DOPING AN ABSORBER LAYER OF A PHOTOVOLTAIC DEVICE VIA DIFFUSION FROM A WINDOW LAYER
Methods for doping an absorbent layer of a p-n heterojunction in a thin film photovoltaic device are provided. The method can include depositing a window layer on a transparent substrate, where the window layer includes at least one dopant (e.g,. copper). A p-n heterojunction can be formed on the window layer, with the p-n heterojunction including a photovoltaic material (e.g., cadmium telluride) in an absorber layer. The dopant can then be diffused from the window layer into the absorber layer (e.g., via annealing).
1 . A method of doping an absorbent layer in a thin film photovoltaic device, the method comprising:
depositing a window layer on a transparent substrate, wherein the window layer comprises a dopant;
forming a p-n heterojunction on the window layer, wherein the p-n heterojunction comprises an absorber layer, and wherein the absorber layer comprises a photovoltaic material; and,
diffusing the dopant from the window layer into the absorber layer.
2 . The method of claim 1 , wherein the dopant comprises copper.
3 . The method of claim 1 , wherein the dopant is diffused into the absorber layer such that the dopant is present in the absorber layer at about 100 ppm to about 1 atomic percent.
4 . The method of claim 1 , wherein the photovoltaic material comprises cadmium telluride.
5 . The method of claim 1 , wherein the p-n heterojunction further comprises an n-type window layer positioned between the window layer and the absorber layer.
6 . The method of claim 5 , wherein the n-type window layer comprises cadmium sulfide.
7 . The method of claim 5 , wherein the window layer defines a resistive transparent buffer layer positioned between a transparent conductive oxide layer and the n-type window layer.
8 . The method of claim 7 , wherein the window layer comprises a zinc tin oxide.
9 . The method of claim 1 , wherein window layer defines a transparent conductive oxide layer.
10 . The method of claim 9 , further comprising:
depositing a resistive transparent buffer layer on the window layer prior to forming the p-n heterojunction such that the resistive transparent buffer layer is positioned between the window layer and the p-n heterojunction.
11 . The method of claim 1 , wherein the window layer comprises a getter layer.
12 . The method of claim 11 , further comprising:
depositing a transparent conductive oxide layer on the transparent substrate to be adjacent to the getter layer.
13 . The method of claim 12 , wherein the transparent conductive oxide layer is formed on the substrate prior to depositing the window layer such that the window layer is positioned between the transparent conductive oxide layer and the p-n heterojunction.
14 . The method of claim 1 , wherein the absorber layer is substantially free from the dopant prior to diffusing.
15 . The method of claim 1 , wherein diffusing the dopant from the window layer into the absorber layer comprises annealing the absorber layer and the window layer together.
16 . The method of claim 15 , wherein annealing comprises heating to an anneal temperature of about 300° C. to about 500° C.
17 . The method of claim 1 , wherein the window layer is depositing via sputtering of a target, wherein the target comprises the dopant.
18 . The method of claim 17 , wherein the target further comprises a cadmium tin oxide such that the window layer defines a transparent conductive oxide layer that includes the dopant.
19 . The method of claim 17 , wherein the target further comprises a zinc tin oxide such that the window layer defines a resistive transparent buffer layer that includes the dopant.
20 . The method of claim 17 , wherein the target further comprises a metal such that the window layer defines a getter layer that includes the dopant.