Method for depositing an amorphous silicon film for photovoltaic devices with reduced light-induced degradation for improved stabilized performance

1. A method of forming a thin film photovoltaic device on a substrate with an electrically conductive contact, comprising:

forming a p-i-n junction semiconductor layer stack comprising:

forming a p-type microcrystalline silicon layer on said electrically conductive contact;

forming a p-type amorphous silicon layer on said p-type microcrystalline silicon layer;

forming an intrinsic type amorphous buffer silicon layer with high hydrogen flux on said p-type amorphous silicon layer and increasing an atomic percentage of hydrogen in said intrinsic type amorphous buffer silicon layer relative to said p-type amorphous silicon layer;

forming an intrinsic type amorphous silicon layer on said intrinsic type amorphous buffer silicon layer; and

forming an n-type silicon layer over the intrinsic type amorphous silicon layer.

2. A method according to claim 1 , wherein the silicon layers comprise hydrogenated silicon generated from a gas mixture comprising at least silane and hydrogen.

3. A method according to claim 2 , wherein the p-type amorphous silicon layer and the buffer silicon layer are deposited in a gas mixture further comprising methane.

4. A method according to claim 1 or 2 , wherein the p-type amorphous silicon layer and the p-type microcrystalline silicon layer are deposited in a gas mixture comprising boron.

5. A method according to claim 3 , wherein a ratio of silane flux in sccm to the hydrogen flux in sccm during deposition of the buffer silicon layer is substantially 10:94, and said ratio during deposition of the intrinsic type amorphous silicon layer is substantially 10:9.

6. A method according to claim 3 wherein a ratio of silane flux in sccm to the hydrogen flux in sccm to methane flux in sccm during deposition of the p-type amorphous silicon layer is substantially 10:18:19.

7. A method according to claim 5 , wherein a ratio of the silane flux in sccm to the hydrogen flux in sccm to methane flux in sccm during deposition of the buffer silicon layer is substantially 10:94:2.

8. A method according to claim 1 , wherein forming the n-type silicon layer comprises

forming an n-type amorphous silicon layer; and

forming an n-type microcrystalline silicon layer.

9. A silicon based thin film photovoltaic device comprising, on a substrate,

an electrically conductive contact and subsequently a p-i-n junction semiconductor layer stack with:

a p-type microcrystalline silicon layer;

a p-type amorphous silicon layer on said p-type microcrystalline silicon layer;

an intrinsic type amorphous buffer silicon layer on said p-type amorphous silicon layer, an atomic percentage of hydrogen in said intrinsic type amorphous buffer silicon layer being increased relative to said p-type amorphous silicon layer;

an intrinsic type amorphous silicon layer on said intrinsic type amorphous buffer silicon layer;

an n-type silicon layer over the intrinsic type amorphous silicon layer.

10. A photovoltaic device according to claim 9 wherein the n-type silicon layer comprises an n-type amorphous silicon layer and an n-type microcrystalline silicon layer.

11. A photovoltaic device according to claim 9 or 10 , wherein the buffer silicon layer comprises an intrinsic type hydrogenated amorphous silicon layer doped with carbon.

12. A method according to claim 1 , further comprising:

elevating the atomic percentage of hydrogen in said intrinsic type amorphous buffer silicon layer relative to said p-type amorphous silicon layer by forming said intrinsic type amorphous buffer silicon layer with a hydrogen-to-silane flow ratio that exceeds ten times the hydrogen-to-silane flow ratio for forming said p-type amorphous silicon layer.

13. A method according to claim 12 , further comprising:

elevating the atomic percentage of hydrogen in said intrinsic type amorphous buffer silicon layer relative to said p-type amorphous silicon layer by forming said intrinsic type amorphous buffer silicon layer with a hydrogen-to-silane flow ratio that exceeds ten times the hydrogen-to-silane flow ratio for forming said intrinsic type amorphous silicon layer.