Systems and methods of intermixing cadmium sulfide layers and cadmium telluride layers for thin film photovoltaic devices
View Patent ↗A process for manufacturing a cadmium telluride based thin film photovoltaic device having an intermixed layer is provided. The process can include introducing a substrate into a deposition chamber, wherein a window layer (e.g., a cadmium sulfide layer) is on a surface of the substrate. A sulfur-containing gas can be supplied to the deposition chamber. In addition, a source vapor can be supplied to the deposition chamber, wherein the source material comprises cadmium telluride. The sulfur-containing gas and the source vapor can be present within the deposition chamber to form an intermixed layer on the window layer. In one particular embodiment, for example, the intermixed layer generally can have an increasing tellurium concentration and decreasing sulfur concentration extending away from the window layer. An apparatus for sequential deposition of an intermixed thin film layer and a sublimated source material on a photovoltaic (PV) module substrate is also provided.
1. A process for manufacturing a cadmium telluride based thin film photovoltaic device having an intermixed layer, the process comprising:
introducing a substrate into a deposition chamber, wherein a window layer is on a surface of the substrate;
supplying a sulfur-containing gas to the deposition chamber; and,
supplying a source vapor to the deposition chamber, wherein the source vapor comprises cadmium telluride;
wherein the sulfur-containing gas and the source vapor form an intermixed layer over the window layer on the substrate.
2. The process as in claim 1 , wherein the window layer comprises cadmium sulfide.
3. The process as in claim 1 , wherein the sulfur-containing gas and the source vapor are present within the deposition chamber such that the intermixed layer deposited on the window layer has an increasing tellurium concentration and decreasing sulfur concentration extending away from the window layer.
4. The process as in claim 1 , further comprising:
depositing a cadmium telluride layer on the intermixed layer.
5. The process as in claim 4 , wherein the source vapor is supplied by sublimating a source material within the deposition chamber.
6. The process as in claim 1 , further comprising:
annealing the device at an anneal temperature of about 150° C. to about 600° C.
7. The process as in claim 1 , wherein the sulfur-containing gas includes chlorine.
8. The process as in claim 7 , wherein the sulfur-containing gas comprises sulfur dichloride, disulfur dichloride, or a mixture thereof.
9. The process as in claim 7 , wherein sulfur and chlorine atoms are included in the intermixed layer.
10. The process as in claim 1 , further comprising:
heating a sulfur-containing liquid to form the sulfur-containing gas.
11. The process as in claim 10 , further comprising:
transporting the sulfur-containing gas to the deposition chamber via a carrier gas.
12. The process as in claim 1 , wherein a partial pressure gradient is formed within the deposition chamber, wherein a first end of the deposition chamber has a higher concentration of the sulfur-containing gas than a second end opposite than the first end.
13. The process as in claim 1 , further comprising:
controlling the flow of the sulfur-containing gas through the gas source line to the substrate.
14. The process as in claim 1 , further comprising:
heating the substrate to a deposition temperature prior to exposure to the sulfur-containing gas, wherein the deposition temperature is about 350° C. to about 700° C.
15. A process for manufacturing a cadmium telluride based thin film photovoltaic device having an intermixed layer, the process comprising:
supplying a sulfur-containing gas to the deposition chamber; and,
sublimating a source material to produce a source vapor within the deposition chamber such that the sulfur-containing gas and the source vapor are present within the deposition chamber, wherein the source material comprises cadmium telluride; and,
directing the sulfur-containing gas and the source vapor onto a substrate to deposit an intermixed layer on a window layer of the substrate, wherein the intermixed layer having an increasing tellurium concentration and decreasing sulfur concentration extending away from the window layer.
16. The process as in claim 15 , wherein a partial pressure gradient is formed within the deposition chamber, wherein a first end of the deposition chamber has a higher concentration of the sulfur-containing gas than a second end opposite than the first end.
17. The process as in claim 15 , further comprising:
directing the source vapor onto the substrate to deposit a cadmium telluride layer on the intermixed layer.