Backside contact solar cells with separated polysilicon doped regions
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 over the backside of the substrate;
a P-type doped region over the first dielectric layer;
an N-type doped region over the first dielectric layer, each of the N-type doped region and the P-type doped region comprising polysilicon;
an isolation region that is disposed between and separates perimeters of the P-type doped region and the N-type doped region;
a second dielectric layer over the P-type doped region and the N-type doped region;
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.
2. The solar cell of claim 1 , wherein the first metal contact finger is electrically connected to the P-type doped region through the second dielectric layer and the second metal contact finger is electrically connected to the N-type doped region through the second dielectric layer.
3. The solar cell of claim 1 , wherein the second dielectric layer comprises silicon nitride.
4. The solar cell of claim 1 , wherein the first dielectric layer comprises silicon dioxide.
5. The solar cell of claim 1 , further comprising:
a passivation region in the substrate and directly under the isolation region.
6. The solar cell of claim 1 , wherein the substrate comprises a silicon substrate.
7. The solar cell of claim 6 , wherein the substrate is doped with N-type dopants.
8. A method of fabricating a solar cell, the method comprising:
providing a substrate;
forming a first dielectric layer over a backside of the substrate;
forming a P-type doped region over the first dielectric layer;
forming an N-type doped region over the first dielectric layer, each of the N-type doped region and the P-type doped region comprising polysilicon;
forming an isolation region that is disposed between and separates perimeters of the P-type doped region and the N-type doped region;
forming a second dielectric layer over the P-type doped region and the N-type doped region;
forming a first metal contact finger that is electrically connected to the P-type doped region; and
forming a second metal contact finger that is electrically connected to the N-type doped region.
9. The method of claim 8 , wherein the first dielectric layer comprises silicon dioxide.
10. The method of claim 8 , further comprising:
forming a passivation region in the substrate and directly under the isolation region.
11. The method of claim 8 , wherein the second dielectric layer comprises silicon nitride.
12. The method of claim 8 , wherein the first metal contact finger is electrically connected to the P-type doped region through the second dielectric layer and the second metal contact finger is electrically connected to the N-type doped region through the second dielectric layer.
13. A solar cell comprising:
an N-type doped silicon substrate;
a silicon dioxide layer on a backside of the N-type doped silicon substrate;
a P-type doped region and an N-type doped on the silicon dioxide layer, the P-type and N-type doped region comprising polysilicon;
an isolation region that is disposed between and separates perimeters of the P-type doped region and the N-type doped region;
a dielectric layer on the P-type doped region and the N-type doped region;
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.
14. The solar cell of claim 13 , wherein the dielectric layer comprises silicon nitride.
15. The solar cell of claim 13 , further comprising:
a passivation region in the N-type doped silicon substrate and directly under the isolation region.
16. The solar cell of claim 13 , wherein the silicon dioxide layer has a thickness in a range of 5 Angstroms to 40 Angstroms.