ULTRA VIOLET RADIATION BLOCKING OPTOELECTRONIC DEVICE
FIELD OF INVENTION
[0001] The invention disclosed herein relates, in general, to optoelectronic devices. More specifically, the present invention relates to optoelectronic devices providing improved ultra¬violet protection.
BACKGROUND
[0002] In manufacturing and even during operational life of optoelectronic devices like the Organic Light Emitting Devices (OLEDs) and Thin-Film Photovoltaic Cells (TF-PVs), preventing degradation of functional layers essential for functioning of the optoelectronic device is a critical aspect that substantially affects the efficiency and life term of such devices.
[0003] The optoelectronic devices have many different layers, for example a organic light emitting device (OLED) is made of multiple organic layers, each of which has a specific task. Further, most of the organic materials used in the multiple organic layers are sensitive to radiations like ultra violet (UV) radiations. Also, the metals used as electrodes in OLEDs are susceptible to degradation on exposure to UV radiations.
[0004] Any such degradation due to exposure to UV radiations can result in a shortened lifetime of the OLED or similar optoelectronic devices. Therefore, it is necessary to that the OLED or similar optoelectronic devices are not exposed to UV radiations. Usually, this is prevented by providing an additional capping layer or a UV blocking layer in the optoelectronic device to protect the functional stack.
[0005] This method of adding an additional layer adds to material cost, manufacturing complexity and increased thickness of the device, which is undesirable.

[0006] not depicted in a drawing, the absence of such a drawing should not be considered as an omission of such design from the specification.
SUMMARY
[0007] The instant exemplary embodiments provide an optoelectronic device that provides improved protection to its functional stack against ultraviolet (UV) rays.
[0008] The instant exemplary embodiments provide an optoelectronic device that provides protection to its functional stack against ultraviolet (UV) rays and also does not have an increased thickness.
[0009] Some embodiments of the invention provide an optoelectronic device that provides protection to its functional stack against ultraviolet (UV) rays. The optoelectronic device includes a substrate having a first surface and a substantially parallel second surface. Further, there is disposed on the substrate at least one of a first light management layer on the first surface and a second light management layer on the second surface. The first light management layer and the second light management layer are configured to facilitate light management in the optoelectronic device. Further, the device is characterized such that, at least one of the first light management layer and the second light management layer includes particles/molecules that are capable of absorbing and blocking radiations having a wavelength in the range of 200 to 380 nm. Further, the optoelectronic device also includes a stack of functional layers supported by said substrate, such that the stack of functional layers includes at least one layer sensitive to the radiations having wavelength in the range of 200 to 380 nm.
[0010] Some embodiments of the invention provide an optoelectronic device having a light management layer that also functions as an UV absorbent layer. The device is structured such that at least one of the two internal and external light management layers include UV absorbing particles, that absorb UV radiations and protect the UV sensitive functional stack without the need of an additional UV protective layer.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0011] Before describing the present invention in detail, it should be observed that the present invention utilizes apparatus components related to an optoelectronic device such as an organic light emitting device. Accordingly the apparatus components have been represented where appropriate by conventional symbols in the drawings, showing only specific details that are pertinent for an understanding of the present invention so as not to obscure the disclosure with details that will be readily apparent to those with ordinary skill in the art having the benefit of the description herein.
[0012] While the specification concludes with the claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawings, in which like reference numerals are carried forward.
[0013] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and ftmctional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.
[0014] The terms "a" or "an", as used herein, are defined as one or more than one. The term "another", as used herein, is defined as at least a second or more. The terms "including" and/or "having" as used herein, are defined as comprising (i.e. open transition). The term "coupled" or

