Backside contact solar cells with separated 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. 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.
1. A solar cell comprising:
a substrate having a front side and a backside;
a first dielectric layer disposed on the backside of the substrate;
a P-type doped polysilicon region; and
an N-type doped polysilicon region that is adjacent to the P-type doped polysilicon region,
wherein the P-type and N-type doped polysilicon regions are disposed on the first dielectric layer, and the P-type doped polysilicon region is physically separated from the N-type doped polysilicon region.
2. The solar cell of claim 1 , further comprising a second dielectric layer disposed between the P-type doped polysilicon region and the N-type doped polysilicon region.
3. The solar cell of claim 1 , wherein the substrate comprises an N-type doped silicon substrate.
4. The solar cell of claim 2 , wherein the second dielectric layer comprises silicon dioxide.
5. A solar cell comprising:
a substrate having a front side and a backside;
a first dielectric layer disposed on the backside of the substrate;
a P-type doped polysilicon region; and
an N-type doped polysilicon region that is adjacent to the P-type doped polysilicon region and disposed on the first dielectric layer; and
an isolation region disposed between and separates perimeters of the P-type doped polysilicon region and the N-type doped polysilicon region.
6. The solar cell of claim 5 , wherein the isolation region divides the first dielectric layer.
7. The solar cell of claim 5 , wherein the isolation region extends into the substrate.
8. The solar cell of claim 5 , further comprising a second dielectric layer formed in the isolation region.
9. The solar cell of claim 5 , further comprising a passivation region in the substrate under the isolation region.
10. A method of fabricating a solar cell, the method comprising:
forming a first dielectric layer on a substrate;
forming a P-type doped polysilicon region on the first dielectric layer;
forming an N-type doped polysilicon region on the first dielectric layer and adjacent to the P-type doped polysilicon region; and
forming an isolation region that separates perimeters of the P-type doped polysilicon region and the N-type doped polysilicon region.
11. The method of claim 10 , further comprising:
forming a second dielectric layer on a surface between the P-type doped polysilicon region and the N-type doped polysilicon region.
12. The method of claim 10 , wherein the isolation region is formed after forming the P-type doped polysilicon region and the N-type doped polysilicon region.
13. The method of claim 10 , wherein the isolation region is formed before forming the P-type doped polysilicon region and the N-type doped polysilicon region.
14. The method of claim 10 , further comprising:
forming a passivation region between the isolation region and the substrate.
15. The method of claim 10 , further comprising:
forming a passivation layer on a surface of the isolation region.
16. The method of claim 10 , further comprising:
forming a first metal contact finger that contacts the P-type doped polysilicon region, and
forming a second metal contact finger that contacts the N-type doped polysilicon region.