WO2001080319A2

WO2001080319A2 - Improved method of fabrication of color changing medium layers in organic light emitting devices resulting in improved light extraction

Info

Publication number: WO2001080319A2
Application number: PCT/US2001/012143
Authority: WO
Inventors: Amalkumar P. Ghosh; Rong Zhang; Ellen F. Macdonald; Webster E. Howard
Original assignee: Emagin Corporation
Priority date: 2000-04-14
Filing date: 2001-04-16
Publication date: 2001-10-25
Also published as: AU2001253472A1; WO2001080319A3

Abstract

A method is described for fabricating an organic light emitting device, which method comprises steps of providing a planar substrate, constructing a plurality of first electrodes on the substrate surface, constructing a set of walls in between the plurality of first electrodes, constructing a layer of organic light emitting material overlying the first electrodes, constructing a second electrode layer overlying the light emitting layer, and removing a portion of the walls that extends away from the planar substrate above the second electrode. Also described are organic light emitting devices fabricated according to the method.

Description

TITLE OF THE INVENTION

IMPROVED METHOD OF FABRICATION AND EXTRACTION OF LIGHT FROM COLOR CHANGING

MEDIUM LAYERS IN ORGANIC LIGHT EMITTING DEVICES

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to United States Provisional Patent Application No. 60/197,414, filed April 14, 2000.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to an Organic Light Emitting Device ("OLED") video display structure for a color video display. More specifically, the present invention relates to color OLEDs which include color changing media. Organic light emitting devices have been known for approximately two decades. OLEDs work on certain general principles. An OLED is typically a laminate formed on a substrate such as soda-lime glass or silicon. A light-emitting layer of a luminescent organic solid, as well as adjacent semiconductor layers, are sandwiched between a cathode and an anode. The semiconductor layers may be hole- injecting or electron-injecting layers. The light-emitting layer may be selected from any of a multitude of fluorescent organic solids and may be a single material or a host material containing another fluorescent molecule that is sometimes referred to as a dopant. The light-emitting layer may consist of multiple sublayers or a single blended layer. When a potential difference is applied across the device, negatively charged electrons move from the cathode to the electron-injecting layer and finally into the layer(s) of organic material. At the same time positive charges, typically referred to as holes, move from the anode to the hole-injecting layer and finally into the same organic light-emitting layer(s). When the positive and negative charges meet in the layer(s) of organic material, they combine, and produce photons.

In a typical OLED, either the anode or the cathode is transparent in order to allow the emitted light to pass through to the viewer. The cathode is typically constructed of a low work function material. The holes are typically injected from the anode, a high work function material, into the organic material via a hole transport layer.

Typically, OLEDs operate with a DC bias of 2 to 30 volts. The OLED brightness may be controlled by adjusting the voltage or current supplied to the anode and cathode. The relative amount of light generated is commonly referred to as the "gray level." OLEDs typically work best when operated in a current mode. The light output is more stable for constant current drive than for a constant voltage drive. This is in contrast to many other display technologies, which are normally operated in a voltage mode. As a result, an active matrix display using OLED technology, requires a specific pixel architecture to provide for a current mode of operation. In a typical matrix-addressed OLED device, numerous OLEDs are formed on a single substrate and arranged in groups in a regular grid pattern. Several OLED groups forming a column of the grid may share a common cathode, or cathode line. Several OLED groups forming a row of the grid may share a common anode, or anode line. The individual OLEDs in a given group emit light when their cathode line and anode line are activated at the same time. A group of OLEDs within the matrix may form one pixel in a display, with each OLED usually serving as one subpixel or pixel cell.

The wavelength — and consequently the color — of the photons depends on the material properties of the organic material in which the photons are generated. The color of light emitted from the OLED can be controlled by the selection of the organic material, or by the selection of dopants, or by other techniques known in the art. Different colored light may be generated by mixing the emitted light from different OLEDs. For example, white light is produced by mixing blue, red, and green light simultaneously. Most color OLED displays are fabricated using either color filters or color changing media (CCM). CCM are fluorescent materials that absorb light at shorter wavelengths (e.g. blue light) and emit light at different and longer wavelengths (e.g. green or red light). Such CCM materials are disclosed for OLEDs, for example, in C. Hosokawa, et. al., J. SID 5/4, 331 (1997); U.S. Patent 5,126,214; C. Tang, D. J. Williams, J. C. Chang, U.S. Patent 5,294,870 (1994); A. Niko, et. al, J. Appl. Phys. 82, 4177 (1997)]; and U.S. Patent 6,137,459.

