WO2023152238A1

WO2023152238A1 - Materials for quantum dot-based color conversion filters for led arrays and displays

Info

Publication number: WO2023152238A1
Application number: PCT/EP2023/053225
Authority: WO
Inventors: Nadejda Krasteva; Clemens WALL; Dennis CHERCKA; Markus Obermaier; Gabriele Nelles
Original assignee: Sony Group Corporation; Sony Europe B.V.
Priority date: 2022-02-10
Filing date: 2023-02-09
Publication date: 2023-08-17

Abstract

The field of the disclosure lies in protective materials for quantum dot-based color conversion filters. The present disclosure relates to quantum dot-based color conversion filters coated with a barrier layer. The present disclosure also relates to LED array or display comprising a quantum dot-based color conversion filter of the present disclosure.

Description

MATERIALS FOR QUANTUM DOT-BASED COLOR CONVERSION FILTERS FOR LED ARRAYS AND DISPLAYS BACKGROUND [0001] The field of the DISCLOSURE lies in protective materials for quantum dot-based color conversion filters. [0002] The present disclosure relates to quantum dot-based color conversion filters coated with a barrier layer. [0003] The present disclosure also relates to LED array or display comprising a quantum dot- based color conversion filter of the present disclosure. DESCRIPTION OF THE RELATED ART [0004] The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure. [0005] Quantum-Dot Color Conversion Filters (QD-CCF) are rapidly becoming an industy standard for display applications such as LCD TVs. The current research is focusing on the application of QD-CCFs as color conversion filters for single LED, LED arrays (e,g, microLED arrays), and LED-based emissive displays. In these applications, a blue or UV emitting single LED of LED arrays is used as excitation light source for each display pixel. Color conversion to red and green is achieved by placing a color conversion layer comprizing semiconductor quantum dots dispersed in a polymer martix on top of the blue emitting LED. [0006] Crucial factor still limiting the aplication of QD-CCFs is the limited photoluminescence stability of the QD nanocrystals under the influence of high power density excitation by blue LED source. The QDs are degrading within a few minutes to hours upon excitation with high light flux used in emissive LED displays typically in the range of several Watt/cm² power density The limited photo stability of the native QD nanocrystals is attributed to degradation processes caused by the presence of oxygen and/or humidity in the environment. [0007] In order to reduce the QD degradation caused by oxygen and humidity influcence, enclosure and sealing of the QD-CCF in glass sandwich structures under inert conditions proved to be a successful method. However, significant disadvantages of the glass sandwich encapsulation are (i) the increae of the physical thickness of the LED display up to several milimeter due to the presence of additional glass slides; (ii) difficultity to realize patterend pixelated color conversion layers; (iii) heating up of the LED color filter assembly due to poor heat dissipation through the glass sandwich. SUMMARY [0008] In the following, the elements of the invention will be described. These elements are listed with specific embodiments, however, it should be understood that they may be combined in any manner and in any number to create additional embodiments. The variously described examples and preferred embodiments should not be construed to limit the present invention to only the explicitly described embodiments. This description should be understood to support and encompass embodiments which combine two or more of the explicitly described embodiments or which combine the one or more of the explicitly described embodiments with any number of the disclosed and/or preferred elements. Furthermore, any permutations and combinations of all described elements in this application should be considered disclosed by the description of the present application unless the context indicates otherwise. [0009] The present disclosure provides a quantum dot-based