Methods of forming interdigitated back contact layers

1. A method comprising:

forming a first layer comprising alternating regions of n-type amorphous hydrogenated silicon and p-type amorphous hydrogenated silicon on a second layer comprising intrinsic amorphous hydrogenated silicon; and

diffusing such that dopants from the first layer diffuse into the second layer;

and crystallizing the first layer and the second layer into polysilicon by annealing the first layer and the second layer at a temperature between 650° C. and 850° C.;

and wherein before the forming of the first layer, depositing the second layer on a third layer comprising silicon oxide;

and wherein before the annealing, the first layer further comprises gaps between adjacent regions of the n-type amorphous hydrogenated silicon and the p-type amorphous hydrogenated silicon:

and wherein, after the annealing, the second layer comprises alternating regions of n-type polycrystalline silicon, intrinsic polycrystalline silicon, and p-type polycrystalline silicon;

and wherein the first layer is formed by plasma-assisted chemical vapor deposition (PECVD).

2. The method according to claim 1 , wherein the first layer is formed by:

using a first shadow mask to deposit the regions of the n-type amorphous hydrogenated silicon; and

depositing the regions of the p-type amorphous hydrogenated silicon using a second shadow mask.

3. A method for using a shadow mask to form a layer of polycrystalline silicon with alternating doping types in a photovoltaic device comprising interdigitated back contact layers of a first layer comprising alternating regions of n-type amorphous hydrogenated silicon and p-type amorphous hydrogenated silicon and further comprising a second layer comprising intrinsic amorphous hydrogenated silicon; and

wherein the method comprises crystallizing and diffusing a dopant by annealing the first layer and the second layer at a temperature between 650° C. and 850° C.; and

wherein the method further comprises depositing a second layer comprising intrinsic amorphous hydrogenated silicon; patterning a first layer comprising alternating regions of n-type amorphous hydrogenated silicon and p-type amorphous hydrogenated silicon;

and wherein, before the forming of the first layer, depositing the second layer on a third layer comprising silicon oxide;

and wherein the first layer is formed by depositing the regions of the n-type amorphous hydrogenated silicon by using a first shadow mask; and

depositing the regions of the p-type amorphous hydrogenated silicon by using a second shadow mask;

and wherein, before the annealing, the first layer further comprises gaps between adjacent regions of the n-type amorphous hydrogenated silicon and the p-type amorphous hydrogenated silicon.