Prior-art methods of laying down CCM materials using shadow masks have involved fabrication of permanent walls that act as shadow masks for organic deposition, but these walls (especially for the blue light emitting OLEDs) act as collimators and limit the viewing angle of the display. Moreover, red and green emitting material necessarily deposited on the side of the walls absorbs either the blue or the green light and emits unwanted red or green light. Both the collimation and unwanted emission reduce the efficiency and color response of the device. Accordingly, there is a need for an OLED display in which the viewing angle of the display is not limited. Furthermore, there is a need for an OLED display in which desired light is not absorbed and unwanted light is not emitted.

BRIEF SUMMARY OF THE INVENTION

In response to this challenge, an innovative, economical method of fabricating an organic light emitting device has been developed.

In a first embodiment, the method comprises the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a plurality of walls between the first electrodes, wherein the walls overlie the planar substrate and extend substantially perpendicular to the planar substrate; constructing a layer of light emitting organic material overlying the first electrode and between the walls; constructing a second electrode layer overlying the layer of light emitting material and between the walls; removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode. In a second embodiment, a method of fabricating an organic light emitting device is disclosed comprising the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a plurality of walls between the first electrodes, wherein the walls overlie the planar substrate and extend substantially perpendicular to the planar substrate; constructing a layer of blue light emitting organic material overlying the first electrodes and between the walls; constructing a second electrode layer overlying the layer of blue light emitting material and between the walls; depositing a first layer of color changing material overlying the second electrode and above a fraction of the plurality of first electrodes; depositing a second layer of color changing material overlying the second electrode layer and above a different fraction of the plurality of first electrodes from the fraction above which lies the first layer of color changing material; depositing a barrier layer overlying the first layer of color changing material and the second layer of color changing material and any of the second electrode layers not underlying the first and second layers of color changing material; removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode; wherein the fraction of the plurality of first electrodes above which overlies the first layer of color changing material is selected by depositing the first color changing material at a first angle relative to the plane of the substrate such that the plurality of walls allows the first color changing material to deposit only on the selected fraction of first electrodes, and the fraction of the plurality of first electrodes above which overlies the second layer of color changing material is selected by depositing the second color changing material at a second angle relative to the plane of the substrate such that the plurality of walls allows the second color changing material to deposit only on the selected fraction of first electrodes.

In a third embodiment, a method of fabricating an organic light emitting device is disclosed comprising the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a layer of blue light emitting organic material overlying the plurality of first electrodes; constructing a second electrode layer overlying the layer of blue light emitting material; constructing an encapsulation structure overlying the second electrode layer; constructing a plurality of walls overlying the encapsulation structure, wherein the walls extend substantially perpendicular to the planar substrate and only lie above the portions of the substrate that are in between the plurality of first electrodes; depositing a first layer of color changing material overlying the encapsulation structure and above a fraction of the plurality of first electrodes; depositing a second layer of color changing material overlying the encapsulation structure and above a different fraction of the plurality of first electrodes from the fraction above which lies the first layer of color changing material; depositing a barrier layer overlying the first layer of color changing material and the second layer of color changing material and any of the encapsulation structure not underlying the first and second layers of color changing material; removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode; wherein the fraction of the plurality of first electrodes above which overlies the first layer of color changing material is selected by depositing the first color changing material at a first angle relative to the plane of the substrate such that the plurality of walls allows the first color changing material to deposit only on the selected fraction of first electrodes, and the fraction of the plurality of first electrodes above which overlies the second layer of color changing material is selected by depositing the second color changing material at a second angle relative to the plane of the substrate such that the plurality of walls allows the second color changing material to deposit only on the selected fraction of first electrodes. Any of the first, second and third embodiments above may encompass any or all of the following variations: the step of constructing a plurality of walls between the first electrodes may comprise steps of spin coating a layer of organic material onto the planar substrate and plurality of electrodes, and selectively removing portions of the layer of the organic material to leave behind the plurality of walls; the organic material may comprise a photoresist (with Novolak-type photoresists being preferred) the step of selectively removing portions of the organic material may comprise steps of patterning the layer of organic material using light or an electron beam, and developing the photoresist to leave behind the plurality of walls; one of the first color changing material and the second color changing material may emit green light while the other of the first color changing material and the second color changing material emits red light; the organic material may comprise a black filter material; the step of selectively removing portions of the organic material may comprise steps of applying a photoresist layer on top of the layer of organic material, patterning the photoresist layer using light or an electron beam, developing the photoresist, and etching the resulting structure to leave behind the plurality of walls; and the barrier layer may comprise light scattering medium. Also claimed for all of the above embodiments and variations are organic light emitting devices fabricated according to the claimed methods. Particularly preferred devices are microdi splay devices comprising green and red color changing material layers.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention, and together with the detailed description serve to explain the principles of the present invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Fig. 1 is a cross-section view of a pixel from an organic light display device during the manufacturing process.

