Back-contact solar cells and methods for fabrication
AssigneeAdvent Solar, Inc.
InventorsJames M. Gee, Peter Hacke
Life of this patent
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Abstract
Methods for fabrication of emitter wrap through (EWT) back-contact solar cells and cells made by such methods. Certain methods provide for higher concentration of dopant in conductive vias compared to the average dopant concentration on front or rear surfaces, and provided increased efficiency. Certain methods provide for selective doping to holes for forming conductive vias by use of printed dopant pastes. Other methods provide for use of spin-on glass substrates including dopant.
Claims17
A method for making an emitter wrap through (EWT) solar cell, the method comprising the steps of:
- providing a semiconductor wafer with a front surface and a rear surface and a plurality of holes connecting the front surface to the rear surface, the rear surface not coated with a diffusion barrier;
- applying a first dopant diffusion source only on first selected regions of the rear surface in a pattern comprising the rear surface holes;
- applying a second dopant diffusion source only on second selected regions of the rear surface in a pattern not comprising the rear surface holes;
- and
- diffusing dopants from the first dopant diffusion source and the second dopant diffusion source into the semiconductor wafer by firing.
A method for making an EWT solar cell, the method comprising the steps of:
- providing a semiconductor wafer with a front surface and a rear surface and a plurality of holes connecting the front surface to the rear surface;
- printing material for forming a diffusion barrier only on selected regions of the rear surface in a pattern not comprising the rear surface holes without removing the material from unwanted regions;
- cleaning the wafer;
- diffusing a first dopant into the wafer;
- etching the wafer;
- and
- applying a first conductivity type metal grid to the rear surface in a pattern comprising the rear surface holes and a second conductivity type metal grid to the rear surface in a pattern separated from the first conductivity type metal grid by the diffusion barrier pattern.
A method for making an EWT solar cell, the method comprising the steps of:
- providing a semiconductor wafer with a front surface and a rear surface and a plurality of holes connecting the front surface to the rear surface;
- applying a first spin-on glass (SOG) diffusion barrier to the rear surface;
- applying a resist in a pattern not comprising the rear surface holes;
- etching the wafer to remove first SOG not covered by the patterned resist;
- stripping the resist from the wafer;
- diffusing a first dopant into the wafer;
- etching the wafer to at least remove remaining first SOG;
- and
- applying a first conductivity type metal grid to the rear surface in a pattern comprising the rear surface holes and a second conductivity type metal grid to the rear surface in a pattern comprising the resist pattern.
A method for making an EWT solar cell, the method comprising the steps of:
- providing a semiconductor wafer with a front surface and a rear surface and a plurality of holes connecting the front surface to the rear surface;
- applying a first SOG comprising a first dopant to the rear surface;
- applying a resist in a pattern not comprising the rear surface holes;
- etching the wafer to remove first SOG not covered by the patterned resist;
- stripping the resist from the wafer;
- applying a second SOG comprising a second dopant of opposite conductivity type to the first dopant to the rear surface;
- firing the wafer to diffuse the first dopant and second dopant into the wafer;
- etching the wafer to at least remove remaining first and second SOG;
- and
- applying a first conductivity type metal grid to the rear surface in a pattern comprising the rear surface holes and a second conductivity type metal grid to the rear surface in a pattern comprising the resist pattern.
Dependencies are inferred from the claim text.