Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133617—Illumination with ultraviolet light; Luminescent elements or materials associated to the cell
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
  • C09K11/025—Use of particular materials as binders, particle coatings or suspension media therefor non-luminescent particle coatings or suspension media
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/66—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing germanium, tin or lead
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
  • C09K11/66—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing germanium, tin or lead
  • C09K11/664—Halogenides
  • C09K11/665—Halogenides with alkali or alkaline earth metals
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/133509—Filters, e.g. light shielding masks
  • G02F1/133514—Colour filters
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
  • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/851—Wavelength conversion means
  • H10H20/8511—Wavelength conversion means characterised by their material, e.g. binder
  • H10H20/8512—Wavelength conversion materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/30—Devices specially adapted for multicolour light emission
  • H10K59/38—Devices specially adapted for multicolour light emission comprising colour filters or colour changing media [CCM]
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
  • H10K2102/301—Details of OLEDs
  • H10K2102/331—Nanoparticles used in non-emissive layers, e.g. in packaging layer

Definitions

• the present invention relates to the field of luminescent crystals (LCs) .
• the invention provides a display device.
• Displays are an integral part of our world and are implemented in different sizes into a broad range of electronic devices.
• color displays are very popular giving rise to various technologies for maximizing their color gamut, i.e. the broad spectrum of colors that can be displayed.
• LCD liquid crystal display
• the color gamut of such displays is limited to the color spectrum emitted by the respective light source, which light source is typically not centred to the primary red, blue, and green wavelengths, and thus renders the displaying of highly saturated colors impossible .
• a display device comprising a light emitter comprising a set of light emitter portions, and a color conversion layer comprising a set of conversion layer portions, at least one of the conversion layer portions of the set is configured to emit light of a wavelength in response to an excitation with light emitted by at least one corresponding light emitter portion of the set.
• the at least one light emitter portion of the set is configured to emit light with an excitation wavelength. This emitted light excites luminescent crystals in the at least one color conversion layer which in response to the excitation emit light of a wavelength different to the shorter excitation wavelength of preferably blue light of a wavelength in a range between 400 and 490 nm.
• the subject color conversion portion com- prises luminescent crystals for emitting the light of the defined wavelength in response to the excitation.
• the luminescent crystals may be embedded in a solid polymer composition comprising a polymer next to the luminescent crystals.
• the solid polymer composition contributes to the color conversion portion in form of a film.
• Suitable luminescent crystals are of the per- ovskite structure.
• perovskite structures are known per se and described as cubic, pseudocubic, tetragonal or orthorhombic crystals of general formula M 1 M 2 X3, where M 1 are cations of coordination number 12 (cuboctaeder ) and M 2 are cations of coordination number 6 (octaeder) and X are anions in cubic, pseudocubic, tetragonal or ortho- rhombic positions of the lattice.
• selected cations or anions may be replaced by other ions (stochastic or regularly) , still maintaining its crystalline structure.
• the manufacturing of such luminescent crystals is known, e.g. from Protesescu et al. (Nano Lett., 2015, 15, 3692-3696).
• the luminescent crystals are selected from compounds of formula (I) :
• M 1 represents Cs
• M 2 represents Pb
• X independently represents anions selected from the group consisting of Cl, Br, I, cyanide and thio- cyanate,
• X may be selected from one of the above named anions or may be a combina ⁇ tion of more than one of the above anions.
• thio- cyanate shall include both resonance structures, i.e. thiocyanate and isothiocyanate .
• M 1 may be doped with up to 30 mol% of one or more other metals hav ⁇ ing coordination number 12 within the perovskite structure.
• M 1 is doped with up to 10 mol% of one or more of such metals.
• Suitable metals 1 are selected from the group consisting of Rb, K, Na, and Li.
• M 2 may be doped with up to 30 mol% of one or more other metals having coordination number 6 within the perovskite structure.
• M 2 is doped with up to 10 mol% of one or more of such metals.
• Suitable metals M 2 are selected from the group consisting of Ge, Sn, Sb and Bi .
• X is selected from one of Cl, Br and I; or X represents independently two of Cl, Br and I; or X represents Cl, Br and I.
• the amount of Cl, Br, I, cyanide and thiocyanate may be determined by routine experiments such as MS or XRF, which are known in the field; the small Cl anion shifts the emission towards the blue, the large I anion towards the red and the medium sized Br anion towards the green part of the visible spectrum.
