Pressure transfer process for thin film solar cell fabrication

1. A method for fabricating a thin film solar cell, the method comprising the steps of:

providing a substrate;

using a first pair of rollers to both i) deposit a first absorber material as a layer A on the substrate while ii) applying pressure to both the substrate and the layer A;

using a second pair of rollers to both i) deposit a second absorber material as a layer B on the layer A while ii) applying pressure to both the substrate and the layer B;

using a third pair of rollers to both i) deposit a third absorber material as a layer C on the layer B while ii) applying pressure to both the substrate and the layer C;

using a fourth pair of rollers to both i) deposit a fourth absorber material as a layer D on the layer C while ii) applying pressure to both the substrate and the layer D; and

annealing the layers A-D while applying pressure to both the substrate and the layer D,

wherein the first absorber material comprises copper, the second absorber material comprises indium, the third absorber material comprises gallium, and the fourth absorber material comprises one or more of sulfur and selenium, and wherein a chalcogenide absorber layer is formed on the substrate, and

wherein the annealing step is performed using a fifth pair of rollers to both i) heat the layers A-D while ii) applying pressure to both the substrate and the layer D.

2. The method of claim 1 , wherein the substrate comprises a metal foil substrate.

3. The method of claim 2 , wherein the metal foil substrate comprises stainless steel.

4. The method of claim 1 , wherein the substrate comprises a glass substrate coated with a molybdenum layer, and wherein the first absorber material is deposited on the molybdenum layer.

5. The method of claim 1 , wherein the annealing step is performed at a temperature of from about 500° C. to about 600° C.

6. The method of claim 1 , wherein the annealing step is performed in a sulfur-containing environment.

7. The method of claim 1 , further comprising the step of:

soft annealing the layers A-C while applying pressure to both the substrate and the layer C,

wherein the soft annealing step is performed using a sixth pair of rollers to both i) heat the layers A-C while ii) applying pressure to both the substrate and the layer C.

8. The method of claim 7 , wherein the soft annealing step is performed at a temperature of from about 100° C. to about 300° C.

9. The method of claim 1 , wherein the first absorber material is deposited from a chemical or electrochemical solution the method further comprising the step of, following deposition of the layer A on the substrate:

heating the layer A while applying pressure to both the substrate and the layer A.

10. The method of claim 1 , wherein the second absorber material is deposited from a chemical or electrochemical solution, the method further comprising the step of, following deposition of the layer B on the layer A:

heating the layer B while applying pressure to both the substrate and the layer B.

11. The method of claim 1 , wherein the layer B is deposited from a molten bath, the method further comprising the step of, following deposition of the layer B on the layer A:

cooling the layer B while applying pressure to both the substrate and the layer B.

12. The method of claim 1 , wherein the layer C is deposited from a chemical or electrochemical solution, the method further comprising the step of, following deposition of the layer C on the layer B:

heating the layer C while applying pressure to both the substrate and the layer C.

13. The method of claim 1 , wherein the layer C is deposited from a molten bath, the method further comprising the step of, following deposition of the layer C on the layer B:

cooling the layer C while applying pressure to both the substrate and the layer C.

14. The method of claim 1 , wherein the layer D is deposited from a chemical or electrochemical solution, the method further comprising the step of, following deposition of the layer D on the layer C:

heating the layer D while applying pressure to both the substrate and the layer D.

15. The method of claim 1 , wherein the layer D is deposited from a molten bath, the method further comprising the step of, following deposition of the layer D on the layer C:

cooling the layer D while applying pressure to both the substrate and the layer D.

16. The method of claim 1 , further comprising the steps of:

depositing the first absorber material onto the first pair of rollers and transferring the first absorber material from the first pair of rollers onto the substrate;

depositing the second absorber material onto the second pair of rollers and transferring the second absorber material from the second pair of rollers onto the layer A;

depositing the third absorber material onto the third pair of rollers and transferring the third absorber material from the third pair of rollers onto the layer B; and

depositing the fourth absorber material onto the fourth pair of rollers and transferring the fourth absorber material from the fourth pair of rollers onto the layer C.

17. The method of claim 16 , wherein electrodeposition is used to deposit at least one of: the first absorber material onto the first pair of rollers, the second absorber material onto the second pair of rollers, the third absorber material onto the third pair of rollers, and the fourth absorber material onto the fourth pair of rollers.

18. The method of claim 1 , wherein at least one of the first pair of rollers, the second pair of rollers, the third pair of rollers, and the fourth pair of rollers comprises two different sized rollers.