LUMINESCENT COMPONENT

Abstract

A luminescent component includes a first element comprising a first solid polymer composition, wherein the first solid polymer composition includes first luminescent crystals, wherein the first luminescent crystals are of the perovskite structure, and are selected from compounds of formula (I): M.sup.1.sub.aM.sup.2.sub.bX.sub.c, wherein M.sup.1 represents Cs, optionally doped with up to 30 mol % of one or more other metals having coordination number 12, M.sup.2 represents Pb, optionally doped with up to 30 mol % of one or more other metals having coordination number 6, X independently represents anions selected from the group consisting of Cl, Br, I, cyanide, and thiocyanate. The first luminescent crystals are of size between 3 nm and 3000 nm, and emit light of a first wavelength in response to excitation by light with a wavelength shorter than the first wavelength. An encapsulation including a polymer or an inorganic matrix encloses the first element.

Claims

1. A luminescent component, comprising a first element comprising a first solid polymer composition, wherein the first solid polymer composition comprises first luminescent crystals and a first polymer, wherein the first luminescent crystals are of the perovskite structure, are selected from compounds of formula (I): M.sup.1.sub.aM.sup.2.sub.bX.sub.c (I), wherein M.sup.1 represents Cs, optionally doped with up to 30 mol % of one or more other metals having coordination number 12, M.sup.2 represents Pb, optionally doped with up to 30 mol % of one or more other metals having coordination number 6, X independently represents anions selected from the group consisting of Cl, Br, I, cyanide, and thiocyanate, a represents 1, b represents 1, c represents 3; are of size between 3 nm and 3000 nm, emit light of a first wavelength in response to excitation by light with a wavelength shorter than the first wavelength, wherein the first polymer is a cyclic olefin copolymer, an encapsulation enclosing the first element, wherein the encapsulation comprises a polymer or an inorganic matrix.

2. The luminescent component according to claim 1, wherein the first solid polymer composition comprises a first polymer, and wherein the first polymer is not dissolvable in the encapsulation polymer, and vice versa.

3. The luminescent component according to claim 1, comprising a second element comprising a second solid polymer composition, wherein the second solid polymer composition comprises second luminescent crystals, wherein the second luminescent crystals are of the perovskite structure are selected from compounds of formula (II): M.sup.1.sub.aM.sup.2.sub.bX.sub.c (II), wherein M.sup.1 represents Cs, optionally doped with up to 30 mol % of one or more other metals having coordination number 12, M.sup.2 represents Pb, optionally doped with up to 30 mol % of one or more other metals having coordination number 6, X independently represents anions selected from the group consisting of Cl, Br, and I, cyanide, and thiocyanate, a represents 1, b represents 1, c represents 3; are of size between 3 nm and 3000 nm, are of a different chemical composition and/or a different size than the first luminescent crystals, emit light of a second wavelength different to the first wavelength in response to excitation by light with a wavelength shorter than each of the first and second wavelength, wherein the encapsulation encloses the second element.

4. The luminescent component according to claim 3, wherein the second solid polymer composition comprises a second polymer, and wherein the second polymer is not dissolvable in the encapsulation polymer, and vice versa.

5. The luminescent component according to claim 3, wherein the first element and the second element are arranged spaced within the encapsulation.

6. The luminescent component according to claim 3, comprising N further elements (nf) with N >=1, each further element (nf) comprising a further solid polymer composition and further luminescent crystals (n1f), wherein the further luminescent crystals (n1f) are of the perovskite structure are selected from compounds of formula (III): M.sup.1.sub.aM.sup.2.sub.bX.sub.c (III), wherein M.sup.1 represents Cs, optionally doped with up to 30 mol % of one or more other metals having coordination number 12, M.sup.2 represents Pb, optionally doped with up to 30 mol % of one or more other metals having coordination number 6, X independently represents anions selected from the group consisting of Cl, Br, and I, cyanide, and thiocyanate, a represents 1, b represents 1, c represents 3; are of size between 3 nm and 3000 nm, are of a different chemical composition and/or a different size than the first, second and any of the N-1 other further luminescent crystals, emit light of a further wavelength in response to excitation by light with a wavelength shorter than the further wavelength, wherein the further wavelength is different from the first wavelength, is different from the second wavelength, and is different of any of the N-1 other further wavelengths, wherein each further polymer composition optionally comprises a further polymer (n2f), and wherein the further polymer (n2f) is not dissolvable in the encapsulation polymer, and vice versa.

