PHOSPHOR-NANOPARTICLE COMBINATIONS
Compositions of matter comprising a seeded semiconductor nanoparticle material and a non-quantum confined phosphor particle material for use in light conversion and light conversion layers comprising such compositions. In various embodiments, spherical core/shell seeded nanoparticles (SNPs) or nanorod seeded nanoparticles (RSNPs) are combined with a phosphor material to provide a composition of matter with small re-absorbance of the phosphor emission in both green and red wavelength regions and small re-absorbance of the SNP emission, In some embodiments, the SNPs or RSNPs are encapsulated in a first host material before being mixed with the phosphor particles. In various embodiments, a SNP/RSNP-phosphor mixture or encapsulated SNP/RSNP-phosphor mixture is incorporated in host matrix.
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This application claims priority from U.S. Provisional Patent Applications No. 61/299,018 filed Jan. 28, 2010 and titled “Phosphor-nanoparticle combination” and 61/299,012 filed Jan. 28, 2010 and titled “Light source with prescribed color emission”, both of which are incorporated herein by reference in their entirety.
FIELD AND BACKGROUNDEmbodiments of the invention relate in general to lighting devices which include light conversion materials and in particular to light conversion materials for use in lighting devices comprising light emitting diodes (LEDs), where the conversion materials include combinations of semiconductor nanoparticles and phosphors based on rare-earth elements for light conversion and light conditioning.
LEDs offer significant advantages over incandescent and fluorescent lamps with respect to their high energy efficiency and long lifetimes. LEDs are applicable in diverse applications including displays, automobile and signage lighting and domestic and street lighting. A LED can emit monochromatic light in different regions of the spectrum, depending on the inorganic semiconductor compound used to fabricate it. However, “white” light, which is required for a very large portion of the lighting industry, cannot be generated using a conventional LED. Current solutions of producing white light include the use of three or more LEDs with various colors (e.g. Red, Green and Blue or “RGB”), or the use of a color conversion layer of phosphor material (e.g. Cerium:YAG) to generate a broad white spectral emission from the ultraviolet (UV) or blue emission of a LED. However, such white light is almost always non-ideal and has in many cases undesired or unpleasant characteristics which may require improvement or correction.
For display purposes, it is important to have three or more basic colours with narrow FWHM spectrum emission, such as that obtained with LEDs (FWHM typically <30 nm). This allows large gamut coverage. “Gamut” is usually defined as: the range of chromaticities that can be obtained by mixing three colours. The solution of using three or more different LED is expensive and complicated for some applications. Therefore it is desirable to have a light source that provides large gamut coverage with one type of LED.
One method for utilizing LEDs to provide a broad-spectrum light source utilizes phosphors which convert the LED light to light having longer wavelengths in a broad spectrum. For example, a phosphor that emits light over a broad range of green wavelengths can be illuminated with blue from an LED that generates a narrow blue spectrum. The phosphor-generated green light is then used as a component of the white light source. By combining several phosphors, one can, in principle, create a broad-spectrum white light source provided the light conversion efficiencies of the phosphors are sufficiently high. More details can be found in “Status and prospects for phosphor-based white LED Packaging”, Z. Liu et al., Xiaobing Front. Optoelectron. China 2009, 2(2): 119-140.
Unfortunately, a lamp designer does not have an arbitrary set of phosphors from which to choose. There are a limited number of conventional phosphors containing rare-earth elements that have sufficient light conversion efficiencies. The emission spectrum of these phosphors is not easily changed. Furthermore, the spectra are less than ideal in that the light emitted as a function of wavelength is not constant. Hence, even by combining several phosphors, an optimum white light source is not obtained.
U.S. Pat. Nos. 7,102,152 7,495,383 and 7,318,651, which are incorporated herein by reference in their entirety, disclose devices and methods for emitting output light utilizing both quantum dots (QD) and non-quantum fluorescent materials to convert at least some of the original light emitted from a light source of the device to longer wavelength light to change the colour characteristics of the output light. QD have high QY and narrow emission spectrum with a central emission wavelength (CWL) tunable by size. Combining both QD and phosphor can enhance the light quality. QD additives can offer improvement, but they suffer from high self absorbance, i.e. they absorb light that is emitted when excited. This lowers their total energy efficiency as light convertors. Moreover and most significantly, the QD also re-absorbs the phosphor emission, which reduces the energetic efficiency and also shifts the output spectrum such that rational color planning is very difficult.
