Transparent conducting layers and photovoltaic devices including the same
Photovoltaic devices having transparent contact layers are described herein.
1. A tandem photovoltaic device comprising:
a thin film junction comprising an absorber layer comprising cadmium and tellurium;
a second junction electrically connected with the thin film junction, wherein the second junction is closer to a back side of the tandem photovoltaic device than the thin film junction; and
a transparent conducting layer disposed between the thin film junction and the second junction, wherein:
the transparent conducting layer comprises a high conductivity layer, a diffusion barrier layer, and a capping layer,
the diffusion barrier layer comprises cadmium stannate,
the capping layer comprises cadmium stannate,
the high conductivity layer comprises cadmium oxide doped “++” type intrinsically or with an oxide dopant, and
the high conductivity layer is between the diffusion barrier layer and the capping layer.
2. The tandem photovoltaic device of claim 1 , wherein at least one of the diffusion barrier layer or the capping layer comprises amorphous cadmium stannate, wherein the amorphous cadmium stannate is a Cd x SnO 4 material, where the value of x is in a range from 0.5 to 2.
3. The tandem photovoltaic device of claim 2 , wherein the cadmium oxide is doped n++ with the oxide dopant and has a charge density greater than 1×10 18 cm −3 .
4. The tandem photovoltaic device of claim 3 , wherein the oxide dopant is In 2 O 3 .
5. The tandem photovoltaic device of claim 3 , wherein the oxide dopant is Ga 2 O 3 .
6. The tandem photovoltaic device of claim 1 , wherein:
the capping layer is in contact with the high conductivity layer.
7. The tandem photovoltaic device of claim 1 , wherein:
the diffusion barrier layer is in contact with the high conductivity layer, and
the diffusion barrier layer is in contact with a back contact layer of the thin film junction.
8. The tandem photovoltaic device of claim 1 , wherein the high conductivity layer is thicker than the diffusion barrier layer, and a thickness of the high conductivity layer is less than 300 nm.
9. The tandem photovoltaic device of claim 1 , wherein the transparent conducting layer has an average transmittance of greater than 85% to light having a wavelength between 800 nm and 1,300 nm, and a thickness of the transparent conducting layer is greater than 40 nm and less than 400 nm.
10. The tandem photovoltaic device of claim 1 , wherein the thin film junction has an average quantum efficiency between 800 nm and 1,300 nm that is less than 20%.
11. The tandem photovoltaic device of claim 10 , wherein the absorber layer of the thin film junction further comprises at least one of: zinc or selenium.
12. The tandem photovoltaic device of claim 1 , wherein:
the thin film junction comprises a back contact layer;
the back contact layer is between the absorber layer and the transparent conducting layer; and
the back contact layer comprises zinc and tellurium.
13. The tandem photovoltaic device of claim 1 , wherein:
the second junction has an average quantum efficiency between 800 nm and 1,300 nm that is greater than 50%; and
the second junction comprises at least one of: amorphous silicon, crystalline silicon, or copper indium gallium selenide.
14. The tandem photovoltaic device of claim 1 , wherein:
the thin film junction comprises a transparent conductive oxide layer; and
the absorber layer of the thin film junction is between the transparent conductive oxide layer and the transparent conducting layer.
15. The tandem photovoltaic device of claim 14 , wherein the transparent conductive oxide layer comprises indium tin oxide.
16. The tandem photovoltaic device of claim 14 , wherein the transparent conductive oxide layer comprises cadmium stannate, and wherein the cadmium stannate is crystalline.
17. A tandem photovoltaic device comprising:
a thin film junction comprising an absorber layer comprising cadmium and tellurium;
a second junction electrically connected with the thin film junction; and
a transparent conducting layer disposed between the thin film junction and the second junction, wherein:
the transparent conducting layer comprises a high conductivity layer, a diffusion barrier layer, and a capping layer,
the diffusion barrier layer comprises cadmium stannate,
the capping layer comprises cadmium stannate,
the high conductivity layer comprises cadmium oxide, and
the high conductivity layer is between the diffusion layer and the capping layer.
18. The tandem photovoltaic device of claim 17 , wherein:
the second junction and the thin film junction are electrically connected in series; and
the transparent conducting layer forms at least a part of a series connection with the thin film junction.
19. The tandem photovoltaic device of claim 17 , wherein:
the thin film junction has an average quantum efficiency between 800 nm and 1,300 nm that is less than 20%;
the second junction has an average quantum efficiency between 800 nm and 1,300 nm that is greater than 50%;
the transparent conducting layer has an average transmittance of greater than 85% to light having a wavelength between 800 nm and 1,300 nm; and
a thickness of the transparent conducting layer is greater than 40 nm and less than 400 nm.
20. The tandem photovoltaic device of claim 17 , wherein:
the high conductivity layer consists essentially of cadmium oxide doped with an oxide dopant, wherein the oxide dopant is selected from one or more of: In 2 O 3 , Ga 2 O 3 , TiO 2 , Dy 2 O 3 , SnO 2 , Y 2 O 3 , or Al 2 O 3 ; and
the high conductivity layer has an n-type charge carrier density greater than about 1×10 18 cm −3 .