Trench process and structure for backside contact solar cells with polysilicon doped regions
View Patent ↗A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. An interrupted trench structure separates the P-type doped region from the N-type doped region in some locations but allows the P-type doped region and the N-type doped region to touch in other locations. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. Among other advantages, the resulting solar cell structure allows for increased efficiency while having a relatively low reverse breakdown voltage.
1. A method of fabricating a solar cell, the method comprising:
forming a P-type doped region and an N-type doped region on a backside of the solar cell, the backside being opposite a front side of the solar cell that faces the sun during normal operation; and
forming a trench that physically separates the P-type doped region and the N-type doped region, the trench having a trench interruption that breaks continuity of the trench and allows the P-type doped region and the N-type doped region to abut through the trench interruption.
2. The method of claim 1 wherein forming the P-type doped region and the N-type doped region on a backside of the solar cell comprises:
forming a polysilicon layer over a solar cell substrate; and
forming the P-type doped region and the N-type doped region in the polysilicon layer.
3. The method of claim 2 wherein the trench is formed by etching the polysilicon layer before the polysilicon layer is doped to form the P-type doped region and the N-type doped region.
4. The method of claim 2 wherein forming the P-type doped region and the N-type doped region in the polysilicon layer comprises:
diffusing P-type dopants from a P-type dopant source layer into the polysilicon layer; and
diffusing N-type dopants from an N-type dopant source layer into the polysilicon layer.
5. The method of claim 1 further comprising:
randomly texturing a surface of the trench.
6. The method of claim 1 further comprising:
electrically coupling a first metal contact finger to the P-type doped region on the backside of the solar cell; and
electrically coupling a second metal contact finger to the N-type doped region on the backside of the solar cell.
7. The method of claim 1 wherein the P-type doped region and the N-type doped region comprise polysilicon.
8. The method of claim 7 wherein the polysilicon is formed over a dielectric layer and the trench is formed by etching through the polysilicon layer and the dielectric layer.
9. The method of claim 1 wherein the trench has a plurality of trench interruptions that break continuity of the trench and allow the P-type doped region and the N-type doped region to abut through the plurality of trench interruptions.
10. A method of fabricating a solar cell, the method comprising:
forming a dielectric layer over a solar cell substrate;
forming a polysilicon layer over the dielectric layer;
forming a P-type doped region and an N-type doped region in the polysilicon layer; and
etching the polysilicon layer to form a trench that physically separates the P-type doped region and the N-type doped region, the trench including a trench interruption that breaks continuity of the trench and allows the P-type doped region and the N-type doped region to touch through the trench interruption.
11. The method of claim 10 wherein forming the P-type doped region and the N-type doped region in the polysilicon layer comprises:
diffusing P-type dopants from a P-type dopant source layer into the polysilicon layer; and
diffusing N-type dopants from an N-type dopant source layer into the polysilicon layer.
12. The method of claim 10 further comprising:
randomly texturing a surface of the trench.
13. The method of claim 10 further comprising:
electrically coupling a first metal contact finger to the P-type doped region on the backside of the solar cell; and
electrically coupling a second metal contact finger to the N-type doped region on the backside of the solar cell.
14. The method of claim 10 wherein the trench has a plurality of trench interruptions that break continuity of the trench and allow the P-type doped region and the N-type doped region to abut through the plurality of trench interruptions.
15. The method of claim 10 further comprising:
depositing silicon nitride in the trench.
16. A method of fabricating a solar cell, the method comprising:
forming a P-type doped region and an N-type doped region on a backside of the solar cell, the backside being opposite a front side of the solar cell that faces the sun during normal operation; and
forming a trench that physically separates the P-type doped region and the N-type doped region, the trench including a plurality of trench interruptions that break continuity of the trench and allow the P-type doped region and the N-type doped region to touch through the trench interruption.
17. The method of claim 16 wherein the P-type doped region and the N-type doped region comprise polysilicon.
18. The method of claim 16 further comprising:
randomly texturing a surface of the trench.
19. The method of claim 16 further comprising:
electrically coupling a first metal contact finger to the P-type doped region on the backside of the solar cell; and
electrically coupling a second metal contact finger to the N-type doped region on the backside of the solar cell.
20. The method of claim 16 further comprising:
depositing silicon nitride in the trench.