• the luminescent crystals are of size between 3 nm and 3000 nm, and in particular between 5 and 100 nm. Accordingly, cesium lead halide nanocrystals and / or doped cesium lead halide nanocrystals, which are of the perovskite structure, are preferably used as lumi ⁇ nescent crystals.
• the emission of light with a specific wavelength depends on a selection of the material of the luminescent crystals within the above constraints, and may depend on a size of the luminescent crystals.
• the color conversion layer comprises a set of at least one and preferably multiple color conversion layer portions.
• a conversion layer portion is understood as a portion that individually converts the blue light from the assigned light emitter portion into a dedicated color.
• the film of a conversion layer portion solely comprises luminescent crystals of one type se- lected according to the formula (I) for emitting light of the dedicated color.
• the light emitter comprises a set of at least one, and preferably multiple light emitter portions.
• a light emitter portion is understood as a portion that is individually addressable and / or controllable to emit light. Multiple light emitter portions can hence be con- . trolled individually such that, for example, individual ones of these light emitter portions can be controlled to emit light while at the same time the remaining ones can be controlled not to emit light or to emit light of different intensity.
• each light emitter portion is provided with individual contacts for receiving a control signal.
• multiple light emitter portions are provided in the corresponding set and multiple conversion layer portions are provided in the corresponding set.
• a dedicated light emitter portion is assigned to one of the conversion layer portions to excite the luminescent crystals comprised
• the number of light emitter portions is equal to the number of conversion layer portions, there is a one-to-one relation between the light emitter portions and the conversion layer portion, such that each conversion layer portion has its own assigned light emitter portion.
• the number of light emitter portions exceeds the number of con- version layer portions, such that each conversion layer portion has an assigned light emitter portion, while a number of light emitter portions do not have an assigned conversion layer portion.
• These remaining light emitter portions emit light that may not be converted by any color conversion portion, but may be used for adding the excitation wavelength to the overall spectrum of emitted light, e.g. as part of a pixel as will be introduced later on, which pixel is tunable as to emit light of variable colors / wavelengths and which pixel contributes to a display.
• a single light emitter portion is provided in the corresponding set in combination with multiple conversion layer portions.
• other control ele- ments - such as liquid crystals - are provided in a path of the excitation light towards each conversion layer portion in order to control an excitation per conversion layer portion.
• each conversion layer portion comprises a film.
• Each film comprises a solid polymer composition, wherein the solid polymer composition comprises the assigned luminescent crystals.
• a film is defined having at least one of a length and a width - and preferably both - exceeding a height / thickness of the film.
• a film in this context may also be referred to as an element.
• Dimensions of the film may include a thickness of the film being one of less, equal or more than each of a length and a width of the film.
• the color conversion layer comprises a first conversion layer portion including a first film.
• the first film is configured to emit red light, preferably in response to an excitation with the blue light stemming from the light emitter.
• the first film comprises a first solid polymer composition which in turn comprises first luminescent crystals.
• the red light emitting property of the first luminescent crystals preferably is a result from the proper selection of the material composition at a defined size. Red light is considered light with a peak wavelength in the range between 590 nm and 700 nm.
• the color conversion layer preferably comprises in addition to the first conversion layer portion a second conversion layer portion including a second film.
• the second film is configured to emit green light, preferably in response to an excitation with the blue light stemming from the light emitter.
• the second film comprises a second solid polymer composition which in turn comprises second luminescent crystals.
• the green light emitting property of the second luminescent crystals preferably is a result from the proper selection of the material composition at a defined size.
• the green luminescent crystals preferably have a different chemical composition and / or a different size than the red luminescent crystals. Green light is considered light with a peak wavelength in a range between 490 nm and 570 nm.
• one or more of the first and the second film may comprise scattering particles, such as Ti0 2 or Zr0 2 .
• the first luminescent crystals are of above formula (I) and the corresponding size
• the second luminescent crystals are of the above formula (I) and of the corresponding size.
• the first luminescent crystals are of formula (1-1)
• Cs, Pb is optionally doped with up to 30mol% as described above, Z represents one or more of CI, Br.
• the first luminescent crystals are of formula CsPbBr x l3-x, where 0 ⁇ x ⁇ 2 and / or of formula CsPbCl y Br 3 - y - z Iz, where 0 ⁇ y ⁇ l, 2 ⁇ z ⁇ 3-y.
• the second luminescent crystals are of formula (1-2)
• Cs, Pb is optionally doped with up to 30mol% as described above,
• Z represents one or more of CI, I.
