Trench process and structure for backside contact solar cells with 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 P-type doped polysilicon region disposed over the backside of the substrate;
an N-type doped polysilicon region disposed over the backside of the substrate, the N-type doped polysilicon region being adjacent to the P-type doped polysilicon region;
a first dielectric layer between the P-type doped polysilicon region and the substrate and between the N-type doped polysilicon region and the substrate;
an isolation region disposed between and separates perimeters of the N-type doped polysilicon region and the P-type doped polysilicon region;
a passivation region disposed in the substrate directly under the isolation region;
a first metal contact finger that is electrically connected to the P-type doped polysilicon region; and
a second metal contact finger that that is electrically connected to the N-type doped polysilicon region.
2. The solar cell of claim 1 , wherein the passivation region comprises N-type dopants.
3. The solar cell of claim 1 , wherein the substrate comprises an N-type doped silicon substrate.
4. The solar cell of claim 1 , wherein the first dielectric layer comprises silicon dioxide.
5. The solar cell of claim 1 , wherein the first dielectric layer comprises silicon nitride.
6. The solar cell of claim 1 , further comprising a second dielectric layer over the P-type doped polysilicon region and the N-type doped polysilicon region.
7. The solar cell of claim 6 , wherein the first metal contact finger and the second metal contact finger are formed through the second dielectric layer.
8. The solar cell of claim 6 , wherein the second dielectric layer comprises silicon nitride.
9. The solar cell of claim 1 , wherein the first metal contact finger and the second metal contact finger are interdigitated.