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

• US 10,084,099 B2
• Filed: 04/20/2015
• Issued: 09/25/2018
• Est. Priority Date: 11/12/2009
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Inc.
• Inventors: Yu, Chentao, Xu, Zheng, Heng, Jiunn Benjamin, Fu, Jianming
• Primary Examiner(s): Mowla, Golam
• Application Number:
  US14/691,403
• Publication Number:
  US 20150270411A1
• Time in Patent Office: 1,254 Days
• CPC Class Codes: H01L 31/0201 comprising specially adapted module bus-bar structures
• CPC Class Codes: H01L 31/02167 for solar cells
• CPC Class Codes: H01L 31/02168 the coatings being antireflective or having enhancing optical properties for the solar cells
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

One embodiment of the present invention provides a solar cell. The solar cell includes a substrate, a first heavily doped crystalline-Si (c-Si) layer situated above the substrate, a lightly doped c-Si layer situated above the first heavily doped crystalline-Si layer, a second heavily doped c-Si layer situated above the lightly doped c-Si layer, a front side electrode grid situated above the second heavily doped c-Si layer, and a backside electrode grid situated on the backside of the substrate.

Claims

1. A solar cell, comprising:

a metallurgical-grade silicon substrate;

a first doped crystalline-silicon layer that is epitaxially formed on the metallurgical-grade silicon substrate;

a lightly doped crystalline-silicon base layer epitaxially formed on the first doped crystalline-silicon layer, wherein a doping concentration of the first doped crystalline-silicon layer is greater than that of the lightly doped crystalline-silicon base layer;

a second doped crystalline-silicon layer which is formed on the lightly doped crystalline-silicon base layer and has a doping concentration greater than that of the lightly doped crystalline-silicon base layer;

a first metal electrode grid; and

a second metal electrode grid;

wherein the lightly doped crystalline-silicon base layer, first doped crystalline-silicon layer, second doped crystalline-silicon layer, and second electrode grid are positioned on a first side of the metallurgical-grade silicon substrate;

wherein the lightly doped crystalline-silicon base layer is between the first doped crystalline-silicon layer and second doped crystalline-silicon layer;

wherein the second metal electrode grid is electrically coupled to the second doped crystalline-silicon layer; and

wherein the first metal electrode grid is positioned on a second side of the metallurgical-grade silicon substrate.

2. The solar cell of claim 1, wherein the second metal electrode grid comprises a number of finger strips and at least one busbar.

3. The solar cell of claim 1, further comprising a dielectric passivation layer between the second doped crystalline-silicon layer and the second metal electrode grid, wherein the dielectric passivation layer is in direct contact with the second doped crystalline-silicon layer.

4. The solar cell of claim 1, wherein the first doped crystalline-silicon layer is in direct contact with the metallurgical-grade silicon substrate.

5. The solar cell of claim 1, wherein the first and second doped crystalline-silicon layers are in direct contact with the lightly doped crystalline-silicon base layer.

6. The solar cell of claim 1, wherein the lightly doped crystalline-silicon base layer is n-type doped.

7. The solar cell of claim 1, wherein the first doped crystalline-silicon layer is p-type doped.

8. The solar cell of claim 1, wherein the second doped crystalline-silicon layer is n-type doped.

9. The solar cell of claim 1, wherein the first and second metal electrode grids comprise Al.

10. The solar cell of claim 9, wherein the first and second metal electrode grids further comprise one or more of the following materials:

frit;

Ag;

Pd;

Cr;

Zn; and

Sn.

11. The solar cell of claim 1, further comprising an anti-reflection layer between the second doped crystalline-silicon layer and the second metal electrode grid.