lg) dissolved in THF (50mL) was added and the mixture stirred for 5 min. when (nBu) ₄NOH (aq) (40%, lmL) was added. The mixture was stirred for Ih and concentrated to a volume of 50mL when trifluoroacetic acid (200mL) was added followed by slow addition of water (50mL) with heating to reflux for 30 min. The mixture was cooled and concentrated. Water (500mL) was added and the mixture was extracted with chloroform (10 x 250mL) . The combined organic phases were washed with NaOH (aq) (1M, 500mL) , dried over (MgS0 ) and evaporated to dryness. The product was purified by preparative HPLC. Yield 7g.

For n = 1 and n = 2 this procedure was repeated and the products purified by preparative GPC.

Compound B-polymeric

tBuOK / (nBu)₄OH(aq)

Compound 13 and 4' ' -Cyanomethyl-2' , 5' -dioctyl-4- formylterphenyl were mixed in the desired ratio in THF such that the concentration was lOg L^~4 tBuOK (0.1 equivalent) was added and the mixture stirred for 5 min. when (nBu)4NOH(aq) (40%,lmL per lOOmL THF) was added and the mixture stirred for 1 hour. The mixture was poured into MeOH (10 volumes) and the solid product isolated by filtration. The products could be purified by preparative GPC. Molecular weights up to 200.000 g mol^-1 could be obtained (compared to a polystyrene standard) .

Application in a solar cell

The disulfide of compound A was dissolved in chloroform at a concentration of 0.1 mg mL^-1. An ITO substrate with a thin semitransparent chromium linked gold film, was immersed into the solution and the system left undisturbed for 24h. The substrates were carefully removed and blown dry with argon. The substrates were subsequently submerged carefully in fresh chloroform containing compound B (n = 0-2) or compound B-polymeric at a concentration of 0.1 mg mL-¹. The system was left undisturbed for 24h where the charge transfer complex formed and organised compound B. The substrates were removed carefully and blown dry with argon. Evaporation of Ca, Al, Mg, Y, Nd, Sm, Eu, Sc, Ag, V, Nb, Cr, Fe or Cu on top (using an optional LiF tunnel barrier for the very low work function metals, deposited by sputtering or evaporation) . Subsequent measurement of the photovoltaic response in vacuum gave efficiencies in the range 1-100% at current densities of

1-10⁹ pA cm².

Claims

1. A photovoltaic cell or electroluminescent cell comprising a first electrode and a second electrode separated by a dye linked block polymer material, the molecules of which comprise in electrical connection with said first electrode an n-type semiconductor polymer block linked via a light absorbing monomeric dye moiety to a p-type semiconductor polymer block in electrical connection with said second electrode, the two polymer blocks being phase separated into distinct layers .

2. A cell as claimed in claim 1, which is a photovoltaic cell.

3. A cell as claimed in claim 1 or claim 2, wherein said n-type semiconductor polymer block and said p-type semiconductor polymer block are each independently formed from selected polymers formed from terphenylene- vinylene, polyaniline, polythiopene, poly (2-vinyl- pyridine) , poly (N-vinylcarbazole) , poly-acetylene, poly (p-phenylenevinylene) , poly-m-phenylene, poly-p- phenylene, poly-2, 6-pyridine, or polypyrrole monomer, said polymers being substituted with electron withdrawing substituents in the case of the n-type polymer block and with electron donating substituents in the case of the p-type polymer block.

4. A cell as claimed in any preceding claim, wherein the dye moiety is a phenanthroimidazole, trioxatriangulene, azadioxatriangulene, diazaoxatriangulene, triazatri- angulene, perylene, porphyrin, or phthalocyanine.

5. A cell as claimed in any preceding claim, wherein the dye moiety is linked to one or both of the polymer blocks by covalent bonding.

6. A cell as claimed in any preceding claim, wherein the dye moiety is linked to one or both of the polymer blocks by ionic interaction.

7. A cell as claimed in any preceding claim, wherein the anode and/or the cathode are covalently bonded to the n-type or p-type polymer blocks respectively.

8. A cell as claimed in any preceding claim, wherein the n-type polymer blocks and the p-type polymer blocks of the diblock polymer material each self assemble into mono-layers separated by said dye moiety.

9. A cell as claimed in any preceding claim, wherein the work function of each electrode is matched to the work function of the polymer in contact with that electrode so that carrier transfer between each polymer and its respective electrode is obtained with substantially no barrier energy.

10. A cell as claimed in any preceding claim, wherein the first electrode has a relatively low work function as compared to the second electrode.

11. A cell as claimed in Claim 10, wherein the work function of the first electrode is from 2.5 to 3.8 and the work function of the second electrode is from 4.0 to 5.7.

12. A cell as claimed in Claim 10, wherein the first electrode is of calcium, aluminium, scandium, neodynium, yttrium, samarium, europium, magnesium or magnesium-indium and the second electrode is of gold, silver, nickel, platinium, tungsten, chromium, or indum-tin-oxide (ITO) .

13. A cell as claimed in any preceding claim, wherein said molecules of the dye linked block polymer material comprise multiple units of n-type semiconductor polymer block - dye moiety - p-type semiconductor polymer block joined head to tail and extending between said electrodes .