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