color conversion filter coated with a barrier layer, wherein said barrier layer comprises an inorganic material, an organic material or a hybrid material of an inorganic material and an organic material, and has a total thickness in the range from about 20 nm to about 10 µm. [0010] The present disclosure provides an LED array or display comprising (a) a blue and/or UV LED source, and (b) a quantum dot-based color conversion filter of the present invention, (c) optionally, a substrate. [0011] The foregoing paragraphs have been provided by way of general introduction and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0012] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: [0013] Figure 1 shows a schematic representation of QD color conversion filter on blue or UV LED array. [0014] Figure 2 shows examples of barrier layer deposition on planar (2D) and patterned (3D) objects. A) barrier layer deposited on planar (2D) QD-CCF and B) patterned (3D) QD-CCF. [0015] Figure 3 shows a schematic representation of different embodiments of barrier layers, in particular single barrier layer of hybrid material, composite bilayer (organic, inorganic, or hybrid sub-layers) and composite multilayer comprising several bilayers (examples), [0016] Figure 4 shows a comparison of the frequency conversion efficiency (FCE) and external quantum efficiency (EQE) retention between a) non-coated, b) glass sandwich sealed, and c) barrier layer-protected QD-CCF after 24h excitation. [0017] Figure 5 shows a comparison of the FCE retention between a) glass sandwich sealed and b) barrier layer-protected QD-CCF after 24h and 72h excitation. [0018] Figure 6 shows a comparison of the frequency conversion efficiency (FCE) retention of barrier layer-protected QD-CCF after LED excitation at more than 40h at 450nm and 1 W/cm² excitation power density of QD films with no barrier layer and coated with different number of inorganic/ organic bilayers with variable thickness. DETAILED DESCRIPTION OF THE EMBODIMENTS [0019] As discussed above, the present disclosure provides a quantum dot-based color conversion filter coated with a barrier layer. [0020] Said barrier layer comprises a combination of an organic and an inorganic material and/or a hybrid material of an inorganic material and an organic material. [0021] Said barrier layer has a total thickness in the range from about 20 nm to about 10 µm. [0022] In an embodiment, the barrier layer comprises a combination of organic and inorganic material, wherein said “combination” refers to a layered structure, such as a bilayer of an organic material layer and an inorganic material layer. [0023] In an embodiment, the barrier layer is selected from (1) a single layer of a hybrid material of an inorganic material and an organic layer, (2) a bilayer, wherein the inorganic material, the organic material or the hybrid material alternate; or (3) a multilayer. [0024] In an embodiment, where the barrier layer is a bilayer, the organic material or the hybrid material is the top layer of the bilayer. [0025] Examples for bilayers are: an organic material on top of an inorganic material; a hybrid material on top of an inorganic material, or an organic material on top of a hybrid material. [0026] In an embodiment, where the barrier layer is a multilayer, the multilayer comprises m alternating single layers of organic material, inorganic material and/or said hybrid material, or n bilayers, wherein m is 1 to 10, preferably 1 to 3, and n is 1 to 10, preferably 1 to 3. [0027] An example of a multilayer is an organic material on top of a hybrid material on top of an inorganic material. [0028] In an embodiment, the inorganic material of the barrier layer is selected from (i) oxides, preferably Al₂O₃, AlTi_xO_y, HfO₂, In₂O₃, MgO, SiO₂, SrTi_xO_y, Nb₂O₅, Ta₂O₅, TiO₂, Y₂O₃, ZnO, ZnO:Al, ZrO₂, La₂O₃, CeO₂, and combinations thereof, (ii) nitrides, preferably AlN, TiAlCN, TiN, and TaNx, (iii) combinations of inorganic oxides and inorganic nitrides. In an embodiment, where the inorganic material is oxide(s), the barrier layer can be a multilayer of different