Manufacture of N-type chalcogenide compositions and their uses in photovoltaic devices
A layer of an n-type chalcogenide compositions provided on a substrate in the presence of an oxidizing gas in an amount sufficient to provide a resistivity to the layer that is less than the resistivity a layer deposited under identical conditions but in the substantial absence of oxygen.
1. A photovoltaic article comprising:
a substrate having a p-type absorber comprising a p-type photovoltaic composition, said p-type photovoltaic composition comprising a p-type chalcogenide comprising (i) one or more of copper, indium, and gallium; and (ii) at least one of sulfur and selenium; and
a layer of an n-type chalcogenide composition on the p-type absorber, wherein the n-type chalcogenide composition comprises at least one sulfide and/or at least one selenide that incorporates at least cadmium, and wherein the n-type chalcogenide composition is formed at a temperature in the range from 20° C. to 30° C. in an oxidizing atmosphere comprising an oxidizing gas and at least one other gas, wherein the oxidizing atmosphere has a pressure less than about 100 mTorr, and wherein the oxidizing gas is present in the oxidizing atmosphere in an amount such that the oxidizing gas comprises from about 0.001 mole % to about 0.7 mole % of the oxidizing atmosphere, and wherein the composition of the n-type chalcogenide composition formed has a resistivity less than the resistivity of an n-type chalcogenide composition formed in an otherwise identical process but in the substantial absence of the oxidizing gas; and
wherein the n-type chalcogenide composition has a resistivity of less than about 1×10 5 ohm-cm.
2. The article of claim 1 , wherein the n-type chalcogenide further comprises one or more constituents selected from Zn, In, and combinations thereof.
3. The article of claim 1 wherein the oxidizing atmosphere comprises from about 0.05 mole % to about 0.7 mole % of the oxidizing gas at a pressure of less than about 100 mTorr.
4. The article of claim 1 , wherein the oxidizing atmosphere is at a pressure in the range of from about 5 to about 20 mTorr.
5. The article of claim 1 , wherein the oxidizing atmosphere comprises from about 0.05 mole % to about 0.3 mole % of the oxidizing gas.
6. The article of claim 1 , wherein the oxidizing atmosphere comprises from about 0.001 mole % to less than about 0.25 mole % of the oxidizing gas.
7. The article of claim 1 , wherein the partial pressure of the oxidizing gas in the oxidizing atmosphere is between about 0.005 to about 0.5 mTorr.
8. The article of claim 7 , wherein the partial pressure of the oxidizing gas in the oxidizing atmosphere is between about 0.005 to about 0.3 mTorr.
9. The article of claim 1 , wherein the oxidizing gas is selected from oxygen, water vapor, nitrous oxide, and ozone.
10. The article of claim 1 , wherein the at least one other gas is selected from nitrogen, a noble gas, and combinations thereof.
11. The article of claim 1 , wherein the oxidizing atmosphere comprises oxygen and a noble gas.
12. The article of claim 1 , wherein the n-type chalcogenide composition comprises cadmium and sulfur.
13. The article of claim 1 , wherein the n-type chalcogenide composition is in electrical contact with a surface of the p-type photovoltaic composition.
14. The article of claim 1 , wherein the n-type chalcogenide composition is formed by evaporation, sputtering, chemical vapor deposition, or atomic layer deposition.
15. The article of claim 1 , wherein the n-type chalcogenide composition is formed by sputtering.