Trench process and structure for backside contact solar cells with polysilicon doped regions

Patent metadata

Field	Value
Publication number	US-9437763-B2
Application number	US-201514945931-A
Country	US
Kind code	B2
Filing date	Nov 19, 2015
Priority date	Jun 12, 2008
Publication date	Sep 6, 2016
Grant date	Sep 6, 2016

Abstract

A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. A trench structure separates the P-type doped region from the N-type doped region. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. The trench structure may include a textured surface for increased solar radiation collection. Among other advantages, the resulting structure increases efficiency by providing isolation between adjacent P-type and N-type doped regions, thereby preventing recombination in a space charge region where the doped regions would have touched.

First claim

What is claimed is:

1. A solar cell, comprising:
a solar cell substrate having a front side configured to face the sun during normal operation and a backside opposite the front side;
a P-type doped region and an N-type doped region of the solar cell over the solar cell substrate;
a first dielectric between the solar cell substrate and the P-type and N-type doped regions;
a trench separating the P-type doped region and the N-type doped region and at least partially dividing the first dielectric, wherein a surface of the trench is textured; and
a second dielectric formed over the surface of the trench.

2. The solar cell of claim 1 , further comprising a third dielectric formed in the trench over the second dielectric.

3. The solar cell of claim 2 , wherein the third dielectric comprises silicon nitride.

4. The solar cell of claim 1 , wherein the second dielectric comprises thermal oxide.

5. The solar cell of claim 1 , wherein the P-type and N-type doped regions comprise polysilicon.

6. The solar cell of claim 1 , wherein the solar cell substrate comprises silicon.

7. The solar cell of claim 6 , wherein the silicon is N-type.

8. The solar cell of claim 1 , wherein the first dielectric comprises silicon dioxide.

9. The solar cell of claim 1 , wherein the second dielectric comprises silicon dioxide.

10. The solar cell of claim 1 , further comprising interdigitated metal contact fingers electrically coupled to the P-type and N-type doped regions.

11. A semiconductor device, comprising:
a P-type doped region and an N-type doped region formed on a backside of a solar cell substrate, wherein the P-type and N-type doped regions are formed over a first dielectric;
a trench structure separating the P-type doped region and the N-type doped region and at least partially dividing the first dielectric, wherein a surface of the trench structure is textured; and
a second dielectric formed on the surface of the trench structure.

12. The semiconductor device of claim 11 , further comprising a third dielectric formed on the second dielectric in the trench structure.

13. The semiconductor device of claim 12 , further comprising metal contacts electrically coupled to the P-type and N-type doped regions through the third dielectric.

14. The semiconductor device of claim 11 , wherein the solar cell substrate comprises silicon.

15. The semiconductor device of claim 14 , wherein the silicon is N-type.

16. The semiconductor device of claim 11 , wherein the P-type doped region and the N-type doped region comprise polysilicon.

17. A method of fabricating a solar cell, the method comprising:
forming a first dielectric on a silicon substrate;
forming a P-type doped region and an N-type doped region over the first dielectric;
forming a trench separating the P-type doped region from the N-type doped region and at least partially separating the first dielectric;
texturing a surface of the trench; and
forming a second dielectric over the surface of the trench.

18. The method of claim 17 , further comprising:
forming a third dielectric over the second dielectric in the trench.

19. The method of claim 17 , wherein said forming the trench includes laser trenching to separate the P-type doped region from the N-type doped region.

20. The method of claim 17 , wherein the second dielectric comprises thermal oxide.

Assignees

• Sunpower Corp

Inventors

• Smith David D

Classifications

• Y02E10/547

  Monocrystalline silicon PV cells · CPC title

• Y02E10/546

  Polycrystalline silicon PV cells · CPC title

• H10F77/1642

  including only Group IV materials · CPC title

• H10F77/935

  for photovoltaic devices or modules · CPC title

• H10F77/707

  of the substrates or of layers on substrates, e.g. textured ITO layer on a glass substrate · CPC title