Halometallate ligand-capped semiconductor nanocrystals
Halometallate-capped semiconductor nanocrystals and methods for making the halometallate-capped semiconductor nanocrystals are provided. Also provided are methods of using solutions of the halometallate-capped semiconductor nanocrystals as precursors for semiconductor film formation. When solutions of the halometallate ligand-capped semiconductor nanocrystals are annealed, the halometallate ligands can act as grain growth promoters during the sintering of the semiconductor nanocrystals.
1. A method of forming a semiconductor film, the method comprising:
forming a solution of halometallate-capped semiconductor nanocrystals, the halometallate-capped semiconductor nanocrystals comprising:
semiconductor nanocrystals, each semiconducting nanocrystal having a surface; and
halometallate ligands bound to the surfaces of the semiconductor nanocrystals;
forming a coating of the solution comprising the halometallate-capped semiconductor nanocrystals on a substrate surface; and
annealing the coating, wherein the nanocrystals are sintered to form the semiconductor film.
2. The method of claim 1 , wherein the halometallate ligands act as grain growth promoters for the semiconductor nanocrystals during the annealing of the coating.
3. The method of claim 1 , wherein the semiconductor nanocrystals are Group II-VI nanocrystals.
4. The method of claim 3 , wherein the Group II-VI nanocrystals comprise a metastable phase of the Group II-VI semiconductor.
5. The method of claim 3 , wherein the Group II-VI nanocrystals comprise CdTe nanocrystals, HgSe nanocrystals, HgTe nanocrystals, HgS nanocrystals, Hg x Cd 1-x Te nanocrystals, Hg x Cd 1-x S nanocrystals, Hg x Cd 1-x Se nanocrystals, Cd x Zn 1-x Te nanocrystals, Cd x Zn 1-x Se nanocrystals, Cd x Zn 1-x S nanocrystals, CdSe nanocrystals, CdS nanocrystals, ZnS nanocrystals, ZnSe nanocrystals, ZnTe nanocrystals, or mixtures of two or more thereof, where 0<x<1.
6. The method of claim 3 , wherein the Group II-VI nanocrystals are CdTe nanocrystals.
7. The method of claim 1 , wherein the halometallate ligands comprise halometallates of metals selected from group 12 or group 13 of the periodic table of the elements.
8. The method of claim 1 , wherein the halometallate ligands are selected from CdCl 3 − anions, CdCl 4 2− anions, CdI 3 − anions, CdBr 3 − anions, CdBr 4 2− anions, InCl 4 − anions, HgCl 3 − anions, ZnCl 3 − anions, ZnCl 4 2− anions, and ZnBr 4 2− anions, and mixtures of two or more thereof.
9. The method of claim 6 , wherein the halometallate ligands comprise CdCl 3 − anions.
10. The method of claim 1 , wherein the semiconductor nanocrystals comprise core-shell nanocrystals; the shells of the core-shell nanocrystals comprise a Group II-VI semiconductor; and the semiconductor film comprises the cores of the nanocrystals dispersed in a matrix comprising the sintered shells of the nanocrystals.
11. The method of claim 10 , wherein the cores of the core-shell nanocrystals comprise a Group III-V semiconductor.
12. The method of claim 10 , wherein the Group II-VI semiconductor is CdTe, HgSe, HgTe, HgS, Hg x Cd 1-x Te, Hg x Cd 1-x S, Hg x Cd 1-x Se, Cd x Zn 1-x Te, Cd x Zn 1-x Se, Cd x Zn 1-x S nanocrystals, CdSe, CdS, ZnS, ZnSe, ZnTe, or mixtures of two or more thereof, where 0<x<1.
13. The method of claim 1 , wherein coating a solution comprising the halometallate-capped semiconductor nanocrystals on a substrate surface comprises doctor blading or spray-coating the solution comprising the halometallate-capped semiconductor nanocrystals onto the substrate surface.
14. The method of claim 5 , wherein the Group II-VI nanocrystals comprise CdTe nanocrystals, HgSe nanocrystals, HgTe nanocrystals, HgS nanocrystals, Hg x Cd 1-x Te nanocrystals, Hg x Cd 1-x S nanocrystals, Hg x Cd 1-x Se nanocrystals, Cd x Zn 1-x Te nanocrystals, Cd x Zn 1-x Se nanocrystals, Cd x Zn 1-x S nanocrystals, ZnS nanocrystals, ZnSe nanocrystals, ZnTe nanocrystals, or mixtures of two or more thereof, where 0<x<1.
15. The method of claim 8 , wherein the halometallate ligands are selected from CdCl 4 2− anions, CdI 3 − anions, CdBr 4 2− anions, ZnCl 3 − anions, and ZnBr 4 2− anions, and mixtures of two or more thereof.