"operatively coupled" as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.
[0015] Referring now to the drawings, there is shown in FIG. 1, an exemplary optoelectronic device 100, in accordance with an embodiment of the present invention. Examples of the optoelectronic device 100 include an Organic Light Emitting Devices (OLEDs), Thin-Film Photovoltaic Devices (TF-PVs), Organic Photovoltaic Devices (OPVs), Crystalline Photovoltaic Devices, other forms of PV, displays, and organic displays.
[0016] Some real life examples of an OLED can include, but are not limited to, White Organic Light Emitting Diode (W-OLED), Active-matrix Organic Light Emitting Diodes (AMOLED), Passive-matrix Organic Light Emitting Diodes (PMOLED), Flexible Organic Light Emitting Diodes (FOLED), Stacked Organic Light Emitting Diodes (SOLED), Tandem Organic Light Emitting Diode, Transparent Organic Light Emitting Diodes (TOLED), Top Emitting Organic Light Emitting Diode, Bottom Emitting Organic Light Emitting Diode, Fluorescence doped Organic Light Emitting Diode (F-OLED) and Phosphorescent Organic Light Emitting Diode (PHOLED).
[0017] Similarly, examples of a TF-PVs can include, but are not limited to, a thin film solar cell, an organic solar cell, an amorphous silicon solar cell, a microcrystalline silicon solar cell, a micromorph silicon tandem solar cell, a Copper Indium Gallium Selenide (CIGS) solar cell, a Cadmium Telluride (CdTe) solar cell, and the like.
[0018] For the purpose of the description, the optoelectronic device 100 illustrated here has been shown to include only those layers that are pertinent to the description of the invention. However, it should be understood that the invention is not limited to the layers listed in the description here. In some cases, the optoelectronic device 100 may include additional layers to enhance efficiency or to improve reliability, without deviating from the scope of the invention.
[0019] The optoelectronic device 100 is shown to include a substrate 102, a first light management layer 104, a second light management layer 106 and a functional layer stack 108.

The functional layer stack 108 is configured to have one or more functional layers therein. The one or more functional layers include a first electrical contact 110, one or more organic layers 112 and 114, a second electrical contact 116 and a cover substrate 118.
[0020] The substrate 102 functions to provide strength to the optoelectronic device 100. Examples of material useful as the substrate include, but are not limited to, glass, flexible glass, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC) and other transparent or translucent material. The substrate 102 is defined by a first surface and a substantially parallel second surface. Further, the substrate 102 is configured to receive the first light management layer 104 on the first surface and the second light management layer 106 on the second surface. In an embodiment, the substrate may only include one of the first light management layer 104 and the second light management layer 106. For example, in case when the optoelectronic device 100 is an OLED, both the first light management layer 104 and the second light management layer 106 are provided and in case when the optoelectronic device 100 is an OPV, only the first light management layer 104 is provided.
[0021] The first light management layer 104 and the second light management layer 106 is generally made up of a curable material and is provided over the substrate 102. It should be appreciated that, the first light management layer 104 may be interchangeably referred to as an internal light management layer and the second light management layer 106 may be interchangeably referred to as an external light management layer, for the purpose of the description.
[0022] The internal light management layer 104 and the external light management layer 106 can be provided on the substrate 102 by using a brush or roller, dispensing, screen printing, slot dye coating, spin-coating, spray coating, diverse replication techniques, or even printing. The curable material has a property to retain any light management texture embossed on it when it is cured by using mediums such as heat or light. The curable material can include, but is not limited to, a ultra-violet curable material, a photo-polymer lacquer, an acrylate, and silica or silica-titania based sol-gel materials. In some embodiments, a texture may also be applied to the

internal light management layer 104 and the external light management layer 104 by use of photolithographic techniques.
[0023] The texture facilitates light management in the optoelectronic device. For example, when the optoelectronic device is an OLED, a light emitted by organic layers of the OLED, needs to pass through the substrate 102. However, when light is incident from a high refractive index material onto an interface with a lower refractive index material or medium, the light undergoes total internal reflection (TIR) for all incidence angles greater than the critical angle 6c, defined by 0c = sin"' (na/ni), where ni and na are the refractive indices of the high refractive index material and low refractive index material, respectively. Due to the same reason, when the light emitted by the one or more organic layers 112 and 114 reaches an interface between the substrate 102 and an ambient medium, a substantial amount of light is reflected back into the OLED.
[0024] Similarly, in case of a TF-PV device, the texture can provide light trapping fimction. The texture 108 is provided is provided in the TF-PV device to increase an optical path of the light transmitted in to the TF-PV device. The texture enables light extraction and light trapping in cases of an OLED and an TF-PV device respectively. The texture is usually micron or sub-micron sized textures that are preferably one of periodic and quasi-periodic in nature.
[0025] In accordance with the present invention, the internal light management layer 104 and the external light management layer 106 are deposited in a manner such that the texture can be provided on a surface of the internal light management layer 104 and the external light management layer 106. The examples of the texture include, but are not limited to, ID or 2D periodic U-shaped features, a ID or 2D periodic sinusoidal grating, ID or 2D periodic upright or inverted pyramids, random upright or inverted pyramids, ID or 2D periodic inverted cones, and other micro and nano-sized structures.
[0026] Moving on, the invention also provides multiple particles/molecules distributed in the first light management layer 104 and the second light management layer 106. The particles/molecules being capable of absorbing and blocking radiations having a wavelength in the range of 200 to 380 nm. In an embodiment, at least one of the first light management layer

