PHOTOVOLTAIC DEVICE AND METHOD FOR MAKING
One aspect of the present invention provides a method to make a film. The method includes providing a target comprising a semiconductor material within an environment comprising oxygen; applying a plurality of direct current pulses to the target to create a pulsed direct current plasma; sputtering the target with the pulsed direct current plasma to eject a material comprising cadmium and sulfur into the plasma; and depositing a film comprising the material onto a substrate. The target includes a semiconductor material that comprises semiconductor material comprises cadmium and sulfur.
1 . A method to make a film, comprising:
providing a target comprising a semiconductor material within an environment comprising oxygen, wherein the semiconductor material comprises cadmium and sulfur;
applying a plurality of direct current pulses to the target to create a pulsed direct current plasma;
sputtering the target with the pulsed direct current plasma to eject a material comprising cadmium and sulfur into the plasma; and
depositing a film comprising the material onto a substrate.
2 . The method as defined in claim 1 , wherein the film comprises oxygen.
3 . The method as defined in claim 1 , wherein the film comprises oxygen in a range from about 0.1 atomic percent to about 50 atomic percent.
4 . The method as defined in claim 1 , wherein the film has a gradient of oxygen concentration within the film.
5 . The method as defined in claim 1 , wherein the sputtering of the target with the pulsed direct current plasma is carried out at a substrate temperature in a range from about 50 degrees Celsius to about 550 degrees Celsius.
6 . The method as defined in claim 1 , wherein the sputtering is carried out at ambient temperature.
7 . The method as defined in claim 1 , wherein the target further comprises zinc.
8 . The method as defined in claim 1 , wherein the film further comprises zinc.
9 . The method as defined in claim 1 , wherein the film further comprises zinc oxide.
10 . The method as defined in claim 1 , wherein the film comprises CdS 1-y O y where y varies from 0.01 to 0.5
11 . The method as defined in claim 1 , wherein the film has a thickness is in a range from about 20 nanometers to about 200 nanometers.
12 . The method as defined in claim 1 , wherein the film has a band gap in a range from about 2.3 electron Volts to about 3.1 electron Volts.
13 . The method as defined in claim 1 , wherein the film is thermally stable at a temperature in a range from about 500 degrees Celsius to about 700 degrees Celsius.
14 . The method as defined in claim 1 , wherein the film comprises a microcrystalline morphology.
15 . The method as defined in claim 1 , wherein the film comprises an amorphous morphology.
16 . The method as defined in claim 1 , further comprising the step of annealing the thin film.