oxide layers. [0029] In an embodiment, the organic material of the barrier layer is selected from polymers. [0030] The polymers are preferably poly(p-xylylene) and its derivatives (known as parylenes);polysilazanes, and poly(tetrafluoroethylene). [0031] Examples for parylenes are parylene C, parylene D, parylene AF-4, parylene M, parylene E, parylene N, and parylene AM-2. [0032] In an embodiment, the hybrid material is or comprises an oxide and a polymer; a nitride and a polymer; or an oxide, a nitride and a polymer. An example is a hybrid material of TiO₂ and parylene, or Al₂O₃ oxide and parylene. [0033] In an embodiment, where the barrier layer is a single layer of organic material or comprises a layer of organic material, the barrier layer has a thickness in the range from about 0.5 µm to about 10 µm, preferably about 0.5 to about 5 µm, more preferably about 0.5 to about 2 µm. [0034] In an embodiment, where the barrier layer comprises a layer of inorganic material, the layer of inorganic material has a thickness in the range from about 10 nm to about 200 nm, preferably less than about 100 nm, more preferably in the range from about 10 to about 50 nm, even more preferably about 10 to about 20 nm. [0035] In an embodiment, where the barrier layer is a multilayer, the barrier layer has a total thickness below about 10 µm, preferably about 5 µm, more preferably about 2 µm. In an embodiment, where the barrier layer is a bilayer, the barrier layer has a total thickness of preferably about 2 µm. [0036] In an embodiment, the barrier layer has an oxygen permeability of less than 1 [g.mm/m².24h at 90% relative humidity and 35°C] and/or a water permeability of less than 0.02 [g.mm/m².24h at 90% relative humidity and 35°C]. [0037] The barrier layer serves to protect the quantum dot-based color conversion filter from degradation due to oxygen and/or humidity, in particular it reduces the QD degradation caused by oxygen and humidity influcence. [0038] In an embodiment, the barrier layer is deposited by a physical or chemical deposition process, preferably a gas phase deposition process. [0039] Examples are atomic layer deposition (ALD), or molecular layer deposition (MLD) for deposition of inorganic material or hybid material; vapor deposition polymerization (VDP), or chemical vapor deposition (CVD) for deposition of organic material / organic layers. [0040] In an embodiment, pre-formed barrier layers are used which are laminated onto the quantum dot color conversion layer. [0041] In an embodiment, the barrier layer is deposited onto a planar or a patterned quantum dot color conversion layer. [0042] Thereby, the barrier layer is preferably surface conform, or both the quantum dot color conversion layer and the barrier layer are patterned / discontinuous structures. [0043] In an embodiment, quantum dot-based color conversion filter comprises semiconductor quantum dots dispersed in a polymer martix comprising elements of several groups of the periodic system, such as but not limited to: (i) type II/VI semiconductor materials, such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, CdSe/ZnS, CdSe/CdS, CdSe/ZnSe, CdTe/CdS, CdTe/ZnS, CdTe/CdS/ZnS, (ii) type III/V semiconductor materials, such as InP, InAs, GaAs, (iii) group IV−VI elements, such as PbSe, PbS, PbTe, (iv) group IB−(III)−VI elements, such as CuInS₂, AgInS₂, Ag₂Se, Ag₂S; CuInZnS/ZnS, (v) group IV elements, such as silicon QDs (Si QDs), carbon dots (C-dots), graphene QDs (GQDs), and/or (vi) organometallic halide perovskites, such as - Pb-based CsPbX₃; (CH₃NH₃)PbX₃, wherein X = Cl, Br, I, or their halide mixtures, - Sn-based CsSnX₃, wherein X = Cl, Cl_0.5Br_0.5, Br, Br_0.5I_0.5, I, - Ge-based (Rb_xCs_1-x)GeBr₃ ; CsGe(Br_xCl_1-x)₃; CH₃NH₃GeX₃, wherein X = Cl, Br, I, - Bi-based CsA₃Bi₂X₉, wherein X=Cl, Br, I; A= CH₃NH₃; (NH4)₃Bi₂I₉; (CH₃NH₃)₃(Bi₂I₉), - Sb-based (NH₄)₃Sb₂I_xBr_9-x (0<x<9); (CH₃NH₃)₃Sb₂I_{9 ;} Cs₃Sb₂I₉, - InAg-based Cs₂InAgCl₆. [0044] As discussed above, the present disclosure provides an LED array or display. [0045] Said LED array or display comprises (a) a blue and/or UV LED