Grain growth for solar cells

Patent metadata

Field	Value
Publication number	US-9466754-B2
Application number	US-201414447526-A
Country	US
Kind code	B2
Filing date	Jul 30, 2014
Priority date	Jul 30, 2014
Publication date	Oct 11, 2016
Grant date	Oct 11, 2016

Abstract

A solar cell can include a silicon layer formed over a silicon substrate. The silicon layer can have a P-type doped region and an N-type doped region. Portions of the silicon layer can have a grain size larger than other portions of the silicon layer. For example, larger grains of the silicon layer formed within a depletion region between P-type and N-type doped regions can minimize recombination loss at the P-type and N-type doped region boundaries and improve solar cell efficiency.

First claim

What is claimed is:

1. A method of fabricating a solar cell, the method comprising:
forming upper regions, angled regions and lower regions of a silicon substrate, wherein the upper regions and the lower regions are substantially coplanar;
forming a silicon layer over the silicon substrate;
applying a laser to the silicon layer resulting in portions of the silicon layer over the upper regions and lower regions having a larger grain size than other portions of the silicon layer over angled regions of the silicon substrate; and
driving dopants into the silicon layer resulting in P-type doped regions and N-type doped regions, the P-type doped regions and N-type doped regions abutting in a contiguous portion of the silicon layer.

2. The method of claim 1 , wherein forming upper regions, angled regions and lower regions comprises performing an etching process on the silicon substrate.

3. The method of claim 2 , wherein performing the etching process comprises etching with potassium hydroxide (KOH).

4. The method of claim 1 , further comprising forming a dielectric region between the silicon layer and the silicon substrate.

5. The method of claim 1 , wherein applying a laser comprises applying a pulsed laser or a continuous wave laser.

6. The method of claim 1 , wherein applying a laser comprises melting portions of the silicon layer.

7. The method of claim 1 , wherein applying a laser comprises applying a laser with a top-hat profile on the on the silicon layer.

8. The method of claim 1 , wherein forming a silicon layer comprises forming an amorphous silicon layer or a polysilicon layer.

9. A method of fabricating a solar cell, the method comprising:
forming upper regions, angled regions and lower regions of a silicon substrate, wherein the upper regions and the lower regions are substantially coplanar;
forming a silicon layer over the silicon substrate; and
applying a laser to the silicon layer resulting in P-type doped regions and N-type doped regions and portions of the silicon layer over the upper regions and lower regions having a larger grain size than other portions of the silicon layer over angled regions of the silicon substrate, the larger grain size formed in a contiguous portion of the silicon layer where the P-type doped regions and N-type doped regions abut.

10. The method of claim 9 , wherein forming upper regions, angled regions and lower regions comprises performing an etching process on the silicon substrate.

11. The method of claim 10 , wherein performing the etching process comprises etching with potassium hydroxide (KOH).

12. The method of claim 9 , further comprising forming a dielectric between the silicon layer and the silicon substrate.

13. The method of claim 9 , wherein applying a laser comprises applying a pulsed laser or a continuous wave laser.

14. The method of claim 9 , wherein applying a laser comprises:
driving dopants into the silicon layer using a laser resulting in P-type doped regions and N-type doped regions; and
melting the portions of the silicon layer using the laser in a single step as the driving, the melting resulting in portions of the silicon layer over the upper regions and lower regions having a larger grain size than other portions of the silicon layer and the larger grain size formed in a contiguous portion of the silicon layer where the P-type doped regions and N-type doped regions abut.

15. The method of claim 9 , wherein applying a laser comprises applying a laser with a top-hat profile on the on the silicon layer.

16. The method of claim 9 , wherein forming a silicon layer comprises forming an amorphous silicon layer or a polysilicon layer.

Assignees

• Kim Taeseok
• Sunpower Corp

Inventors

• Kim Taeseok

Classifications

• H10F77/1642

  including only Group IV materials · CPC title

• H10F77/147

  Shapes of bodies · CPC title

• H10F71/131

  Recrystallisation; Crystallization of amorphous or microcrystalline semiconductors · CPC title

• H10F71/128 Primary

  Annealing · CPC title

• H10F71/121

  The active layers comprising only Group IV materials · CPC title