Photovoltaic devices and method of manufacturing
View Patent ↗Disclosed are methods for the surface cleaning and passivation of PV absorbers, such as CdTe substrates usable in solar cells, and devices made by such methods. In some embodiments, the method involves an anode layer ion source (ALIS) plasma discharge process to clean and oxidize a CdTe surface to produce a thin oxide layer between the CdTe layer and subsequent back contact layer(s).
1. A photovoltaic device having a front contact stack including a front contact layer, a semiconductor stack disposed on the front contact stack, and a back contact stack disposed on the semiconductor stack, wherein the semiconductor stack comprises cadmium, tellurium, and at least one of: sulfur, selenium, zinc, or oxygen; the photovoltaic device further comprising:
an oxide layer formed on the semiconductor stack between the semiconductor stack and the back contact stack, the oxide layer being from about 5 Å to about 50 Å thick.
2. The photovoltaic device of claim 1 , wherein the semiconductor stack comprises selenium.
3. The photovoltaic device of claim 1 , wherein the semiconductor stack comprises in addition to the oxide layer:
a window layer comprising cadmium and at least one of sulfur, selenium, zinc or oxygen; and
an absorber layer comprising cadmium and tellurium and at least one of sulfur, selenium, or zinc.
4. The photovoltaic device of claim 1 , wherein the back contact stack comprises a bilayer of a metal layer and a second layer comprising zinc and tellurium.
5. The photovoltaic device of claim 1 , wherein the oxide layer thickness is from about 5 Å to about 30 Å thick.
6. The photovoltaic device of claim 1 , wherein the oxide layer comprises CdTeO 3 .
7. The photovoltaic device of claim 1 , wherein the semiconductor stack, in addition to the oxide layer, comprises:
an n-type layer, comprising at least one of: cadmium selenide, zinc magnesium oxide, cadmium tin oxide, indium tin oxide, indium-doped cadmium oxide, aluminum-doped zinc oxide, indium zinc oxide, zinc tin oxide, cadmium oxide, zinc aluminum oxide, zinc silicon oxide, zinc zirconium oxide, tin aluminum oxide, tin silicon oxide, or tin zirconium oxide; and
an absorber layer comprising cadmium, tellurium, and at least one of selenium or zinc.
8. The photovoltaic device of claim 1 , wherein the semiconductor stack, in addition to the oxide layer, comprises:
an n-type layer, comprising at least one of: cadmium selenide, zinc magnesium oxide, cadmium tin oxide, indium tin oxide, indium-doped cadmium oxide, or cadmium oxide; and
an absorber layer comprising cadmium, tellurium, and selenium.
9. The photovoltaic device of claim 1 , wherein the back contact stack comprises at least one of: tellurium, tungsten, tantalum, titanium, palladium, nickel, silver, calcium, lead, mercury, graphite, ZnTe, CdZnTe, ZnTe:Cu, HgTe, PbTe, aluminum, copper, nickel, gold, silver, molybdenum, chromium, indium nitride, or molybdenum nitride.
10. A photovoltaic device having a front contact stack including a front contact layer, a semiconductor stack disposed on the front contact stack, and a back contact stack disposed on the semiconductor stack, wherein the back contact stack comprises a bilayer of a metal layer and a second layer comprising zinc and tellurium; the photovoltaic device further comprising:
an oxide layer formed on the semiconductor stack between the semiconductor stack and the back contact stack, the oxide layer being from about 5 Å to about 50 Å thick.
11. The photovoltaic device of claim 10 , wherein the semiconductor stack comprises cadmium, tellurium, and at least one of selenium, zinc, or oxygen.
12. The photovoltaic device of claim 10 , wherein the semiconductor stack comprises:
an n-type layer comprising cadmium and at least one of sulfur, selenium, zinc or oxygen; and
a p-type layer comprising cadmium, tellurium, and at least one of selenium or zinc.
13. The photovoltaic device of claim 10 , wherein the back contact stack comprises at least one of: tellurium, tungsten, tantalum, titanium, palladium, nickel, silver, calcium, lead, mercury, graphite, ZnTe, CdZnTe, ZnTe:Cu, HgTe, PbTe, aluminum, copper, nickel, gold, silver, molybdenum, chromium, indium nitride, or molybdenum nitride.
14. The photovoltaic device of claim 10 , wherein the oxide layer thickness is from about 5 Å to about 30 Å thick.
15. The photovoltaic device of claim 10 , wherein the oxide layer comprises CdTeO 3 .
16. The photovoltaic device of claim 10 , wherein the semiconductor stack, in addition to the oxide layer, comprises:
an n-type layer, comprising at least one of: cadmium selenide, zinc magnesium oxide, cadmium tin oxide, indium tin oxide, indium-doped cadmium oxide, aluminum-doped zinc oxide, indium zinc oxide, zinc tin oxide, cadmium oxide, zinc aluminum oxide, zinc silicon oxide, zinc zirconium oxide, tin aluminum oxide, tin silicon oxide, or tin zirconium oxide; and
an absorber layer comprising cadmium, tellurium, and at least one of selenium or zinc.
17. The photovoltaic device of claim 10 , wherein:
the semiconductor stack comprises:
an n-type layer, comprising at least one of: cadmium selenide, zinc magnesium oxide, cadmium tin oxide, indium tin oxide, indium-doped cadmium oxide, or cadmium oxide; and
an absorber layer comprising cadmium, tellurium, and selenium;
the front contact stack comprises a substrate layer and a transparent conductive oxide layer; and
the back contact stack comprises a back contact layer and a metal electrode layer, wherein the back contact layer is directly on and in contact with the oxide layer.
18. A photovoltaic device comprising:
a front contact stack comprising a transparent conductive oxide;
a semiconductor stack disposed over the front contact stack, wherein the semiconductor stack comprises cadmium, tellurium, and at least one of: selenium, zinc, or oxygen;
an oxide layer on the semiconductor stack, the oxide layer having a thickness from about 2 Å to about 100 Å; and
a back contact stack over the oxide layer.
19. The photovoltaic device of claim 18 , wherein the oxide layer thickness is from about 3 Å to about 50 Å.
20. The photovoltaic device of claim 18 , wherein the back contact stack comprises at least one of ZnTe, CdZnTe, or ZnTe:Cu.