source, and (b) a quantum dot-based color conversion filter of the present disclosure, (c) optionally, a substrate. [0046] In an embodiment, the LED array or display is a micro-LED array or display. [0047] In an embodiment, the LED array or display is a LED TV display, micro display in wearable augmented reality glasses, in mobile devices, or in camera. [0048] The substrate is optional. The QD layer and/or the substrate can be transmissive or semi- transmissive, such as only transmissive for UV and/or blue light. [0049] Note that the present technology can also be configured as described below. (1) A quantum dot-based color conversion filter coated with a barrier layer, wherein said barrier layer comprises a layered combination of an organic and an inorganic material, and/or a hybrid material of an inorganic material and an organic material, and has a total thickness in the range from about 20 nm to about 10 µm. (2) The quantum dot-based color conversion filter of embodiment 1, wherein the barrier layer is selected from (1) a single layer of hybrid material of an inorganic material and an organic material, (2) a bilayer, wherein the inorganic material, the organic material or the hybrid material alternate, and wherein the organic material or the hybrid material is preferably the top layer, more preferably organic material on top of inorganic material; hybrid material on top of inorganic material, or organic material on top of hybrid material; or (3) a multilayer, which can comprise m alternating single layers of organic material, inorganic material and/or said hybrid material, or n bilayers, wherein m is 1 to 10, preferably 1 to 3, and n is 1 to 10, preferably 1 to 3. (3) The quantum dot-based color conversion filter of embodiment 1 or 2, wherein the inorganic material of the barrier layer is selected from (i) oxides, preferably Al₂O₃, AlTi_xO_y, HfO₂, In₂O₃, MgO, SiO₂, SrTi_xO_y, Nb₂O₅, Ta₂O₅, TiO₂, Y₂O₃, ZnO, ZnO:Al, ZrO₂, La₂O₃, CeO₂, and combinations thereof, (ii) nitrides, preferably AlN, TiAlCN, TiN, and TaNx, (iii) combinations of inorganic oxides and inorganic nitrides, wherein, in case the inorganic material is oxide(s), the barrier layer can be a multilayer of different oxide layers. (4) The quantum dot-based color conversion filter of any one of embodiments 1 to 3, wherein the organic material of the barrier layer is selected from polymers, preferably poly(p-xylylene) and its derivatives (parylenes); polysilazanes, and poly(tetrafluoroethylene). (5) The quantum dot-based color conversion filter of any one of embodiments 1 to 4, wherein the hybrid material comprises an oxide and a polymer, a nitride and a polymer, or an oxide, a nitride and a polymer, such as TiO₂ and parylene, or Al₂O₃ oxide and parylene (6) The quantum dot-based color conversion filter of any one of embodiments 1 to 5, wherein the barrier layer has a thickness in the range from about 0.5 µm to about 10 µm, preferably about 0.5 to about 5 µm, more preferably about 0.5 to about 2 µm, for a single layer of organic material; a thickness in the range from about 10 nm to about 200 nm, preferably less than about 100 nm, more preferably in the range from about 10 to about 50 nm, even more preferably about 10 to about 20 nm, for a single layer of inorganic material, and/or a total thickness below about 10 µm, preferably about 5 µm, more preferably about 2 µm for a multilayer, and/or a total thickness of about 2 µm for a bilayer. (7) The quantum dot-based color conversion filter of any one of the preceding embodiments, wherein the barrier layer has an oxygen permeability of less than 1 [g.mm/m².24h at 90% relative humidity and 35°C] and/or a water permeability of less than 0.02 [g.mm/m².24h at 90% relative humidity and 35°C]. (8) The quantum dot-based color conversion filter of any one of the preceding embodiments, wherein the barrier layer is deposited by a physical or chemical deposition process, preferably a gas phase deposition process, such as atomic layer deposition (ALD), molecular layer deposition (MLD), vapor deposition polymerization (VDP), or chemical vapor