104 and the second light management layer 106 include the particles/molecules. The particles/molecules are configured to absorb or block radiations in the ultra violet range. Further, details of the structure and composition of the particles has been provided with reference to FIGs. 2a and 2b.
[0027] Once the first light management layer 104 has been deposited, the first electrical contact 110 is provided over the lacquer layer 104. In an embodiment, the first electrical contact 110 can be implemented using a transparent conducting oxide (TCO). TCOs are doped metal oxides, examples of TCOs include, but are not limited to. Zinc Oxide, Tin Oxide, Aluminum-doped Zinc Oxide (AZO), Boron doped Zinc Oxide (BZO), Gallium doped Zinc Oxide (GZO), Fluorine doped Tin Oxide (FTO), Indium Zinc Oxide and Indium doped Tin Oxide (ITO). TCOs have more than 80% transmittance of incident light and have conductivities higher than 10'' S/cm for efficient carrier transport. The transmittance of TCOs, just as in any transparent material, is limited by light scattering at defects and grain boundaries. In another embodiment, the first electrical contact 110 can also be implemented with a PEDOT-PSS, or any other transparent polymers, or thin metal layers.
[0028] The first electrical contact 110 may be deposited by processes such as Physical Vapor Deposition (PVD), Low Pressure Chemical Vapor Deposition (LPCVD), Atmospheric Pressure Chemical Vapor Deposition (APCVD), or even Plasma Enhanced Chemical Vapor Deposition (PECVD) and the like.
[0029] Moving on to the next set of layers, the one or more organic layers 112 and 114. Generally, the one or more organic layers 112 and 114 are deposited using methods such as dip coating, spin coating, doctored blade, spray coating, screen printing, sputtering, glass mastering, photoresist mastering, all kinds of CVD, electroforming, and evaporation. In an embodiment, the one or more organic layers 112 and 114 can be implemented with any organic electroluminescent material such as a light-emitting polymer, evaporated small molecule materials, light-emitting dendrimers or molecularly doped polymers. For the purpose of this description, the organic layers are shown to include only two layers, however, it will be readily

apparent to those skilled in the art that the optoelectronic device 100 can include or exclude one or more organic layers without deviating from the scope of the invention.
[0030] Following the one or more organic layers 112 and 114, the second electrical contact 116 is deposited. In one embodiment, the second electrical contact 116 can includes a second layer of TCO, a layer of silver, and a layer of aluminum. In other embodiments, the second electrical contact 116 can be implemented with metals with appropriate work function to make injection of charge carriers, for example, calcium, aluminum, gold, and silver. In an embodiment, the first electrical contact 110 and the second electrical contact 116 act as electrode layers. For example the first electrical contact 110 acts as an anode and the second electrical contact 116 acts as a cathode. Thereafter, all the above mentioned layers are encapsulated using a cover substrate 118 between the substrate 102 and the cover substrate 118.
[0031] Moving on there is illustrated in FIGs. 2a and 2b, two exemplary views of the optoelectronic device 100, in accordance with two embodiments of the present invention. In FIG. 2a, for example, the optoelectronic device 100 is shown to include the first light management layer 104 having particles/molecules 200 distributed across the first light management layer 104. The optoelectronic device 100, in this embodiment, is shown not to include the second light management layer 106. Similarly, in FIG. 2b, the optoelectronic device 100 is shown to include the first light management layer 104 and the second light management layer 106. Further, the second light management layer 106 is shown to include the particles/molecules 200 but not the first light management layer 104. In other embodiments, both the first light management layer 104 and the second light management layer 106 can include the particles 200.
[0032] The particles/molecules 200 are configured to absorb and/or block radiations in the wavelength of 200 to 380 nm. The particles/molecules 200 include UV interception material that intercepts UV rays irradiated on the optoelectronic device 100. The UV rays may be irradiated from the exterior or while UV curing of the second light management layer 106. Once, the UV rays irradiated towards the stack of functional layers 108 of the optoelectronic device 100 is intercepted, the life span of the optoelectronic device 100 may be increased because the stack of