• the second luminescent crystals are of formula CsPbCl y Br z l3-y-z, where 0 ⁇ y ⁇ l, l ⁇ z ⁇ 3-y, and / or of formula CsPbBr x i3-x, where 2 ⁇ x ⁇ 3.
• the first luminescent crystals designed for emitting red light are compounds of formula CsPbBr x I 3 - x whereby 0 ⁇ x ⁇ 2, or of formula CsPbClyBr3-y-zI z , where 0 ⁇ y ⁇ l, 2 ⁇ z 3-y, and show a peak wavelength in the range between 590 ran and 700 nm, preferably with an FWHM between 15 and 50 nm.
• the second luminescent crystals are designed for emitting green light are compounds of formula CsPbCl y Br 2 l3-y-z, whereby 0 ⁇ y ⁇ l, Kz ⁇ 3-y, or of formula CsPbBr x I 3 - x , whereby 2 ⁇ x 3, and show a peak wavelength in the range between 490 nm and 570 nm, preferably with an FM H between 15 and 50 nm.
• a size of each of the first and second luminescent crystals is between 5 nm and 100 nm.
• the first film comprises first luminescent crystals only and is free from second luminescent crystals, while the second film comprises second luminescent crystals only and is free from first lumines- cent crystals.
• the first film comprises first luminescent crystals only and is free from any other luminescent crystals, and the second film comprises second luminescent crystals only and is free from any other luminescent crystals.
• the present color conversion layer provides for a spatial separation of the first and the second luminescent crystals.
• the separation is achieved by an ar- rangement of the first luminescent crystals in the dedicated first film only and by an arrangement of the second luminescent crystals in the dedicated second film only, and possibly in addition by means of a gap between the first film and second film.
• an exchange of cations and anions between the first luminescent crystals and the second luminescent crystals is avoided.
• the fabrication of each of the films preferably is performed in a separate suspension, a mixing of first luminescent crystals and second luminescent crystals in a common suspension is avoided.
• Such mixing would result in a conversion of the origin first and second luminescent crystals into different luminescent crystals by way of reaction / recombination based on the above mentioned ion exchange.
• such different lumines- cent crystals would emit light of a different wavelength than the first or second luminescent crystals.
• a resulting formulation of above red and green luminescent crystals would, depending on the effective compo- sitions of the red and green particles emit a light with a wavelength between the original red and green emission peaks.
• the first and the second luminescent crystals are separated at the stage of manufacturing, and hence are added to different portions of the suspension resulting in the above first and second films after hardening / curing / drying.
• the luminescent crystals emitting green light do not interact with luminescent crystals emitting red light (also referred to as red luminescent crystals).
• Each portion of the suspension preferably com- prises the assigned luminescent crystals, a solvent, a ligand, and a polymer.
• the resulting films are solid films, an interaction of the first luminescent crystals in the first film with the second luminescent crystals in the second film is avoided. In case of an ad- jacent arrangement of the first film and the second film, such interaction is avoided to a large extent, given that only cations / anions of the LCs residing at the interface of the first and the second film may recombine.
• the present device provides an excellent pho- toluminescence quantum yield.
• Quantum yield is known in the field and relates to the amount of times a specific event occurs per photon that is absorbed in the system.
• quantum yield refers to the "photoluminescence quantum yield” of the described substance and both terms are used with identical meaning.
• the "photoluminescence quantum yield” defines how many photons of a higher wavelength (lower energy) are emitted by the described system per photon that is absorbed by the system.
• the quantum yield of the solid polymer compositions suggested to be used in the present films is in total > 60%, and preferably > 80%, most preferably > 90%, preferably when excited by blue light.
• the FWHM (Full Width at Half Maximum) of the solid polymer composition of each of the first film and the second film for visible emissions is ⁇ 50nm, preferably, ⁇ 40nm, and most preferably ⁇ 30 nm, each in the range of red or green light respectively.
• an FWHM for the emission peak at 500 nm of 22 nm can be observed, at the same time measuring a high luminescence quantum yield of e.g. 76%.
• Embodiments of the present device comply with RoHS ("Restriction of Hazardous Substances") Directive by the European Union.
• the applicable di- rective 2011/65/EU generally restricted the use of the following elements: Lead (Pb) ⁇ 1000 ppm by weight, Mercury (Hg) ⁇ 1000 ppm, Cadmium (Cd) ⁇ 100 ppm, Hexavalent chromium (Cr6+) ⁇ 1000 ppm, Polybrominated biphenyls (PBB) ⁇ 1000 ppm, Polybrominated diphenyl ether (PBDE) ⁇ 1000 ppm.