16. The method of claim 8 , wherein the halometallate ligands are HgCl 3 − anions.
17. A method of forming an optoelectronic device, the method comprising:
forming a solution of halometallate-capped semiconductor nanocrystals, the halometallate-capped semiconductor nanocrystals comprising:
semiconductor nanocrystals, each semiconducting nanocrystal having a surface; and
halometallate ligands bound to the surfaces of the semiconductor nanocrystals;
forming a coating of the solution comprising the halometallate-capped semiconductor nanocrystals on a surface of a first electrode;
annealing the coating, wherein the semiconductor nanocrystals are sintered to form a photoactive, light-absorbing semiconductor film;
forming a layer of charge transporting material over the photoactive, light-absorbing semiconductor film; and
forming a second electrode on the layer of charge transporting material.
18. The method of claim 17 , wherein the semiconductor nanocrystals comprise CdTe nanocrystals, HgSe nanocrystals, HgTe nanocrystals, HgS nanocrystals, Hg x Cd 1-x Te nanocrystals, Hg x Cd 1-x S nanocrystals, Hg x Cd 1-x Se nanocrystals, Cd x Zn 1-x Te nanocrystals, Hg x Cd 1-x Se nanocrystals, Hg x Cd 1-x S nanocrystals, CdSe nanocrystals, CdS nanocrystals, ZnS nanocrystals, ZnSe nanocrystals, ZnTe nanocrystals, or mixtures of two or more thereof, where 0<x<1.
19. The method of claim 17 , wherein the semiconductor nanocrystals are CdTe nanocrystals.
20. The method of claim 17 , wherein the halometallate ligands are selected from CdCl 4 2− anions, CdI 3 − anions, CdBr 4 2− anions, ZnCl 3 − anions, and ZnBr 4 2− anions, and mixtures of two or more thereof.
21. The method of claim 17 , wherein the halometallate ligands are HgCl 3 − anions.
22. The method of claim 18 , wherein the Group II-VI nanocrystals comprise CdTe nanocrystals, HgSe nanocrystals, HgTe nanocrystals, HgS nanocrystals, Hg x Cd 1-x Te nanocrystals, Hg x Cd 1-x S nanocrystals, Hg x Cd 1-x Se nanocrystals, Cd x Zn 1-x Te nanocrystals, Cd x Zn 1-x Se nanocrystals, Cd x Zn 1-x S nanocrystals, ZnS nanocrystals, ZnSe nanocrystals, ZnTe nanocrystals, or mixtures of two or more thereof, where 0<x<1.
23. The method of claim 19 , wherein the halometallate ligands comprise CdCl 3 − anions.
24. A method of forming a field effect transistor, the method comprising:
forming a solution of halometallate-capped semiconductor nanocrystals, the halometallate-capped semiconductor nanocrystals comprising:
semiconductor nanocrystals, each semiconducting nanocrystal having a surface; and
halometallate ligands bound to the surfaces of the semiconductor nanocrystals;
forming a coating of the solution comprising the halometallate-capped semiconductor nanocrystals on a surface of a gate dielectric layer;
annealing the coating, wherein the semiconductor nanocrystals are sintered to form a semiconductor film that provides a conducting channel layer for the field effect transistor;
forming a source electrode on the semiconductor film;
forming a drain electrode on the semiconductor film; and
forming a gate electrode on the gate dielectric layer.
25. The method of claim 24 , wherein the semiconductor nanocrystals comprise CdTe nanocrystals, HgSe nanocrystals, HgTe nanocrystals, HgS nanocrystals, Hg x Cd 1-x Te nanocrystals, Hg x Cd 1-x S nanocrystals, Hg x Cd 1-x Se nanocrystals, Cd x Zn 1-x Te nanocrystals, Cd x Zn 1-x Se nanocrystals, Cd x Zn 1-x S nanocrystals, CdSe nanocrystals, CdS nanocrystals, ZnS nanocrystals, ZnSe nanocrystals, ZnTe nanocrystals, or mixtures of two or more thereof, where 0<x<1.
26. Halometallate-capped Group II-VI nanocrystals comprising:
Group II-VI nanocrystals selected from the group consisting of CdTe nanocrystals, HgSe nanocrystals, HgTe nanocrystals, HgS nanocrystals, Hg x Cd 1-x Te nanocrystals, Hg x Cd 1-x S nanocrystals, Hg x Cd 1-x Se nanocrystals, Cd x Zn 1-x Te nanocrystals, Cd x Zn 1-x Se nanocrystals, Cd x Zn 1-x S nanocrystals, ZnS nanocrystals, ZnSe nanocrystals, ZnTe nanocrystals, or mixtures of two or more thereof, where 0<x<1, each nanocrystals having a surface; and
halometallate ligands bound to the surfaces of the Group II-VI nanocrystals, wherein the halometallate ligands are anions having one of the formulas MX 3 − , MX 4 − , and MX 4 2 − , where M is an element selected from group 12 of the periodic table and X is a halide atom.
27. The nanocrystals of claim 26 , wherein the Group II-VI nanocrystals are CdTe nanocrystals.
28. A method of making the halometallate-capped Group II-VI nanocrystals of claim 26 , the method comprising forming a solution comprising organic ligand-capped Group II-VI nanocrystals and the anions under conditions that facilitate the exchange of the anions with the organic ligands capping the Group II-VI nanocrystals, whereby the halometallate-capped Group II-VI nanocrystals of claim 19 are formed.