Moreover, in some applications cluster of close-packed QDs is desired. Close-packed QD clusters exhibit the phenomenon known as Fluorescence Resonant Energy Transfer (FRET), see e.g. Joseph R. Lakowicz, “Principles of Fluorescence Spectroscopy”, 2nd edition, Kluwer Academic/Plenum Publishers, New York, 1999, pp. 367-443. FRET occurs between a donor QD which emits at a shorter (e.g. bluer) wavelength relative to an acceptor QD positioned in close proximity and which emits at longer wavelength. There is a dipole-dipole interaction between the donor emission transition dipole moment and the acceptor absorption transition dipole moment. The efficiency of the FRET process depends on the spectral overlap of the absorption of the donor with the emission of the acceptor. The FRET distance between quantum dots is typically 10 nm or smaller. The efficiency of the FRET process is very sensitive to distance. FRET leads to colour change (red shift) and losses in the efficiency of light conversion. Hence, in prior work efforts were made to avoid clustering of QDs in light conversion materials.
Core/shell nanoparticles (NPs) are known. These are discrete nanoparticles characterized by a heterostructure in which a “core” of one type of material is covered by a “shell” of another material. In some cases, the shell is grown over the core which serves as a “seed”, the core/shell NP known then as a “seeded” NP or SNP. The term “seed” or “core” refers to the innermost semiconductor material contained in the heterostructure.
Typically the core has a nearly spherical shape. However, cores of various shapes such as pseudo-pyramid, cube-octahedron and others can be used. Typical core diameters range from about 1 nm to about 20 nm.
As known, a SNP may include additional external shells which can provide better optical and chemical properties such as higher quantum yield (QY) and better durability. The combination may be tuned to provide emitting colors as required for the application. In a RSNP, the length of the first shell can range in general between 10 nm and 200 nm and in particular between 15 nm and 160 nm. The thicknesses of the first shell in the other two dimensions (radial axis of the rod shape) may range between 1 nm and 10 nm. The thickness of additional shells may range in general between 0.3 nm and 20 nm and in particular between 0.5 nm and 10 nm.
In view of the numerous deficiencies of known light conversion materials mentioned above, including known QD-conventional phosphor combinations there is a need for and it would be advantageous to nanoparticle-phosphor combinations and compositions of materials including such combinations which do not suffer from such deficiencies. In particular, there is a need for and it would be advantageous to have nanoparticle-phosphor combinations with small to negligible re-absorption of the phosphor emission by the nanoparticles and with small self-absorbance of the nanoparticles, thus leading to high conversion efficiencies and ultimate color gamut control. In addition, these combinations should have negligible FRET upon clustering and high-loading in the conversion materials.
SUMMARYEmbodiments of the invention disclose materials or compositions of material (also referred to as combinations or mixtures) which combine at least one phosphor species with at least one species of a semiconductor nanoparticle, specifically a SNP or RSNP. As used herein, “phosphor-SNP combination”, “phosphor-RSNP combination”, “phosphor-SNP mixture” or “phosphor-RSNP mixture” mean any combination which combines at least one with at least one phosphor type (“species”) with at least one SNP or RSNP species. The resulting material can be a bulk material, a powder material, a thick or thin film material, self-supporting, incorporated in or combined with a matrix, and/or including added materials such as ligands. As used herein, the term “phosphor” refers to a fluorescent material present in a particulate form with an emitting center being usually an atom or ion species of a rare-earth element such as Ce, Eu or Er or others. Examples of common phosphors include Garnet-based phosphors, Silicate-based phosphors, Orthosilicate-based phosphors, Thiogallate-based phosphors, Sulfide-based phosphors and Nitride-based phosphors. Phosphor particles which can be used in combinations of the invention do not exhibit effects of quantum confinement. Non-quantum confined phosphor particles may be phosphor particles with or without a silica coating.
