Composite having semiconductor structures embedded in a matrix

Abstract

Composites having semiconductor structures embedded in a matrix are described. In an example, a composite includes a matrix material. A plurality of semiconductor structures is embedded in the matrix material. Each semiconductor structure includes an anisotropic nanocrystalline core composed of a first semiconductor material and having an aspect ratio between, but not including, 1.0 and 2.0. Each semiconductor structure also includes a nanocrystalline shell composed of a second, different, semiconductor material at least partially surrounding the anisotropic nanocrystalline core. An insulator layer encapsulates each nanocrystalline shell and anisotropic nanocrystalline core pairing.

What is claimed is: 
     
         1 . A composite, comprising:
 a matrix material; and   a plurality of semiconductor structures embedded in the matrix material, each semiconductor structure comprising:
 an anisotropic nanocrystalline core comprising a first semiconductor material and having an aspect ratio between, but not including, 1.0 and 2.0; 
 a nanocrystalline shell comprising a second, different, semiconductor material at least partially surrounding the anisotropic nanocrystalline core; and 
 an insulator layer encapsulating the nanocrystalline shell and anisotropic nanocrystalline core. 
   
     
     
         2 . The composite of  claim 1 , wherein each of the plurality of semiconductor structures is cross-linked with, polarity bound by, or tethered to the matrix material. 
     
     
         3 . The composite of  claim 1 , wherein each of the plurality of semiconductor structures is bound to the matrix material by a covalent, dative, or ionic bond. 
     
     
         4 . The composite of  claim 1 , wherein one or more of the semiconductor structures further comprises a coupling agent covalently bonded to an outer surface of the insulator layer. 
     
     
         5 . The composite of  claim 4 , wherein the insulator layer comprises a layer of silica (SiO x ), and the coupling agent is a silane coupling agent. 
     
     
         6 . The composite of  claim 5 , wherein the silane coupling agent has the formula X n SiY 4-n , where X is a functional group capable of bonding with the matrix material and is selected from the group consisting of hydroxyl, alkoxy, isocyanate, carboxyl, epoxy, amine, urea, vinyl, amide, aminoplast and silane, Y is a functional group selected from the group consisting of hydroxyl, phenoxy, alkoxy, hydroxylether, silane and aminoplast, and n is 1, 2 or 3. 
     
     
         7 . The composite of  claim 4 , wherein the coupling agent is selected from the group consisting of a titanate coupling agent and a zirconate coupling agent. 
     
     
         8 . The composite of  claim 1 , wherein the insulator layer comprises a layer of silica (SiO x ), and the matrix material comprises a siloxane copolymer. 
     
     
         9 . The composite of  claim 1 , wherein the matrix material has a UV-Vis spectroscopy transmission of greater than 90% for light in the range of 400-700 nanometers. 
     
     
         10 . The composite of  claim 1 , wherein the matrix material has a refractive index approximately in the range of 1-2 for light in the range of 400-700 nanometers. 
     
     
         11 . The composite of  claim 1 , wherein the matrix material is thermally stable in a temperature range of −40-250 degrees Celsius. 
     
     
         12 . The composite of  claim 1 , wherein the matrix material comprises a polymer selected from the group consisting of polypropylene, polyethylene, polyesters, polyacetals, polyamides, polyacrylamides, polyimides, polyethers, polyvinylethers, polystyrenes, polyoxides, polycarbonates, polysiloxanes, polysulfones, polyanhydrides, polyamines, epoxies, polyacrylics, polyvinylesters, polyurethane, maleic resins, urea resins, melamine resins, phenol resins, furan resins, polymer blends, polymer alloys, and mixtures thereof. 
     
     
         13 . The composite of  claim 12 , wherein the matrix material comprises a polysiloxane selected from the group consisting of polydimethylsiloxane (PDMS), polymethylphenylsiloxane, polydiphenylsiloxane and polydiethylsiloxane. 
     
     
         14 . The composite of  claim 1 , wherein the matrix material comprises a siloxane selected from the group consisting of dimethylsiloxane and methylhydrogen siloxane. 
     
     
         15 . The composite of  claim 1 , wherein the plurality of semiconductor structures embedded homogeneously in the matrix material. 
     
     
         16 . The composite of  claim 1 , further comprising:
 a compounding agent embedded in the matrix material, the compounding agent selected from the group consisting of an antioxidant, a pigment, a dye, an antistatic agent, a filler, a flame retardant, an ultra-violet (UV) stabilizer, and an impact modifier.   
     
     
         17 . The composite of  claim 1 , further comprising:
 a catalyst embedded in the matrix material, the catalyst selected from the group consisting of a thiol catalyst and a platinum (Pt) catalyst.   
     