Fig. 2 is a cross-section view of a pixel from an organic light display device during the manufacturing process. Fig. 3 is a cross-section view of a pixel from an organic light emitting display device during the manufacturing process.

Fig. 4 is a cross-section view of a pixel from an organic light emitting display device during the manufacturing process.

Fig. 5 is a cross-section view of a pixel from an organic light emitting display according to the present invention.

Fig. 6 is a cross-section view of a pixel of another embodiment of an organic light emitting display device according to the present invention.

Fig. 7 is a cross-section view of a pixel from an organic light emitting display device during the manufacturing process showing parameters needed to determine a deposition angle.

Fig. 8 is a cross-section view of a pixel from an organic light display device during the manufacturing process. Fig. 9 is a cross-section view of a pixel from an organic light display device during the manufacturing process.

Fig. 10 is a cross-section view of a pixel from an organic light display device during the manufacturing process. Fig. 11 is a cross-section view of two pixels of another embodiment of an organic light emitting display device according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a full-color OLED display device comprising green and red color changing means (CCM) and to a method of manufacturing that display. The method of manufacturing the display employs a shadow masking technique for laying down the CCM layers, where the shadow masking is accomplished using materials that are capable of being eliminated from the device using a reactive ion etching (RIE) process. In the devices of the present invention, a barrier layer is laid down on top of the CCM layers prior to the RIE step so that the CCM materials remain unaffected by the RIE.

In one embodiment, the OLED display device according to the present invention is constructed in the following manner. Referring to Figure 1 , partially constructed OLED device 100 has a planar substrate 110 that underlies what in the finished device will be the three subpixels 120 (green), 130 (red), and 140 (blue) shown in Figure 1. In each subpixel, a bottom electrode 150 overlies the substrate 110. Each electrode 150 is in contact with a row conductor 160 which traverses the substrate layer 110. The conductors 160 are part of a matrix of conductors overlying the substrate 110. The matrix of conductors may be energized as necessary to activate specific subpixels. Insulating material 170 surrounds conductor 160. Walls 180 are constructed between the green and blue and blue and red subpixels. Walls 180 are substantially perpendicular to substrate 100. Preferably, walls 180 are fabricated using an organic material such as a Novolak type positive or negative photoresist. Other organic materials preferred for use in forming the walls include but are not limited to BCB, and parylene; the walls 180 may be formed of any organic material that has very low moisture retention properties, is rigid enough to form wall structures, can adhere to a substrate, and is capable of being eliminated using RIE. An RIE process may also be used to shape the walls 180 into the desired profile. Figure 2 shows partially constructed OLED device 200, which includes the partial device of Figure 1 to which one or more layers of organic light emitting material 201 have been deposited overlying the bottom electrode 150. In this embodiment, The organic light emitting material 201 is an emitter of blue light. A top electrode 202 is constructed overlying the layer(s) of organic light emitting material. When it is desired to emit light from the device, a potential difference is established between the top and bottom electrodes causing light to be emitted from the organic material 201.

Preferably, layer 202 comprises an optional first charge injection layer adjacent to bottom electrode 150 followed by a first charge transport layer adjacent to the charge injection layer, followed by an emitter layer adjacent to the first charge transport layer, followed by a second charge transport layer adjacent to the emitter layer, followed by an optional second charge injection layer between the second charge transport layer and the top electrode 202. Where the bottom electrode is an anode, the optional first charge injection and charge transport layers are hole injection and hole transport layers and the second charge transport and charge injection layers are electron transport and electron injections layers, and the top electrode is a cathode. Where the bottom electrode is a cathode, the optional first charge injection and charge transport layers are electron injection and electron transport layers and the second charge transport and charge injection layers are hole transport and hole injections layers, and the top electrode is an anode.

More preferably, bottom electrode 150 comprises an anode and organic layer 202 comprises a hole injection layer adjacent to the anode, a hole transport layer adjacent to the hole injection layer, an emitter layer adjacent to the hole transport layer, and an electron transport layer between the emitter layer and a top cathode 202. Most preferably, the bottom anode is a chromium molybdenum alloy, the hole injection layer comprises copper phthallocyanine (CuPC)or an aromatic amine such as 3 -(N,N-di(8 ' -amino-N' -naphth- 1 -yl-N' -phenylbiphen-3 ' -yl))biphenylamine (DP A- DNPB), the hole transport layer comprises an aromatic amine such as 3-(N,N-di(8'- carbazolylbiphen-3'-yl))biphenylamine (BPA-BCA), the emitter layer comprises spiro-PVBi or tris(hydroxyquinoline) aluminum (ALQ) doped with a distyrylarylene, the electron transport layer comprises ALQ, and the top cathode comprises either a 10: 1 Mg:Ag alloy or a thin (e.g. 7.5 A) layer of LiF followed by a thicker (e.g. 500 A) layer of Al; where the top cathode is 10:1 Mg:Ag alloy, the top cathode preferably further comprises a layer of ITO above the Mg:Ag layer.