The inventors have found that SNPs in general and RSNPs in particular have superior optical properties which render them a much better choice for combining with phosphors in lighting applications. Specifically, the inventors have found that using a phosphor-SNP and phosphor-RSNP combinations of the invention, re-absorption effects of the phosphor emission by the SNP and self absorption of the SNP emission by SNP are small, leading to controlled color and high efficiency. In addition, in combinations containing phosphor-SNP clusters, and high loading, FRET and its undesired consequences are suppressed. RSNPs have very low photoluminescence (PL) self-absorbance and also small absorbance of the phosphor emission and thus are more energy efficient, especially in optically dense layers. A phosphor-SNP and phosphor-RSNP combination of the invention has low self absorption and re-absorption.
In some embodiments, the SNP/RSNP material is combined with a phosphor material such as listed above forming a mixture in weight percentage of 0.1-10% of SNP or RSNP relative to the phosphor. This mixture can be further inserted into a host material, typically silicone, with a 5-50% mix of conversion material to encapsulant by weight, according to the desired optical characteristic of the application. In some embodiments, a layer comprising a phosphor-SNP or phosphor-RSNP combination is used to modulate the emission spectrum of a light source. In some embodiments, the light source is a LED.
In some embodiments, a SNP-phosphor mixture may be include a layered structure comprising at least one phosphor layer and at least one SNP or RSNP layer. Various SNP and RSNP light conversion layers are disclosed in a co-pending PCT patent application by the same inventors titled “Lighting device with prescribed color emission”, filed simultaneously with this application, which claims the same priority as this application and which is incorporated herein by reference in its entirety. The phosphor layer may include a single phosphor species (“type”) or a mixture of several phosphor species. Alternatively, the phosphor layer may include a plurality of sub-layers, each sub-layer including a different phosphor species. A phosphor layer may have a minimum thickness limited by the size of the phosphor particles. The SNP/RSNP layer may include a single type of SNP or RSNPs, a mixture of several SNP or RSNP species or a plurality of sub-layers, each sub-layer including a different SNP or RSNP species. In some embodiments, the layered structure may comprise alternating layers of phosphors and RSNP. The thickness of a RSNP layer (without phosphor) may be smaller than 500 μm, better even smaller than 50 μm, or, for a densely-packed layer, smaller than 1 μm and even smaller than 0.2 μm. The thickness of a mixed phosphor-SNP layer can range from a few millimetres to tens of microns or even to a few microns, mainly constrained by the phosphor particle size and the required optical characteristics.
In embodiments involving modulation of the emission of a LED, a single layer or a layered structure can be formed on the LED. Alternatively, the layer or layered structure may be a separate and distinct layer or layered structure, placed directly on the LED or spaced from the LED by air, vacuum, or a filler material. The filler material (for example silicone or epoxy) may serve as a thermal isolation and/or as an optical scattering layer.
The modulation of the LED emission spectrum may be for illumination purposes, in order to produce broad-spectrum colour output light, for example “white” light, having a high colour rendering index (CRI) and the desired correlated colour temperature (CCT). The broad-spectrum colour output light is produced by converting some of the original light generated by the LED into longer wavelength light. Adding power or intensity to Red is important for obtaining “warmer” light with lower CCT (e.g. 2700-3500K), but “smoothing” specific regions in the spectrum such in the transition from blue to green can also improve the CRI. The modulation of the LED illumination may also be used for optical display purposes. The invented lighting conversion materials are also of use in agricultural applications of specific lighting demands and other areas of applications of lighting.
Aspects, embodiments and features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. In the drawings:
The term “core material” to the semiconductor material from which the core is made. The material may be II-VI, III-V, IV-VI, or I-III-VI2 semiconductors or combinations thereof. For example, the seed/core material may be selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb, Cu2S, Cu2Se, CuInS2, CuInSe2, Cu2(ZnSn)S4, Cu2(InGa)S4, alloys thereof, and mixtures thereof.
