Solar cell having an emitter region with wide bandgap semiconductor material
View Patent ↗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 solar cell, comprising:
a silicon substrate;
a first emitter region disposed on a surface of the silicon substrate and comprising an aluminum nitride (AlN) layer doped to a first conductivity type and disposed on a thin aluminum oxide (Al 2 O 3 ) layer;
a second emitter region disposed on the surface of the silicon substrate and comprising a semiconductor material doped to a second, opposite, conductivity type and disposed on a thin dielectric layer; and
first and second contacts disposed on, and conductively coupled to, the first and second emitter regions, respectively.
2. The solar cell of claim 1 , wherein the AlN layer is substantially transparent in the visible spectrum.
3. The solar cell of claim 1 , wherein the semiconductor material has a bandgap at least approximately 0.2 electron Volts (eV) above the bandgap of the silicon substrate.
4. The solar cell of claim 1 , wherein the semiconductor material comprises polycrystalline silicon.
5. The solar cell of claim 1 , wherein the first emitter region is disposed on a textured portion of the surface of the silicon substrate, and the second emitter region is disposed on a flat portion of the surface of the silicon substrate.
6. The solar cell of claim 1 , wherein the first and second emitter regions are disposed on a back-contact surface of the semiconductor substrate, the silicon substrate further comprising:
a light-receiving surface opposite the back-contact surface, the light receiving surface comprising a thin aluminum oxide (Al 2 O 3 ) layer disposed thereon, and an aluminum nitride (AlN) layer disposed on the thin aluminum oxide (Al 2 O 3 ) layer.
7. The solar cell of claim 1 , wherein a portion of the aluminum nitride (AlN) layer is disposed over at least a portion of the second emitter region.
8. A method of fabricating a solar cell, the method comprising:
forming a first emitter region on a surface of a semiconductor substrate of the solar cell, the first emitter region comprising a semiconductor material doped to a first conductivity type and formed on a first thin dielectric layer; and
forming a second emitter region on the surface of the semiconductor substrate, the forming comprising:
forming, in a process tool having a controlled atmosphere, a second thin dielectric layer on the surface of the semiconductor substrate, the semiconductor substrate having a bandgap; and, without removing the semiconductor substrate from the controlled atmosphere of the process tool,
forming a wide bandgap semiconductor layer on the second thin dielectric layer, the wide bandgap semiconductor layer having a bandgap at least approximately 0.2 electron Volts (eV) above the bandgap of the semiconductor substrate; and
doping the wide bandgap semiconductor layer with charge carrier dopant impurity atoms of a second, opposite, conductivity type, wherein the doping is performed in situ during the forming of the wide bandgap semiconductor layer.
9. The method of claim 8 , wherein the semiconductor substrate comprises single-crystalline N-type silicon, and wherein forming the wide bandgap semiconductor layer comprises forming a semiconductor layer having a bandgap greater than approximately 1.5 eV and comprising a material selected from the group consisting of amorphous silicon (a-Si), silicon carbide, aluminum nitride (AlN), aluminum gallium nitride (Al x Ga 1-x N, where 0<x<1), and boron nitride (BN).
10. The method of claim 8 , wherein forming the semiconductor material comprises forming a material having a bandgap at least approximately 0.2 electron Volts (eV) above the bandgap of the single-crystalline N-type silicon substrate.
11. The method of claim 8 , forming the semiconductor material comprises forming a layer of polycrystalline silicon.
12. The method of claim 8 , wherein forming the second thin dielectric layer on the surface of the semiconductor substrate comprises consuming a portion of the semiconductor substrate by thermal oxidation.
13. The method of claim 8 , wherein forming the second thin dielectric layer on the surface of the semiconductor substrate comprises depositing a dielectric material layer on the surface of the semiconductor substrate.
14. The method of claim 8 , wherein forming the wide bandgap semiconductor layer comprises forming a portion over at least a portion of the first emitter region.
15. A method of fabricating a solar cell, the method comprising:
forming a first emitter region on a surface of a semiconductor substrate of the solar cell, the first emitter region comprising a semiconductor material doped to a first conductivity type and formed on a first thin dielectric layer; and
forming a second emitter region on the surface of the semiconductor substrate, the forming comprising:
forming, in a process tool having a controlled atmosphere, a second thin dielectric layer on the surface of the semiconductor substrate, the semiconductor substrate having a bandgap; and, without removing the semiconductor substrate from the controlled atmosphere of the process tool,
forming a wide bandgap semiconductor layer on the second thin dielectric layer, the wide bandgap semiconductor layer having a bandgap at least approximately 0.2 electron Volts (eV) above the bandgap of the semiconductor substrate; and
doping the wide bandgap semiconductor layer with charge carrier dopant impurity atoms of a second, opposite, conductivity type, wherein the doping is performed subsequent to the forming of the wide bandgap semiconductor layer.
16. The method of claim 15 , wherein the semiconductor substrate comprises single-crystalline N-type silicon, and wherein forming the wide bandgap semiconductor layer comprises forming a semiconductor layer having a bandgap greater than approximately 1.5 eV and comprising a material selected from the group consisting of amorphous silicon (a-Si), silicon carbide, aluminum nitride (AlN), aluminum gallium nitride (Al x Ga 1-x N, where 0<x<1), and boron nitride (BN).
17. The method of claim 15 , wherein forming the semiconductor material comprises forming a material having a bandgap at least approximately 0.2 electron Volts (eV) above the bandgap of the single-crystalline N-type silicon substrate.
18. The method of claim 15 , forming the semiconductor material comprises forming a layer of polycrystalline silicon.
19. The method of claim 15 , wherein forming the second thin dielectric layer on the surface of the semiconductor substrate comprises consuming a portion of the semiconductor substrate by thermal oxidation.
20. The method of claim 15 , wherein forming the wide bandgap semiconductor layer comprises forming a portion over at least a portion of the first emitter region.