• PBB Polybrominated biphenyls
• PBDE Polybrominated diphenyl ether
• the limit for Pb according to the RoHS Directive Version 2 is 1000 ppm, which is achieved in the present embodiments on a per-film ba- sis, and is achieved in total for each conversion layer portion and the color conversion layer as such.
• the total Pb concentration for each conversion layer portions according to any of the present embodiments is below 1000 ppm, more preferably in a range of 30 ppm and 1000 ppm, and most preferably between 100 ppm and 900 ppm.
• the RoHS compliance may be achieved by selecting an appropriate concentration of the first and second luminescent crystals in the first and second film respectively, and by dimensioning a thickness of the first and the second film.
• the subject concentration can be measured by MS or XRF measurements.
• a concentration of the respective luminescent crystals with respect to a polymer matrix of the solid polymer composition per film is within a range of 0,01 wt% and 0,5 wt%.
• the concentration of the first luminescent crystals preferably is between 0,01 wt% and 0,5 wt%, preferably between 0,05 wt% and 0,38 wt%, most preferably between 0.1 wt% and 0.35 wt%; and preferably between 0,01 wt% and 0,50 wt%, preferably between 0,05 wt% and 0,31 wt%, most preferably between 0.1 wt% and 0.28 wt% for a second film emitting green light.
• the upper limit of this concentration range supports RoHS compliance on the one hand, while the lower limit of this con ⁇ centration range provides for a sufficient emission at reasonable film thicknesses of the conversion layer portions on the other hand.
• a thickness per film is between 5 pm and 500 pm.
• a thickness of the film is between 5 m and 500pm, for absorbing the blue light emit- ted by the corresponding light emitter portion of the set.
• a thickness of a first film emitting red light is between 5 pm and 500 pm, more preferably between 10 pm and 500 pm, most preferably between 40 pm and 200 pm and a thickness of a second film emitting green light is between 30 pm and 500 pm, preferably between 50 pm and 500 pm, most preferably between 70 pm and 400 pm.
• the amount of luminescent crystals in respect to the film surface is very low, typically in the range of below 2.0 g/m 2 and very preferably below 1.5 g/m 2 .
• the same absorption rate of such films can only be achieved by a roughly 1.8 times higher amount of material. For example, it was found that absorption of 99.9% of blue light requires 2.2 g/m 2 for CdSe compared to 1.2 g/m2 for CsPbBr3 only.
• the film comprising 1.0 g/m 2 to 1.5 g/m 2 luminescent crystals (such as 1.2 g/m 2 CsPbBr 3 ) , has a thickness of around 400 to 500 ⁇ , in particular 500 ⁇ , and absorbs completely the blue light of the corresponding light emitter portion (in particular 99.9% of it).
• This layer emits light of a longer wavelength, in particular green or red light.
• the conversion layer portion of the present invention provides both, a good quantum yield, low peak FWHM and RoHS conformity. This is achieved by selecting appropriate materials for LCs, applying appropriate LC concentrations and film thicknesses and at the same time arranging the different LCs in different films, as a result separating the LCs from each other to avoid ion exchange reactions.
• both of the first and the sec- ond film has a haze between 10 and 99%.
• a haze may be introduced by scattering particles with RI > 2.0 and size of 100 - 1000 nm, or by microstructures or microcrystal- line polymer structures.
• a concentration of scattering particles in the color conversion layer preferably is be- tween 1 and 40 wt%, and preferably between 3 and 20 wt% .
• the films of the various conversion layer portions of the set are separated from each other, e.g. by a gap filled with air or by a different solid material (e.g. such as black matrix structures in LCD displays) .
• the films of the various conversion layer portions of the set are arranged adjacent to each other.
• the color conversion layer not necessarily requires continuous portions thereof. Instead, separate portions, preferably arranged on the same level, may contribute to the color conversion layer .
• the portions of the light emitter are separated from each other, e.g. by a gap filled with air or by a different solid material (e.g. such as black matrix structures in LCD displays) .
• the light emitter not necessarily requires continuous portions thereof. Instead, separate light emitter por ⁇ tions, preferably arranged on the same level, may contribute to the light emitter.
• the light emitter has a flat shape having at least one of a length and a width - and preferably both - exceeding a height / thickness of the light emitter. This preferably is also true for individual light emitter portions contributing to the light emitter.