The term “shell material” refers to the semiconductor material from which each of the non-spherical elongated shells is made. The material may be a II-VI, III-V, IV-VI, or I-III-VI2 semiconductor or combinations thereof. For example, the shell material may be selected from CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, GaAs, GaP, GaAs, GaSb, GaN, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb, Cu2S, Cu2Se, CuInS2, CuInSe2, Cu2(ZnSn)S4, Cu2(InGa)S4, alloys thereof, and mixtures thereof.
The term “host material” refers to a matrix material which incorporates the SNPs or other suitable nanoparticles as well as the phosphor materials. The matrix material may be a silicone, a polymer (formed from liquid or semisolid precursor material such as monomer), an epoxy, glass or a hybrid of silicone and epoxy. Specific (but not limiting) examples of polymers include fluorinated polymers, polymers of ployacrylamide, polymers of polyacrylic acids, polymers of polyacrylonitrile, polymers of polyaniline, polymers of polybenzophenon, polymers of poly(methyl mathacrylate), silicone polymers, aluminium polymers, polymers of polybisphenol, polymers of polybutadiene, polymers of polydimethylsiloxane, polymers of polyethylene, polymers of polyisobutylene, polymers of polypropylene, polymers of polystyrene and polyvinyl polymers, polyvinyl-butyral polymers or perfluorocyclobutyl polymers. Silicones may include Gel, Elastomers and Resins such as Gel: Dow Corning® OE-6450, Elastomer Dow Corning® OE-6520, Dow Corning® OE-6550, Dow Corning® OE-6630, Resins: Dow Corning® OE-6635, Dow Corning® OE-6665, Nusil LS-6143 and other products from Nusil, Momentive RTV615, Momentive RTV656 and many other products from other vendors.
The term “ligand” refers to an outer surface coating of the nanoparticles. The coating passivates the SNP to prevent agglomeration or aggregation. Ligands in common use: phosphines and phosphine oxides such as trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), tributylphosphine (TBP), phosphonic acids such as dodecylphosphonic acid (DDPA), tridecylphosphonic acid (TDPA), octadecylphosphonic acid (ODPA) or hexylphosphonic acid (HPA), amines such as dodecyl amine (DDA), tetradecyl amine (TDA), hexadecyl amine (HDA) or octadecyl amine (ODA), thiols such as hexadecane thiol or hexane thiol, mercapto carboxylic acids such as mercapto propionic acid or mercapto undecanoic acid and other acids such as oleic, myristic or palmitic acid.
DETAILED DESCRIPTIONReference is now made to
The PL quantum yield (QY) of both QD and RSNP original nanoparticles was similar and on the order of 50%. This is a typical value. In other prepared samples, the QY ranged from 5-100%, more often between 20-90% and even more often between 50-80%. The absorption is measured in relative optical density (OD) units, where the scale shown is normalized to the range [0 1] for convenience. Significantly, for the green light emitting layers in
A combination of material in a layer disclosed herein can be realized using semiconducting nanocrystals, in particular particles from II-VI, III-V and I-III-VI2 groups, more particularly II-VI RSNPs with a core diameter from 2 to 7 nm, a shell length from 8 to 500 nm long and a shell diameter from 5 to 20 nm, or II-VI or III-V or I-III-VI2 core shell nanocrystals with a very thick shell that covers the core with a layer of more than 3 nm thickness, resulting in particles with diameter larger than 8 nm. The RSNP material is combined with phosphor material from the list above with a mixture in weight percentage of 0.2-10% of SNP or RSNP. This mixture can be further inserted into a host material, typically silicone, with a 5-50% mix of conversion material to encapsulant by weight, according to the desired thickness of the layer and the desired optical characteristic of the emission spectrum.
In an exemplary procedure, a host matrix is prepared in non-solid form (e.g. as a gel). SNP material is dissolved in organic solvents such as Toluene. The weight of the SNP material divided by the phosphor powder weight is between 0.2% and 10%. The SNP in organic solvent solution is first added to the host mixture while stirring. The phosphor powder is added and the SNP/phosphor/host mixture is stirred to obtain a homogenous mixture. The SNP/phosphor/host mixture in then vacuumed until no bubbles or organic solvent are left. The mixture is then ready for dispensing on a LED and for the following curing process.