7. The luminescent component according to claim 6, wherein the encapsulation polymer is a polymer selected from the list of acrylate polymers, carbonate polymers, sulfone polymers, epoxy polymers, vinyl polymers, urethane polymers, ester polymers, styrene polymers, silicone polymers, olefin polymers and cyclic olefin copolymers, and wherein the second polymer if present, and any further polymer (n2f) if present is independently selected from the group of polyacrylates, including copolymers, polystyrenes, silicones, and cyclic olefin copolymers.

8. The luminescent component according to claim 6, wherein the first luminescent crystals, the second luminescent crystals if present, and any luminescent crystals (n1f) if present independently are of size between 5 nm and 100 nm, and/or wherein a mean diameter of the first elements, second elements if present, and any further elements (nf) if present independently is between 1 μm and 500 μm.

9. The luminescent component according to claim 3, wherein the first luminescent crystals are selected from the group consisting of: CsPbBr.sub.xI.sub.3-x, whereby 0≦x<2 CsPbCl.sub.yBr.sub.3-y-zI.sub.z, where 0<y<1, 2≦z≦3-y, and wherein the second luminescent crystals are selected from the group consisting of: —CsPbBr.sub.xI.sub.3-x, where 2≦x ≦3 —CsPbCl.sub.yBr.sub.zI.sub.3-y-z, where 0<y<1, 1<z≦3-y.

10. The luminescent component according to claim 6, wherein N is between 3 and 28.

11. The luminescent component according to claim 6, wherein the first element comprises first luminescent crystals only and is free from any other luminescent crystals, wherein the second element, if present, comprises second luminescent crystals only and is free from any other luminescent crystals wherein the further element, if present, comprises further luminescent crystals (n1f) only and is free from any other luminescent crystals.

12. A light emitting device, comprising a luminescent component according to claim 1, a light source for emitting blue light, wherein the light source is arranged for exciting the luminescent component and/or wherein the light emitting device is one of an LCD display, an OLED display, a Light Emitting Diode (LED) or an Organic Light Emitting Diode (OLED).

13. The light emitting device according to claim 12, wherein the light source is an LED chip, and wherein the luminescent component at least partly encloses the LED chip.

14. The light emitting device according to claim 12, wherein the light source is an LED chip, and wherein the luminescent component is arranged distant from the LED chip.

15. Use of a luminescent component of claim 1, for emitting white light in response to the luminescent component being radiated by blue light, in particular as a backlight in a liquid crystal display.

16. A method for manufacturing a luminescent component according to claim 1, comprising providing a first polymer solution comprising the first luminescent crystals, one of a) extracting multiple first elements from the first polymer solution by one of spray-drying, or precipitation, or b) hardening the first polymer solution into the first solid polymer composition, and crushing the first solid polymer composition resulting in multiple first elements, mixing the first elements into a solution including the encapsulation polymer, and providing the luminescent component by hardening and/or drying the encapsulation polymer.

17. The luminescent component according to claim 6, wherein the first luminescent crystals, the second luminescent crystals if present, and any luminescent crystals (n1f) if present independently are of size between 5 nm and 100 nm, and/or wherein a mean diameter of the first elements, second elements if present, and any further elements (nf) if present independently is between 5 μm and 100 μm.

18. The luminescent component according to claim 5, wherein the first polymer and the second polymer are identical.

19. The luminescent component according to claim 7, wherein the encapsulation polymer has a water vapor transmission rate of less than 0.2 g mm m.sup.−2 day.sup.−1.

20. The luminescent component according to claim 14, wherein the LED chip is at least partly covered by a phosphor-free enclosure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Embodiments, examples, experiments representing or leading to embodiments, aspects and advantages of the invention will be better understood from the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:

[0101] FIG. 1 illustrates a schematic perspective view of a luminescent component according to an embodiment of the present invention;

[0102] FIG. 2 illustrates a method for manufacturing a luminescent component according to an embodiment of the present invention;

[0103] FIG. 3 illustrates a light emitting device according to an embodiment of the present invention;

[0104] FIG. 4 illustrates a light emitting device according to another embodiment of the present invention; and

[0105] FIG. 5 illustrates a light emitting device according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0106] FIG. 1 illustrates a schematic perspective view of a luminescent component according to an embodiment of the present invention. The luminescent component 4 comprises an encapsulation 3, e.g. made from a nonopaque polymer. In the present embodiment, the encapsulation 3 is of a thin film shape whereby the length (x-axis) and width (y-axis) are of much greater size than the thickness in z-direction. However, the encapsulation 3 may take a different shape if needed.

