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 dielectric layer on the back surface of the substrate;
a p-type silicon layer on the first dielectric layer;
a second dielectric layer over a plurality of non-continuous regions at the back surface of the substrate;
a plurality of isolated n-type silicon layer features on the second dielectric layer;
a first conductive contact structure electrically connected to the p-type silicon layer;
an insulator layer on the p-type silicon layer, wherein the first conductive contact structure is through the insulator layer, and wherein a portion of the plurality of isolated n-type silicon layer features 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 n-type silicon layer features, wherein the second conductive contact structure is over the plurality of isolated n-type silicon layer features and a first portion of the insulator layer; and
a third dielectric layer between the p-type silicon layer and at least one of the plurality of isolated n-type silicon layer features, the third dielectric layer having an uppermost surface co-planar with an uppermost surface of the p-type silicon layer.
2. The solar cell of claim 1 , wherein the portion of the first portion of the insulator layer is 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 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 dielectric layer is physically separated from the first conductive contact structure.
9. The solar cell of claim 1 , wherein the p-type silicon layer is laterally adjacent to at least one of the plurality of isolated n-type silicon layer features and is electrically isolated from the plurality of isolated n-type silicon layer features by the third dielectric layer, the third dielectric layer non-continuous with the second dielectric layer.
10. The solar cell of claim 9 , wherein the third dielectric layer has a vertical thickness and a lateral thickness, and the vertical thickness is greater than the lateral thickness.