CADMIUM SULFIDE LAYERS FOR USE IN CADMIUM TELLURIDE BASED THIN FILM PHOTOVOLTAIC DEVICES AND METHODS OF THEIR MANUFACTURE
Methods are generally provided for forming a cadmium sulfide layer on a substrate. In one particular embodiment, the method can include sputtering a cadmium sulfide layer on a substrate in a sputtering atmosphere comprising an inorganic fluorine source gas. Methods are also generally provided for manufacturing a cadmium telluride based thin film photovoltaic device. Cadmium telluride based thin film photovoltaic devices are also generally provided. The device can include a substrate; a transparent conductive oxide layer on the substrate; a cadmium sulfide layer on the transparent conductive oxide layer; and, a cadmium telluride layer on the cadmium sulfide layer. The cadmium sulfide layer includes fluorine.
1 . A method of doping a cadmium sulfide thin film layer with fluorine, the method comprising:
sputtering a cadmium sulfide layer on a substrate in a sputtering atmosphere comprising an inorganic fluorine source gas.
2 . The method as in claim 1 , wherein the inorganic fluorine source gas comprises sulfur hexafluoride, sulfur tetrafluoride, nitrogen trifluoride, nitrosyl fluoride, bromine trifluoride, bromine pentafluoride, chlorine pentafluoride, chlorine trifluoride, chlorine monofluoride, iodine pentafluoride, or mixtures thereof.
3 . The method as in claim 1 , wherein the inorganic fluorine source gas comprises sulfur hexafluoride.
4 . The method as in claim 1 , wherein the inorganic fluorine source gas comprises nitrogen trifluoride.
5 . The method as in claim 1 , wherein the inorganic fluorine source gas is substantially free from elemental fluorine gas.
6 . The method as in claim 1 , wherein the sputtering atmosphere is substantially free from organic materials.
7 . The method as in claim 1 , wherein the sputtering atmosphere comprises greater than 0% to about 15% by volume of the inorganic fluorine source gas.
8 . The method as in claim 1 , wherein the sputtering atmosphere comprises about 1% to about 10% by volume of the inorganic fluorine source gas.
9 . The method as in claim 8 , wherein the sputtering atmosphere further comprises oxygen from greater than 0% to about 15% by volume.
10 . A method of manufacturing a cadmium telluride based thin-film photovoltaic device, the method comprising:
depositing a cadmium sulfide layer on a substrate in the presence of an inorganic fluorine source gas such that the cadmium sulfide layer is fluorine doped; and,
depositing a cadmium telluride layer on the cadmium sulfide layer.
11 . The method as in claim 10 , wherein the inorganic fluorine source gas comprises sulfur hexafluoride, sulfur tetrafluoride, nitrogen trifluoride, nitrosyl fluoride, bromine trifluoride, bromine pentafluoride, chlorine pentafluoride, chlorine trifluoride, chlorine monofluoride, iodine pentafluoride, or mixtures thereof.
12 . The method as in claim 10 , wherein the inorganic fluorine source gas is substantially free from elemental fluorine gas.
13 . The method as in claim 10 , wherein the cadmium sulfide layer is sputtered onto the substrate from a cadmium sulfide target, wherein the sputtering atmosphere comprises greater than 0% to about 15% by volume of the inorganic fluorine source gas.
14 . The method as in claim 13 , wherein the sputtering atmosphere is substantially free from organic materials.
15 . The method as in claim 10 further comprising sputtering a second cadmium sulfide layer on the cadmium sulfide layer such that the second cadmium sulfide layer is positioned between the cadmium sulfide layer and the cadmium telluride layer, wherein the second cadmium sulfide layer is sputtered on the cadmium sulfide layer in a second sputtering atmosphere that is substantially free from fluorine.
16 . The method as in claim 10 , wherein the amount of fluorine in the sputtering atmosphere is decreased during sputtering such that the cadmium sulfide layer has a decreasing concentration of fluorine.
17 . A cadmium telluride based thin film photovoltaic device, the device comprising:
a substrate;
a transparent conductive oxide layer on the substrate;
a cadmium sulfide layer on the transparent conductive oxide layer, wherein the cadmium sulfide layer comprises cadmium sulfide doped with fluorine; and,
a cadmium telluride layer on the cadmium sulfide layer.
18 . The device as in claim 17 further comprising a second cadmium sulfide layer between the cadmium sulfide layer and the cadmium telluride layer, wherein the second cadmium sulfide layer is substantially free from fluorine.
19 . The device as in claim 18 , wherein the second cadmium sulfide layer consists of cadmium sulfide.
20 . The device as in claim 17 , wherein the cadmium sulfide layer comprises fluorine in a graded concentration that decreases in a direction from the resistive transparent buffer layer to the cadmium telluride layer.