Quantum dot white and colored light-emitting devices

• US 6,803,719 B1
• Filed: 07/09/1999
• Issued: 10/12/2004
• Est. Priority Date: 04/01/1998
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Heine, Jason, Bawendi, Moungi E., Jensen, Klavs F., Moon, Ronald L., Miller, Jeffrey N.
• Primary Examiner(s): TRAN, MINH LOAN
• Application Number:
  US09/350,956
• Time in Patent Office: 1,922 Days
• Field of Search: 257/88, 257/89, 257/98, 257/100, 257/99, 313/501-503
• US Class Current: 313/501
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• 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 11/883 with zinc or cadmium
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials
• CPC Class Codes: H01S 3/169 Nanoparticles, e.g. doped nanoparticles acting as a gain material
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 977/95 Electromagnetic energy

Abstract

A light-emitting device comprising a population of quantum dots (QDs) embedded in a host matrix and a primary light source which causes the QDs to emit secondary light and method of making such a device. The size distribution of the QDs is chosen to allow light of a particular color to be emitted therefrom. The light emitted from the device may be of either a pure (monochromatic) color, or a mixed (polychromatic) color, and may consist solely of light emitted from the QDs themselves, or of a mixture of light emitted from the QDs and light emitted from the primary source. The QDs desirably are composed of an undoped semiconductor such as CdSe, and may optionally be overcoated to increase photoluminescence.

Claims

1. A device comprising:

a primary light source; and

a population of photoluminescent quantum dots (QDs) disposed in a host matrix,

wherein;

each QD of the population comprises a core of an independently selected size and composition, and the population comprises a selected size distribution of QDs;

at least a portion of the QDs have a band gap energy smaller than the energy of at least a portion of the light produced by the light source; and

the matrix is in optical communication with the light source and is disposed so as to allow the light to pass therethrough, thereby causing the QDs to photoluminesce light of a color characteristic of the size, size distribution, composition, or combination thereof, wherein the matrix allows both light from the light source and photoluminesced light to pass therethrough.

2. The device of claim 1, wherein the host matrix is transparent to photoluminescent light emitted by the QDs.

3. The device of claim 1, wherein the host matrix is transparent to light produced by the light source and to photoluminescent light emitted by the QDs.

4. The device of claim 1, wherein the core of each QD comprises a material independently selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb, alloys thereof, and mixtures thereof.

5. The device of claim 4, wherein the QDs further comprise a core overcoat comprising a material independently selected from the group consisting of ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaAs, GaSb, HgO, HgS, HgSe, HgTe, InAs, InN, InP, InSb, AlAs, AlN, AlP, AlSb, alloys thereof, and mixtures thereof.

6. The device of claim 5, wherein the overcoated core further comprises a coat having an affinity for the host matrix.

7. The device of claim 1, wherein the primary light source is in physical contact with the host matrix.

8. The device of claim 1, further comprising a medium interposed between the primary light source and the host matrix.

9. The device of claim 1, wherein the host matrix comprises at least one material selected from the group consisting of liquids, polymers, epoxies, silica glasses, and silica gels.

10. The device of claim 1, wherein the host matrix comprises at least one polymer selected from the group consisting of polyacrylate, polystyrene, polyimide, polyacrylamide, polyethylene, polyvinyl, poly-diacetylene, polyphenylene-vinylene, polypeptide, polysaccharide, polysulfone, polypyrrole, polyimidazole, polythiophene, polyether, epoxies, silica glass, silica gel, siloxane, polyphosphate, hydrogel, agarose, and cellulose.

11. The device of claim 1, wherein the QDs further comprise a core coat comprising a material having an affinity for the host matrix.

12. The device of claim 11, wherein the host matrix comprises a polymer and the coat material comprises a related monomer.

13. The device of claim 1, wherein the 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.

14. The device of claim 1, wherein the population of QDs has a size distribution having less than a 10% rms deviation in diameter of the core.

15. A composition comprising a population of quantum dots (QDs) dispersed without substantial flocculation in a host matrix, wherein each QD of the population comprises a core of an independently selected size and composition and the population comprises a selected size distribution of QDs, and further wherein the QDs are selected to photoluminesce light when QDs in the host matrix are irradiated with light from a primary source whose energy is greater than the energy of at least a portion of the photoluminesced light.

16. The composition of claim 15, wherein the core comprises a material independently selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb, alloys thereof, and mixtures thereof.

17. The composition of claim 16, wherein the QDs further comprise a core overcoat comprising a material independently selected from the group consisting ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaAs, GaSb, HgO, HgS, HgSe, HgTe, InAs InN, InP, InSb, AlAs, AlN, AlP, AlSb, alloys thereof, and mixtures thereof.

