Photovoltaic thin-film cell produced from metallic blend using high-temperature printing

• US 20050183768A1
• Filed: 04/30/2004
• Published: 08/25/2005
• Est. Priority Date: 02/19/2004
• Status: Active Grant

• Current Assignee: Aeris Capital Sustainable IP, Ltd.
• Original Assignee: Nanosolar Incorporated
• Inventors: Roscheisen, Martin R., Sager, Brian M.
• Granted Patent: US 7,605,328 B2
• Time in Patent Office: Days
• US Class Current: 136/263
• 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 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 5/00 Nanobiotechnology or nanomedicine, e.g. protein engineering or drug delivery
• CPC Class Codes: C23C 18/1204 inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
• CPC Class Codes: C23C 18/1266 Particles formed in situ
• CPC Class Codes: C23C 18/127 Preformed particles
• CPC Class Codes: C23C 18/1295 with after-treatment of the deposited inorganic material
• CPC Class Codes: H01L 31/0322 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
• CPC Class Codes: H01L 31/042 PV modules or arrays of single PV cells supporting structures for PV modules H02S20/00
• CPC Class Codes: H01L 31/06 characterised by potential barriers
• CPC Class Codes: H01L 31/0749 including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: H01L 31/186 Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
• CPC Class Codes: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

The metallic components of a IB-IIIA-VIA photovoltaic cell active layer may be directly coated onto a substrate by using relatively low melting point (e.g., less than about 500° C.) metals such as indium and gallium. Specifically, CI(G)S thin-film solar cells may be fabricated by blending molten group IIIA metals with solid nanoparticles of group IB and (optionally) group IIIA metals. The molten mixture may be coated onto a substrate in the molten state, e.g., using coating techniques such as hot-dipping, hot microgravure and/or air-knife coating. After coating, the substrate may be cooled and the film annealed, e.g., in a sulfur-containing or selenium-containing atmosphere.

Claims

1. A method for forming an active layer coating, the method comprising the steps of:

forming a molten mixture of one or more metals of group IIIA and metallic nanoparticles containing elements of group IB; and

coating a substrate with a film formed from the molten mixture.

2. The method of claim 1 wherein the nanoparticles are between about 1 nanometer and about 1 micron in size.

3. The method of claim 2 wherein the nanoparticles are between about 1 nanometer and about 500 nanometers in size.

4. The method of claim 3 wherein the nanoparticles are between about 1 nanometer and about 100 nanometers in size.

5. The method of claim 4 wherein the nanoparticles are between about 1 nanometer and about 50 nanometers in size.

6. The method of claim 1 wherein the nanoparticles have a substantially uniform size distribution characterized by an average particle size D.

7. The method of claim 6 wherein, if D is greater than about 5 nm, the nanoparticles have sizes within about 40% of D.

8. The method of claim 6 wherein, if the average particle size is less than about 5 nm, the nanoparticles have sizes within about 2 nm of D.

9. The method of claim 1 wherein the molten mixture includes one or more metals with melting points of less than about 525°

C.

10. The method of claim 1 wherein forming the nanoparticles includes laser ablation, mechanical milling, grinding, nucleation from vapor, exploding wires by electrical current surge, thermal treatment, sonolysis, pulse radiolysis, electrochemical reduction or chemical reduction.

11. The method of claim 1, wherein coating a substrate with a film formed from the molten mixture includes microgravure coating the molten mixture onto a surface of the substrate.

12. The method of claim 1, wherein coating a substrate with a film formed from the molten mixture includes hot-dip coating the molten mixture onto the substrate.

13. The method of claim 1 wherein coating a substrate with a film formed from the molten mixture includes extruding the molten mixture to form a film.

14. The method of claim 13 further comprising laminating the film to the substrate.

15. The method of claim 1 wherein coating a substrate with a film formed from the molten mixture includes plasma spray coating the molten mixture onto the substrate.

16. The method of claim 1, further comprising adjusting a thickness of the film formed from the molten mixture.

17. The method of claim 16 wherein adjusting a thickness of the film formed from the molten mixture includes doctoring the film.

18. The method of claim 17 wherein doctoring the film includes the use of an air knife.

19. The method of claim 1, further comprising incorporating one or more elements of group VIA into the film.

20. The method of claim 19 wherein incorporating one or more elements of group VIA into the film includes exposing the film to a vapor containing selenium, sulfur, H₂S or H₂Se.

21. The method of claim 20 wherein the group VIA element is selenium (Se) or sulfur (S).

22. The method of claim 1 wherein the group IB element is copper (Cu), and one or more metals of group IIIA include indium and (optionally) gallium.

23. The method of claim 22 wherein the group VIA element is selenium (Se) or sulfur (S) and wherein a stoichiometric ratio of the Cu, In and Se or S in the active layer coating is approximately CuIn_1-xGa_x(S or Se)₂, where x is between 0 and 1.

24. The method of claim 22 wherein a stoichiometric ratio of copper to indium in the film is about 0.9.

25. The method of claim 1, further comprising cooling the substrate to rapidly solidify the coating on the substrate.

26. The method of claim 1 further comprising melting the nanoparticles in the molten mixture.

27. The method of claim 1 further comprising maintaining the molten mixture at a sufficiently low temperature that the nanoparticles do not melt in the molten mixture.

28. The method of claim 1 further comprising annealing the film formed from the molten mixture.

29. The method of claim 28 wherein the group IB element is copper and annealing the film includes heating the film to a temperature sufficient to cause Cu atoms to diffuse through the material of the film.

31. The cell of claim 29 wherein at least one of the base electrode and top electrode is transparent.

32. The cell of claim 29 further comprising a layer of cadmium sulfide (CdS), zinc sulfide (ZnS), or zinc selenide (ZnS) or some combination of two or more of these disposed between the active layer and the top electrode.

30. A photovoltaic cell, comprising:

a base electrode;

a top electrode; and

an active layer disposed between the base electrode and top electrode, the active layer containing a IB-IIIA-VIA alloy, wherein the active layer is formed from a molten mixture containing one or more metals of group IIIA and metallic nanoparticles containing elements of group IB.