Active Matrix Enhanced Organic Light Emitting Diode Displays for Large Screen Graphic Display Applications

Abstract

A light emitting photonic crystal composed of chiral liquid crystalline material and having an organic light emitting diode and methods of making the same are disclosed. An organic light emitting diode disposed within a photonic structure having a band-gap, or stop-band, allows the photonic structure to emit light at wavelengths occurring at the edges of the band-gap.

Claims

1. A light emitting device comprising: a light emitting photonic crystal having organic electroluminescent emitter material disposed within the photonic crystal; and a photo luminescent material disposed upon a surface of the light emitting photonic crystal, such that light emitted by the light emitting photonic crystal causes photoexcitation within the photoluminescent material; and wherein the light emitting phonic crystal is composed of polymerized chiral nematic liquid crystal material.

2. The light emitting device of claim 1 wherein the polymerized chiral nematic liquid crystal material comprises: a hole transporting layer comprising a polymerized chiral nematic liquid crystal material; a light emitting layer comprising a polymerized chiral nematic liquid crystalline material; and an electron transporting layer comprising a polymerized chiral nematic liquid crystal material; wherein each of said layers has a thickness and said light emitting layer has a thickness that is 10% or less of the total thickness of all the polymerized chiral nematic liquid crystal material containing layers combined.

3. The light emitting device of claim 2 wherein each layer has a plane and the polymerized chiral nematic liquid crystal material comprising each layer comprises molecules having long axes aligned parallel with said plane of said layer.

4. The light emitting device of claim 2 wherein the polymerized chiral nematic material in each layer spontaneously adopts a helical structure with a helical pitch, and the helical pitch of the helical structure of the polymerized chiral nematic material in each layer is the same.

5. The light emitting device of claim 2 wherein the layers comprising polymerized chiral liquid crystal combine together to form a photonic crystal.

6. The light emitting device of claim 2 wherein said light emitting layer further comprises an electroluminescent material which emits light into the band edge light propagation modes of the photonic crystal.

7. The light emitting device of claim 2 wherein the layers comprising polymerized chiral liquid crystal ail have the same ordinary and extraordinary refractive indices.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 illustrates an embodiment of the invention.

DETAILED DESCRIPTION

[0006] FIG. 1 illustrates a single RGB color pixel within an alternative and improved embodiment 100 of the invention. described in PC/US16/39802 the vacuum deposited layered structures that make up a BE-OLED are replaced by a chiral liquid crystalline structure built up by solvent casting layers and then photopolymerizing them. This embodiment utilizes OLED devices of the type described in International Patent Application Number PCT/US17/21867, chiral liquid crystalline, band edge emission enhanced organic light emitting diodes (C-OLEDs). Embodiment 100 comprises a transparent substrate 102 that may be formed from glass or clear plastic; red (104a), green (104b) and blue (104c) photoluminescent material layers that delineate the sub-pixels that make up the ROB color pixel sub-pixel anodes 106a, 106b and 106c; liquid crystal photoalignment and hole injection layer 108; p-doped, polymerized chiral liquid crystalline hole transporting layer 110; polymerized chiral liquid crystalline hole transporting layer 112; polymerized chiral liquid crystalline light emitting layer 114; polymerized chiral liquid crystalline electron transporting layer 116; n-doped, polymerized chiral liquid crystalline electron transporting layer 118; electron injection layer 122; and row cathode 124. Each row cathode/sub-pixel anode combination addresses a single sub-pixel and is connected to and driven by a dedicated. TFT-based microcircuit (not shown) that is built up on the transparent substrate. Microcircuits of this type that are used to drive pixels in active matrix OLEDs are well-known in the art. A helical structure (portrayed by 120) is spontaneously formed when the chiral liquid crystalline layers are sequentially solvent east down onto the liquid crystal photoalignment and hole injection layer 108 and photopolymerized. This structure pervades the entirety of layers 110, 112, 114, 116, and 118. The thickness of the polymerized chiral liquid crystalline light emitting layer may be 10% or less than the total combined thicknesses of all of the polymerized chiral liquid crystalline layers. Each layer has a plane and the polymerized chiral nematic liquid crystal material comprising each layer comprises molecules having long axes aligned parallel with said plane of said layer. The polymerized chiral nematic material in each layer spontaneously adopts helical structure with a helical pitch, and the helical pitch of the helical structure of the polymerized chiral nematic material in each layer is the same. The polymerized chiral liquid crystalline layers may all have the same chiral pitch. The light emitting layer further comprises an electroluminescent material which emits light into the band edge light propagation modes of the photonic crystal. The polymerized chiral liquid crystalline layers may all have the same ordinary and extraordinary retractive indices.

[0007] The layers of chiral nematic material are each laid down by a solvent casting method and then polymerized by exposure with radiation such as ultraviolet light. Each layer is laid down on top of the previous layer and then polymerized in succession.

[0008] Component layers 106a, 106b, 106c, 108, 110, 112, 114, 116, 118, 122, and 124 combine to make up C-OLEDs as are described in PCT/US17/21867. That patent application describes greater detail how a C-OLED may be fabricated and how the helical structure 120 functions photonic crystal. The photonic crystal formed the chiral liquid crystalline material in layers 110, 112, 114, 116, and 118 induces stimulated light emission in band edge modes from the luminescent material in layer 114. The light thus emitted is emitted ally and is well collimated. The luminescent material in layer 114 is a deep blue or violet emitting electroluminescent material such as fac-Iridium(III) tris(1-phenyl-3-methylbenzimidazolin-2-ylidene-C,C2). When a particular sub-pixel such as that overlaying photoluminescent layer 104a is energized by application of a potential difference between its anode and cathode by means of its dedicated TFT microcircuit, deep blue or violet light is emitted vertically either in the direction of layer 104a or cathode 124. Cathode 124 is fabricated from a reflective metal and is properly located in relation to the chiral structure such that it reflects light back in the direction of layer 104a. Thus substantially all light produced strikes layer 104a producing tin this case) red photoluminescence. Similarly layers 104b and 104c can be induced to produce green and blue light respectively when the proper TFT microcircuits and anode/cathode combinations are energized. In this way display screen composed of a great many pixel structures like that shown in FIG. 1 can be induced to display video information.

[0009] Embodiment 100 is a bottom emitting device in that the light that is produced passes out through the transparent anodes and substrate. The same principle can be used to produce a top emitting device. In this case a reflector is positioned under anodes 106a, 106b, and 106c; row cathodes 124 are transparent cathodes as are well-known in the art; and photoluminescent layers 104a, 104b, and 104c are formed on top of row cathodes 124.

[0010] If not otherwise stated herein, any and all patents, patent applications, patent publications, articles and other printed publications discussed or mentioned herein are hereby incorporated by reference as if set forth in their entirety herein.

[0011] It will be appreciated by those of ordinary skill in the art that the disclosed apparatus may be comprised of a wide and equivalent range of apparatus and components and nothing herein is intended to limit the scope of the disclosed inventions or any embodiments thereof.