In Figure 3, a layer of green CCM 303 has been added to the partially constructed OLED device of Figure 2 to yield partially constructed OLED device 300. Due to the angle of deposition, shown inexactly by the arrows in Figure 3, a layer of green CCM 304 may also adhere to the side of the walls 180. Figure 4 takes the partially constructed OLED device of Figure 300 on which has been deposited a layer of red CCM 405 to generate partially constructed OLED device 400 (the arrows, again inexactly indicate an angle of deposition). As with to the green CCM, the red CCM may also adhere to the side of the walls forming separate layers of red CCM 406.

Fig. 5 discloses an embodiment of the present invention in which, following the deposition of the blue emitter material 201, the top electrode 202, the green CCM 203 and red CCM 405 materials, a passivation or barrier layer 507 has been deposited over the entire structure to generate OLED device 500. The passivation layer 507 may comprise Si0 , SiO, MgO, or Al O and is deposited

Where wall 180 comprises an organic material such as photoresist that may be eliminated using a reactive ion etching (RIE) process, the wall structure 180 in Figure 5 may be eliminated to generate OLED device 600 in Figure 6. Such RIE processes including but are not limited to oxygen plasma etching and carbon tertrafluoride plasma etching; oxygen is preferred for all materials except those containing silicon, for which carbontetrafluoride is preferred. The deposition of barrier 507 in Figure 5 creates a cap 508 on top of walls 180. An isotropic RIE process with suitable gas and pressure/wattage parameters may be used to undercut the wall 180 and make the entire structure collapse, creating device structure 600 illustrated in Figure 6 That has green (620), red (630), and blue (640) pixels. The barrier layer 507 (of e.g. SiO₂ or SiO or MgO or Al₂O₃) over the CCM and the blue material act as an etch stop for the RIE process, thereby protecting the CCM and underlying materials from damage due to contact with the reactive ions. A UV-absorbing material may be used as the barrier layer 507 to reduce the possibility of photo-oxidation of the blue emitter material, as well as the CCM materials. SiO is an example of UV-absorbing material that is transparent in the visible spectrum.

Figure 7 illustrates how to take advantage of the masking characteristics of the walls 180 in order to deposit a particular CCM layer on top of the desired subpixel but to avoid laying the CCM on the subpixels that are to be a different color from that emitted by the CCM. The correct angle 713 to use between the deposition source of the CCM layer and the substrate (also designated i n Figure 7) depends on the distance 710 between subpixel centers (interpixel distance; also designated a in Figure 7) and the wall height 712 (also designated b in Figure 7). The angle i s equal to the inverse tangent of the quotient of the wall height over the interpixel distance ( = tan^"'(b/a).

For a Novolak-type photoresist, the wall height can be up to three-and-one- half times the wall thickness. Based on the formula, above, for a pixel size of 3.5 m , an interpixel distance of 5 m, a wall thickness of 0.5 m and a wall height of 1.5 m, the proper angle between source and substrate is 16.7 degrees. The deposition stream of CCM material may be effectively collimated for accurate angular control by moving the deposition source away from the device on which it is being deposited or by other well-known means such as nozzles and slits between the source and the device. Preferably, an evaporation technique is used to deposit the CCM layers, and the crucible from which the CCM is evaporated is moved at least 50 cm from the deposition target, and more preferably, at least 100 cm from the deposition target. In order to assure even deposition of the CCM material, the substrate may be mounted on a wedge affixed to a turntable, with the wedge having an angle equal to the desired angle between the source and the substrate. Rotating the turntable and wedge during deposition maintains the proper deposition angle at the same time that it evens out the rate of deposition over the desired area for the CCM layer. Alternatively, the substrate may be moved back and forth in the directions parallel to the shadow mask walls in order to accomplish the goal of even deposition of CCM layers.

In another embodiment, by using a suitable light scattering medium as the barrier layer over the CCM and the blue materials, the present invention also substantially reduces the light collimation problem exhibited by some other OLED displays. An example of such a light scattering medium would be fine glass particles (such as Si0 or fused silica) that can be deposited using a volatile solvent so that following spin coating the solvent can be eliminated by simple evaporation.