One-part materials (e.g. silicones, epoxies or polymers) contain all the ingredients needed to produce a cured material. They use external factors—such as moisture in the air, heat, or the presence of ultraviolet light—to initiate, speed, or complete the curing process. It is also possible to use hosts that are single part to mix the SNP and phosphor inside. A particular embodiment is to embed the phosphor and SNP components in one-part hosts that are UV-curable.
Many hosts (e.g. silicones, epoxies) are available as two-part systems that segregate the reactive ingredients to prevent premature initiation of the cure process. They often use the addition of heat to facilitate or speed cure. We define the non-reactive part as “Part A” and the reactive part as “Part B”, In these systems we mix the SNP material to either part of the two-part system, preferably to the non-reactive part, Part A. In such an embodiment, the SNP in Part A can be stored for long time and applied to create a mixture with the phosphor and Part B when needed. In other embodiments, the SNP can be added directly into the host during the mixing of the reactive part of the host with the non-reactive part.
In another embodiment the insertion procedure is divided into two steps. In the first step, the SNPs covered by ligands, are inserted into a host A (e.g. a polymer, a silicone, a clay, silica, etc.) to provide a homogenous mixture with no clusters and bubbles and no “extra” chemical interaction between SNPs or ligands and the host. Host A is then dried and hardened (e.g. via polymerization, heating, vacuum treatment, UV curing, etc.) with the NP encapsulated in it (see
Tables 1 and 2 summarize various exemplary embodiments of phosphor+RSNP and phosphor+SNP combinations made according to the invention. In some embodiments, these combinations may be included in a host matrix such as silicone or polymer. In some embodiments, these combinations may be included in layers with a host matrix such as a silicone or a polymer. These combinations have advantageous physical parameters and optical performances for lighting and display applications. The exemplary embodiments summarized in Tables 1 and 2 should not be considered as limiting the invention in any way.
35×5.6 nm CdSe/CdS RSNPs emitting at 638 nm were first prepared using a procedure similar to that described in L. Carbone et al. “Synthesis and Micrometer-Scale Assembly of Colloidal CdSe/CdS Nanorods Prepared by a Seeded Growth Approach” Nano Letters, 2007, 7 (10), pp 2942-2950. 0.5 g of RTV615A (Momentive, 22 Corporate Woods Boulevard, Albany, N.Y. 12211 USA) was stirred with 0.15 g of RTV615B for 10 minutes. 4.0 mg of the RSNPs were dissolved in 0.4 ml Toluene. 615 mg of yellow phosphor (BYW01A, PhosphorTech, 351 Thornton Rd Ste. 130, Lithia Springs, Ga. 30122, USA) were provided to give a RSNP to Phosphor weight ratio of 4/615, i.e. ˜0.65%. The RSNP solution was added to the silicone RTV mixture while stirring. The BYW01A phosphor was then added and the RSNP/phosphor/silicone solution was stirred for 15 minutes. The RSNP/phosphor/silicone solution in then vacuumed until no bubbles were left. The solution was then poured on a glass substrate and sandwiched using another glass substrate, with 520 μm-thick spacers between them. The mixture conversion material was then placed on a hot plate at 100 C for 1 hour, after which the solution became solid. The final film thickness was 520 μm.