     
         18 . The composite of  claim 1 , wherein the insulator layer is bonded directly to the nanocrystalline shell, passivates an outermost surface of the nanocrystalline shell, and provides a barrier for the nanocrystalline shell. 
     
     
         19 . The composite of  claim 1 , wherein the insulator layer encapsulates only a single nanocrystalline shell/anisotropic nanocrystalline core pairing. 
     
     
         20 . The composite of  claim 1 , wherein the insulator layer comprises a layer of silica (SiO x ). 
     
     
         21 . The semiconductor structure of  claim 1 , wherein the anisotropic nanocrystalline core and the nanocrystalline shell form a quantum dot. 
     
     
         22 . The composite of  claim 21 , wherein the quantum dot has a photoluminescence quantum yield (PLQY) of at least 90%. 
     
     
         23 . A composite, comprising:
 a matrix material; and   a plurality of semiconductor structures cross-linked with, polarity bound by, or tethered to the matrix material, each semiconductor structure comprising:
 a nanocrystalline core comprising a first semiconductor material; 
 a nanocrystalline shell comprising a second, different, semiconductor material at least partially surrounding the nanocrystalline core; and 
 an insulator layer encapsulating the nanocrystalline shell and core. 
   
     
     
         24 . The composite of  claim 23 , wherein one or more of the semiconductor structures further comprises a coupling agent covalently bonded to an outer surface of the insulator layer. 
     
     
         25 . The composite of  claim 24 , wherein the insulator layer comprises a layer of silica (SiO x ), and the coupling agent is a silane coupling agent. 
     
     
         26 . The composite of  claim 25 , wherein the silane coupling agent has the formula X n SiY 4-n , where X is a functional group capable of bonding with the matrix material and is selected from the group consisting of hydroxyl, alkoxy, isocyanate, carboxyl, epoxy, amine, urea, vinyl, amide, aminoplast and silane, Y is a functional group selected from the group consisting of hydroxyl, phenoxy, alkoxy, hydroxylether, silane and aminoplast, and n is 1, 2 or 3. 
     
     
         27 . The composite of  claim 24 , wherein the coupling agent is selected from the group consisting of a titanate coupling agent and a zirconate coupling agent. 
     
     
         28 . The composite of  claim 23 , wherein the insulator layer comprises a layer of silica (SiO x ), and the matrix material comprises a siloxane copolymer. 
     
     
         29 . The composite of  claim 23 , wherein the matrix material has a UV-Vis spectroscopy transmission of greater than 90% for light in the range of 400-700 nanometers. 
     
     
         30 . The composite of  claim 23 , wherein the matrix material has a refractive index approximately in the range of 1-2 for light in the range of 400-700 nanometers. 
     
     
         31 . The composite of  claim 23 , wherein the matrix material is thermally stable in a temperature range of −40-150 degrees Celsius. 
     
     
         32 . The composite of  claim 23 , wherein the matrix material comprises a polymer selected from the group consisting of polypropylene, polyethylene, polyesters, polyacetals, polyamides, polyacrylamides, polyimides, polyethers, polyvinylethers, polystyrenes, polyoxides, polycarbonates, polysiloxanes, polysulfones, polyanhydrides, polyamines, epoxies, polyacrylics, polyvinylesters, polyurethane, maleic resins, urea resins, melamine resins, phenol resins, furan resins, polymer blends, polymer alloys, and mixtures thereof. 
     
     
         33 . The composite of  claim 32 , wherein the matrix material comprises a polysiloxane selected from the group consisting of polydimethylsiloxane (PDMS), polymethylphenylsiloxane, polydiphenylsiloxane and polydiethylsiloxane. 
     
     
         34 . The composite of  claim 23 , wherein the matrix material comprises a siloxane selected from the group consisting of dimethylsiloxane and methylhydrogen siloxane. 
     
     
         35 . The composite of  claim 23 , wherein the plurality of semiconductor structures embedded homogeneously in the matrix material. 
     
     
         36 . The composite of  claim 23 , further comprising:
 a compounding agent embedded in the matrix material, the compounding agent selected from the group consisting of an antioxidant, a pigment, a dye, an antistatic agent, a filler, a flame retardant, an ultra-violet (UV) stabilizer, and an impact modifier.   
     
     
         37 . The composite of  claim 23 , further comprising:
 a catalyst embedded in the matrix material, the catalyst selected from the group consisting of a thiol catalyst and a platinum (Pt) catalyst.   
     
     
         38 . The composite of  claim 23 , wherein the insulator layer is bonded directly to the nanocrystalline shell, passivates an outermost surface of the nanocrystalline shell, and provides a barrier for the nanocrystalline shell. 
     
     
         39 . The composite of  claim 23 , wherein the insulator layer encapsulates only a single nanocrystalline shell/nanocrystalline core pairing. 
     