The space between the sub-pixels is typically non-emitting. Preferably, a black matrix in this interpixel space is used in order to eliminate any wave-guiding effects, (which effects are seen primarily from the blue emitter), as well as to improve the contrast of the display. The black interpixel matrix may be made of an electrically non-conducting material (in order to electronically isolate the sub-pixels). The walls 180 may serve as the black matrix. For this purpose, the walls 180 are fabricated using a commercially available black color filter material, which is similar to a photoresist. This material can be patterned, using well-known photo-lithography methods, into the required wall structure prior to deposition of the layers of the light emitting device. Other methods for patterning include laser ablation, inkjet printing, stamping, scribing, and offset printing methods. Following the deposition of all the layers and construction of the sub-pixels, the black matrix wall may be removed, as described above, using RIE etching. The portion of the wall that is of equal height to the OLED stack will, however, remain as a black matrix , as shown in Fig. 6.

In another embodiment of the present invention, instead of making electrical connection to the bottom electrode through a set of row conductors traversing the surface of the substrate, such connection is made from underneath the electrode, through the substrate, preferably using via plugs. In this embodiment, the substrate preferably contains embedded drive circuitry for the OLED or OLEDs on the substrate surface, and more preferably, the substrate is formed of silicon with embedded circuits formed using well-known MOS techniques. Most preferably in this embodiment, the device so formed is a microdisplay device having a sufficient number of OLEDs in rows and columns along with the necessary circuitry to display video signals of at least VGA resolution (640 columns by 480 rows). The pixelated area forming the display of such a microdisplay device preferably is less than 100 square centimeters, more preferably less than 25 square centimeters, and even more preferably less than 6.25 square centimeters. In yet another embodiment of the present invention, an encapsulation structure is layered over or above the top electrode before the walls that provide the shadow mask are set up. The encapsulation structure may be layered directly over and in contact with the top electrode, or may form a separate barrier with a gap between the top electrode and the barrier (for example, as a glass or other transparent cover that is hermetically sealed around the periphery of the display) Preferably, the encapsulation structure is layered directly on top of and in contact with the top electrode as shown in Figures 8 through 11. Figure 8 shows an OLED display device 800 that includes a substrate 810, one or more electrodes 820, an emitter layer 830 that preferably emits blue light, a top electrode layer 840, and an encapsulation layer 850 layered directly over the top electrode 840. Preferably, although not shown in the figure, the bottom surface of layer 850 is in direct contact with the top surface of substrate 810. More preferably, the encapsulation structure includes at least on additional encapsulation layer whose bottom surface is in direct contact with the top surface of layer 850. Most preferably, layer 850 comprises a highly conformal dielectric oxide such as aluminum oxide laid down by atomic layer deposition (also known as ALD, or ALCVD). Other such conformal oxides include but are not limited to TiO₂, ZrO₂, MgO, HfO₂, Ta O₅, and multilayer oxides such as aluminum titanium oxide and tantalum hafnium oxide. Most preferably, as well, where layer 850 comprises a highly conformal dielectric oxide, the additional encapsulation layer comprises an organic polymer capable of polymerizing from the vapor phase on contact with layer 850.

In another preferred embodiment, the encapsulation structure comprises three layers, layer 850, the additional encapsulation layer, and an additional thin hard layer on top of the additional encapsulation layer of a chemically-resistant material such as SiO₂.

Figure 9 shows partially constructed device 900 which is the device shown in Figure 8 with a pre-wall layer 980 in place. Layer 980 preferably is applied by spin coating, but may also be formed by another process such as but not limited to evaporation.

Figure 10 shows how walls 1060 may be formed from the pre-wall layer. Where pre-wall layer is a photoresist, the wall are formed using a lithography mask to expose and pattern the layer followed by development of the layer to remove the material between the walls. Alternatively, if an non-photoresist material is used for pre-wall layer 960, an additional step of laying a photoresist on top of the non- photoresist material prior to masking, exposing and developing the material is necessary. Other well-known methods such as RIE and other etching techniques, as well as laser ablation, may also be used to form walls 1060. After the walls are formed, angular deposition of the CCM layers is accomplished in the same fashion as for the preceding embodiments, and the walls are then removed using an RIE or analogous process.

Figure 11 shows a full-color device 1100 following layering of the CCM materials and removal of the walls by RIE or another process. The blue subpixel has only barrier material 1190 on top of the encapsulation layer or layers. The red and green subpixels has the green CCM 1170 and red CCM 1180 underneath the barrier layer.

While not preferred, in the embodiment of Figures 8 through 11, it is possible to use the additional encapsulation layer as the wall-forming layer 960 used to construct walls 1060. For example, if parylene is used as a layer on top of a conformal oxide, the parylene may be laid down to a thickness of the desired wall height. Then a photoresist layer may be used followed by lithography processing to form the walls. For this embodiment, it is preferable to remove only so much of the additional encapsulation layer as would leave a thin layer of the additional encapsulation layer in place covering the first encapsulation layer underneath the CCM and barrier materials, in which case the additional encapsulation layer is laid down to a thickness of the wall height plus the desired thickness that is to remain covering the first encapsulation layer.