deposition (CVD), or wherein pre-formed barrier layers are used which are laminated onto the quantum dot color conversion layer. (9) The quantum dot-based color conversion filter of any one of the preceding embodiments, wherein the barrier layer is deposited onto a planar or a patterned quantum dot color conversion layer, wherein the barrier layer is preferably surface conform, or wherein, preferably, both the quantum dot color conversion layer and the barrier layer are patterned. (10) The quantum dot-based color conversion filter of any one of the preceding embodiments, comprising semiconductor quantum dots dispersed in a polymer martix comprising elements of several groups of the periodic system, such as but not limited to: (i) type II/VI semiconductor materials, such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, CdSe/ZnS, CdSe/CdS, CdSe/ZnSe, CdTe/CdS, CdTe/ZnS, CdTe/CdS/ZnS, (ii) type III/V semiconductor materials, such as InP, InAs, GaAs, (iii) group IV−VI elements, such as PbSe, PbS, PbTe, (iv) group IB−(III)−VI elements, such as CuInS₂, AgInS₂, Ag₂Se, Ag₂S; CuInZnS/ZnS, (v) group IV elements, such as silicon QDs (Si QDs), carbon dots (C-dots), graphene QDs (GQDs), and/or (vi) organometallic halide perovskites, such as - Pb-based CsPbX₃; (CH₃NH₃)PbX₃, wherein X = Cl, Br, I, or their halide mixtures, - Sn-based CsSnX₃, wherein X = Cl, Cl_0.5Br_0.5, Br, Br_0.5I_0.5, I, - Ge-based (RbxCs_1-x)GeBr₃ ; CsGe(Br_xCl_1-x)₃; CH₃NH₃GeX₃, wherein X = Cl, Br, I, - Bi-based CsA₃Bi₂X₉, wherein X=Cl, Br, I; A=CH₃NH₃; (NH₄)₃Bi₂I₉; (CH₃NH₃)₃(Bi₂I₉), - Sb-based (NH₄)₃Sb₂I_xBr_9-x (0<x<9); (CH₃NH₃)₃Sb₂I_{9 ;} Cs₃Sb₂I₉, - InAg-based Cs₂InAgCl₆. (11) An LED array or display comprising (a) a blue and/or UV LED source, and (b) a quantum dot-based color conversion filter of any one of the preceding embodiments, (c) optionally, a substrate, wherein the LED array or display is preferably a micro-LED array or display. (12) The LED array or display of embodiment 11, which is a LED TV display, micro display in wearable augmented reality glasses, in mobile devices, or in camera. [0050] In accordance with the present disclosure, the term “quantum dot” refers to semiconductor nanocrystals which can emit pure monochromatic red, green, and blue light. [0051] In accordance with the present disclosure, the term “parylenes” refers to a polymer whose backbone consists of para-benzenediyl rings – C₆H₄– connected by 1,2-ethanediyl bridges –CH₂–CH₂–. It can be obtained by polymerization of para-xylylene H₂C= C₆H₄=CH₂. Parylene N is the un-substituted polymer obtained by polymerization of the para-xylylene intermediate. Derivatives of parylene can be obtained by replacing hydrogen atoms on the phenyl ring and/or the aliphatic bridge by other functional groups, such as halogens (Cl, F) or alkyl groups. A derivate is parylene C which has one hydrogen atom in the aryl ring replaced by chlorine. Another derivate is parylene D, with two Cl substitutions on the ring. Another derivate is parylene AF-4, with the four hydrogen atoms on the aliphatic chain replaced by fluorine atoms. Replacement of one hydrogen on the phenyl ring by a methyl group or an ethyl group yields parylene M and parylene E, respectively. Replacement of one hydrogen by methyl on each carbon of the ethyl bridge yields parylene AM-2, [–(CH₃)CH–(C₆H₄)–(CH₃)CH–]_n. [0052] In accordance with the present disclosure, the terms “color conversion filter” and “color conversion layer” are used interchangeably. [0053] To overcome the problems of the state of the art, the inventors provide the use of thin layers based on organic, inorganic, or hybrid materials as oxygen and humidity barrier coatings on top of the QD-CCF. [0054] These barrier layers are deposited by physical or chemical deposition process, e.g. atomic layer deposition (ALD), molecular layer deposition (MLD), vapor deposition polymerization (VDP), or chemical vapor deposition (CVD) starting typically from gas-phase precursors. Another deposition possibility is utilizing of pre-formed barrier layers which are laminated onto the carrier object. [0055] The