CIGS nanoparticle ink formulation having a high crack-free limit

Patent metadata

Field	Value
Publication number	US-9893220-B2
Application number	US-201414513001-A
Country	US
Kind code	B2
Filing date	Oct 13, 2014
Priority date	Oct 15, 2013
Publication date	Feb 13, 2018
Grant date	Feb 13, 2018

Abstract

A method for formulating a CIGS nanoparticle-based ink, which can be processed to form a thin film with a crack-free limit (CFL) of 500 nm or greater, comprises: dissolving or dispersing Cu(In,Ga)S 2 and Cu(In,Ga)Se 2 nanoparticles; mixing the nanoparticle solutions/dispersions and adding oleic acid to form an ink; depositing the ink on a substrate; annealing to remove the organic components of the ink formulation; forming a film with a CFL ≧500 nm; and, repeating the deposition and annealing process to form a CIGS film having a thickness ≧1 μm. The film so produced may be incorporated into a thin film photovoltaic device.

First claim

What is claimed is:

1. A method for forming a photovoltaic film on a substrate comprising:
dissolving only CuInSe 2 nanoparticles in a first solvent to form a first solution;
dissolving only CuInS 2 nanoparticles in a second solvent to form a second solution;
combining only the first solution and the second solution to form a third solution;
adding only oleic acid to the third solution to form a binder-free ink;
depositing the ink on the substrate to form a first film;
annealing the first film in an inert atmosphere;
depositing additional ink on the first film on the substrate to form a second film; and
annealing the second film in an inert atmosphere,
wherein, the first and second films are further annealed under a selenium-rich atmosphere comprising H 2 Se gas in an inert carrier gas, the H 2 Se gas being at a concentration of 2 to 10% by volume, and
wherein after annealing each of the first film and the second film are crack-free films that comprise a crystalline CuIn(S,Se) 2 layer with grain sizes on the order of 480 nm.

2. The method recited in claim 1 further comprising sintering at least one of the first and the second films.

3. The method recited in claim 1 wherein the CuInSe 2 and CuInS 2 nanoparticles are capped with an organic ligand.

4. The method recited in claim 3 wherein the CuInSe 2 nanoparticles are capped with an organoselenol ligand.

5. The method recited in claim 3 wherein the CuInS 2 nanoparticles are capped with an organothiol ligand.

6. The method recited in claim 1 wherein at least one of the first solvent and the second solvent is toluene.

7. The method recited in claim 1 wherein the first solvent and the second solvent are selected from the group consisting of: alkanes; chlorinated solvents; ketones; ethers; and, terpenes.

8. The method recited in claim 1 wherein the ratio of the first solution and the second solution in the third solution is between about 0.8:1 and about 1:0.8.

9. The method recited in claim 1 wherein the oleic acid concentration in the ink is between about 2 and about 5 percent by weight.

10. The method recited in claim 1 wherein the substrate is indium tin oxide-coated glass.

11. The method recited in claim 1 wherein the substrate is molybdenum-coated glass.

12. The method recited in claim 1 wherein the substrate is molybdenum-coated soda-lime glass.

13. The method recited in claim 1 wherein one or both of the first and second annealing steps comprises annealing at a first, lower temperature between about 250° C. and about 300° C. for about 0.2 to about 7 minutes followed by annealing at a second, higher temperature between about 400° C. and about 460° C. for about 0.2 to about 7 minutes.

14. The method as recited in claim 1 wherein the inert carrier gas is molecular nitrogen.

15. The method as recited in claim 1 wherein the concentration of the H 2 Se gas is between about 2 and about 5 percent by volume.

16. A photovoltaic film on a substrate prepared by the process comprising the steps of:
dissolving only CuInSe 2 nanoparticles in a first solvent to form a first solution;
dissolving only CuInS 2 nanoparticles in a second solvent to form a second solution;
combining only the first solution and the second solution to form a third solution;
adding only oleic acid to the third solution to form a binder-free ink;
depositing the ink on the substrate to form a first film;
annealing the first film in an inert atmosphere;
depositing additional ink on the first film on the substrate to form a second film; and,
annealing the second film in an inert atmosphere,
wherein, the first and second films are further annealed under a selenium-rich atmosphere comprising H 2 Se gas in an inert carrier gas, the H 2 Se gas being at a concentration of 2 to 10% by volume, to produce a crystalline CuIn(S,Se) 2 layer with grain sizes on the order of 480 nm and
wherein after annealing each of the first film and the second film are crack-free films.

17. A photovoltaic device prepared by the process comprising the steps of:
dissolving only CuInSe 2 nanoparticles in a first solvent to form a first solution;
dissolving only CuInS 2 nanoparticles in a second solvent to form a second solution;
combining only the first solution and the second solution to form a third solution;
adding only oleic acid to the third solution to form a binder-free ink;
depositing the ink on a substrate to form a first film;
annealing the first film in an inert atmosphere;
depositing additional ink on the first film on the substrate to form a second film;
annealing the second film in an inert atmosphere;
depositing an n-type semiconductor layer on the second film;
depositing intrinsic ZnO on the n-type semiconductor layer;
depositing a window layer on the intrinsic ZnO;
depositing a metal grid on the window layer to form a multi-layer assembly; and,
encapsulating the multi-layer assembly,
wherein, the first and second films are further annealed under a selenium-rich atmosphere comprising H 2 Se gas in an inert carrier gas, the H 2 Se gas being at a concentration of 2 to 10% by volume, to produce a crystalline CuIn(S,Se) 2 layer with grain sizes on the order of 480 nm and
wherein after annealing each of the first film and the second film are crack-free films.

18. A photovoltaic device as recited in claim 17 wherein the n-type semiconductor layer comprises cadmium sulfide (CdS).

19. A photovoltaic device as recited in claim 17 wherein the n-type semiconductor layer comprises zinc sulfide (ZnS).

20. A photovoltaic device as recited in claim 17 wherein the window layer comprises aluminum zinc oxide.

21. A photovoltaic device as recited in claim 17 wherein the window layer comprises indium tin oxide.

Assignees

• Nanoco Technologies Ltd

Inventors

• Liu Zugang
• Newman Christopher

Classifications

• C09D11/52

  Electrically conductive inks · CPC title

• Y02E10/50

  Photovoltaic [PV] energy · CPC title

• Y02E10/541

  CuInSe2 material PV cells · CPC title

• H01L31/0322 Primary

  Electricity · mapped topic

• H10F71/00

  Manufacture or treatment of devices covered by this subclass (patterning processes to connect thin photovoltaic cells in integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/33; manufacture or treatment of encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/80; manufacture or treatment of integrated devices, or assemblies of multiple devices, comprising at least one element in which radiation controls the flow of current H10F39/00) · CPC title