SEMICONDUCTOR NANOPARTICLE-BASED LIGHT-EMITTING DEVICES AND ASSOCIATED MATERIALS AND METHODS

• US 20100123155A1
• Filed: 11/19/2009
• Published: 05/20/2010
• Est. Priority Date: 11/19/2008
• Status: Active Grant

• Current Assignee: Nanoco Technologies Limited (Nanoco Group Plc)
• Original Assignee: Nanoco Technologies Limited (Nanoco Group Plc)
• Inventors: Pickett, Nigel, Harris, James
• Granted Patent: US 8,921,827 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: C09K 11/02 Use of particular materials as binders, particle coatings or suspension media therefor
• CPC Class Codes: C09K 11/565 with zinc cadmium
• CPC Class Codes: C09K 11/70 containing phosphorus
• CPC Class Codes: C09K 11/883 with zinc or cadmium
• CPC Class Codes: G01N 33/588 with semiconductor nanocrystal label, e.g. quantum dots
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 2933/005 relating to encapsulations
• CPC Class Codes: H01L 33/005 Processes
• CPC Class Codes: H01L 33/04 with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/56 Materials, e.g. epoxy or silicone resin

Abstract

Embodiments of the present invention relate to a formulation for use in the fabrication of a light-emitting device, the formulation including a population of semiconductor nanoparticles incorporated into a plurality of discrete microbeads comprising an optically transparent medium, the nanoparticle-containing medium being embedded in a host light-emitting diode encapsulation medium. A method of preparing such a formulation is described. There is further provided a light-emitting device including a primary light source in optical communication with such a formulation and a method of fabricating the same.

Claims

1. A formulation for use in the fabrication of a light-emitting device, said formulation comprising:

a population of semiconductor nanoparticles incorporated into a plurality of discrete microbeads comprising an optically transparent medium, said nanoparticle-containing medium being embedded in a host light-emitting diode (LED) encapsulation medium.

2. A formulation according to claim 1, wherein each of said discrete microbeads incorporates a plurality of said semiconductor nanoparticles.

3. A formulation according to claim 2, wherein said microbeads possess an average diameter of around 20 nm to around 0.5 mm.

4. A formulation according to claim 1, wherein said optically transparent medium comprises a material selected from the group consisting of a polymer, a resin, a monolith, a glass, a sol gel, an epoxy, a silicone, and a (meth)acrylate.

5. A formulation according to claim 1, wherein said optically transparent medium comprises a material selected from the group consisting of poly(methyl (meth)acrylate), poly(ethylene glycol dimethacrylate), poly(vinyl acetate), poly(divinyl benzene), poly(thioether), silica, polyepoxide, and combinations thereof.

6. A formulation according to claim 1, wherein said optically transparent medium comprises a material selected from the group consisting of a copolymer of poly(methyl(meth)acrylate), poly(ethylene glycol dimethacrylate) and poly(vinyl acetate);

polystyrene, polydivinyl benzene and a polythiol; and

a copolymer of 3-(trimethoxysilyl)propylmethacrylate and tetramethoxy silane.

7. A formulation according to claim 1, wherein at least some of the nanoparticle-containing microbeads include a core comprising a first optically transparent medium and one or more outer layers of the same or one or more different optically transparent media deposited on said core.

8. A formulation according to claim 7, wherein said semiconductor nanoparticles are confined to the core of the microbeads or are dispersed throughout the core and/or one or more of the outer layers of the microbeads.

9. A formulation according to claim 1, wherein said LED encapsulation medium comprises a material selected from the group consisting of a polymer, an epoxy, a silicone, and a (meth)acrylate.

10. A formulation according to claim 1, wherein said LED encapsulation medium is selected from the group consisting of silica glass, silica gel, siloxane, sol gel, hydrogel, agarose, cellulose, epoxy, polyether, polyethylene, polyvinyl, poly-diacetylene, polyphenylene-vinylene, polystyrene, polypyrrole, polyimide, polyimidazole, polysulf one, polythiophene, polyphosphate, poly(meth)acrylate, polyacrylamide, polypeptide, polysaccharide, and combinations thereof.

11. A formulation according to claim 1, wherein said semiconductor nanoparticles contain ions selected from group 11, 12, 13, 14, 15 and/or 16 of the periodic table, or said quantum dots contain one or more types of transition metal ion or d-block metal ion.

