THIN FILM SOLAR CELLS

• US 20140038344A1
• Filed: 08/01/2012
• Published: 02/06/2014
• Est. Priority Date: 08/01/2012
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Bojarczuk, Nestor A., Fogel, Keith E., Guha, Supratik, Shin, Byungha
• Granted Patent: US 8,987,590 B2
• Time in Patent Office: Days
• US Class Current: 438/86
• CPC Class Codes: H01L 31/022466 made of transparent conductive layers, e.g. TCO, ITO layers
• CPC Class Codes: H01L 31/022475 composed of indium tin oxide [ITO]
• CPC Class Codes: H01L 31/022483 composed of zinc oxide [ZnO]
• CPC Class Codes: H01L 31/0326 comprising AIBIICIVDVI kesterite compounds, e.g. Cu2ZnSnSe4, Cu2ZnSnS4
• CPC Class Codes: H01L 31/0392 including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate textured substrates H01L31/02366
• CPC Class Codes: H01L 31/03925 including AIIBVI compound materials, e.g. CdTe, CdS
• CPC Class Codes: H01L 31/03926 comprising a flexible substrate
• CPC Class Codes: H01L 31/072 the potential barriers being only of the PN heterojunction type
• CPC Class Codes: H01L 31/073 comprising only AIIBVI compound semiconductors, e.g. CdS/CdTe solar cells
• CPC Class Codes: H01L 31/1896 for thin-film semiconductors
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02E 10/543 Solar cells from Group II-VI materials
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Embodiments relate to a method including forming a layer of copper zinc tin sulfide (CZTS) on a first layer of molybdenum (Mo) and annealing the CZTS layer and the first Mo layer to form a layer of molybdenum disulfide (MoS₂) between the layer of CZTS and the first layer of Mo. The method includes forming a back contact on a first surface of the CZTS layer opposite the first Mo layer and separating the first Mo layer and the MoS₂ layer from the CZTS layer to expose a second surface of the CZTS layer opposite the first surface. The method further includes forming a buffer layer on the second surface of the CZTS layer.

Claims

1. A method, comprising:

forming a layer of copper zinc tin sulfide (CZTS) on a first layer of molybdenum (Mo);

annealing the CZTS layer and the first Mo layer to form a layer of molybdenum disulfide (MoS₂) between the layer of CZTS and the first layer of Mo;

forming a back contact on a first surface of the CZTS layer opposite the first Mo layer;

separating the first Mo layer and the MoS₂ layer from the CZTS layer to expose a second surface of the CZTS layer opposite the first surface; and

forming a buffer layer on the second surface of the CZTS layer.

2. The method of claim 1, wherein separating the first Mo layer and the MoS₂ layer from the CZTS layer comprises:

forming a conducting epoxy on the back contact;

applying a substrate to the conducting epoxy; and

applying a tensile force to the substrate to pull the MoS₂ layer away from the CZTS layer.

3. The method of claim 2, wherein the substrate is a flexible substrate.

4. The method of claim 3, wherein the substrate is one of a metal foil and a polymer film.

5. The method of claim 1, further comprising:

etching the second surface of the CZTS layer to remove zinc sulfide (ZnS) formed by the annealing.

6. The method of claim 5, wherein the etching is performed using hydrochloride (HCl).

7. The method of claim 1, wherein the CZTS and first Mo layers are annealed at a temperature greater than 500 degrees Celsius.

8. The method of claim 1, wherein the back contact is a second Mo layer.

9. The method of claim 1, further comprising:

forming a transparent conducting oxide (TCO) layer on the buffer layer.

10. The method of claim 9, wherein the TCO layer comprises at least one of a mixture including aluminum and zinc oxide (Al:

ZnO) and a mixture including indium, tin, and oxygen (ITO).

11. The method of claim 1, further comprising forming a top electrode wherein the first Mo layer is coated on a soda-lime glass substrate by sputtering, and

separating the first Mo layer and MoS₂ layer from the CZTS layer includes separating the soda-lime glass substrate from the CZTS layer.

12. The method of claim 1, wherein the copper, tin, zinc and sulfur are deposited on the first Mo layer by thermal evaporation.

13. A method, comprising:

forming a first layer of molybdenum (Mo);

forming an absorber layer including zinc and sulfur on the first Mo layer;

annealing the first Mo layer and the absorber layer to form a molybdenum disulfide (MoS₂) layer between the first Mo layer and the absorber layer;

forming a back contact on a first surface of the absorber layer opposite the first Mo layer;

separating the first Mo layer from the absorber layer to expose a second surface of the absorber layer opposite the first surface; and

forming a buffer layer on the second surface of the absorber layer.

14. The method of claim 13, wherein the absorber layer comprises copper zinc tin sulfide (CZTS).

15. The method of claim 13, wherein the back contact is a second Mo layer.

16. The method of claim 13, wherein the buffer layer is cadmium sulfide (CdS).

17. The method of claim 13, further comprising:

forming a transparent conducting oxide (TCO) on the buffer layer.

18. The method of claim 17, wherein the TCO comprises at least one of a mixture including aluminum and zinc oxide (Al-ZnO) and a mixture including indium, tin, and oxygen (ITO).

19. The method of claim 17, wherein the buffer layer has a thickness between 60-70 nm (nanometers) and the TCO has a thickness between 80-100 nm.

20. The method of claim 13, further comprising:

etching the second surface of the absorber layer to remove zinc sulfide (ZnS) formed by the annealing.