In all cases, because the barrier material is chosen to be un-etchable in the RIE process, there may be debris from un-etched material over the active area (principally, for example from the layer 508 on top of walls 180 in Figure 5 or from analogous layers in other embodiments). The debris may be removed by suitable anti-static high pressure inert gas together with appropriate suction. The debris may also be removed by using high pressure cryogenic cleaning such as CO₂ gas. For the embodiments incorporating an encapsulation structure, cleaning may also be accomplished using suitable solvent-based systems.

Another embodiment of the present invention may include eliminating the walls, post evaporation and deposition of the OLED layers using only high pressure cryogenic cleaning instead of using an intermediate step of isotropic RIE etch. The CCM materials useful in the present invention are fluorescent materials that may be deposited at a controlled angle relative to the substrate. Such materials, preferably are volatile enough to undergo evaporative deposition. Examples of fluorescent dye capable of changing light emitted by blue, blue-green or white emitting layers into green emission are coumarin dyes such as 2,3,5,6-lH,4H- tetrahydro-8-trifluoromethylquinolidino(9,9a, 1 -gh)coumarin (hereinafter referred to as Coumarin 153), 3-(2'-benzothiazolyl)-7-diethylaminocournarin (hereinafter referred to as Coumarin 6), and 3-(2'-benzimidazolyl)-7-N,N-diethylaminocoumarin (hereinafter referred to as Coumarin 7); other coumarin dyes such as Basic Yellow 51; and naphthalimide dyes such as Solvent Yellow 1 1 , and Solvent Yellow 116. Examples of fluorescent dye capable of changing light emitted by blue to green or white emitting layers into orange to red emission are cyanine dyes such as 4- dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (hereinafter referred to as DCM); pyridine dyes such as l-ethyl-2-(4-(p-dimethylaminophenyl)- l,3-butadienyl)-pyridinium perchlorate (hereinafter referred to as Pyridine 1); rhodamine dyes such as Rhodamine B, and Rhodamine 6G; and oxazine dyes.

The thickness of the fluorescent layers is not specifically defined, provided that the layers can satisfactorily receive (absorb) light emission from the overlying organic EL element, without interfering with their function of fluorescent emission, but is generally from 10 nm to 1 mm, preferably from 0.1 m to 0.5 mm, more preferably from 0.2 to 0.5 m. The optical density of the CCM layer needs to be high enough that the underlying blue emission is essentially fully absorbed, and thus the optical density should be at least 2.5 and preferably, above 3.

While less preferred, any of the preceding embodiments may also use white emitting materials in place of blue emitting materials and color filter materials in place of color changing means. Also, for either CCM or filter materials, the layer may consist of a dye alone or a dye with a binder material (provided that the concentration of the dye provides a sufficiently high optical density as discussed above and in accordance with Beer's law (also known as the Lambert-Beer equation). It will be apparent to those skilled in the art that various modifications and variations can be made in the construction, configuration, and/or operation of the present invention without departing from the scope or spirit of the invention. For example, in the embodiments mentioned above, various changes may be made to the composition of the organic material layers without departing from the scope and spirit of the invention. Further, it may be appropriate to make additional modifications or changes to the wall structure without departing from the scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the invention provided they come within the scope of the appended claims and their equivalents. All references mentioned above are incorporated herein by reference for all purposes as though their disclosures were fully set forth above.

Claims

1. A method of fabricating an organic light emitting device comprising the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a plurality of walls between the first electrodes, wherein the walls overlie the planar substrate and extend substantially perpendicular to the planar substrate; constructing a layer of light emitting organic material overlying the first electrode and between the walls; constructing a second electrode layer overlying the layer of light emitting material and between the walls; removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode.

2. The method according to Claim 1, wherein the walls may be constructed using black matrix material.

3. The method according to Claim 1 further comprising, prior to the step of removing a portion of the plurality of walls, steps of depositing at least one layer of color changing medium overlying the second electrode; and depositing a barrier layer overlying the at least one layer of color changing medium.

