Aluminum grid as backside conductor on epitaxial silicon thin film solar cells

1. A solar cell, comprising:

an MG-Si substrate with a purity of at least 99.99%;

a lightly doped crystalline-Si (c-Si) epitaxial layer situated above the MG-Si substrate, wherein the lightly doped c-Si epitaxial layer acts as a base layer for the solar sell;

a first heavily doped c-Si epitaxial layer acting as an emitter layer situated above the lightly doped c-Si base layer;

a second heavily doped c-Si epitaxial layer situated between the MG-Si substrate and the light-doped c-Si base layer, wherein the second heavily doped c-Si epitaxial layer is formed independently of the lightly doped base layer, wherein the second heavily doped c-Si epitaxial layer has a doping concentration of 1×10 20 /cm 3 and serves as a back surface field (BSF) layer, thereby ensuring the solar cell to have an efficiency greater than 17%;

a front side electrode grid situated above the emitter layer; and

a backside electrode grid situated below the substrate, wherein the backside electrode grid is in direct contact with a backside of the MG-Si substrate.

2. The solar cell of claim 1 , wherein the backside electrode grid comprises Al paste.

3. The solar cell of claim 2 , wherein the Al paste comprises Al and one or more of the following materials:

frit;

Ag;

Pd;

Cr;

Zn; and

Sn.

4. The solar cell of claim 1 , wherein the backside electrode grid is formed using:

screen-printing; or

aerosol-jet printing.

5. The solar cell of claim 4 , wherein the backside electrode grid is solderable, and wherein the backside electrode grid is formed using a single printing step.

6. The solar cell of claim 1 , wherein the backside electrode grid comprises one or more of:

straight lines;

crossed lines;

zigzagged lines; and

circles.

7. The solar cell of claim 1 , wherein the second heavily doped c-Si layer and the lightly doped c-Si base layer are p-type doped, and wherein the first heavily doped c-Si layer is n-type doped.

8. The solar cell of claim 1 , wherein the second heavily doped c-Si layer and the lightly doped c-Si base layer are deposited using a chemical-vapor-deposition (CVD) technique.

9. The solar cell of claim 1 , further comprising a dielectric layer stack situated above the first heavily doped c-Si layer, wherein the dielectric layer stack includes a SiO 2 layer, and wherein the SiO 2 layer has a thickness between 100 Å and 200 Å.

10. The solar cell of claim 9 , wherein the dielectric stack further includes a SiN x :H layer, and wherein the SiN x :H layer has a thickness between 500 Å and 1000 Å.

11. The solar cell of claim 1 , wherein the MG-Si substrate has a thickness of less than 50 microns.