12. A formulation according to claim 1, wherein said semiconductor nanoparticles contain one or more semiconductor materials selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, InP, InAs, InSb, AlP, AIS, AIAs, AISb, GaN, GaP, GaAs, GaSb, PbS, PbSe, Si, Ge, MgS, MgSe, MgTe, and combinations thereof.

27. A light-emitting device according to claim 25, wherein said formulation is in accordance with claim 1.

30. A method according to claim 28, wherein said formulation is in accordance with claim 1.

13. A method for preparing a formulation for use in the fabrication of a light-emitting device, said method comprising:

incorporating a population of semiconductor nanoparticles into a plurality of discrete microbeads comprising an optically transparent medium; and

embedding said nanoparticle-containing medium into a host light-emitting diode encapsulation material.

14. A method according to claim 13, wherein said incorporation of semiconductor nanoparticles into the optically transparent medium comprises the polymerisation of one or more polymerisable monomers from which the optically transparent medium is to be formed in the presence of at least a portion of the semiconductor nanoparticles to be incorporated into the optically transparent medium.

15. A method according to claim 14, wherein the method of said polymerisation is selected from the group consisting of suspension, dispersion, emulsion, living, anionic, cationic, RAFT, ATRP, bulk, ring closing metathesis, and ring opening metathesis.

16. A method according to claim 14, wherein the method of said polymerisation is suspension polymerisation comprising thermal curing of the one or more polymerisable monomers.

17. A method according to claim 14, wherein said polymerisable monomers comprise methyl(meth)acrylate, ethylene glycol dimethacrylate, and vinyl acetate.

18. A method according to claim 13, wherein said incorporation of semiconductor nanoparticles into the optically transparent medium comprises physical attachment of at least a portion of the semiconductor nanoparticles to prefabricated polymeric beads.

19. A method according to claim 18, wherein said attachment is achieved by at least one of immobilisation of the portion of the semiconductor nanoparticles within the polymer matrix of the prefabricated polymeric beads or by chemical, covalent, ionic, or physical connection between the portion of semiconductor nanoparticles and the prefabricated polymeric beads.

20. A method according to claim 19, wherein said prefabricated polymeric beads comprise polystyrene, polydivinyl benzene, and a polythiol.

21. A method according to claim 13, wherein said nanoparticle-containing medium is embedding into the host light-emitting diode encapsulation material by mixing said nanoparticle-containing medium with said encapsulation material until the nanoparticle-containing medium is substantially evenly dispersed throughout said encapsulation medium.

22. A method according to claim 13, wherein said semiconductor nanoparticles are produced by converting a nanoparticle precursor composition to the material of the nanoparticles in the presence of a molecular cluster compound under conditions permitting seeding and growth of the nanoparticles on the cluster compound.

23. A method according to claim 22, wherein the semiconductor 8 nanoparticles incorporate first and second ions and the nanoparticle precursor composition comprises separate first and second nanoparticle precursor species containing said first and second ions respectively for incorporation into the growing nanoparticles.

24. A method according to claim 22, wherein the nanoparticles incorporate first and second ions, and the nanoparticle precursor composition comprises a single molecular species containing said first and second ions for incorporation into the growing nanoparticles.

25. A light-emitting device comprising:

a primary light source in optical communication with a formulation including a population of semiconductor nanoparticles incorporated into a plurality of discrete microbeads comprising an optically transparent medium, said nanoparticle-containing medium being embedded in a host light-emitting diode encapsulation medium.

26. A light-emitting device according to claim 25, wherein said primary light source is selected from the group consisting of a light-emitting diode, a laser, an arc lamp, and a black-body light source.

28. A method of fabricating a light-emitting device comprising:

providing a population of semiconductor nanoparticles in a plurality of discrete microbeads comprising an optically transparent medium;

embedding said nanoparticle-containing medium in a host light-emitting diode encapsulation material to produce a nanoparticle-containing formulation; and

depositing said formulation onto a primary light source such that said primary light source is in optical communication with said population of semiconductor nanoparticles.

29. A method according to claim 28, wherein said encapsulation medium is cured after being deposited onto said primary light source.