4. A method of fabricating an organic light emitting device comprising the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a plurality of walls between the first electrodes, wherein the walls overlie the planar substrate and extend substantially perpendicular to the planar substrate; constructing a layer of blue light emitting organic material overlying the first electrodes and between the walls; constructing a second electrode layer overlying the layer of blue light emitting material and between the walls; depositing a first layer of color changing material overlying the second electrode and above a fraction of the plurality of first electrodes; depositing a second layer of color changing material overlying the second electrode layer and above a different fraction of the plurality of first electrodes from the fraction above which lies the first layer of color changing material; depositing a barrier layer overlying the first layer of color changing material and the second layer of color changing material and any of the second electrode layer not underlying the first and second layers of color changing material; and removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode; wherein the fraction of the plurality of first electrodes above which overlies the first layer of color changing material is selected by depositing the first color changing material at a first angle relative to the plane of the substrate such that the plurality of walls allows the first color changing material to deposit only on the selected fraction of first electrodes, and the fraction of the plurality of first electrodes above which overlies the second layer of color changing material is selected by depositing the second color changing material at a second angle relative to the plane of the substrate such that the plurality of walls allows the second color changing material to deposit only on the selected fraction of first electrodes.

5. The method according to claim 4 wherein the step of constructing a plurality of walls between the first electrodes comprises steps of: spin coating a layer of organic material onto the planar substrate and plurality of electrodes; and selectively removing portions of the layer of the organic material to leave behind the plurality of walls .

6. The method according to claim 4 wherein the organic material comprises a photoresist and the step of selectively removing portions of the organic material comprises steps of patterning the layer of organic material using light or an electron beam, and developing the photoresist to leave behind the plurality of walls.

7. The method according to claim 6 wherein the photoresist comprises a Novolak-type photoresist.

8. The method according to claim 4 wherein one of the first color changing material and the second color changing material emits green light and the other of the first color changing material and the second color changing material emits red light.

9. The method according to claim 4 wherein the organic material comprises a black filter material.

10. The method according to claim 4 wherein the step of selectively removing portions of the organic material comprises steps of forming a structure by applying a photoresist layer on top of the layer of organic material, patterning the photoresist layer using light or an electron beam, developing the photoresist, and etching the resulting structure to leave behind the plurality of walls.

11. The method according to claim 10 wherein the organic material comprises a black filter material.

12. The method according to claim 4 wherein the barrier layer comprises a light scattering medium.

13. A method of fabricating an organic light emitting device comprising the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a layer of blue light emitting organic material overlying the plurality of first electrodes; constructing a second electrode layer overlying the layer of blue light emitting material; constructing an encapsulation structure overlying the second electrode layer; constructing a plurality of walls overlying the encapsulation structure, wherein the walls extend substantially perpendicular to the planar substrate and only lie above the portions of the substrate that are in between the plurality of first electrodes; depositing a first layer of color changing material overlying the encapsulation structure and above a fraction of the plurality of first electrodes; depositing a second layer of color changing material overlying the encapsulation structure and above a different fraction of the plurality of first electrodes from the fraction above which lies the first layer of color changing material; depositing a barrier layer overlying the first layer of color changing material and the second layer of color changing material and any of the encapsulation structure not underlying the first and second layers of color changing material; removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode; wherein the fraction of the plurality of first electrodes above which overlies the first layer of color changing material is selected by depositing the first color changing material at a first angle relative to the plane of the substrate such that the plurality of walls allows the first color changing material to deposit only on the selected fraction of first electrodes, and the fraction of the plurality of first electrodes above which overlies the second layer of color changing material is selected by depositing the second color changing material at a second angle relative to the plane of the substrate such that the plurality of walls allows the second color changing material to deposit only on the selected fraction of first electrodes.

14. The method according to claim 13 wherein the step of constructing a plurality of walls between the first electrodes comprises steps of: spin coating a layer of organic material onto the planar substrate and plurality of electrodes; and selectively removing portions of the layer of the organic material to leave behind the plurality of walls.

15. The method according to claim 13 wherein the organic material comprises a photoresist and the step of selectively removing portions of the organic material comprises steps of patterning the layer of organic material using light or an electron beam, and developing the photoresist to leave behind the plurality of walls.

16. The method according to claim 15 wherein the photoresist comprises a Novolak-type photoresist.

17. The method according to claim 13 wherein the organic material comprises a black filter material.

18. The method according to claim 13 wherein the step of selectively removing portions of the organic material comprises steps of applying a photoresist layer on top of the layer of organic material, patterning the photoresist layer using light or an electron beam, developing the photoresist, and etching the resulting structure to leave behind the plurality of walls.

19. The method according to claim 18 wherein the organic material comprises a black filter material.

20. The method according to claim 13 wherein the barrier layer comprises a light scattering medium.

21. The method according to claim 13 wherein one of the first color changing material and the second color changing material emits green light and the other of the first color changing material and the second color changing material emits red light.