In an embodiment, a combination as in Example 1 with 490 μm thickness was deposited on a 455 nm LED. The performance of this layer and LED are shown in
The RSNPs prepared as described in Example 1 were embedded in PVB with 3% loading ratio (weight) and were ground to fine powder. The final powder mean particle size was less than 15 μm. 1.5 g of RTV615A (Momentive, 22 Corporate Woods Boulevard, Albany, N.Y. 12211 USA) was stirred with 0.15 g of RTV615B for 10 min 77 mg of the RSNP/PVB powder was added to the silicone mixture while stirring. 345 mg of Yttrium Aluminum Garnet phosphor (BYW01A, PhosphorTech, 351 Thornton Rd Ste. 130, Lithia Springs, Ga. 30122, USA) were added and the solution was stirred for 15 minutes. The RSNP/phosphor/silicone RTV solution was then vacuumed until no bubbles were left. The solution was then poured on a glass substrate and sandwiched using another glass substrate. 250 μm-thick spacers were positioned between the two glass substrates to obtain the desired film thickness. The sandwiched structure was then placed on a hot plate at 100 C for 1 hour, after which the solution became solid. The final film thickness was ˜250 μm.
The invention has been described with reference to embodiments thereof that are provided by way of example and are not intended to limit its scope. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the described invention and embodiments of the invention comprising different combinations of features than those noted in the described embodiments will occur to persons of ordinary skill in the art. The scope of the invention is limited only by the following claims.
All patents and publications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual patent or publication was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art.
Claims
1. A material composition for use in light conversion comprising:
- a) a phosphor material; and
- b) at least one type of semiconductor seeded nanoparticle (SNP) material having a central emission wavelength (CWL) in the range 580-680 nm, wherein the phosphor material and the SNP materials are mixed in an appropriate amount to provide an absorption ratio (AR) of optical absorbance at 455 nm to a maximum value of optical absorbance in the range of 580-700 nm greater than 3.5:1.
2. The material composition of claim 1, wherein the appropriate amount includes a weight ratio between the SNPs and phosphor materials between 0.1 and 10%.
3. The material composition of claim 1, wherein the SNP is a nanorod SNP (RSNP).
4. The material composition of claim 1, wherein the AR is greater than 7:1.
5. The material composition of claim 1, further characterized by having an AR between absorbance at 455 nm and a maximum value of absorbance in the wavelength range of 520-580 nm greater than 2.5:1.
6. The material composition of claim 4, further characterized by having an AR between absorbance at 455 nm and a maximum value of absorbance in the wavelength range of 520-580 nm greater than 6:1.
7. The material composition of claim 1, further comprising at least one of the following: (i) at least one type of excess organic ligands not bound to any SNP surface; and (ii) a host matrix material which incorporates the phosphor and SNP or RSNP materials.
8. The material composition of claim 1, further comprising a host matrix material which incorporates the phosphor and SNP or RSNP materials, the host matrix material being a silicone, epoxy or polymer.
9. (canceled)
10. The material composition of claim 1, further comprising a host matrix material which incorporates the phosphor and SNP or RSNP materials, wherein a weight percentage of the phosphor-SNP composition relative to the host matrix material is in the range of 5-50%.
11. The material composition of claim 1, wherein the phosphor material includes particulates with emitting centers of a rare-earth element.
12. The material composition of claim 1, characterized by at least one of the following: (1) the phosphor material is selected from the group consisting of Garnet-based phosphors, Silicate-based phosphors, Orthosilicate-based phosphors, Thiogallate-based phosphors, Sulfide-based phosphors and Nitride-based phosphors; and (2) the SNP material includes a material selected from the group consisting of II-VI, III-V IV-VI and I-III-VI2 semiconductors.
13. The material composition of claim 1, wherein the SNP material includes a material selected from the group consisting of II-VI, III-V IV-VI and I-III-VI2 semiconductors, the SNPs or RSNPs having one of the following configurations: (a) a core/shell structure with materials selected from the group consisting of CdSe/CdS, CdSeS/CdS, ZnSe/CdS, ZnCdSe/CdS, CdSe/CdZnS, CdTe/CdS, InP/ZnSe, InP/CdS, InP/ZnS and CuInS2/ZnS, and (b) a core/double shell structure with materials selected from the group consisting of CdSe/CdS/ZnS, CdSe/CdZnS/ZnS, ZnSe/CdS/ZnS, InP/ZnSe/ZnS, InP/CdS/ZnS and InP/CdZnS/ZnS.
14-15. (canceled)
16. The material composition of claim 1, further characterized by having a photoluminescence (PL) shift smaller than about 5 nm, wherein the PL shift represents the difference between a CWL measured for the SNP in Toluene at OD<0.1 and a CWL measured in the conversion layer.