• each conversion layer portion is attached to the light emitter portion assigned.
• a substrate is provided for supporting the light emitter.
• the light emitter portions are attached to the substrate, e.g. by bonding or an attachment layer inbetween, which may supply control signals for the light emitter portions.
• the substrate may be a polymer substrate, such as a polyethylenterephthalat substrate or an inorganic material such as glass.
• the substrate preferably is a sheet- like structure, preferably of a length and a width both exceeding a height / thickness of the substrate, and preferably both exceeding its thickness at least ten times.
• the light emitter is arranged between the color conversion layer and the substrate.
• one or more barrier layers may be provided, preferably each barrier layer having a water vapor transmission rate of less than 0.2 (g*mm) / (m A 2*day) at a temperature of 20 - 50°C / 90% relative humidity and atmospheric pressure.
• the device may include a barrier layer on top of an otherwise exposed surface of the color conversion layer.
• Such barrier layer may in particular have a low water vapour transmission rate in order to avoid a degradation of the LCs in the film/s in response to being exposed to water.
• the barrier layer may in one embodiment be permeable for O2, or, in a different embodiment, may also be impermeable for oxygen.
• the barrier layer is transmissive for light, and preferably, such barrier layer may be present in the form of a single layer or in the form of multilayers.
• the bar- rier layer preferably comprises organic polymers and / or inorganic materials. Suitable organic polymers may be selected from the group consisting of polyvinylidene chlorides (PVdC), cyclic olefin copolymer (COC) , high-density polyethylene (HDPE) ; suitable inorganic materials may be selected from the group consisting of metal oxides, SiO x , SixNy. Most preferably, a polymer barrier layer comprises materials selected from the group of PVdC and COC.
• the color conversion layer is arranged between the light emitter and the bar- rier layer.
• the barrier layer preferably encompasses the color conversion layer as a whole or the conversion layer portions. Encompassing may refer to a covering of the color conversion layer after having deposited the color conversion layer onto the light emitter.
• the barrier layer may also directly cover light emitter portions that are not covered by an assigned conversion layer portion.
• the substrate if any may also act as a barrier layer such that an exposed surface of the substrate may not necessarily be covered by a dedicated barrier layer. In a different embodiment, however, and in particular when the substrate is transmissive to water, an otherwise exposed surface of the substrate may also be covered by a barrier film.
• the substrate, the light emitter, the color conversion layer, and the barrier layer are vertically stacked, i.e. orthogonal to their plane extensions.
• the various films of the con- version layer portions are arranged lateral to each other .
• the display device may have a planar extension with a diagonal of more than 3 inches, e.g. as a display of a handhelds or preferably with a diagonal of more than 15 inches as a display for a computer or a TV.
• the above requires a rectangular plane extension of each of the substrate if any, the first film and the second film, it is emphasized that the scope is not limited to rectangular components.
• the display device may also take a different basic shape, such as a shape of a circle, an ellipse, etc.
• one or more intermediate layers in particular of light transmissive property, may be arranged between one or more of the substrate and the light emitter, the light emitter and the color conversion layer, the color conversion layer and the barrier layer, if any. It is noted that the size of each individual piece of the film of a conversion layer portion preferably is below a size that is detectable by eye in the final application (comparable to the pixel size in LCD screens) .
• any of above embodiments of the device are not limited to a single first film and a single second film. It is preferred, that multiple first films comprising the first solid polymer composition and multiple sec- ond films comprising the second solid polymer composition are arranged on the same level and contribute to the color conversion layer.
• an arrangement of a conversion layer portion in combination with an assigned light emitter portion is considered as a sub-pixel.
• a pixel is formed by a first sub-pixel including the first film with red luminescent crystals, a second sub- pixel including the second film with green luminescent crystals, and a third sub-pixel that does not include a film with any luminescent crystals, but that emits blue light in case the assigned light emitter portion is activated.
• the color conversion layer may comprise portions that do not include a film comprising luminescent crystals, i.e. the portion that is part of the third sub-pixel. Such portions may, for example, solely include a non-opaque polymer.
• non-lumines- cent portions provide for a transmission of the light, preferably the blue light that is emitted by the light emitter portion underneath.
• Those three sub-pixels may form a pixel of the display device.
• an area ratio between the three sub-pixles may differ from 1:1:1.
• the display device may have multiple pixels.
• the color con- version layer preferably comprises a multitude of first films, a multitude of second films, and a multitude of non-luminescent portions, a single one of each contributing to one pixel.