22. An organic light emitting device fabricated according to the method of claim 1.

23. An organic light emitting device fabricated according to the method of claim 2.

24. An organic light emitting device fabricated according to the method of claim 3.

25. An organic light emitting device fabricated according to the method of claim 4.

26. An organic light emitting device fabricated according to the method of claim 5.

27. An organic light emitting device fabricated according to the method of claim 6.

28. An organic light emitting device fabricated according to the method of claim 7.

29. An organic light emitting device fabricated according to the method of claim 8.

30. An organic light emitting device fabricated according to the method of claim 9.

31. An organic light emitting device fabricated according to the method of claim 10.

32. An organic light emitting device fabricated according to the method of claim 11.

33. An organic light emitting device fabricated according to the method of claim 12.

34. An organic light emitting device fabricated according to the method of claim 13.

35. An organic light emitting device fabricated according to the method of claim 14.

36. An organic light emitting device fabricated according to the method of claim 15.

37. An organic light emitting device fabricated according to the method of claim 16.

38. An organic light emitting device fabricated according to the method of claim 17.

39. An organic light emitting device fabricated according to the method of claim 18.

40. An organic light emitting device fabricated according to the method of claim 19.

41. An organic light emitting device fabricated according to the method of claim 20.

42. An organic light emitting device fabricated according to the method of claim 21.

43. An organic light emitting device fabricated by a method comprising the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a plurality of walls between the first electrodes, wherein the walls overlie the planar substrate and extend substantially perpendicular to the planar substrate; constructing a layer of blue light emitting organic material overlying the first electrodes and between the walls; constructing a second electrode layer overlying the layer of blue light emitting material and between the walls; depositing a first layer of color changing material overlying the second electrode and above a fraction of the plurality of first electrodes; depositing a second layer of color changing material overlying the second electrode layer and above a different fraction of the plurality of first electrodes from the fraction above which lies the first layer of color changing material; depositing a barrier layer overlying the first layer of color changing material and the second layer of color changing material and any of the second electrode layer not underlying the first and second layers of color changing material; removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode; wherein the fraction of the plurality of first electrodes above which overlies the first layer of color changing material is selected by depositing the first color changing material at a first angle relative to the plane of the substrate such that the plurality of walls allows the first color changing material to deposit only on the selected fraction of first electrodes, and the fraction of the plurality of first electrodes above which overlies the second layer of color changing material is selected by depositing the second color changing material at a second angle relative to the plane of the substrate such that the plurality of walls allows the second color changing material to deposit only on the selected fraction of first electrodes; and wherein one of the first color changing material and the second color changing material emits green light and the other of the first color changing material and the second color changing material emits red light; and wherein the device is a microdisplay.

44. An organic light emitting device fabricated by a method comprising the steps of: providing a planar substrate; constructing a plurality of first electrodes over the planar substrate; constructing a layer of blue light emitting organic material overlying the plurality of first electrodes; constructing a second electrode layer overlying the layer of blue light emitting material; constructing an encapsulation structure overlying the second electrode layer; constructing a plurality of walls overlying the encapsulation structure, wherein the walls extend substantially perpendicular to the planar substrate and only lie above the portions of the substrate that are in between the plurality of first electrodes; depositing a first layer of color changing material overlying the encapsulation structure and above a fraction of the plurality of first electrodes; depositing a second layer of color changing material overlying the encapsulation structure and above a different fraction of the plurality of first electrodes from the fraction above which lies the first layer of color changing material; depositing a barrier layer overlying the first layer of color changing material and the second layer of color changing material and any of the encapsulation structure not underlying the first and second layers of color changing material; removing a portion of the plurality of walls that extends away from the planar substrate above the second electrode; wherein the fraction of the plurality of first electrodes above which overlies the first layer of color changing material is selected by depositing the first color changing material at a first angle relative to the plane of the substrate such that the plurality of walls allows the first color changing material to deposit only on the selected fraction of first electrodes, and the fraction of the plurality of first electrodes above which overlies the second layer of color changing material is selected by depositing the second color changing material at a second angle relative to the plane of the substrate such that the plurality of walls allows the second color changing material to deposit only on the selected fraction of first electrodes; and wherein one of the first color changing material and the second color changing material emits green light and the other of the first color changing material and the second color changing material emits red light; and wherein the device is a microdisplay.

45. The device according to claim 44 wherein the top electrode has an upper and a lower surface; wherein the encapsulation structure comprises a dielectric oxide layer having a lower surface and an upper surface and is formed using ALCVD; wherein the encapsulation structure further comprises a polymer layer having a lower surface and an upper surface; and wherein the lower surface of the oxide layer is in contact with the upper surface of the top electrode and the lower surface of the polymer layer is in contact with the upper surface of the oxide layer.

45. The device according to claim 45 wherein the plurality of walls is constructed out of the polymer layer.