Semiconductor nanocrystal heterostructures

• US 20040110002A1
• Filed: 08/12/2003
• Published: 06/10/2004
• Est. Priority Date: 08/13/2002
• Status: Active Grant

• Current Assignee: Moungi G. Bawendi, Sungjee Kim
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Kim, Sungjee, Bawendi, Moungi G.
• Granted Patent: US 7,390,568 B2
• Time in Patent Office: Days
• US Class Current: 428/379
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• 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: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C09K 11/883 with zinc or cadmium
• CPC Class Codes: C30B 29/605 Products containing multiple oriented crystallites, e.g. columnar crystallites
• CPC Class Codes: C30B 33/00 After-treatment of single crystals or homogeneous polycrystalline material with defined structure C30B31/00 takes precedence
• CPC Class Codes: C30B 7/00 Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions from molten solvents C30B9/00; by normal or gradient freezing C30B11/00; under a protective fluid C30B27/00
• CPC Class Codes: G01N 33/588 with semiconductor nanocrystal label, e.g. quantum dots
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/02409 Selenides
• CPC Class Codes: H01L 21/02411 Tellurides
• CPC Class Codes: H01L 21/02521 Materials
• CPC Class Codes: H01L 21/0256 Selenides
• CPC Class Codes: H01L 21/02562 Tellurides
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: H01L 29/0665 the shape of the body defining a nanostructure nanotechnology per se B82B
• CPC Class Codes: H01L 29/0673 oriented parallel to a substrate
• CPC Class Codes: H01L 29/165 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/205 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/225 : in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/267 : in different semiconductor regions , e.g. heterojunctions H01L29/263 takes precedence
• CPC Class Codes: H10K 30/35 : comprising inorganic nanostructures, e.g. CdSe nanoparticles
• CPC Class Codes: Y02E 10/549 : Organic PV cells
• CPC Class Codes: Y10S 977/773 : Nanoparticle, i.e. structure having three dimensions of 100 nm or less
• CPC Class Codes: Y10S 977/774 : Exhibiting three-dimensional carrier confinement, e.g. quantum dots
• CPC Class Codes: Y10S 977/777 : Metallic powder or flake
• CPC Class Codes: Y10S 977/811 : Of specified metal oxide composition, e.g. conducting or semiconducting compositions such as ITO, ZnOx
• CPC Class Codes: Y10T 428/12021 : having composition or density gradient or differential porosity
• CPC Class Codes: Y10T 428/12528 : Semiconductor component
• CPC Class Codes: Y10T 428/12986 : Adjacent functionally defined components
• CPC Class Codes: Y10T 428/294 : including metal or compound thereof [excluding glass, ceramic and asbestos]
• CPC Class Codes: Y10T 428/2991 : Coated
• CPC Class Codes: Y10T 428/315 : Surface modified glass [e.g., tempered, strengthened, etc.]

Abstract

A semiconductor nanocrystal heterostructure has a core of a first semiconductor material surrounded by an overcoating of a second semiconductor material. Upon excitation, one carrier can be substantially confined to the core and the other carrier can be substantially confined to the overcoating.

Claims

1. A method of preparing a coated nanocrystal comprising:

introducing a core nanocrystal including a first semiconductor material into an overcoating reaction mixture; and

overcoating a second semiconductor material on the core nanocrystal, wherein the first semiconductor material and the second semiconductor material are selected so that, upon excitation, one carrier is substantially confined to the core and the other carrier is substantially confined to the overcoating.

2. The method of claim 1, wherein the conduction band of the first semiconductor material is at higher energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at higher energy than the valence band of the second semiconductor material.

3. The method of claim 1, wherein the conduction band of the first semiconductor material is at lower energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at lower energy than the valence band of the second semiconductor material.

4. The method of claim 1, wherein the nanocrystal further comprises an organic layer on a surface of the coated nanocrystal.

5. The method of claim 1, further comprising exposing the nanocrystal to an organic compound having affinity for a surface of the coated nanocrystal.

6. The method of claim 1, wherein the coated nanocrystal is dispersible in a liquid.

7. The method of claim 1, where in the first semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

8. The method of claim 1, wherein the first semiconductor material is ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

9. The method of claim 1, wherein the second semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

10. The method of claim 1, wherein the second semiconductor material is ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgO, MgS, MgSe, MgTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

11. The method of claim 1, wherein the first semiconductor material is CdTe and the second semiconductor material is CdSe.

12. The method of claim 1, wherein the first semiconductor material is CdSe and the second semiconductor material is ZnTe.

13. The method of claim 1, further comprising overcoating a third semiconductor material on the second semiconductor material.

14. The method of claim 13, wherein the third semiconductor material has a mismatched band offset compared to the second semiconductor material.

15. The method of claim 13, wherein the third semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

16. The method of claim 13, wherein the third semiconductor material is ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgO, MgS, MgSe, MgTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

17. A coated nanocrystal comprising:

a core nanocrystal including a first semiconductor material;

an overcoating including a second semiconductor material on the core nanocrystal; and

an organic layer on a surface of the coated nanocrystal,

wherein the first semiconductor material and the second semiconductor material are selected so that, upon excitation, one carrier is substantially confined to the core and the other carrier is substantially confined to the overcoating.