• each light emitter portion is represented by an organic light emitting diode (OLED) .
• OLED organic light emitting diode
• the OLED may be embodied as an integrated layered element, possibly including a top glass layer, onto which the assigned color conversion layer may be arranged, e.g. by ink jet printing.
• the display de- vice is an OLED display.
• Multiple pixels as defined above are comprised in the OLED display, each pixel comprising three OLEDs as light emitter portions, each OLED emitting blue light.
• each light emitter portion is represented by an inorganic light emitting diode (LED) .
• the LED may be embodied as an integrated layered element, possibly including a top glass layer, onto which the assigned color conversion layer may be arranged, e.g. by ink jet printing.
• the display device is a LED display. Multiple pixels as defined above are comprised in the LED display, each pixel comprising three or more LEDs as light emitter portions, each LED emitting blue light.
• the display device is a liquid crystal display (LCD) , wherein the light emitter is a backlight of the liquid crystal display.
• the color conversion layer may replace the color filter layer of a conventional display that solely filters incoming light, but does not emit light in response to an excitation. Accordingly, this display device addi- tionally may comprise a first polarizer, a first substrate, a number of liquid crystals, a second substrate, and a second polarizer.
• the display device may be used as a display of a mobile or stationary computing, telecommunication, or television device.
• Luminescent crystals preferably are made from semiconductor materials.
• a luminescent crystal shall include a quantum dot, typically in the range of 3 - 12 nm and a nanocrystal of up to 100 nm and a luminescent crystal of up to 3 pm.
• luminescent crystals are approximately isometric (such as spherical or cubic) . Particles are considered approximately isometric, in case the aspect ratio (longest : shortest direction) of all 3 orthogonal dimensions is 1 - 2.
• LCs show, as the term in- dicates, luminescence or more specifically defined photo- luminescence.
• a luminescent crystal typically is a single-crystalline particle spatially separated from other particles due to the presence of a surfactant. It is a semiconducting ma- terial which exhibits a direct bandgap (typically in the range 1.1 - 3.8 eV, more typically 1.4 - 3.5 eV, even more typically 1.7 - 3.2 eV) .
• a direct bandgap typically in the range 1.1 - 3.8 eV, more typically 1.4 - 3.5 eV, even more typically 1.7 - 3.2 eV
• the formed exciton then radiatively recombines in the form of photolumines ⁇ cence, with maximum intensity centered around the LC bandgap value and exhibiting photoluminescence quantum yield of at least 1 %.
• LC could exhibit electroluminescence.
• LCs do not exhibit mechano-luminescence (e.g. piezolumines- cence) , chemiluminescence, electrochemiluminescence nor thermoluminescence .
• a quantum dot particularly relates to a semiconductor nanocrystal, which has a diameter typically between 3 - 12 nm. In this range, the physical diameter of the QD is smaller than the bulk excitation Bohr radius, causing quantum confinement effect to predominate.
• the electronic states of the QD, and therefore the bandgap are a function of the QD composition and physical size, i.e. the color of absorption/emission is linked with the QD size.
• the optical quality of the QDs sample is directly linked with their homogeneity (more monodisperse QDs will have smaller FWHM of the emission) .
• QDs are a specific sub-group of nanocrystals , defined in particular by its size and size distribution. Properties of the QDs are directly linked with these parameters, distinguishing them from nanocrystals.
• Each of the first and the second solid poly- mer compositions comprise in addition to the luminescent crystals of the respective type, a hardened, cured or dried polymer, preferably of the same type in both the first solid polymer composition and the second solid polymer composition, including an organic and / or an inor- ganic synthetic material.
• the polymer is selected from the group of acrylate polymers (including copolymers), carbonate polymers, sulfone polymers, epoxy polymers, vinyl polymers, urethane polymers, ester polymers, cyclic olefin copolymers, styrene polymers and silicone polymers.
• the polymer is selected from the list of acrylate polymers (including co-poly- mers) , polystyrene, silicones and cyclic olefin copolymers. Furthermore the polymer can be linear or cross- linked .
• the polymer of the first film differs from the polymer of the second film in order to avoid potential intermixing of the first film with the second film.
• the hardened / cured / dried polymer preferably is light transmissive , i.e. non-opaque for allowing light emitted by the luminescent crystals, and possible light of a light source used for exciting the luminescent crystals to pass.