use of thin barrier layers of the present disclosure have the following advantages: - High protection efficiency to the QD-CCF against chemical oxidative degradation. - High oxygen and humidity diffusion barrier properties. - Precise thickness control from nanometer thin to several hundred nm, total thickness up to several micrometer. - Good optical transparency of > 99% transmittance in the UV-Vis-NIR spectral range. - Good heat dissipation due to the use of thermally conductive materials and the small layer thickness. - Morphology control with smooth coatings, sharp interfaces, homogenous across large/complex surfaces and defect/pinhole free. - Surface comformality – can be deposited on both planar (2D) and patterend (3D) surfaces. - Low process temperature (below 80°C) compatible with the QD materials. EXAMPLES EXAMPLE 1: Barrier layers for InP-based QD-CCF [0056] To prove the effect of the barrier coatings, the photostability of InP-based QD-CCF was investigated by exposing them to continuous illumination by a blue LED source at 450 nm and 1W/cm² excitation power density for 24 and 72 hours. The frecuency conversion efficiency (FCE) retention and the external quantum efficiency (EQE) retention were considered as photostability characteristic parameters. Samples without protective coating, samples sealed in glass sandwich structures, as well as samples coated by a barrier coating comprising a bilayer of 50 nanometer TiO₂ (ALD) and 5 micrometer Parylene C (CVD), were compared. [0057] In Figure 4, the frequency conversion efficiency (FCE) and external quantum efficiency (EQE) retention of InP QD-CCF after LED excitation during 24 hours at 450nm and 1 W/cm² excitation power density of a) non-coated, b) glass sandwich sealed, and c) ALD/Parylene coated QD films is compared. [0058] In Figure 5, the FCE retention of InP QD-CCF after LED excitation during 24h and 72h at 450nm and 1 W/cm² excitation power density of a) glass sandwich sealed, and b) ALD/Parylene coated QD films is compared. [0059] It is demonstrated that the barrier layer of only ~ 5 micrometer thickness significantly increases the photostability of the InP QD-CCF film. [0060] It is demonstrated that the protective effect of the barrier coating is comparable to the glass sandwich sealing. [0061] In Figure 6, the FCE retention of InP QD-CCF after LED excitation at more than 40h at 450nm and 1 W/cm² excitation power density of QD films with no barrier layer and coated with barrier film comprising different number of inorganic/ organic bilayers or bilayers with variable thickness is compared. [0062] It is demonstrated that the photostability is significantly improved.

Claims

Claims 1. A quantum dot-based color conversion filter coated with a barrier layer, wherein said barrier layer comprises a layered combination of an organic and an inorganic material, and/or a hybrid material of an inorganic material and an organic material, and has a total thickness in the range from about 20 nm to about 10 µm. 2. The quantum dot-based color conversion filter of claim 1, wherein the barrier layer is selected from (1) a single layer of hybrid material of an inorganic material and an organic material, (2) a bilayer, wherein the inorganic material, the organic material or the hybrid material alternate, and wherein the organic material or the hybrid material is preferably the top layer, more preferably organic material on top of inorganic material; hybrid material on top of inorganic material, or organic material on top of hybrid material; or (3) a multilayer, which can comprise m alternating single layers of organic material, inorganic material and/or said hybrid material, or n bilayers, wherein m is 1 to 10, preferably 1 to 3, and n is 1 to 10, preferably 1 to 3. 3. The quantum dot-based color conversion filter of claim 1 or 2, wherein the inorganic material of the barrier layer is selected from (i) oxides, preferably Al₂O₃, AlTi_xO_y, HfO₂, In₂O₃, MgO, SiO₂, SrTi_xO_y, Nb₂O₅, Ta₂O₅, TiO₂, Y₂O₃, ZnO, ZnO:Al, ZrO₂, La₂O₃, CeO₂, and combinations thereof, (ii) nitrides, preferably AlN, TiAlCN, TiN, and TaNx, (iii) combinations of inorganic oxides and inorganic nitrides, wherein, in case the inorganic material is oxide(s), the barrier layer can be a multilayer of different oxide layers. 