18. The composition of claim 17, wherein the overcoated core further comprise a coat comprising a material having an affinity for the host matrix.

19. The composition of claim 15, wherein the host matrix comprises a material selected from the group consisting of liquids, polymers, epoxies, a silica glass, a silica gel and a combination thereof.

20. The composition of claim 15, wherein the host matrix comprises a polymer selected from the group consisting of polyacrylate, polystyrene, polyimide, polyacrylamide, polyethylene, polyvinyl, poly-diacetylene, polyphenylene-vinylene, polypeptide, polysaccharide, polysulfone, polypyrrole, polyimidazole, polythiophene, polyether, epoxies, silica glass, silica gel, siloxane, polyphosphate, hydrogel, agarose, and cellulose.

21. The composition of claim 15, wherein the QDs further comprise a core coat comprising a material having an affinity for the host matrix.

22. The composition of claim 21, wherein the host matrix comprises a polymer and the coat material comprises a related monomer.

23. The composition of claim 15, wherein the population of QDs has a size distribution having less than a 10% rms deviation in diameter of the core.

24. A prepolymer composition, comprising:

a precursor material capable of being reacted to form a solid host matrix that allows light to pass therethrough; and

a population of quantum dots (QDs) dispersed in the precursor material without substantial flocculation, wherein each QD of the population comprises a core of an independently selected size and composition, and the population comprises a selected size distribution of QDs.

25. The composition of claim 24, wherein the precursor material is a monomer capable of being reacted to form a polymer.

26. The composition of claim 25, wherein the precursor material comprises a monomer selected from the group consisting of acrylics, imides, acrylamides, ethylenes, vinylenes, diacetylenes, phenylene-vinylenes, peptides, saccharides, sulfones, pyrroles, imidazoles, thiophenes, ethers, epoxides, silanes, phosphates, styrenes, acids, peroxides, anhydrides, amines, and alcohols.

27. The composition of claim 24, wherein the core comprises a material independently selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb, alloys thereof, and mixtures thereof.

28. The composition of claim 27, wherein the QDs further comprise a core overcoat comprising a material selected from the group consisting of ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaAs, GaSb, HgO, HgS, HgSc, HgTe, InAs, InN, InP, InSb, AlAs, AlN, AlP, AlSb, alloys thereof, and mixtures thereof.

29. The composition of claim 24, wherein the QDs further comprise a core coat comprising a material having an affinity for the precursor material.

30. The composition of claim 28, wherein the overcoated core further comprises a coat comprising a material having an affinity for the precursor material.

31. The composition of claim 30, wherein the overcoated core further comprises a coat that is a material that is a related monomer to the polymer formed from the precursor material.

32. The composition of claim 24, wherein the population of QDs has a size distribution having less than a 10% rms deviation in diameter of the core.

33. A method of producing light of a selected color, comprising:

(a) providing a population of quantum dots (QDs), wherein each QD of the population comprises a core of an independently selected size and composition, the population comprises a selected size distribution of QDs, and the QDs have a surface adapted to allow the QDs to be dispersed in a host matrix;

(b) dispersing the QDs in the host matrix without substantial flocculation; and

(c) illuminating the QDs disposed in the host matrix with primary light of an energy greater than the characteristic band gap energy of at least a portion of the QDs,

whereby the selected color is photoluminescent light emitted by the QDs, light transmitted from the primary light source through the host matrix or a combination thereof.

34. The method of claim 33, wherein the host matrix allows photoluminescent light emitted by the QDs to pass therethrough.

35. The method of claim 34, wherein the photoluminescent light emitted by the QDs is detected.

36. The method of claim 33, wherein the light of the selected color is the photoluminescent light emitted by the QD.

37. The method of claim 33, wherein the core comprises a material independently selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, GaAs, GaP, GaAs, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, AlSb, alloys thereof, and mixtures thereof.

38. The method of claim 33, wherein step (a) further comprises coating the core with an overcoat.

39. The method of claim 38, wherein the core overcoat comprises a material independently selected from the group consisting of ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaAs, GaSb, HgO, HgS, HgSe, HgTe, InAs, InN, InP, InSb, AlAs, AlN, AlP, AlSb, alloys thereof, and mixtures thereof.

40. The method of claim 38, wherein step (a) further comprises coating the QDs with a coat material having an affinity for the host matrix.

41. The method of claim 38, wherein step (a) further comprises coating the overcoated core with a coat material having an affinity for the host matrix.

42. The method of claim 33, wherein step (a) comprises,

(i) providing a precursor material having QDs disposed therein; and

(ii) reacting the precursor material to form a solid host matrix having QDs disposed therein.

43. The method of claim 33, wherein the host matrix comprises at least one material selected from the group consisting of polymers, epoxies, silica glasses, and silica gels.