• one or more of the first and second polymer compositions comprises a surfactant selected from the group of non-ionic, anionic, cationic and zwitter- ionic surfactants; preferably selected from the group of amine or carboxy terminated surfactants.
• surfactant "ligand”, “disper- sant” and “dispersing agent” are known in the field and have essentially the same meaning. In the context of the present invention, these terms denote an organic substance, other than a solvent, which is used in suspen- sions or colloids to improve the separation of particles and to prevent agglomeration or settling. Without being bound to theory, it is believed that surfactants are physically or chemically attached on the particle surface either before or after adding the particles to the sol- vent and thereby provide the desired effects.
• surfactants includes polymer materials and small molecules; surfactants typically contain polar end-groups and apolar end-groups. In the context of the present invention, solvents (e.g. toluene) are not considered surfactants .
• a "suspension" as used above in the aspect related to manufacturing is known and relates to a heterogeneous fluid of an internal phase (i.p.) that is a solid and an external phase (e.p.) that is a liquid.
• the external phase comprises one or more dispersants/surfac- tants, optionally one or more solvents and optionally one or more pre-polymers or dissolved polymers.
• each type of luminescent crystal first, second
• Further processing includes the application of one or each portion of suspension to the desired area on the substrate.
• the lumincescent crystals of a conversion layer portion are embedded in a matrix such as a polymer matrix or an inorganic matrix, in order to spatially separate the first LCs from each other in the first film, and the second LCs from each other in the second film.
• a matrix such as a polymer matrix or an inorganic matrix
• the resulting "LC/QD composite” denotes a solid inorganic/organic composite material comprising LCs/QD, surfactant and a matrix and contributes to the respective first or second film.
• FIG. 1 shows an exploded view of a display device according to an embodiment of the present invention
• Fig. 2 shows an exploded view of a liquid crystal display according to a preferred embodiment of the invention
• Fig. 3 shows an exploded view of a display device according to another embodiment of the present invention.
• Fig. 4 shows the light spectrum passing through a color conversion layer embodied as a polymeric foil containing green or red emitting LCs according to an embodiment of the present invention, when excited with the 450 niti blue backlight of a Samsung SUHD TV (Model UE48JS8580T) .
• FIG. 1 illustrates an exploded view of a display device according to an embodiment of the present invention.
• the display device comprises a light emitter comprising a set 3 of three light emitter portions 31, 32, 33 with each having a front side FS and a back side BS .
• the display device comprises a color conversion layer 2.
• the conversion layer comprises a set 2 of a first and a second conversion layer portion 21, 22, wherein each conversion layer portion 21, 22, of the set corresponds to a light emitter portion 31, 32 of the set 3.
• the set of conversion layer portions 2 can be arranged directly on a front side FS of the set of light emitter portions 3, wherein each conversion layer portion 21, 22 of the set 2 is in direct contact with the corresponding light emitter portion 31, 32 of the set 3, or there can be layers, e.g. for protecting the set 2 of conversion layers, interposed between the set of conversion layer portions 21, 22 and light emitter portions 31, 32.
• a conversion layer portion 21, and the corre- sponding light emitter portion 31 can be arranged adjacent to or spaced to a next pair of conversion layer portion 22 and corresponding light emitter portion 32.
• Each of the first conversion layer portion 21, the second conversion layer portion 22, and the set 3 of light emitter portions have a length along the x-axis, a width along the y-axis, and a thickness along the z- axis .
• the first conversion layer portion 21 comprises a first solid polymer composition in form of a first film.
• the first solid polymer composition at least comprises a first polymer and first luminescent crystals 11, wherein the first luminescent crystals 11 are selected from compounds of formula (I) as defined herein.
• the first luminescent crystals 11 have a size between 3 nm and 3000 nm. In response to excitation by the corresponding first light emitter portion 31, the first luminescent crystals 11 emit red light RD.
• the second conversion layer portion 2 comprises a second solid polymer composition in form of a second film.
• the second solid polymer composition comprises at least a second polymer and second luminescent crystals 12.
• the second luminescent crystals 12 are selected from compounds of formula (I) as defined herein.
• the second luminescent crystals 12 have a size between 3 nm and 3000 nm. In response to excitation by the corresponding second light emitter portion 32, the second luminescent crystals 12 emit green light GR.
• First and second polymer preferably but not necessarily are the same.
• the first luminescent crystals 11 are excited and emit red light RD.
• the second luminescent crystals 12 are excited and emit green light GR.
• the third light emitter portion 33 is emitting blue light BL and does not correspond to one of the conversion layer portions of the set.
