Preparation of cuxinygazsen (X=0-2, Y=0-2, Z=0-2, N=0-3) precursor films by electrodeposition for fabricating high efficiency solar cells

• US 5,730,852 A
• Filed: 12/12/1995
• Issued: 03/24/1998
• Est. Priority Date: 09/25/1995
• Status: Expired due to Term

• Current Assignee: Davis, Joseph And Negley Electric, Inc.
• Original Assignee: Davis, Joseph And Negley Electric, Inc.
• Inventors: Tuttle, John R., Ramanathan, Kannan, Contreras, Miguel A., Tennant, Andrew L., Keane, James, Bhattacharya, Raghu N., Noufi, Rommel
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US08/571,150
• Time in Patent Office: 833 Days
• Field of Search: 205/103-104, 205/192, 205/915, 205/239, 437/5, 437/108, 437/111, 427/76, 136/260, 136/264, 136/265, 257/184, 204/DIG. 8
• US Class Current: 205/192
• CPC Class Codes: C23C 28/023 only coatings of metal elements only
• CPC Class Codes: C25D 3/56 of alloys
• CPC Class Codes: C25D 5/18 Electroplating using modulated, pulsed or reversing current
• CPC Class Codes: G03C 1/22 with an even number of CH groups
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/02568 Chalcogenide semiconducting materials not being oxides, e.g. ternary compounds
• CPC Class Codes: H01L 21/02614 Transformation of metal, e.g. oxidation, nitridation
• CPC Class Codes: H01L 21/02628 using solutions
• 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 31/0749 including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
• CPC Class Codes: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y10S 205/915 Electrolytic deposition of semiconductor
• CPC Class Codes: Y10S 438/93 Ternary or quaternary semiconductor comprised of elements from three different groups, e.g. I-III-V

Abstract

High quality thin films of copper-indium-gallium-diselenide useful in the production of solar cells are prepared by electrodepositing at least one of the constituent metals onto a glass/Mo substrate, followed by physical vapor deposition of copper and selenium or indium and selenium to adjust the final stoichiometry of the thin film to approximately Cu(In,Ga)Se₂. Using an AC voltage of 1-100 KHz in combination with a DC voltage for electrodeposition improves the morphology and growth rate of the deposited thin film. An electrodeposition solution comprising at least in part an organic solvent may be used in conjunction with an increased cathodic potential to increase the gallium content of the electrodeposited thin film.

Claims

1. A process for preparing a metal-containing thin film, the process comprising the steps of:

electrodepositing a layer of Cu_x In_y Ga_z Se_n (x=0-2, y=0-2, z=0-2, n=0-3) on a substrate, the electrodeposition proceeding at a DC voltage of approximately 1-10 V and an AC voltage of approximately 0.2-5.0 V at 1-100 KHz superimposed upon said DC voltage; and

depositing a sufficient amount of either In+Se or Cu+Se on said layer of Cu_x In_y Ga_z Se_n by vapor deposition to produce a thin film of Cu(In,Ga)Se₂ on the substrate wherein said thin film has stoichiometric ratios of approximately Cu=1-1.2;

(In,Ga)=1-1.2;

Se=2-2.5.

2. The process of claim 1 wherein said layer of Cu_x In_y Ga_z Se_n (x=0-2, y=0-2, z=0-2, n=0-3) comprises In_1-2 Se_1-3.

3. The process of claim 1 wherein said layer of Cu_x In_y Ga_z Se_n (x=0-2, y=0-2, z=0-2, n=0-3) comprises Cu_1-2 Se_1-3.

4. The process of claim 1 wherein said layer of Cu_x In_y Ga_z Se_n (x=0-2, y=0-2, z=0-2, n=0-3) comprises Cu_1-2 In_1-2 Se_1-3.

5. The process of claim 1 wherein said layer of Cu_x In_y Ga_z Se_n (x=0-2, y=0-2, z=0-2, n=0-3) comprises Cu_1-2 In_1-2 Ga₀.01-1 Se_1-3 (x=1-2, y=1-2, z=0.01-1, n=1-3).

6. The process of claim 1 wherein the vapor deposition comprises physical vapor deposition.

7. The process of claim 6 wherein the physical vapor deposition proceeds at a temperature of approximately 550°

C.

8. The process of claim 1 wherein the electrodeposition proceeds in an aqueous electrodeposition solution, said DC voltage is approximately 1-5 volts, and said AC voltage is approximately 0.3-1.0 volts at approximately 10-30 KHz.

9. The process of claim 8 wherein said DC voltage is approximately 2 volts and said AC voltage is approximately 0.45 volts at approximately 18.1 KHz.

10. The process of claim 1 wherein said DC voltage is approximately 3-10 volts, and the electrodeposition proceeds in an electrodeposition solution comprising at least one organic solvent, and the electrodeposition further proceeds at an AC voltage of approximately 0.2-5.0 volts at approximately 1-100 KHz superimposed upon said DC voltage.

11. The process of claim 10 wherein said AC voltage is approximately 0.45 volts at approximately 18.1 KHz.

12. The process of claim 1 wherein the electrodeposition step proceeds in an electrodeposition solution comprising at least one supporting electrolyte for raising the conductivity of the electrodeposition solution and increasing the deposition rate of the Cu_x In_y Ga_z Se_n layer.

13. The process of claim 12 wherein said supporting electrolyte comprises at least one compound selected from the group consisting of NaCl, LiCl, and Na₂ SO₄.

14. The process of claim 1 further comprising the steps of:

depositing a CdS layer on the Cu_x In_y Ga_z Se_n film by chemical bath deposition; and

depositing a ZnO layer on the CdS layer by RF sputtering.

15. A process for preparing a solar cell precursor thin film, the process comprising the steps of:

(a) providing an electrodeposition solution containing copper, indium, gallium, and selenium ions;

(b) immersing a substrate into said electrodeposition solution; and

(c) electroplating said copper, indium, gallium, and selenium ions simultaneously onto said substrate by applying a cathodic potential thereto of 1-10 VDC voltage and 0.2-5.0 VAC at 1-100 KHZ superimposed thereon.

16. The process according to claim 15, wherein said electrodeposition solution includes at least one organic solvent.

17. The process according to claim 16, wherein said cathodic potential is approximately 2 VDC and approximately 0.45 VAC at 10-30 KHz superimposed thereon.

18. The process according to claim 15, wherein said cathodic potential is approximately 1-5 VDC and 0.3-1.0 VAC at 10-30 KHz superimposed thereon.

19. The process according to claim 18, wherein said electrodeposition solution comprises approximately 2.49 gm/l Cu(NO₃)₂.6H₂ O, 26.7 gm/l InCl₃, 10.2 gm/l Ga(NO₃)₃, and 4.0 gm/l H₂ SeO₃).

20. The process according to claim 19, wherein said electrodeposition solution includes at least one organic solvent.