4. The quantum dot-based color conversion filter of any one of claims 1 to 3, wherein the organic material of the barrier layer is selected from polymers, preferably poly(p-xylylene) and its derivatives (parylenes); polysilazanes, and poly(tetrafluoroethylene). 5. The quantum dot-based color conversion filter of any one of claims 1 to 4, wherein the hybrid material comprises an oxide and a polymer, a nitride and a polymer, or an oxide, a nitride and a polymer, such as TiO₂ and parylene, or Al₂O₃ oxide and parylene 6. The quantum dot-based color conversion filter of any one of claims 1 to 5, wherein the barrier layer has a thickness in the range from about 0.5 µm to about 10 µm, preferably about 0.5 to about 5 µm, more preferably about 0.5 to about 2 µm, for a single layer of organic material; a thickness in the range from about 10 nm to about 200 nm, preferably less than about 100 nm, more preferably in the range from about 10 to about 50 nm, even more preferably about 10 to about 20 nm, for a single layer of inorganic material, and/or a total thickness below about 10 µm, preferably about 5 µm, more preferably about 2 µm for a multilayer, and/or a total thickness of about 2 µm for a bilayer. 7. The quantum dot-based color conversion filter of any one of the preceding claims, wherein the barrier layer has an oxygen permeability of less than 1 [g.mm/m².24h at 90% relative humidity and 35°C] and/or a water permeability of less than 0.02 [g.mm/m².24h at 90% relative humidity and 35°C]. 8. The quantum dot-based color conversion filter of any one of the preceding claims, wherein the barrier layer is deposited by a physical or chemical deposition process, preferably a gas phase deposition process, such as atomic layer deposition (ALD), molecular layer deposition (MLD), vapor deposition polymerization (VDP), or chemical vapor deposition (CVD), or wherein pre-formed barrier layers are used which are laminated onto the quantum dot color conversion layer. 9. The quantum dot-based color conversion filter of any one of the preceding claims, wherein the barrier layer is deposited onto a planar or a patterned quantum dot color conversion layer, wherein the barrier layer is preferably surface conform, or wherein, preferably, both the quantum dot color conversion layer and the barrier layer are patterned. 10. The quantum dot-based color conversion filter of any one of the preceding claims, comprising semiconductor quantum dots dispersed in a polymer martix comprising elements of several groups of the periodic system, such as but not limited to: (i) type II/VI semiconductor materials, such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, CdSe/ZnS, CdSe/CdS, CdSe/ZnSe, CdTe/CdS, CdTe/ZnS, CdTe/CdS/ZnS, (ii) type III/V semiconductor materials, such as InP, InAs, GaAs, (iii) group IV−VI elements, such as PbSe, PbS, PbTe, (iv) group IB−(III)−VI elements, such as CuInS₂, AgInS₂, Ag₂Se, Ag₂S; CuInZnS/ZnS, (v) group IV elements, such as silicon QDs (Si QDs), carbon dots (C-dots), graphene QDs (GQDs), and/or (vi) organometallic halide perovskites, such as - Pb-based CsPbX₃; (CH₃NH₃)PbX₃, wherein X = Cl, Br, I, or their halide mixtures, - Sn-based CsSnX₃, wherein X = Cl, Cl_0.5Br_0.5, Br, Br_0.5I_0.5, I, - Ge-based (RbxCs_1-x)GeBr₃ ; CsGe(BrxCl_1-x)₃; CH₃NH₃GeX₃, wherein X = Cl, Br, I, - Bi-based CsA₃Bi₂X₉, wherein X=Cl, Br, I; A=CH₃NH₃; (NH4)₃Bi₂I₉; (CH₃NH₃)₃(Bi₂I₉), - Sb-based (NH₄)₃Sb₂I_xBr_9-x (0<x<9); (CH₃NH₃)₃Sb₂I_{9 ;} Cs₃Sb₂I₉, - InAg-based Cs₂InAgCl₆. 11. An LED array or display comprising (a) a blue and/or UV LED source, and (b) a quantum dot-based color conversion filter of any one of the preceding claims, (c) optionally, a substrate, wherein the LED array or display is preferably a micro-LED array or display. 12. The LED array or display of claim 11, which is a LED TV display, micro display in wearable augmented reality glasses, in mobile devices, or in camera.