Thin film stacks for group V doping, photovoltaic devices including the same, and methods for forming photovoltaic devices with thin film stacks
According to the embodiments provided herein, a method for forming a photovoltaic device can include depositing a plurality of semiconductor layers. The plurality of semiconductor layers can include a doped layer that is doped with a group V dopant. The doped layer can include cadmium selenide or cadmium telluride. The method can include annealing the plurality of semiconductor layers to form an absorber layer.
1. A method for forming a photovoltaic device comprising:
depositing a plurality of semiconductor layers by vapor transport deposition, wherein:
the plurality of semiconductor layers comprise a doped layer that is doped with a group V dopant, and
the doped layer comprises cadmium selenide, cadmium telluride, or a combination thereof; and
forming a blended material composition from the plurality of semiconductor layers by annealing the plurality of semiconductor layers, whereby an absorber layer is formed, wherein:
the absorber layer comprises cadmium, selenium, and tellurium, and
a total dosage of the group V dopant in the absorber layer is greater than 0 atomic percent and less than 0.1 atomic percent; and
wherein the plurality of semiconductor layers are deposited on a buffer layer.
2. The method of claim 1 , wherein the doped layer comprises cadmium telluride, and the plurality of semiconductor layers includes an additional layer comprising cadmium selenide.
3. The method of claim 2 , wherein the additional layer is doped with arsenic.
4. The method of claim 2 , wherein the doped layer is thicker than the additional layer.
5. The method of claim 4 , wherein a ratio of a thickness of the doped layer to a thickness of the additional layer is greater than 6.
6. The method of claim 2 , wherein the plurality of semiconductor layers comprises a third layer comprising cadmium telluride.
7. The method of claim 1 , comprising forming a back contact layer over the absorber layer, wherein the back contact layer is substantially free of copper.
8. The method of claim 7 , wherein:
the absorber layer has a first surface and a second surface offset by a thickness;
the back contact layer is formed upon the second surface of the absorber layer; and
an average concentration of oxygen in the absorber layer measured between the first surface of the absorber layer and a midpoint of the absorber layer is between 5×10 15 cm −3 and 3×10 17 cm −3 .
9. The method of claim 7 , wherein the back contact layer comprises nitrogen-doped zinc telluride.
10. The method of claim 9 , comprising forming a conducting layer over the back contact layer.
11. The method of claim 1 , wherein the doped layer is further from the buffer layer than any other layer of the plurality of semiconductor layers.
12. The method of claim 1 , wherein:
the absorber layer has a first surface provided upon a second surface of the buffer layer;
an absorber buffer interface region is formed adjacent to the first surface of the absorber layer;
a percent concentration profile of the Group V dopant is formed in the absorber layer with distance from the first surface of the absorber layer; and
the percent concentration profile of the Group V dopant at the absorber buffer interface differs from the percent concentration profile of the Group V dopant in a bulk portion of the absorber layer.
13. The method of claim 1 , wherein the buffer layer comprises intrinsic tin dioxide, zinc magnesium oxide, silicon dioxide, aluminum oxide, aluminum nitride, or a combination thereof.
14. The method of claim 1 , wherein the group V dopant is arsenic.
15. The method of claim 1 , wherein the absorber layer has a thickness between about 0.5 μm to about 10 μm.
16. A method for forming a photovoltaic device comprising:
depositing a plurality of semiconductor layers on a buffer layer, wherein:
the plurality of semiconductor layers comprise a doped layer and an additional layer, wherein:
the doped layer comprises cadmium telluride doped with a group V dopant, wherein the group V dopant comprises arsenic, phosphorous, antimony, or a combination thereof,
the additional layer comprises cadmium selenide,
the doped layer is thicker than the additional layer, and
a ratio of a thickness of the doped layer to a thickness of the additional layer is greater than 6;
forming a blended material composition from the plurality of semiconductor layers by annealing the plurality of semiconductor layers, whereby an absorber layer is formed, wherein:
the absorber layer has a first surface provided upon a second surface of the buffer layer,
the absorber layer comprises cadmium, selenium, and tellurium, and
a total dosage of the group V dopant in the absorber layer is greater than 0 atomic percent and less than 0.1 atomic percent; and
forming a back contact layer on the absorber layer, wherein the back contact is substantially free of copper.
17. The method of claim 1 , wherein the absorber layer comprises a ternary of cadmium, selenium, and tellurium.
18. The method of claim 17 , wherein the absorber layer comprises greater than about 0 atomic percent and less than about 20 atomic percent of selenium compared to cadmium.
19. A method for forming an absorber layer of a photovoltaic device comprising:
first, depositing a first semiconductor layer over a buffer layer by vapor transport deposition, wherein the first semiconductor layer comprises cadmium selenide;
second, depositing a second semiconductor layer over the first semiconducting layer by vapor transport deposition, wherein the second semiconductor layer comprises cadmium telluride;
third, depositing a third semiconductor layer over the second semiconductor layer by vapor transport deposition, wherein the third semiconductor layer comprises cadmium telluride doped with arsenic; and
forming a blended material composition from the first, second, and third semiconductor layers by annealing the first, second, and third semiconductor layers, whereby the absorber layer is formed, wherein:
the absorber layer has a first surface provided upon a second surface of the buffer layer,
the absorber layer comprises cadmium, selenium, and tellurium, and
a total dosage of the arsenic dopant in the absorber layer is greater than 0 atomic percent and less than 0.1 atomic percent.
20. The method of claim 19 , wherein the third semiconductor layer is thicker than the first semiconductor layer, and a ratio of the thickness of the third semiconductor layer to the thickness of the first semiconductor layer is greater than 4:1.