SOLAR CELL WITH METAL GRID FABRICATED BY ELECTROPLATING

1 . A solar cell, comprising:

a photovoltaic structure;

a transparent-conductive-oxide (TCO) layer situated above the photovoltaic structure, wherein the TCO layer is in contact with the front surface of the photovoltaic structure; and

a front-side metal grid situated above the TCO layer, wherein the front-side metal grid includes:

a first metal layer comprising Cu, and

a second metal layer covering a top surface and sidewalk of the first metal layer, wherein the second metal layer comprises at least one of: Ag and Sn.

2 . The solar cell of claim 1 , wherein the resistivity of the front-side metal grid is less than 2×10 −5 Ω·cm.

3 . The solar cell of claim 1 , wherein the first metal layer is formed using an electroplating process.

4 . The solar cell of claim 1 , wherein the second metal layer is formed using a metal immersion process.

5 . The solar cell of claim 4 , wherein the metal immersion process is conducted in an acidic environment, thereby preventing deposition of the second metal layer on the TCO layer.

6 . The solar cell of claim 4 , wherein the metal immersion process involves a complexing agent that comprises Thiourea.

7 . The solar cell of claim 1 , further comprising:

a back-side TCO layer situated on the back side of the photovoltaic structure, wherein the back-side TCO layer is in contact with the back surface of the photovoltaic structure; and

a back-side metal grid situated on the back-side TCO layer, wherein the back-side metal, grid includes:

an inner metal core comprising Cu, and

an outer metal layer covering a top surface and sidewalls of the inner metal core, wherein the outer metal layer comprises at least one of: Ag and Sn.

8 . A method for fabricating a solar cell, comprising:

depositing one or more layers of amorphous-Si (a-Si) on top of a crystalline Si (c-Si) substrate with thin oxide formed on the surface to form a photovoltaic structure;

depositing a layer of transparent-conductive-oxide (TCO) on top of the a-Si layers;

forming a front-side electrode grid comprising a metal stack on top of the TCO layer, wherein the metal stack includes:

a first metal layer comprising Cu, and

a second metal layer covering a top surface and sidewalls of the first metal layer, wherein the second metal layer comprises at least one of: Ag and Sn; and

forming a back-side electrode on the back side of the Si substrate.

9 . The method of claim 8 , wherein the resistivity of the front-side electrode grid is less than 2×10 −5 Ω·cm.

10 . The method of claim 8 , wherein forming the first metal layer involves electroplating the first metal layer on top of the TCO layer.

11 . The method of claim 10 , wherein forming the first metal layer further involves depositing and/or removing a patterned masking layer on top of the TCO.

12 . The method of claim 8 , wherein forming the second metal layer involves a metal immersion process.

13 . The method of claim 12 , wherein the metal immersion process is conducted in an acidic environment, thereby preventing deposition of the second metal layer on the TCO layer.

14 . The method of claim 12 , wherein the metal immersion process involves a complexing agent that comprises Thiourea.

15 . The method of claim 8 , further comprising:

depositing a back-side TCO layer on the back side of the photovoltaic structure, wherein the back-side TCO layer is in contact with the back surface of the photovoltaic structure; and

fabricating a back-side electrode grid on the back-side TCO layer, wherein the back-side electrode grid includes:

an inner metal core comprising Cu, and

an outer metal layer covering a top surface and sidewalk of the inner metal core, wherein the outer metal layer comprises at least one of: Ag and Sn.