Solar cell emitter region fabrication with differentiated P-type and N-type architectures and incorporating dotted diffusion
Methods of fabricating solar cell emitter regions with differentiated P-type and N-type architectures and incorporating dotted diffusion, and resulting solar cells, are described. In an example, a solar cell includes a substrate having a light-receiving surface and a back surface. A first polycrystalline silicon emitter region of a first conductivity type is disposed on a first thin dielectric layer disposed on the back surface of the substrate. A second polycrystalline silicon emitter region of a second, different, conductivity type is disposed on a second thin dielectric layer disposed in a plurality of non-continuous trenches in the back surface of the substrate.
1. A solar cell, comprising:
a substrate having a light-receiving surface and a back surface;
a first thin dielectric layer disposed on the back surface of the substrate;
a first polycrystalline silicon emitter region of first conductivity type disposed on the first thin dielectric layer;
a second thin dielectric layer disposed over a plurality of non-continuous regions at the back surface of the substrate;
a plurality of isolated second polycrystalline silicon emitter regions of second conductivity type disposed on the second thin dielectric layer;
a first conductive contact structure electrically connected to the first polycrystalline silicon emitter region;
an insulator layer disposed on the first polycrystalline silicon emitter region, wherein the first conductive contact structure is disposed through the insulator layer, and wherein a portion of the second polycrystalline silicon emitter region overlaps the insulator layer but is separated from the first conductive contact structure;
a second conductive contact structure electrically connected to the plurality of isolated second polycrystalline silicon emitter regions, wherein the second conductive contact structure is disposed over the plurality of isolated second polycrystalline silicon emitter regions and a first portion of the insulator layer; and
a third thin dielectric layer between the first polycrystalline silicon emitter region and at least one of the plurality of isolated second polycrystalline silicon emitter regions, the third dielectric layer having an uppermost surface co-planar with an uppermost surface of the first polycrystalline silicon emitter region.
2. The solar cell of claim 1 , wherein the portion of the first portion of the insulator layer is disposed between two non-continuous regions at the back surface of the substrate.
3. The solar cell of claim 1 , wherein each of the plurality of non-continuous regions has a width approximately in the range of 30-60 microns, and wherein successive ones of the plurality of non-continuous regions are spaced apart at a distance approximately in the range of 50-300 microns.
4. The solar cell of claim 1 , wherein each of the plurality of non-continuous regions has a depth approximately in the range of 0.5-10 microns from the back surface and into the substrate.
5. The solar cell of claim 1 , wherein each of the non-continuous regions has an approximately circular shape.
6. The solar cell of claim 1 , wherein each of the non-continuous regions has a texturized surface.
7. The solar cell of claim 6 , wherein the second thin dielectric layer is confined to the plurality of non-continuous regions and is conformal with the texturized surface of the plurality of non-continuous regions.
8. The solar cell of claim 1 , wherein the second thin dielectric layer is physically separated from the first conductive contact structure.
9. The solar cell of claim 1 , wherein the first polycrystalline silicon emitter region is laterally adjacent to at least one of the plurality of isolated second polycrystalline silicon emitter region and is electrically isolated from the plurality of isolated second polycrystalline silicon emitter region by the third thin dielectric layer, the third thin dielectric layer non-continuous with the second thin dielectric layer.
10. The solar cell of claim 9 , wherein the third thin dielectric layer has a vertical thickness and a lateral thickness, and the vertical thickness is greater than the lateral thickness.
11. A solar cell, comprising:
a substrate having a light-receiving surface and a back surface;
a first thin dielectric layer disposed on the back surface of the substrate;
a first polycrystalline silicon emitter region of N+ conductivity type disposed on the first thin dielectric layer;
a second thin dielectric layer disposed over a plurality of non-continuous regions at the back surface of the substrate;
a plurality of isolated second polycrystalline silicon emitter region of P+ conductivity type disposed on the second thin dielectric layer;
a first conductive contact structure electrically connected to the first polycrystalline silicon emitter region;
an insulator layer disposed on the first polycrystalline silicon emitter region, wherein the first conductive contact structure is disposed through the insulator layer, and wherein a portion of the plurality of isolated second polycrystalline silicon emitter region overlaps the insulator layer but is separated from the first conductive contact structure;
a second conductive contact structure electrically connected to the plurality of isolated second polycrystalline silicon emitter regions, wherein the second conductive contact structure is disposed over the isolated second polycrystalline silicon emitter regions and a first portion of the insulator layer; and
a third thin dielectric layer between the first polycrystalline silicon emitter region and the plurality of isolated second polycrystalline silicon emitter regions, the third dielectric layer having an uppermost surface co-planar with an uppermost surface of the first polycrystalline silicon emitter region.
12. The solar cell of claim 11 , wherein the first portion of the insulator layer is disposed between two non-continuous regions at the back surface of the substrate.
13. The solar cell of claim 11 , wherein each of the plurality of non-continuous regions has a width approximately in the range of 30-60 microns, and wherein successive ones of the plurality of non-continuous regions are spaced apart at a distance approximately in the range of 50-300 microns.
14. The solar cell of claim 11 , wherein each of the plurality of non-continuous regions has a depth approximately in the range of 0.5-10 microns from the back surface and into the substrate.
15. The solar cell of claim 11 , wherein each of the non-continuous regions has an approximately circular shape.
16. The solar cell of claim 11 , wherein the second thin dielectric layer is physically separated from the first conductive contact structure.
17. The solar cell of claim 11 , wherein the first polycrystalline silicon emitter region is laterally adjacent to the plurality of isolated second polycrystalline silicon emitter region and is electrically isolated from the plurality of isolated second polycrystalline silicon emitter region by the third thin dielectric layer, the third thin dielectric layer non-continuous with the second thin dielectric layer.
18. The solar cell of claim 17 , wherein the third thin dielectric layer has a vertical thickness and a lateral thickness, and the vertical thickness is greater than the lateral thickness.