18. The nanocrystal of claim 17, wherein the conduction band of the first semiconductor material is at higher energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at higher energy than the valence band of the second semiconductor material.

19. The nanocrystal of claim 17, wherein the conduction band of the first semiconductor material is at lower energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at lower energy than the valence band of the second semiconductor material.

20. The nanocrystal of claim 17, wherein the organic layer is obtained by exposing the nanocrystal to an organic compound having affinity for a surface of the coated nanocrystal.

21. The nanocrystal of claim 17, wherein the coated nanocrystal is dispersible.

22. The nanocrystal of claim 17, where in the first semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

23. The nanocrystal of claim 17, wherein the first semiconductor material ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

24. The nanocrystal of claim 17, wherein the second semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

25. The nanocrystal of claim 17, wherein the second semiconductor material is ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgO, MgS, MgSe, MgTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, TlN, TlP, TlAs, TiSb, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

26. The nanocrystal of claim 17, wherein the nanocrystal emits light upon excitation, wherein the wavelength of maximum emission intensity is longer than 700 nm.

27. The nanocrystal of claim 17, wherein the nanocrystal emits light upon excitation, wherein the wavelength of maximum emission intensity is between 700 nm and 1500 nm.

28. A population of coated nanocrystals comprising:

a plurality of coated nanocrystals, each coated nanocrystal including a core nanocrystal and an overcoating on each core nanocrystal, wherein each core includes a first semiconductor material and each overcoating includes a second semiconductor material, the plurality of core nanocrystals forming a population of nanocrystals,

wherein the first semiconductor material and the second semiconductor material are selected so that, upon excitation, one carrier is substantially confined to the core and the other carrier is substantially confined to the overcoating; and

the plurality of nanocrystals is monodisperse.

29. The population of claim 28, wherein the conduction band of the first semiconductor material is at higher energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at higher energy than the valence band of the second semiconductor material.

30. The population of claim 28, wherein the conduction band of the first semiconductor material is at lower energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at lower energy than the valence band of the second semiconductor material.

31. The population of claim 28, further comprising an organic layer on a surface of each coated nanocrystal.

32. The population of claim 31, wherein the organic layer is obtained by exposing the population to an organic compound having affinity for a surface of a coated nanocrystal.

33. The population of claim 28, where in the first semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

34. The population of claim 28, wherein the first semiconductor material is ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

35. The population of claim 28, wherein the second semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

36. The population of claim 28, wherein the second semiconductor material is ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgO, MgS, MgSe, MgTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

37. The population of claim 28, wherein the population emits light upon excitation, wherein the wavelength of maximum emission intensity is longer than 700 nm.

38. The population of claim 28, wherein the population emits light upon excitation, wherein the wavelength of maximum emission intensity is between 700 nm and 1500 nm.

39. A coated nanocrystal comprising:

a core nanocrystal including a first semiconductor material;

a first overcoating including a second semiconductor material on the core nanocrystal; and

a second overcoating including a third semiconductor material on the first overcoating.

40. The nanocrystal of claim 39, wherein the first semiconductor material and the second semiconductor material are selected so that, upon excitation, one carrier is substantially confined to the core and the other carrier is substantially confined to the first overcoating.

41. The nanocrystal of claim 39, wherein the conduction band of the first semiconductor material is at higher energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at higher energy than the valence band of the second semiconductor material.

42. The nanocrystal of claim 39, wherein the conduction band of the first semiconductor material is at lower energy than the conduction band of the second semiconductor material and the valence band of the first semiconductor material is at lower energy than the valence band of the second semiconductor material.

43. The nanocrystal of claim 39, wherein the third semiconductor material has a mismatched band offset to the second semiconductor material.

44. The nanocrystal of claim 39, further comprising an organic layer on a surface of the coated nanocrystal.

45. The nanocrystal of claim 44, wherein the organic layer is obtained by exposing the nanocrystal to an organic compound having affinity for a surface of the coated nanocrystal.

46. The nanocrystal of claim 39, where in the first semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

47. The nanocrystal of claim 39, wherein the first semiconductor material is ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

48. The nanocrystal of claim 39, wherein the second semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

49. The nanocrystal of claim 39, wherein the second semiconductor material is ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgO, MgS, MgSe, MgTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

50. The nanocrystal of claim 39, wherein the third semiconductor material is a Group II-VI compound, a Group II-V compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group I-III-VI compound, a Group II-IV-VI compound, or a Group II-IV-V compound.

51. The nanocrystal of claim 39, wherein the third semiconductor material is ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgO, MgS, MgSe, MgTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, TlN, TlP, TlAs, TiSb, TlSb, PbS, PbSe, PbTe, or mixtures thereof.

52. The nanocrystal of claim 39, wherein the nanocrystal emits light upon excitation, wherein the wavelength of maximum emission intensity is longer than 700 nm.

53. The nanocrystal of claim 39, wherein the nanocrystal emits light upon excitation, wherein the wavelength of maximum emission intensity is between 700 nm and 1500 nm.

54. The nanocrystal of claim 53, wherein the quantum efficiency is greater than 10%.