Semiconductor nanocrystal heterostructures having specific charge carrier confinement
View Patent ↗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.
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 of the nanocrystal to form an exciton, one charge carrier of the exciton is substantially confined to the core and the other charge carrier of the exciton 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, GaSh, 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, GaSh, 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;
a chemically formed 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 of the nanocrystal to form an exciton, one charge carrier of the exciton is substantially confined to the core and the other charge carrier of the exciton 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, TlSb, 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 a chemically formed 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 of the nanocrystal to form an exciton, one charge carrier of the exciton is substantially confined to the core and the other charge carrier of the exciton 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.