[0107] First elements 1, second elements 2, and first further elements if are embedded in the encapsulation 3, only one of each is shown in a cut mode in FIG. 1.

[0108] The first element 1 comprises a first solid polymer composition including first luminescent crystals 11 but no other luminescent crystals, and a first polymer 12. The first luminescent crystals 11 are selected from compounds of formula (I) introduced above. The first luminescent crystals 11 have a size between 3 nm and 3000 nm. In response to excitation by blue light DL as indicated by the arrow, the first luminescent crystals 11 emit red light RD, for example.

[0109] The second element 2 comprises a second solid polymer composition including second luminescent crystals 21 but no other luminescent crystals, and a second polymer 22. The second luminescent crystals 21 are selected from compounds of formula (II) introduced above. The second luminescent crystals 21 have a size between 3 nm and 3000 nm. In response to excitation by the blue light BL, the second luminescent crystals 21 emit green light GR, for example.

[0110] Generally, different further elements nf with n ∈ [1, N] may be comprised in the encapsulation 3 including a first further element 1f, preferably a second further element 2f, . . . an Nth further element Nf. Each further element nf comprises a further solid polymer composition including further luminescent crystals n1f but no other luminescent crystals, and a further polymer n2f.

[0111] Presently, only first further elements 1f are included in the encapsulation 3. Each first further element if comprises first further luminescent crystals 11f and a first further polymer 12f. The first further luminescent crystals 11f are selected from compounds of formula (III) introduced above. The first further luminescent crystals 11f have a size between 3 nm and 3000 nm. In response to excitation by the blue light BL, the first further luminescent crystals 11f emit yellow light YL, for example.

[0112] In one embodiment of the invention there can also be multiple further elements nf emitting multiple different colors.

[0113] The first, second and further luminescent crystals 11, 21, n1f are separated from each other by means of the separated elements 1, 2, nf. In this embodiment, the encapsulation 3 builds the separation. Hence, the first, second and further luminescent elements 1, 2, nf are stable, also in a long-term.

[0114] As is indicated in FIG. 1, once such luminescent component is exposed to radiation of a shorter wavelength than the emitted wavelength, and in particular to blue radiation BL, the first, second and first further luminescent crystals 11, 21, 11f are excited and emit red, green and yellow light RD, GR, YL, respectively. Together with a portion of the blue light BL passing the luminescent component 4 the output of the luminescent component is a mixture of these colors and can be tuned by the amount of first, second and first further elements 1, 2, 11f in the luminescent component.

[0115] In case the luminescent component 4 of FIG. 1 comprises first and second elements 1 and 2 emitting red and green light only, the luminescent component 4 may in combination with a light source emitting the blue light BL represent a backlight film that can be used in an LCD given that the combination of red, green and blue light emitted result in white light. An intensity proportion of the red, green and blue light emitted preferably is in the range of a 1/3 each.

[0116] FIG. 2 illustrates a method for manufacturing a luminescent component according to an embodiment of the present invention. According to diagram 2a), a first polymer solution is provided comprising first luminescent crystals 11 but no different kind of luminescent crystals, a first polymer 12 and a solvent 13. In step S1, the solution is hardened, cured or dried in order to generate a solid first polymer composition shown in diagram 2b) which includes the first luminescent crystals 11 and the first polymer 12 but no longer the solvent 13.

[0117] According to step S2, the first solid polymer composition of diagram 2b) is crushed according to diagram 2c), e.g. by milling. The result of this processing step are multiple first elements 1, each of a solid polymer composition including the first polymer and the first luminescent crystals.

[0118] In step S3, these first elements 1 are added to and/or mixed into an encapsulation polymer solution or liquid monomer or liquid oligomer. Subject to the application of the resulting luminescent component other elements configured to emit light of one or more different wavelengths than the first elements may be added to and/or mixed into the encapsulation polymer solution or liquid monomer or liquid oligomer. After hardening and/or curing and/or drying, the luminescent component 4 is generated including the encapsulation 3, and enclosed by the encapsulation 3 the multiple first elements 1.

[0119] As an alternative to steps S1 and S2, the first polymer solution of diagram 2a) may in its liquid form be processed for extracting multiple first elements 1 therefrom. For example, step S4 may represent spraydrying, or precipitation. The result of these processes again are the multiple solid first element 1.