     
         40 . The composite of  claim 23 , wherein the insulator layer comprises a layer of silica (SiO x ). 
     
     
         41 . The semiconductor structure of  claim 23 , wherein the nanocrystalline core and the nanocrystalline shell form a quantum dot. 
     
     
         42 . The composite of  claim 41 , wherein the quantum dot has a photoluminescence quantum yield (PLQY) of at least 90%. 
     
     
         43 . A lighting apparatus, comprising:
 a light emitting diode; and   a composite coating the light emitting diode, the composite comprising:
 a matrix material; and 
 a plurality of semiconductor structures embedded in the matrix material, each semiconductor structure comprising:
 a quantum dot comprising a nanocrystalline core comprising a first semiconductor material and a nanocrystalline shell comprising a second, different, semiconductor material at least partially surrounding the nanocrystalline core, the quantum dot having a photoluminescence quantum yield (PLQY) of at least 90%; and 
 an insulator layer encapsulating the quantum dot. 
 
   
     
     
         44 . The lighting apparatus of  claim 43 , wherein emission from each quantum dot is mostly, or entirely, from the nanocrystalline core. 
     
     
         45 . The lighting apparatus of  claim 44 , wherein emission from the nanocrystalline core is at least approximately 75% of the total emission from the quantum dot. 
     
     
         46 . The lighting apparatus of  claim 43 , wherein an absorption spectrum and an emission spectrum of each quantum dot are essentially non-overlapping. 
     
     
         47 . The lighting apparatus of  claim 43 , wherein an absorbance ratio of each quantum dot for absorbance at 400 nanometers versus absorbance at an exciton peak for the quantum dot is approximately in the range of 5-35. 
     
     
         48 . The lighting apparatus of  claim 43 , wherein each quantum dot is a down-converting quantum dot. 
     
     
         49 . A method of fabricating a composite, the method comprising:
 forming a plurality of semiconductor structures, the forming of each semiconductor structure comprising:
 forming an anisotropic nanocrystalline core comprising a first semiconductor material and having an aspect ratio between, but not including, 1.0 and 2.0; 
 forming a nanocrystalline shell from a second, different, semiconductor material to at least partially surround the anisotropic nanocrystalline core; and 
 forming an insulator layer encapsulating the nanocrystalline shell and anisotropic nanocrystalline core; and 
   embedding the plurality of semiconductor structures in a matrix material.   
     
     
         50 . The method of  claim 49 , wherein embedding the plurality of semiconductor structures in the matrix material comprises cross-linking, reactive tethering, or ionic bonding the plurality of semiconductor structures with the matrix material. 
     
     
         51 . The method of  claim 49 , wherein forming the insulator layer comprises forming a layer of silica (SiO x ). 
     
     
         52 . The method of  claim 49 , wherein embedding the plurality of semiconductor structures in the matrix material comprises embedding homogeneously in the matrix material. 
     
     
         53 . The method of  claim 49 , further comprising:
 surface-functionalizing the insulator layer prior to embedding the plurality of semiconductor structures in the matrix material.   
     
     
         54 . The method of  claim 53 , wherein surface-functionalizing the insulator layer comprises treating the insulator layer with a silane coupling agent. 
     
     
         55 . The method of  claim 54 , wherein treating the insulator layer with the silane coupling agent comprises using a coupling agent selected from the group consisting of vinyltrimethoxysilane, allyltrimethoxysilane, and octyltrimethoxysilane. 
     
     
         56 . The method of  claim 49 , wherein embedding the plurality of semiconductor structures in the matrix material comprises embedding the semiconductor structures using a ligand-free insulator layer. 
     
     
         57 . A method of fabricating a composite, the method comprising:
 embedding a plurality of semiconductor structures in a matrix material, each semiconductor structure comprising a nanocrystalline core comprising a first semiconductor material, a nanocrystalline shell comprising a second, different, semiconductor material at least partially surrounding the nanocrystalline core, and an insulator layer encapsulating the nanocrystalline shell and core, the embedding comprising cross-linking, reactive tethering, or ionic bonding the plurality of semiconductor structures with the matrix material.   
     
     
         58 . The method of  claim 57 , wherein embedding the plurality of semiconductor structures in the matrix material comprises embedding homogeneously in the matrix material. 
     
     
         59 . The method of  claim 57 , further comprising:
 surface-functionalizing the insulator layer prior to embedding the plurality of semiconductor structures in the matrix material.   
     
     
         60 . The method of  claim 59 , wherein surface-functionalizing the insulator layer comprises treating the insulator layer with a silane coupling agent. 
     
     
         61 . The method of  claim 60 , wherein treating the insulator layer with the silane coupling agent comprises using a coupling agent selected from the group consisting of vinyltrimethoxysilane, allyltrimethoxysilane, and octyltrimethoxysilane.