Methods of forming a conductive transparent oxide film layer for use in a cadmium telluride based thin film photovoltaic device
View Patent ↗Methods are generally provided for forming a conductive oxide layer on a substrate. In one particular embodiment, the method can include sputtering a transparent conductive oxide layer on a substrate at a sputtering temperature from about 10° C. to about 100° C. A cap layer including cadmium sulfide can be deposited directly on the transparent conductive oxide layer. The transparent conductive oxide layer can be annealed at an anneal temperature from about 450° C. to about 650° C. Methods are also generally provided for manufacturing a cadmium telluride based thin film photovoltaic device. An intermediate substrate is also generally provided for use to manufacture a thin film photovoltaic device.
1. A method for forming a conductive oxide layer on a substrate, the method comprising:
sputtering a transparent conductive oxide layer on a substrate at a sputtering temperature from about 10° C. to about 100° C.;
depositing a cap layer directly on the transparent conductive oxide layer, wherein the cap layer comprises cadmium sulfide; and,
annealing the transparent conductive oxide layer at an anneal temperature of about 450° C. to about 650° C. to remove the cap layer, wherein less than 25% of the cap layer remains on the TCO layer after annealing.
2. The method as in claim 1 , wherein the transparent conductive oxide layer comprises cadmium and tin.
3. The method as in claim 1 , wherein the transparent conductive oxide layer is sputtered from a target comprising cadmium stannate.
4. The method as in claim 1 , wherein the cap layer is sputtered onto the transparent conductive oxide layer from a target comprising cadmium sulfide.
5. The method as in claim 4 , wherein the cap layer consists essentially of cadmium sulfide.
6. The method as in claim 4 , wherein the cap layer is sputtered to a thickness of about 10 nm to about 150 nm.
7. The method as in claim 1 , wherein the transparent conductive oxide layer is annealed in an annealing atmosphere comprising an inert gas.
8. The method as in claim 7 , wherein the inert gas is argon.
9. The method as in claim 7 , wherein the annealing atmosphere has a pressure of about 1 mTorr to about 100 mTorr.
10. The method as in claim 1 , wherein the anneal temperature is of about 575° C. to about 625° C.
11. The method as in claim 1 , wherein the transparent conductive oxide layer is annealed for about 1 minute to about 30 minutes.
12. The method as in claim 1 , further comprising:
monitoring sublimation of the cap layer while annealing the transparent conductive oxide layer.
13. The method as in claim 1 , further comprising:
cooling the substrate after annealing; and,
chemically etching the cap layer.
14. The method as in claim 13 , wherein the cap layer is chemically etched with an etchant comprising hydrochloric acid, nitric acid, or mixtures thereof.
15. The method as in claim 1 , wherein the transparent conductive oxide layer is annealed open-faced.
16. The method as in claim 1 , further comprising:
removably positioning a cover shield over the cap layer prior to annealing such that the cap layer is shielded during annealing.
17. A method for manufacturing a cadmium telluride based thin film photovoltaic device, the method comprising:
sputtering a transparent conductive oxide layer on a substrate at a sputtering temperature of about 10° C. to about 100° C.;
depositing a cap layer directly on the transparent conductive oxide layer, wherein the cap layer comprises cadmium sulfide;
annealing the transparent conductive oxide layer at an anneal temperature of about 450° C. to about 650° C.;
thereafter forming a resistive transparent buffer layer over the transparent conductive oxide layer;
forming a cadmium sulfide layer over the resistive transparent layer; and,
forming a cadmium telluride layer over the cadmium sulfide layer.
18. The method as in claim 17 , further comprising:
cooling the substrate after annealing; and,
chemically etching the cap layer prior to forming the resistive transparent layer over the transparent conductive oxide layer.
19. The method as in claim 17 , wherein the cap layer is sputtered onto the transparent conductive oxide layer from a target comprising cadmium sulfide.