Solar cells having junctions retracted from cleaved edges
Methods of fabricating solar cells having junctions retracted from cleaved edges, and the resulting solar cells, are described. In an example, a solar cell includes a substrate having a light-receiving surface, a back surface, and sidewalls. An emitter region is in the substrate at the light-receiving surface of the substrate. The emitter region has sidewalls laterally retracted from the sidewalls of the substrate. A passivation layer is on the sidewalls of the emitter region.
1. A solar cell, comprising:
a substrate having a light-receiving surface, a back surface, and outer sidewalls;
an emitter region on the substrate at the light-receiving surface of the substrate, the emitter region having outer sidewalls laterally spaced inward from the outer sidewalls of the substrate at locations where the outer sidewalls of the substrate meet the light-receiving surface of the substrate; and
a passivation layer on the outer sidewalls of the emitter region, wherein the passivation layer is in a recess between a corresponding outer sidewall of the emitter region and a corresponding outer sidewall of the substrate.
2. The solar cell of claim 1 , wherein a corresponding edge of the passivation layer is vertically aligned with the corresponding outer sidewall of the substrate.
3. The solar cell of claim 1 , further comprising:
a passivation layer on the light-receiving surface of the substrate, wherein the passivation layer on the outer sidewalls of the emitter region is continuous with the passivation layer on the light-receiving surface of the substrate.
4. The solar cell of claim 3 , wherein the passivation layer on the light-receiving surface of the substrate and the passivation layer on the outer sidewalls of the emitter region comprise silicon oxide (SiOx) and silicon nitride (SiNx).
5. The solar cell of claim 1 , wherein the emitter region comprises a concentration of dopants of a conductivity type, the solar cell further comprising:
regions within a perimeter of the emitter region, the regions having a higher concentration of dopants of the conductivity type than the concentration of dopants of the conductivity type of the emitter region.
6. The solar cell of claim 5 , wherein the conductivity type is n-type, and the dopants are selected from the group consisting of phosphorous dopants and arsenic dopants.
7. The solar cell of claim 5 , further comprising:
conductive contacts electrically connected to the regions within the perimeter of the emitter region.
8. The solar cell of claim 7 , wherein the conductive contacts are screen printed and fired through a passivation layer on the light-receiving surface of the substrate.
9. The solar cell of claim 7 , wherein the conductive contacts comprise silver.
10. The solar cell of claim 1 , wherein the substrate is a p-type monocrystalline silicon substrate.
11. The solar cell of claim 1 , wherein the emitter region comprises n-type dopants, the solar cell further comprising:
regions of p-type dopants at the back surface of the substrate.
12. The solar cell of claim 11 , further comprising:
a conductive contact electrically connected to the regions of p-type dopants at the back surface of the substrate.
13. The solar cell of claim 12 , wherein the conductive contact is disposed through openings in a bottom passivation and capping layer on the back surface of the substrate.