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 trench between the P-type doped region and the N-type doped region, the trench physically separating the P-type doped region from the N-type doped region and extending into the solar cell substrate;
a first metal contact finger that is electrically connected to the P-type doped region; and
a second metal contact finger that is electrically connected to the N-type doped region,
wherein the trench extends into a textured backside surface of the solar cell substrate.
2. The solar cell of claim 1 , wherein the P-type doped region and the N-type doped region comprise polysilicon.
3. The solar cell of claim 1 , wherein the first metal contact finger and the second metal contact finger are interdigitated.
4. The solar cell of claim 1 , wherein the solar cell substrate comprises an N-type silicon wafer.
5. The solar cell of claim 1 , further comprising:
a dielectric layer formed in the trench.
6. The solar cell of claim 5 , wherein the first metal contact finger is electrically connected to the P-type doped region through the dielectric layer and the second metal contact finger is electrically connected to the N-type doped region through the dielectric layer.
7. The solar cell of claim 6 , wherein the dielectric layer comprises silicon nitride.
8. The solar cell of claim 1 , further comprising a passivation region in the solar cell substrate under the trench.
9. A solar cell comprising:
a P-type doped polysilicon region and an N-type doped polysilicon region on a backside surface of a solar cell substrate;
a trench between the P-type doped polysilicon region and the N-type doped polysilicon region, the trench physically separating the P-type doped polysilicon region from the N-type doped polysilicon region;
a first metal contact finger that is electrically connected to the P-type doped polysilicon region;
a second metal contact finger that is electrically connected to the N-type doped polysilicon region; and
a dielectric layer formed in the trench,
wherein the first metal contact finger is electrically connected to the P-type doped polysilicon region through the dielectric layer and the second metal contact finger is electrically connected to the N-type doped polysilicon region through the dielectric layer.
10. The solar cell of claim 9 , wherein the trench extends into a textured backside surface of the solar cell substrate.
11. The solar cell of claim 9 , wherein the first metal contact finger is interdigitated with the second metal contact finger.
12. The solar cell of claim 9 , wherein the solar cell substrate comprises an N-type silicon wafer.
13. The solar cell of claim 9 , wherein the dielectric layer comprises silicon nitride.
14. 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 trench between the P-type doped region and the N-type doped region, the trench physically separating the P-type doped region from the N-type doped region and extending into the solar cell substrate;
a dielectric layer over the trench;
a first metal contact finger that is electrically connected to the P-type doped region through the dielectric layer; and
a second metal contact finger that is electrically connected to the N-type doped region through the dielectric layer.
15. The solar cell of claim 14 , wherein the trench extends into a textured backside surface of the solar cell substrate.
16. The solar cell of claim 14 , wherein the P-type doped region and the N-type doped region comprise polysilicon.
17. The solar cell of claim 14 , wherein the first metal contact finger and the second metal contact finger are interdigitated.