Method of fabricating high-efficiency Cu(In,Ga)(SeS).sub.2 thin films for solar cells

• US 5,441,897 A
• Filed: 02/16/1994
• Issued: 08/15/1995
• Est. Priority Date: 04/12/1993
• Status: Expired due to Term

• Current Assignee: Alliance For Sustainable Energy LLC
• Original Assignee: Midwest Research Institute
• Inventors: Tuttle, John R., Gabor, Andrew M., Carapella, Jeffrey J., Noufi, Rommel, Contreras, Miguel A., Tennant, Andrew L., Albin, David S.
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US08/197,204
• Time in Patent Office: 545 Days
• Field of Search: 437/5, 437/108-109, 437/234, 427/76, 427/255.2, 427/255.7, 136/264, 136/265
• US Class Current: 438/95
• 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: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A process for producing a slightly Cu-poor thin film of Cu(In,Ga)(Se,S)₂ comprises depositing a first layer of (In,Ga)_x (Se,S)_y followed by depositing just enough Cu+(Se,S) or Cu_x (Se,S) to produce the desired slightly Cu-poor material. In a variation, most, but not all, (about 90 to 99%) of the (In,Ga)_x (Se,S)_y is deposited first, followed by deposition of all the Cu+(Se,S) or Cu_x (Se,S) to go near stoichiometric, possibly or even preferably slightly Cu-rich, and then in turn followed by deposition of the remainder (about 1 to 10%) of the (In,Ga)_x (Se,S)_y to end with a slightly Cu-poor composition. In yet another variation, a small portion (about 1 to 10%) of the (In,Ga)_x (Se,S)_y is first deposited as a seed layer, followed by deposition of all of the Cu+(Se,S) or Cu_x (Se,S) to make a very Cu-rich mixture, and then followed deposition of the remainder of the (In,Ga)_x (Se,S)_y to go slightly Cu-poor in the final Cu(In,Ga)(Se,S)₂ thin film.

Claims

1. A process for fabricating thin film semiconductor devices, comprising the steps of:

depositing a layer of (In,Ga)_x (Se,S)_y on a substrate, and

depositing a sufficient amount of Cu+(Se,S) or Cu_x (Se,S) onto the layer of (In,Ga)_x (Se,S)_y to produce a slightly Cu-poor thin film of Cu(In,Ga)(Se,S)₂ on the substrate wherein said slightly Cu-poor thin film comprises a ratio of Cu to (In,Ga) in the range of about 0.8<

Cu/(In,Ga)<

0.99.

2. The process of claim 1, including the steps of depositing said layer of (In,Ga)_x (Se,S)_y at a temperature in the range of ambient to 600°

C.

3. The process of claim 1, including the step of depositing said layer of (In,Ga)_x (Se,S)_y at a temperature of about 260°

C.

4. The process of claim 1, including the step of depositing said Cu+(Se,S) or Cu_x (Se,S) at a temperature in the range of about 350°

C. to 1,200°

C.

5. The process of claim 1, including the step of depositing said Cu+(Se,S) or Cu_x (Se,S) at a temperature in the range of about 350°

C. to 1,000°

C.

6. The process of claim 1, including the step of depositing said Cu+(Se,S) or Cu_x (Se,S) at a temperature in the range of about 565°

C.

7. The process of claim 1, including the step of holding a flux of (Se,S) to said substrate and thin film after stopping deposition of said Cu or Cu_x (Se,S) while cooling said substrate and said thin film down to a temperature of about 350°

C.

8. The process of claim 1 wherein said slightly Cu-poor thin film comprises CuInSe₂ with no Ga and has a composition ratio of Cu/In of about 0.96.

9. The process of claim 1 wherein said slightly Cu-poor thin film comprises a composition ratio of (Cu/In,Ga) of about 0.92.

10. A process for fabricating thin film semiconductor devices, comprising the steps of:

depositing a layer of (In,Ga)_x (Se,S)_y on a substrate;

depositing a sufficient amount of Cu+(Se,S) or Cu_x (Se,S) on said layer of (In,Ga)_x (SeS)_y to produce a near stoichiometric composition of Cu(In,Ga)(Se,S)₂ thin film wherein said near stoichiometric composition comprises about 0.9<

Cu/(In,Ga)<

1.2;

depositing enough additional (In,Ga)+(Se,S) on said near stoichiometric composition to change said thin film to a slightly Cu-poor composition of Cu(In,Ga)(Se,S)₂ wherein said slightly Cu-poor film comprises a composition of about 0.8<

Cu/(In,Ga)<

0.99.

11. The method of claim 10 wherein said near stoichiometric composition comprises CuInSe₂ with no Ga and has a ratio of Cu/In of about 1.08.

12. The method of claim 10, wherein said near stoichiometric composition comprises a ratio of Cu/(In,Ga) of about 1.02.

13. The method of claim 10, wherein said slightly Cu-poor composition comprises CuInSe₂ with no Ga and has a Cu/In ratio of about 0.96.

14. The method of claim 10, wherein said slightly Cu-poor composition comprises a Cu/(In,Ga) ratio of about 0.92.

15. The method of claim 10, wherein said near stoichiometric composition of Cu(In,Ga)(Se,S)₂ is slightly Cu-rich with about 1.01<

Cu/(In,Ga)<

1.2.

16. The process of claim 10, wherein said layer of (In,Ga)_x (Se,S)_y is deposited at a temperature in the range of about ambient to 600°

C.

17. The process of claim 10, wherein said layer of (In,Ga)_x (Se,S)_y is deposited at a temperature of about 260°

C.

18. The process of claim 10, wherein said Cu+(Se,S) or Cu_x (Se,S) is deposited at a temperature in the range of about 350°

C. to 1,200°

C.

19. The process of claim 10, wherein said Cu+(Se,S) or Cu_x (Se,S) is deposited at a temperature in the range of about 350°

C. to 1,000°

C.

20. The process of claim 19, wherein said Cu+(Se,S) or Cu_x (Se,S) is deposited at a temperature of about 565°

C.

21. The process of claim 10, wherein said additional (In,Ga)+(Se,S) is deposited at a temperature in the range of about 350°

C. to 1,200°

C.

22. The process of claim 10, wherein said additional (In,Ga)+(Se,S) is deposited at a temperature in the range of about 350°

C. to 1,000°

C.

23. The process of claim 10, wherein said additional (In,Ga)+(Se,S) is deposited at a temperature of about 565°

C.

24. A process for fabricating thin film semiconductor devices, comprising the steps of:

depositing a seed layer of (In,Ga)_x (Se,S)_y on a substrate;

depositing Cu+(Se,S) or Cu_x (Se,S) on said layer of (In,Ga)_x (Se,S)_y in sufficient quantity to produce a very Cu-rich composition wherein said Cu-rich composition comprises about 10<

Cu/(In,Ga)<

100; and

depositing sufficient additional (In,Ga)+(Se,S) on said Cu-rich composition to produce a slightly Cu-poor composition of thin film Cu(In,Ga)(Se,S)₂ wherein said slightly Cu-poor thin film comprises, a composition of about 0.8<

Cu/(In,Ga)<

0.99.

25. The process of claim 24, wherein said very Cu-rich composition comprises a Cu/(In,Ga) of about 10.

26. The process of claim 24, wherein said slightly Cu-poor thin film comprises CuInSe₂ with no Ga and has a Cu/In ratio of about 0.96.

27. The process of claim 24, wherein said slightly Cu-poor thin film comprises a Cu/(In,Ga) ratio of about 0.92.