[0120] FIG. 3 illustrates a light emitting device according to an embodiment of the present invention. The light emitting device presently is a Light Emitting Diode LED. The device includes a luminescent component 4 of a sphere-like shape. As is indicated in FIG. 3, the luminescent component 4 includes multiple first elements 1. Each first element 1 includes first luminescent crystals in addition to a first polymer, but no other luminescent crystals. The first elements 1 are embedded in the encapsulation 3 separate from each other, which encapsulation 3 is transmissive to light. Subject to the application of the resulting device other elements configured to emit light of one or more different wavelengths than the first elements may be incorporated in the encapsulation.

[0121] Reference numeral 6 indicates an LED chip as a light source that is arranged on a carrier 5. The luminescent component 4 partly encloses—the top and the sides of—the LED chip 6. The LED chip 6 preferably is configured to emit blue light. In response to an excitation by blue light emitted from the LED chip 6, the luminescent crystals in the first elements 1 and/or further elements of the luminescent component 4 emit light of a different colour, e.g. red, green and/or yellow light. Hence, the present embodiment schematically illustrates an LED emitting e.g. additive colour mixtures of red and/or green and/or yellow with LED chip 6 blue light light. As to the manufacturing of the device of FIG. 3, the LED chip 6 may be preassembled onto the carrier 5, and the luminescent component 4 may be dropped onto the LED chip 6/carrier 5 arrangement in liquid form, and then be hardened, cured or dried.

[0122] In view of the luminescent component 4 being arranged directly on the LED chip 6, the luminescent component 4 preferably includes heat resistant materials. For example, the first polymer in the first elements 1 and the encapsulation may be a temperature stable polymer, and preferably may be Silicone or Polysilazane.

[0123] FIG. 4 illustrates a light emitting device according to another embodiment of the present invention. The light emitting device presently is a Light Emitting Diode LED. The device includes a luminescent component 4 of a film-like shape. As is indicated in FIG. 4, the luminescent component 4 includes multiple first elements 1. Each first element 1 includes first luminescent crystals in addition to a first polymer but no other luminescent crystals. The first elements 1 are embedded in the encapsulation 3 separate from each other, which encapsulation 3 is transmissive to light. Subject to the application of the resulting device other elements configured to emit light of one or more different wavelengths than the first elements may be incorporated in the encapsulation.

[0124] The luminescent component 4 is arranged on a transparent plate 9, e.g. of a housing or a front. The luminescent component 4/plate 9—combination is arranged distant from an LED chip 6 acting as a light source that is arranged on a carrier 5. The distant arrangement may be achieved by means of a housing 8. The LED chip 6 preferably is configured to emit blue light. Presently, the LED chip 6 is partly enclosed by a phosphor-free enclosure 7. In response to an excitation by blue light emitted from the LED chip 6, the luminescent crystals in the first elements 1 and/or further elements of the luminescent component 4 emit light of a different colour, e.g. red, green and/or yellow light. Hence, the present embodiment schematically illustrates an LED emitting e.g. additive colour mixtures of red and/or green and/or yellow with LED chip 6 blue light. As to the manufacturing of the device of FIG. 4, the LED chip 6 may be preassembled onto the carrier 5, while the luminescent component 4 may in its hardened form be attached to the plate 9.

[0125] In contrast to the embodiment illustrated in FIG. 3, the luminescent component is arranged distant form the LED chip 6 such that the luminescent component may not be required to stand heat in the same way.

[0126] FIG. 5 illustrates a light emitting device according to an embodiment of the present invention. The light emitting device presently is an Organic Light Emitting Diode OLED. The device includes a luminescent component 4 of flat shape. As is indicated in FIG. 5, the luminescent component 4 includes multiple first elements 1. Each first element 1 includes first luminescent crystals in addition to a first polymer, but no other luminescent crystals. The first elements 1 are embedded in the encapsulation 3 separate from each other, which encapsulation 3 is transmissive to light. Subject to the application of the resulting device other elements configured to emit light of one or more different wavelengths than the first elements may be incorporated in the encapsulation.

[0127] Reference numeral 10 indicates an OLED stack as a light source that may be arranged on further carrier. The OLED stack 10 preferably is configured to emit blue light. In response to an excitation by blue light emitted from the OLED stack 10, the luminescent crystals in the first elements 1 and/or further elements of the luminescent component 4 emit light of a different colour, e.g. red, green and/or yellow light. Hence, the present embodiment schematically illustrates an OLED device emitting e.g. additive colour mixtures of red and/or green and/or yellow with LED chip 6 blue light. As to the manufacturing of the device of FIG. 5, the OLED stack 10 may be preassembled onto a carrier, and the luminescent component 4 may be coated onto the OLED stack 10 in liquid form, and then be hardened, cured or dried.

