Photovoltaic device including a p-n junction and method of manufacturing
A photovoltaic device includes a substrate structure and a p-type semiconductor absorber layer. A photovoltaic device may include a CdSeTe layer. A process for manufacturing a photovoltaic device includes forming a CdSeTe layer over a substrate. The process includes forming a p-type cadmium selenide telluride absorber layer.
1. A method for forming a photovoltaic structure, comprising:
providing a substrate structure comprising a transparent conductive oxide (TCO) layer;
forming a CdSeTe layer over the substrate structure;
alloying the CdSeTe layer whereby an absorber layer is formed over the substrate structure, wherein:
the absorber layer comprises a p-type cadmium selenide telluride layer,
the p-type cadmium selenide telluride layer is composed of a CdSe x Te 1−x compound, wherein a value of x is between 0 and 1; and
forming a back contact over the absorber layer;
wherein:
the absorber layer has a compositional profile having a gradient of selenium, wherein a concentration of Se is greater adjacent the TCO layer than adjacent the back contact; and
the step of forming the CdSeTe layer includes sequentially depositing a CdSe layer followed by depositing a CdTe layer.
2. The method of claim 1 , wherein the step of forming the CdSeTe layer comprises depositing multiple layers by vapor transport deposition.
3. The method of claim 1 , wherein the CdSe x Te 1−x layer, has a compositional gradient wherein x varies across a thickness of the CdSe x Te 1−x layer, and wherein x has a value within a range of 0.01 to 0.25.
4. The method of claim 1 , further comprising depositing a CdTe layer over the CdSeTe layer, wherein a thickness of the CdTe layer is between about 250 nm to about 3500 nm.
5. The method of claim 1 , wherein a thickness of the absorber layer is between 1000 nm to 3500 nm.
6. The method of claim 1 , wherein the CdSe x Te 1−x compound has a compositional profile such that x varies in value through a thickness of the cadmium selenide telluride layer, and the value of x is in a range of 0.01 to 0.40.
7. The method of claim 1 , further comprising incorporating a dopant into the absorber layer.
8. The method of claim 1 , wherein the alloying step occurs concurrently with the step of depositing the CdSeTe layer over the substrate structure.
9. The method of claim 1 , wherein the alloying step occurs after the step of depositing the CdSeTe layer over the substrate structure.
10. The method of claim 1 , wherein the p-type cadmium selenide telluride layer of the absorber layer forms a p-n junction with the substrate structure, wherein the substrate structure does not include a window layer comprising CdS, and wherein the substrate structure does not include a window layer comprising CdSSe.
11. The method of claim 1 , wherein the alloying step further comprises:
annealing with a CdCl 2 flux at a temperature in a range from 420° C. to 460° C. for a duration in a range from five minutes to sixty minutes.
12. The method of claim 1 , further comprising an activation step of contacting a material containing chlorine to the CdSeTe layer, and annealing the absorber layer.
13. The method of claim 12 , wherein the material containing chlorine comprises an aqueous solution of CdCl 2 , wherein the aqueous solution has a concentration in a range of 50 g/L to 500 g/L.
14. The method of claim 12 , wherein the activation step comprises contacting the CdSeTe layer with CdCl 2 and another material containing chlorine.
15. The method of claim 12 , wherein the activation step comprises contacting the CdSeTe layer with CdCl 2 and another material containing chlorine selected from the group consisting of: MnCl 2 , MgCl 2 , NHCl 2 , ZnCl 2 , or TeCl 2 .
16. The method of claim 1 , wherein the back contact comprises an ohmic electrode comprising an electrically conductive material.
17. A method for forming a photovoltaic structure, comprising:
providing a substrate structure comprising a transparent conductive oxide (TCO) layer;
forming a CdSeTe layer over the substrate structure;
alloying the CdSeTe layer whereby an absorber layer is formed over the substrate structure, wherein:
the absorber layer comprises a p-type cadmium selenide telluride layer,
the p-type cadmium selenide telluride layer is composed of a CdSe x Te 1−x compound, wherein a value of x is between 0 and 1; and
forming a back contact over the absorber layer;
wherein:
the absorber layer has a compositional profile having a gradient of selenium, wherein a concentration of Se is greater adjacent the TCO layer than adjacent the back contact; and
wherein the step of depositing the CdSeTe layer includes sequentially depositing a CdSe layer over the substrate structure, followed by depositing a CdTe layer, and wherein the alloying step occurs after the step of depositing the CdTe layer over the CdSe layer.
18. The method of claim 17 , wherein the step of forming the CdSeTe layer comprises depositing multiple layers by vapor transport deposition.
19. The method of claim 17 , wherein the CdSe x Te 1−x layer, has a compositional gradient wherein x varies across a thickness of the CdSe x Te 1−x layer, and wherein x has a value within a range of 0.01 to 0.25.
20. The method of claim 17 , further comprising depositing a CdTe layer over the CdSeTe layer, wherein a thickness of the CdTe layer is between about 250 nm to about 3500 nm.
21. The method of claim 17 , wherein a thickness of the absorber layer is between 1000 nm to 3500 nm.
22. The method of claim 17 , wherein the CdSe x Te 1−x compound has a compositional profile such that x varies in value through a thickness of the cadmium selenide telluride layer, and the value of x is in a range of 0.01 to 0.40.
23. The method of claim 17 , further comprising incorporating a dopant into the absorber layer.
24. The method of claim 17 , wherein the alloying step occurs concurrently with the step of depositing the CdSeTe layer over the substrate structure.
25. The method of claim 17 , wherein the alloying step occurs after the step of depositing the CdSeTe layer over the substrate structure.
26. The method of claim 17 , wherein the p-type cadmium selenide telluride layer of the absorber layer forms a p-n junction with the substrate structure, wherein the substrate structure does not include a window layer comprising CdS, and wherein the substrate structure does not include a window layer comprising CdSSe.
27. The method of claim 17 , wherein the alloying step further comprises:
annealing with a CdCl 2 flux at a temperature in a range from 420° C. to 460° C. for a duration in a range from five minutes to sixty minutes.
28. The method of claim 17 , further comprising an activation step of contacting a material containing chlorine to the CdSeTe layer, and annealing the absorber layer.
29. The method of claim 28 , wherein the material containing chlorine comprises an aqueous solution of CdCl 2 , wherein the aqueous solution has a concentration in a range of 50 g/L to 500 g/L.
30. The method of claim 28 , wherein the activation step comprises contacting the CdSeTe layer with CdCl 2 and another material containing chlorine.
31. The method of claim 28 , wherein the activation step comprises contacting the CdSeTe layer with CdCl 2 and another material containing chlorine selected from the group consisting of: MnCl 2 , MgCl 2 , NHCl 2 , ZnCl 2 , or TeCl 2 .
32. The method of claim 17 , wherein the back contact comprises an ohmic electrode comprising an electrically conductive material.