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. 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 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 backside of the solar cell substrate;
a first dielectric layer between the solar cell substrate and the P-type and N-type doped regions; and
a trench structure separating the P-type doped region and the N-type doped region, and dividing the first dielectric layer.
2. The solar cell of claim 1 wherein the P-type and N-type doped regions comprise polysilicon.
3. The solar cell of claim 1 wherein the solar cell substrate comprises an N-type doped silicon substrate.
4. The solar cell of claim 1 wherein the first dielectric layer comprises silicon dioxide formed to a thickness between 5 to 40 Angstroms on a backside surface of the solar cell substrate.
5. The solar cell of claim 1 wherein the trench has a textured surface that absorbs solar radiation incident on the backside of the solar cell substrate.
6. The solar cell of claim 1 further comprising a second dielectric layer in the trench.
7. The solar cell of claim 6 further comprising:
a passivation layer between the second dielectric layer and the solar cell substrate.
8. The solar cell of claim 1 further comprising a diffused passivation region in the solar cell substrate under the trench, wherein the diffused passivation region is doped with an N-type dopant.
9. The solar cell of claim 1 further comprising interdigitated metal contact fingers electrically coupled to the P-type and N-type doped regions.
10. A solar cell comprising:
a P-type doped region and an N-type doped region formed on a backside of a solar cell substrate, each of the P-type and N-type doped regions being formed over a first dielectric layer; and
a trench structure separating the P-type doped region and the N-type doped region, and dividing the first dielectric layer.
11. The solar cell of claim 10 further comprising:
a second dielectric layer formed in the trench structure.
12. The solar cell of claim 11 further comprising metal contacts electrically coupled to the P-type and N-type doped regions through the second dielectric layer.
13. The solar cell of claim 10 wherein the solar cell substrate comprises an N-type silicon substrate.
14. The solar cell of claim 10 wherein the P-type doped region and the N-type doped region comprise polysilicon.
15. The solar cell of claim 10 wherein a surface of the trench structure is randomly textured.