functional layers include layers sensitive to the radiations having wavelength in the range of 200 to 380 nm, for example, the one or more organic layers and the first electrical contact degrade on being exposed to UV radiations.
[0033] Moving on, usually, the particles 200 include ultra violet (UV) absorbing particles and molecules. The UV absorbing particles are have a concentration ranging from 5 wt% to 70 wt% and the UV absorbing molecules have a concentration ranging from 0.5 wt% to 5 wt%. Examples of UV absorbing particles include, but are not limited to, zinc oxide (ZnO), titanium oxide (Ti02), iron oxide (Fe203), magnesium oxide (MgO) and mixture thereof Similarly, examples of the UV absorbing molecules include, but are not limited to, Benzotriazol (Tinuvin 900, Ciba), Hydroxyphenyl triazin (Tinuvin 400, Ciba), Hydroxy benzophenone (Uvinul 3040, BASF) etc.
[0034] Further, as illustrated in the FIGs. 2a and 2b, the particles/molecules 200 may be uniformly distributed across the light management layers 104 and 106. In some embodiments, the particles/molecules 200 may not be uniformly distributed across the light management layers 104 and 106 and instead be randomly distributed or have a biased distribution based upon specific requirements, without deviating from the scope of the inventions.
[0035] Also, in an embodiment, the particles 200 may have a diameter ranging from 10 to 500 nm. This size of the particles 200 enables easy mixing of the particles 200 in the curable lacquer material before application onto the substrate 102.
[0036] Various embodiments, as described above, provide an optoelectronic device that has several advantages. The optoelectronic device according to the invention provides improved protection of the fianctional stack from UV radiations. Further, since the light management layer also fiinctions to protect the functional stack from UV radiations, the optoelectronic device according to the present invention does not require additional material for UV protective layers, thereby saving on cost, complexity and increased thickness of the optoelectronic device.

[0037] While the invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those ordinarily skilled in the art. Accordingly, the spirit and scope of the present invention is not to be limited by the foregoing examples, but is to be imderstood in the broadest sense allowable by law.
[0038] All docimients referenced herein are hereby incorporated by reference.

CLAIMS What is claimed is:
1. An optoelectronic device comprising:
a substrate having a first surface and a substantially parallel second surface, wherein said substrate having disposed thereon at least one of a first light management layer on said first surface of said substrate and a second light management layer on said second surface of said substrate, and wherein said first light management layer and said second light management layer £ire configured to facilitate light management in said optoelectronic device;
fiirther wherein at least one of said first light management layer and said second light management layer comprising particles and molecules distributed across said first light management layer and said second light management layer, said particles and molecules capable of absorbing and blocking radiations having a wavelength in the range of 200 to 380 nm; and
a stack of fimctional layers supported by said substrate, said stack of fiinctional layers including at least one layer sensitive to said radiations having wavelength in the range of 200 to 380 nm.
2. The optoelectronic device of Claim 1, wherein said particles comprise ultra violet (UV) absorbing particles, said UV absorbing particles having a concentration ranging fi-om 5 wt% to 70 wt%.
3. The optoelectronic device of Claim 1, wherein said particles comprise UV absorbing molecules, said UV absorbing molecules having a concentration ranging from 0.5 wt% to 5.0 wt%.

4. The optoelectronic device of Claim 1, wherein a diameter of each of said multiple particles in said first light management layer and said second light management layer ranging fi-om 10 to 500 nanometers.
5. The optoelectronic device of Claim 1, wherein said particles and molecules having ultra¬violet wavelength absorbing and blocking properties are selected from the group of titaniom oxide, cerium oxide, zinc oxide, Benzotriazol (e.g. Tinuvin 900, Ciba), Hydroxy-phenyl-triazine (e.g. Tinuvin 400, Ciba) or hydroxy benzophenone (e.g. Uvinul 3040, BASF)
6. The optoelectronic device of Claim 1, wherein said first light management layer is an internal light extraction layer and said second light management layer is an external light extraction layer, when said optoelectronic device is an organic light emitting device.
7. The optoelectronic device of Claim 1, wherein said optoelectronic device is selected from the group comprising a photovoltaic device, a thin film photovoltaic device, an organic photovoltaic device, a light emitting device, an organic light emitting device, a liquid crystalline display, and other organic displays.
8. The optoelectronic device of Claim 1, wherein said functional stack comprises a first electrical contact, one or more organic layers and a second electrical contact.
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