Solar cell having an emitter region with wide bandgap semiconductor material
Solar cells having emitter regions composed of wide bandgap semiconductor material are described. In an example, a method includes forming, in a process tool having a controlled atmosphere, a thin dielectric layer on a surface of a semiconductor substrate of the solar cell. The semiconductor substrate has a bandgap. Without removing the semiconductor substrate from the controlled atmosphere of the process tool, a semiconductor layer is formed on the thin dielectric layer. The semiconductor layer has a bandgap at least approximately 0.2 electron Volts (eV) above the bandgap of the semiconductor substrate.
1. A method of fabricating a solar cell, the method comprising:
forming a first thin dielectric layer on a semiconductor substrate;
forming a first semiconductor region of a first conductivity type on the first thin dielectric layer, wherein the first semiconductor region is a first emitter region;
forming a second thin dielectric layer on the semiconductor substrate; and
forming a second semiconductor region of a second conductivity type on the second thin dielectric layer, wherein the second semiconductor region is a second emitter region, the second conductivity type opposite the first conductivity type, wherein the second thin dielectric layer is formed on a lateral surface of the first semiconductor region, and the second dielectric layer separates the first and second semiconductor regions, and wherein a portion of the second semiconductor region is partially disposed over the first semiconductor region.
2. The method of claim 1 , wherein the first semiconductor region is a first polysilicon region, and the second semiconductor region is a second polysilicon region.
3. The method of claim 1 , wherein the first thin dielectric layer is a first oxide layer, and the second thin dielectric layer is a second oxide layer.
4. The method of claim 3 , wherein the first oxide layer and the second oxide layer comprise silicon.
5. The method of claim 1 , wherein the second thin dielectric layer covers at least a portion of the first semiconductor region.
6. The method of claim 1 , further comprising:
forming a contact opening through the second thin dielectric layer and the second semiconductor region; and
forming a metal contact in the contact opening, wherein the metal contact contacts the first semiconductor region.
7. The method of claim 1 , wherein the first conductivity type is N-type, and the second conductivity type is P-type.
8. The method of claim 1 , wherein the first conductivity type is P-type, and the second conductivity type is N-type.
9. The method of claim 1 , wherein the second semiconductor region has a dopant concentration approximately in the range of 1×10 17 −1×10 21 atoms/cm 3 .
10. The method claim 1 , further comprising:
forming an oxide layer over a light receiving surface of the semiconductor substrate, the light receiving surface opposite the first thin dielectric layer and the second thin dielectric layer;
forming an amorphous silicon layer on the oxide layer; and
forming an anti-reflective coating (ARC) layer on the amorphous silicon layer, the ARC layer comprising silicon nitride.