• the light emitter por- tion 31, 32, 33 of the set can be controlled independently, in particular the intensity of the individual light emitter portions 31, 32, 33 can be controlled individually .
• the mixture of the emitted light in three colors gives the color hue that is emitted by the display device.
• the present device can preferably be used as a building block of a display screen.
• Fig. 2 shows a preferred embodiment of the present invention, wherein the display device can be used as a building block for an LCD screen.
• the LCD screen essentially comprises a first 52 and a second 54 substrate, in particular glass substrates, wherein a layer of liquid crystals 53 is interposed between the first substrate 52 and the second substrate 54.
• the first substrate 52 com- prises a wire layer for selectively applying an electric field to the liquid crystal layer 53.
• a first polarizer 51 is arranged on a side of the first substrate 52 which is directed away from the liquid crystal layer 53.
• the second substrate 54 comprises a common electrode directed towards the liquid crystal layer 53.
• a second polarizer 55 is disposed on a surface of the second substrate 54 directed away from the liquid crystal layer 53.
• the polarization directions of the first 51 and the second 55 polarizers are rotated preferably by 90° to each other.
• Light emitted from a backlight 50 passes the first polarizer 51 and gets linearly polarized before entering the liquid crystal layer 53.
• the orientation of the polarization direction of the light entering the liquid crystal layer 53 is rotated, in particular the polarization direction is rotated by 90°. Only if the polarization direction of the light entering the liquid crystal layer 53 is polarized such that it can pass the second polarization filter 55, the light is emitted by the LCD screen.
• the first, second, and third light emitter portions 31, 32, 33 of the set 3 in Fig. 1 correspond to a first, second, and third portion 310, 320, 330 of a LCD display respectively, wherein a portion of the LCD display essentially comprises a portion of the backlight 50, a portion of the first polarizer 51, a portion of the first substrate 52, a group of liquid crystal molecules 53, a portion of the second substrate 54 and a portion of the second polarization filter 55. If the light exits the portion of the second polarization filter 55 and enters the first and second corresponding conversion layer 21, 22 of the set 2, it excites the respective luminescent crystals.
• the first luminescent crystals 11 In response to being excited by the corresponding first light emitter portion 310, the first luminescent crystals 11 emit red light RD. In response to being excited by the corresponding second light emitter portion 320, the second luminescent crystals 12 emit green light GR.
• the third portion 330 of the LCD display is not assigned to a conversion layer portion of the set, such that the third portion 330 of the LCD display emits the preferably blue light BL of the backlight .
• the backlight 50 may be considered as light emitter on its own, while the selec- tive emission of blue light to the individual conversion layer components is controlled by control elements which in the present case are the addressable liquid crystal molecules 53.
• Fig. 3 shows an alternative embodiment of the display device wherein like numbers refer to like ele- ments.
• the first, second, and third light emitter portion 31, 32, 33 of the set 3 in Fig. 1 correspond to a first, second, and third organic light emitting diode (OLED) 61, 62, 63 preferably emitting blue light.
• OLED organic light emitting diode
• the conversion layer portions 21, 22 of the set 2 can be directly ar- ranged onto a front side FS of the respectively first 61 and second 62 OLED or can be arranged onto a packaging of the respective OLED.
• the third OLED 63 does not correspond to any of the conversion layer portions 21, 22, of the set 2.
• Luminescent crystals with green emission were synthesized according to literature procedure presented by Protesescu et al. (Nano Lett., 2015, 15, 3692-3696).
• the LCs concentration was defined as 0.54% by heating up the dispersion to 450°C, which led to evaporation of the solvent and burning away the ligands.
• the dispersion was optically characterized with a Quantaurus C11347-11 Total Quantum Yield device (equipped with an integration sphere) .
• the LCs dispersion, excited at 450 nm had a photoluminescence peak centered at 500 nm with a FWHM of 23 nm and a photoluminescence quantum yield of 89%.
• Red emitting LCs were synthesized according to literature procedure presented by Protesescu et al.
• the LCs concentration was defined as 0.06% by heating up the dispersion to 450 °C, which led to evaporation of the solvent and burning away the ligands.
• the dispersion was optically char- acterized with a Quantaurus C11347-11 Total Quantum Yield device (equipped with an integration sphere) .
• the LCs dispersion, excited at 450 nm) had a photoluminescence peak centered at 638 nm with a FWHM of 33 nm and a photoluminescence quantum yield of 72%.

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