EXAMPLES AND EXPERIMENTS

Example 1

[0128] Luminescent crystals emitting red light were produced as described by Protesescu et al. (Nano Lett., 2015, 15, 3692-3696). The resulting solids load was measured to be 0.06 wt % by heating up to 450° C. and thus evaporating the solvent and burning away the ligands. The optical properties of the resulting nanocrystal formulation were measured with a Hamamatsu Quantaurus C11347-11 device (equipped with an integrating sphere) and a quantum yield of 72% at an emission peak wavelength of 638 nm with a FWHM of 33 nm were achieved.

[0129] 33 wt % of this formulation were mixed with 67 wt % of previously prepared solution of 30 wt % PMMA (Plexiglas 7N) in toluene and immediately poured onto a glass substrate which was heated to 60° C. After complete drying (12h) at 60° C. a luminescent, transparent foil of approximately 1 mm thickness was obtained. The foil showed the following optical properties: Quantum yield 70%, emission peak wavelength 641 nm, FWHM 31 nm.

[0130] This foil was then cut into pieces of approximately 1 cm×1 cm size, cooled down to −196° C. with liquid nitrogen. The foil was subsequently pulverized with a commercially available coffee grinder. The obtained luminescent polymer particle size was estimated to be in the range of a few 100 μm. The obtained powder showed the following optical properties: Quantum yield 69%, emission peak wavelength 640 nm, FWHM 32 nm.

[0131] 33wt % of the hereby obtained powder was mixed with 67 wt % of Electrolube SC3001 silicone resin (resin:hardener 13.5:1) coated onto a glass substrate and cured at 60° C. for 2 hours. The resulting film was approximately 1-2 mm thick and showed the following optical properties: Quantum yield 69%, emission peak wavelength 638 nm, FWHM 32 nm. Based on the measured solids load of the starting formulation the film had a Pb concentration of approximately 60 ppm.

Example 2

[0132] Luminescent crystals emitting green light were produced as described by Protesescu et al. (Nano Lett., 2015, 15, 3692-3696). The resulting solids load was measured to be 0.54 wt % by heating up to 450° C. and thus evaporating the solvent and burning away the ligands. The optical properties of the resulting nanocrystal formulation were measured with a Hamamatsu Quantaurus C11347-11 device (equipped with an integration sphere) and a quantum yield of 89% at an emission peak wavelength of 500 nm with a FWHM of 23 nm were achieved.

[0133] 11 wt % of this formulation were mixed with 89 wt % of a previously prepared solution of 25 wt % Polystyrene (Sigma Al-drich) in toluene and subsequently processed analogously to example 1 to receive a green luminescent polymer powder with the following optical properties: Quantum yield 66%, emission peak wavelength 518 nm, FWHM 28 nm

[0134] According to example 1 33 wt % of the hereby obtained powder was mixed with 67 wt % of Electrolube SC3001 silicone resin (resin:hardener 13.5:1) coated onto a glass substrate and cured at 60° C. for 2 hours. The resulting film was approximately 1-2mm thick and showed the following optical properties: Quantum yield 45%, emission peak wavelength 514 nm, FWHM 30 nm. Based on the measured solids load of the starting formulation the film had a Pb concentration of approximately 400 ppm.

Example 3

[0135] The red and green luminescent polymer powder—previously also referred to as first and second elements—obtained in example 1 and 2 were mixed at 1:1 weight ratio, and 33 wt % of the mixture was mixed with 67 wt % of Electrolube SC3001 silicone resin (resin:hardener 13.5:1) coated onto a glass substrate and cured at 60° C. for 2 hours. The resulting film was approximately 1-2 mm thick and showed the following optical properties: Quantum yield 57% (measured with the same device as in example 1), emission peak wavelengths 514 nm and 638 nm, FWHM 30 nm and 32 nm, respectively. Based on the measured solids load of the starting formulations the film had a Pb concentration of approximately 230 ppm.

[0136] Accordingly the red and green luminescent polymer powder obtained in example 1 and 2 were mixed at 1:2 weight ratio, and 33 wt % of the mixture was mixed with 67 wt % of Electrolube SC3001 silicone resin (resin:hardener 13.5:1) coated onto a glass substrate and cured at 60° C. for 2 hours. The resulting film was approximately 1-2 mm thick and showed the following optical properties: Quantum yield 55%, emission peak wavelengths 513 nm and 638 nm, FWHM 30 nm and 32 nm, respectively. This result shows that a mixture of the red and green polymer powder does neither result in a degradation of the particle (shifting of emission peak wavelengths) nor a loss in performance. Based on the measured solids load of the starting formulations the film had a Pb concentration of approximately 290 ppm.

