Back contact structure for photovoltaic devices such as copper-indium-diselenide solar cells
View Patent ↗A back contact configuration for a CIGS-type photovoltaic device is provided. According to certain examples, the back contact configuration includes an optical matching layer and/or portion of or including MoSe 2 having a thickness substantially corresponding to maxima of absorption of reflected light in CIGS-type absorbers used in certain photovoltaic devices. Certain example methods for making the back contact configuration wherein a thickness of the MoSe 2 layer and/or portion can be controlled to be within thickness ranges that correspond to maxima of CIGS light absorption for reflected solar light are also provided.
1. A back contact structure for use in a photovoltaic device, comprising:
a substrate;
a first conductive back contact layer comprising Mo on the substrate;
a foundational seed layer comprising MoOx formed over said first conductive back contact layer, said foundational seed layer comprising MoOx being less conductive than said first conductive back contact layer comprising Mo, wherein a thickness of said foundational seed layer comprising MoOx is in a range selected from the group consisting of: from 35-45 nm, and from 60-70 nm, and wherein the first conductive back contact layer is located between at least the substrate and the foundational seed layer; and
wherein the foundational seed layer comprising MoOx is transformable, as a result of a selenization process, into a layer comprising MoSe 2 having a thickness in a range selected from the group consisting of: from about 35-45 nm, and from about 60-70 nm.
2. The back contact of claim 1 , wherein the substrate comprises glass.
3. The back contact of claim 1 , wherein the substrate comprises metal foil.
4. The back contact of claim 1 , wherein a thickness of said foundational seed layer comprising MoOx is selected from the group consisting of: about 40 nm, and about 65 nm.
5. The back contact of claim 1 , wherein a thickness of said first conductive back contact layer comprising Mo is in a range of from about 300-600 nm.
6. The back contact of claim 1 , wherein a thickness of said first conductive back contact layer comprising Mo is about 400 nm.
7. The back contact of claim 1 , wherein a dielectric layer comprising silicon nitride and/or silicon oxynitride is provided between at least the substrate and said first conductive back contact layer comprising Mo.
8. The back contact of claim 1 , wherein said foundational seed layer consists essentially of MoOx.
9. The back contact of claim 1 , wherein said first conductive back contact layer consists essentially of Mo.
10. The back contact structure of claim 1 , wherein the thickness of said foundational seed layer comprising MoOx is in a range of from 35-45 nm.
11. The back contact structure of claim 1 , wherein the thickness of said foundational seed layer comprising MoOx is in a range of from 60-70 nm.
12. The back contact structure of claim 1 , wherein the foundational seed layer comprising MoOx is sputter deposited to have an as-coated density lower than that of the first conductive back contact layer comprising Mo.
13. The back contact structure of claim 12 , wherein:
the foundational seed layer comprising MoOx is sputter deposited in an argon and oxygen inclusive atmosphere having an argon to oxygen ration of (30-100)/1; and
the first conductive back contact layer comprising Mo is sputter deposited.
14. The back contact structure of claim 13 , wherein:
the thickness of said foundational seed layer comprising MoOx is in a range of from 35-45 nm; and
the foundational seed layer comprising MoOx is transformable, as a result of the selenization process, into a layer comprising MoSe 2 having a thickness in a range of from about 35-45 nm.
15. The back contact structure of claim 13 , wherein:
the foundational seed layer comprising MoOx is sputter deposited to have an as-coated density lower than that of the first conductive back contact layer comprising Mo;
the thickness of said foundational seed layer comprising MoOx is in a range of from 35-45 nm; and
the foundational seed layer comprising MoOx is transformable, as a result of the selenization process, into a layer comprising MoSe 2 having a thickness in a range of from about 35-45 nm.