Thin film solar cell and method of forming same

1. A method for fabricating a solar cell, comprising:

forming a back contact layer directly physically contacting a substrate, wherein the back contact layer comprises a metal;

forming an absorber layer directly physically contacting the back contact layer;

forming a buffer layer directly physically contacting the absorber layer; and

depositing a transparent conductive oxide (TCO) layer directly physically contacting the buffer layer;

annealing said deposited TCO layer in a vacuum environment to provide an annealed TCO front contact layer;

scribing through the back contact layer to form a first scribe line, wherein the first scribe line is filled with material of the absorber layer and directly contacts the substrate;

scribing through the buffer layer and the absorber layer to form a second scribe line, wherein the second scribe line is filled with material of the annealed TCO layer; and

scribing through the annealed TCO front contact layer, the buffer layer, and the absorber layer after the annealing to form a third scribe line that exposes the back contact layer at an end of the third scribe line.

2. The method as in claim 1 , wherein said depositing step comprises depositing said TCO layer by chemical vapor deposition.

3. The method as in claim 1 , wherein said deposited TCO layer comprises a doped metal oxide.

4. The method as in claim 1 , wherein said annealing step comprises annealing said deposited TCO layer at a temperature in a range of about 60° C. to about 300° C.

5. The method as in claim 1 , wherein said annealing step comprises annealing said deposited TCO layer at a temperature in a range of about 100° C. to about 200° C.

6. The method as in claim 1 , wherein said annealing step comprises annealing said deposited TCO layer for a period of about 1 hour or less.

7. The method as in claim 1 , wherein said annealing step comprises annealing said deposited TCO layer for a period of about 10 minutes or more.

8. The method as in claim 1 , wherein said annealing step is performed in an annealing chamber.

9. The method as in claim 8 , wherein said depositing step is performed in a deposition chamber.

10. The method as in claim 1 , wherein said depositing step and said annealing step are performed in a single in-line chamber.

11. The method as in claim 1 , wherein said deposited TCO layer comprises a material selected from the group consisting of zinc oxide, indium oxide, indium tin oxide, and cadmium oxide.

12. The method as in claim 1 , wherein said deposited TCO layer comprises a metal oxide material comprising dopants selected from the group consisting of aluminum, boron, tin, and indium.

13. The method as in claim 1 , wherein said annealed TCO front contact layer has a transmittance of at least 80% at wavelengths from about 400 to about 1200 nm.

14. The method as in claim 1 , wherein said annealed TCO front contact layer has a sheet resistance of less than 15 ohms per square.

15. The method as in claim 14 , wherein said annealed TCO front contact layer has a transmittance of at least 80% at wavelengths from about 400 to about 1200 nm.

16. The method as in claim 1 , wherein said annealing step comprises annealing said deposited TCO layer at a temperature in a range of about 80° C. to about 150° C.

17. The method as in claim 1 , wherein said annealing step is performed under the vacuum environment at a temperature in a range of about 80° C. to about 150° C. for a period of about 30 minutes to about 1 hour.

18. A method for fabricating a solar cell, comprising:

forming a back contact layer directly physically contacting a substrate, wherein the back contact layer comprises a metal;

forming an absorber layer directly physically contacting the back contact layer;

forming a buffer layer directly physically contacting the absorber layer; and

depositing a transparent conductive oxide (TCO) layer to directly physically contact the buffer layer;

annealing said deposited TCO layer in a vacuum environment at a temperature in a range of about 80° C. to about 150° C. for a period of about 30 minutes to about 1 hour to provide an annealed TCO front contact layer;

scribing through the back contact layer to form a first scribe line, wherein the first scribe line is filled with material of the absorber layer and directly contacts the substrate;

scribing through the buffer layer and the absorber layer to form a second scribe line, wherein the second scribe line is filled with material of the annealed TCO layer; and

scribing through the annealed TCO front contact layer, the buffer layer, and the absorber layer after the annealing to form a third scribe line that exposes the back contact layer at an end of the third scribe line.

19. A method for fabricating a solar cell, comprising:

forming a back contact layer directly physically contacting a substrate, wherein the back contact layer comprises a metal;

forming an absorber layer directly physically contacting the back contact layer;

forming a buffer layer directly physically contacting the absorber layer; and

depositing a transparent conductive oxide (TCO) layer to directly physically contact the buffer layer;

scribing through the back contact layer to form a first scribe line, wherein the first scribe line is filled with material of the absorber layer and directly contacts the substrate;

scribing through the buffer layer and the absorber layer to form a second scribe line, wherein the second scribe line is filled with material of the TCO layer; and

scribing through the TCO front contact layer, the buffer layer, and the absorber layer to form a third scribe line that exposes the back contact layer at an end of the third scribe line.

20. The method of claim 19 , further comprising annealing said deposited TCO layer in a vacuum environment at a temperature in a range of about 80° C. to about 150° C. for a period of about 30 minutes to about 1 hour to provide an annealed TCO front contact layer.