17. A material composition for use in light conversion comprising:
- a) a phosphor material;
- b) a first host material; and
- c) at least one type of semiconductor seeded nanoparticle (SNP) material having a central emission wavelength (CWL) in the range 580-680 nm, wherein each SNP is encapsulated in the first host material and wherein the phosphor material and the encapsulated SNPs are mixed in an appropriate amount to provide an absorption ratio (AR) of optical absorbance at 455 nm to a maximum value of optical absorbance in the range of 580-700 nm greater than 3.5:1.
18. The material composition of claim 17, characterized by a weight percentage between the SNPs and the first host material between 0.5 and 10%.
19. The material composition of claim 17, wherein the appropriate amount includes a weight ratio of encapsulated SNPs to phosphor between 1 and 50%.
20. The material composition of claim 17, wherein the SNP is a nanorod SNP (RSNP).
21. The material composition of claim 17, wherein the AR is greater than 7:1.
22. The material composition of claim 17, further characterized by having an AR between absorbance at 455 nm and a maximum value of absorbance in the wavelength range of 520-580 nm greater than 2.5:1.
23. The material composition of claim 21, further characterized by having an AR between absorbance at 455 nm and a maximum value of absorbance in the wavelength range of 520-580 nm greater than 6:1.
24. The material composition of claim 17, further comprising at least one of the following: (i) at least one type of excess organic ligands not bound to any SNP surface; (ii) a second host material which incorporates the phosphor and the encapsulated SNP or RSNP materials.
25. The material composition of claim 17, further comprising a second host material which incorporates the phosphor and the encapsulated SNP or RSNP materials, the second host material being a polymer, epoxy or a silicone.
26. (canceled)
27. The material composition of claim 17, further comprising a second host material which incorporates the phosphor and the encapsulated SNP or RSNP materials, wherein the weight percentage of the phosphor-encapsulated SNP composition relative to the second host material is in the range of 5-50%.
28. The material composition of claim 17, wherein the phosphor material includes particulates with emitting centers of a rare-earth element.
29. The material composition of claim 17, wherein the phosphor material is selected from the group consisting of Garnet-based phosphors, Silicate-based phosphors, Orthosilicate-based phosphors, Thiogallate-based phosphors, Sulfide-based phosphors and Nitride-based phosphors.
30. The material composition of claim 17, wherein the SNP material includes a material selected from the group consisting of II-VI, III-V IV-VI and I-III-VI2 semiconductors.
31. The material composition of claim 30, wherein the SNPs or RSNPs have one of the following configurations: (1) have a core/shell structure with materials selected from the group consisting of CdSe/CdS, CdSeS/CdS, ZnSe/CdS, ZnCdSe/CdS, CdSe/CdZnS, CdTe/CdS, InP/ZnSe, InP/CdS, InP/ZnS and CuInS2/ZnS; (2) have a core/double shell structure with materials selected from the group consisting of CdSe/CdS/ZnS, CdSe/CdZnS/ZnS, ZnSe/CdS/ZnS, InP/ZnSe/ZnS, InP/CdS/ZnS and InP/CdZnS/ZnS.
32. (canceled)
33. The material composition of claim 17, further characterized by having a photoluminescence (PL) shift smaller than about 8 nm, wherein the PL shift represents the difference between a CWL measured in Toluene at OD<0.1 and a CWL measured in the conversion layer.
34. A light conversion layer comprising the composition of matter of claim 1.
35. A light conversion layer comprising the composition of matter of claim 17.
Type: Application
Filed: Jan 27, 2011
Publication Date: Feb 7, 2013
Applicant: Yissum Research Development Company of the Hebrew University of Jerusalem Ltd. (Jerusalem)
Inventors: Hagai Arbell (Jerusalem), Assaf Aharoni (Tel Aviv), Uri Banin (Mevasseret Zion)
Application Number: 13/575,871
International Classification: G02B 5/20 (20060101); B82Y 30/00 (20110101);