[0137] Experiment 4:

[0138] Luminescent crystals emitting green and red light were produced as described by Protesescu et al. (Nano Lett., 2015, 15, 3692-3696). The resulting solids load was measured to be 0.52 wt % for green and 0.53 wt % for red, by heating up to 450° C. and thus evaporating the solvent and burning away the ligands. The optical properties of the resulting nanocrystal formulation were measured with a Hamamatsu Quantaurus C11347-11 device (equipped with an integration sphere, 45 nm excitation) and a quantum yield of 60% at an emission peak wavelength of 528 nm with a FWHM of 25 nm for green and a quantum yield of 90% at an emission peak wavelength of 645 nm with a FWHM of 38 nm for red were achieved.

[0139] These nanocrystal formulations were mix with a cyclic olefin copolymer (TOPAS 5013S-04) solution in toluene (20 wt % polymer in solvent) to yield a polymer:nanocrystal ratio of 20:1 and subsequently diluted with toluene to a final polymer content in the formulation of 4 wt %. Spray drying in an inert loop (nitrogen) of the green and red polymer solution was used to obtain a powder exhibiting a particle size of 1-20 μm as confirmed by scanning electron microscopy. The green powder showed a quantum yield of 45%, peak position of 527 nm, and FWHM of 24 nm whereas the red powder showed a quantum yield of 80%, peak position of 647 nm, and FWHM of 36 nm.

[0140] 0.075 g of the green and 0.025 g of the red powder were mixed with an epoxy resin (Eposun, 2.66 g resin and 1.33 g standard hardener) in a speed mixer and the resulting mixture was cured between two glass slides for 24 h at ambient condition. This film sample showed a total quantum yield of 69%, a peak at 528 nm with FWHM of 24nm and a peak at 648 nm with FWHM of 37 nm.

[0141] Experiment 5:

[0142] The sample in experiment 4 was compared to commercially available QD films containing InP and CdSe quantum dots. Table 1 shows the optical performance of the film as measured with a Hamamatsu Quantaurus C11347-11 device (equipped with an integrating sphere). The performance, indicated as quantum yield, of the current CsPbX3 QD samples is similar to the CdSe containing commercial film 1 while showing a higher quantum yield and decreased FWHM compared to InP containing commercial film 2.

TABLE-US-00001 TABLE 1 Peak Peak Total posi- posi- Quan- quantum tion FWHM tion FWHM tum yield green green red red Sample dot (%) (nm) (nm) (nm) (nm) this in- exp.4 69 528 24 645 37 vention Commer- CdSe 77 543 34 607 40 cial film based 1 Commer- InP 59 531 41 632 56 cial film based 2

[0143] film 1, QD film taken from tablet Kindle Fire HDX 7 manufactured by Amazon, not compliant with RoHS, comparable quantum yield and FWHM.

[0144] film 2, QD film taken from TV model UE48JS8580 manufactured by Samsung; RoHS compliant but low quantum yield, broad FWHM.

[0145] Experiment 6 (comparative experiment): The green and red luminescent formulations of example 1 and 2 were mixed together in dry weight ratios of red:green 1:1 (9:1 in formulation weight). Due to the ion exchange reaction the resulting formulation became orange with a low intensity yellow luminescence. The formulation was measured and showed the following optical properties: Quantum yield 9.5% (measured with the same device as in example 1), emission peak wavelength 554 nm, FWHM 28 nm.

[0146] This experiment clearly demonstrates that red and green LC's cannot be combined in the same liquid formulations nor in the same polymer matrix without substantially affecting the optical properties.

[0147] Experiment 7 (comparative experiment): The green and red luminescent formulations containing dissolved polymer from example 1 and 2 were mixed at a weight ratio of 1:1. The resulting mixture changed its color from initial orange to yellow with green emission within a few seconds, thus indicating the ongoing ion exchange. The resulting mixture was cast onto a glass slide and dried at 60° C. The resulting film was approximately 100 μm thick and showed the following optical properties: Quantum yield 45% (measured with the same device as in example 1), emission peak wavelength 520 nm, FWHM 27 nm. The fact that no red emission peak could be detected anymore reinforces the fact that red and green emitting particles cannot be mixed within one polymer phase.