44. The method of claim 33, wherein the host matrix comprises a polymer selected from the group consisting of polyacrylate, polystyrene, polyimide, polyacrylamide, polyethylene, polyvinyl, poly-diacetylene, polyphenylene-vinylene, polypeptide, polysaccharide, polysulfone, polypyrrole, polyimidazole, polythiophene, polyether, epoxies, silica glass, silica gel, siloxane, polyphosphate, hydrogel, agarose, and cellulose.

45. A method of producing light of a selected color, comprising:

(a) providing a population of quantum dots (ODs), wherein each OD of the population comprises a core of an independently selected size and composition, the population comprises a selected size distribution of ODs, and the ODs have a surface adapted to allow the ODs to be dispersed in a host matrix;

(b) dispersing the ODs in the host matrix; and

(c) illuminating the ODs disposed in the host matrix with primary light of an energy greater than the characteristic band gap energy of at least a portion of the ODs,

whereby the selected color is photoluminescent light emitted by the ODs, light transmitted from the Primary light source through the host matrix or a combination thereof;

and wherein the host matrix allows light produced by the light source and photoluminescent light emitted by the QDs to pass therethrough.

46. The method of claim 45, wherein the photoluminescent light emitted by the QDs is detected.

47. The method of claim 45, wherein both the light produced by the light source and the photoluminescent light emitted by the QDs are detected.

48. The method of claim 45, wherein the light of the selected color is the photoluminescent light emitted by the QD.

49. The method of claim 45, wherein the light of the selected color is the combination of photoluminescent light emitted by the QDs and light transmitted from the primary light source through the host matrix.

50. A method of producing light of a selected color, comprising:

(a) providing a population of guantum dots (ODs), wherein each OD of the population comprises a core of an independently selected size and composition, the population comprises a selected size distribution of ODs, and the ODs have a surface adapted to allow the ODs to be dispersed in a host matrix;

(b) dispersing the ODs in the host matrix; and

(c) illuminating the ODs disposed in the host matrix with primary light of an energy greater than the characteristic band gap energy of at least a portion of the ODs.

wherein the light of the selected color is the combination of photoluminescent light emitted by the QDs and light transmitted from the primary light source through the host matrix.

51. A method of producing light of a selected color, comprising:

(a) providing a population of quantum dots (ODs), wherein each OD of the population comprises a core of an independently selected size and composition, the population comprises a selected size distribution of ODs, and the ODs have a surface adapted to allow the ODs to be dispersed in a host matrix;

(b) dispersing the ODs in the host matrix; and

(c) illuminating the ODs disposed in the host matrix with primary light of an energy greater than the characteristic band gap energy of at least a portion of the ODs,

whereby the selected color is photoluminescent light emitted by the ODs, light transmitted from the primary light source through the host matrix or a combination thereof;

and wherein step (a) comprises,

(i) providing at least two precursor materials, wherein each precursor material has disposed therein a population of QDs having a size, size distribution, composition or combination thereof, selected to be different from that of the population of QDs in any of the other precursor materials,

(ii) combining the precursor materials, and

(iii) reacting the precursor materials to form a solid host matrix having QDs disposed therein.

52. The method of claim 51, wherein first and second precursor materials are provided, and further wherein the first precursor material has a first population of QDs having a first size, size distribution, composition or combination thereof disposed therein and the second precursor material has a second population of QDs having a second size, size distribution, composition or combination thereof disposed therein.

53. The method of claim 51, wherein step (ii) comprises admixing the precursor materials.

54. A method of producing light of a selected color, comprising:

(a) providing a population of quantum dots (QDs), wherein each QD of the population comprises a core of an independently selected size and composition, the population comprises a selected size distribution of ODs, and the ODs have a surface adapted to allow the ODs to be dispersed in a host matrix;

(b) dispersing the QDs in the host matrix; and

(c) illuminating the ODs disposed in the host matrix with Primary light of an energy greater than the characteristic band gap energy of at least a portion of the ODs,

whereby the selected color is photoluminescent light emitted by the QDs, light transmitted from the primary light source through the host matrix or a combination thereof;

and wherein step (a) comprises,

(i) providing at least two precursor materials, wherein each precursor material has disposed therein a population of QDs having a size, size distribution, composition or combination thereof, selected to be different from that of the population of QDs in any of the other precursor materials,

(ii) forming a layer of a precursor material;

(iii) reacting the layer of precursor material to form a solid host matrix layer having QDs disposed therein; and

(iv) repeating steps (ii) and (iii) on the solid host matrix layer formed in step (iii).

55. The method of claim 54, wherein step (iv) comprises repeating steps (ii) and (iii) with the same precursor material.

56. The method of claim 54, wherein step (iv) comprises repeating steps (ii) and (iii) with a different precursor material.