Photovoltaic devices and method of manufacturing
A photovoltaic device includes a substrate structure and at least one Se-containing layer, such as a CdSeTe layer. A process for manufacturing the photovoltaic device includes forming the CdSeTe layer over a substrate by at least one of sputtering, evaporation deposition, CVD, chemical bath deposition process, and vapor transport deposition process. The process can also include controlling a thickness range of the Se-containing layer.
1. A photovoltaic device comprising:
a substrate;
a transparent conductive oxide (TCO) layer formed on the substrate;
a back contact;
a CdSeTe absorber layer formed between the TCO layer and the back contact, wherein:
the CdSeTe absorber layer contacts the back contact,
the CdSeTe absorber layer is composed of cadmium, selenium, and tellurium in varying amounts,
a ratio of Te atoms to a sum of Se atoms and the Te atoms throughout the CdSeTe absorber layer compound is between about 99 to 100 and about 60 to 100; and
a buffer layer formed between the TCO layer and the CdSeTe absorber layer,
and wherein the buffer layer comprises magnesium,
and wherein a peak concentration of Se is located at an interface between the buffer layer and the CdSeTe absorber layer.
2. The photovoltaic device of claim 1 , further comprising a window layer formed between the TCO layer and the CdSeTe absorber layer.
3. The photovoltaic device of claim 2 , wherein the window layer is one of CdS and CdSSe.
4. The photovoltaic device of claim 1 , wherein the back contact is formed from one of ZnTe, CdZnTe, ZnTe:Cu, and a bi-layer including a layer of ZnTe and a layer of CdZnTe.
5. The photovoltaic device of claim 3 , further comprising a back metal electrode formed on the back contact.
6. The photovoltaic device of claim 5 , wherein the back metal electrode includes a layer of MoN x .
7. The photovoltaic device of claim 6 , wherein the back metal electrode further includes a layer of aluminum formed between a layer of chromium and the layer of MoN x .
8. The photovoltaic device of claim 5 , further comprising an interfacial layer formed from copper formed between the back metal electrode and the back contact.
9. The photovoltaic device of claim 1 , wherein the CdSeTe absorber layer is formed from CdSe x Te 1−x where x is from about 0.01 to about 0.4.
10. The photovoltaic device of claim 9 , wherein x is from about 0.01to about 0.25.
11. The photovoltaic device of claim 1 , wherein the CdSeTe absorber layer has a concentration gradient of Se formed therein.
12. The photovoltaic device of claim 11 , wherein a concentration of Se adjacent the TCO layer is higher than a concentration of Se adjacent the back contact.
13. The photovoltaic device of claim 1 , wherein the TCO layer is formed from SnO x .
14. The photovoltaic device of claim 1 , the buffer layer comprises zinc magnesium oxide.
15. The photovoltaic device of claim 1 , wherein the TCO layer comprises indium tin oxide.
16. The photovoltaic device of claim 1 , wherein the TCO layer comprises cadmium stannate.
17. The photovoltaic device of claim 1 , wherein the photovoltaic device does not include a window layer.
18. A photovoltaic device comprising:
a substrate;
a transparent conductive oxide (TCO) layer formed on the substrate;
a back contact comprising ZnTe, a CdZnTe alloy, or ZnTe and the CdZnTe alloy; and
a CdSeTe absorber layer formed between the TCO layer and the back contact,
wherein a concentration of Se of the CdSeTe absorber layer adjacent the TCO layer is higher than a concentration of Se of the CdSeTe absorber layer adjacent the back contact,
and wherein a ratio of Se atoms to a sum of the Se atoms and Te atoms throughout the CdSeTe absorber layer is between about 5 to 100 and about 10 to 100.
19. The photovoltaic device of claim 18 , comprising a MoN x back metal electrode formed on the back contact.
20. The photovoltaic device of claim 18 , wherein the CdSeTe absorber layer is intermixed from a CdSe layer and a CdTe layer with a layer of CdSeTe disposed therebetween.
21. The photovoltaic device of claim 18 , wherein the TCO layer is formed from a layer of SnO x adjacent the substrate, a layer of SiO 2 formed on the layer of SnO x , a layer of SnO 2 :F formed on the layer of SiO 2 , and a layer of SnO 2 formed between the layer of SnO 2 :F and the CdSeTe absorber layer.
22. The photovoltaic device of claim 18 , comprising a buffer layer formed between the TCO layer and the CdSeTe absorber layer, and wherein the buffer layer comprises zinc magnesium oxide.
23. The photovoltaic device of claim 18 , further comprising a back metal electrode formed on the back contact.
24. The photovoltaic device of claim 23 , wherein the back metal electrode includes a layer of aluminum formed between a layer of chromium and a layer of MoN x .
25. The photovoltaic device of claim 18 , wherein the TCO layer comprises indium tin oxide.
26. The photovoltaic device of claim 18 , wherein the TCO layer comprises cadmium stannate.
27. The photovoltaic device of claim 18 , wherein the back contact s formed from a bi-layer including a layer of ZnTe and a layer of CdZnTe.
28. The photovoltaic device of claim 18 , wherein the photovoltaic device does not include a window layer.