Silicon solar cells with polysilicon contacts
A concentrator cell contact technology with improved minority carrier recombination properties was developed. Polycrystalline silicon (polysilicon) deposited by low pressure chemical vapor deposition and doped by phosphorus furnace diffusion was used in conjunction with a low resistivity base line n + /p silicon concentrator cell process. Test cells with contact coverages of 5, 10, 20 and 40% fabricated on low resistivity substrates showed saturation current densities which increased with increasing contact coverage when simple metal contacts were employed. With polysilicon contacts, the saturation currents were lower and decreased slightly with increasing contact coverage. The data suggest that the effective recombination velocity at the polysilicon/silicon interface is very low. The use of a chemically grown interfacial oxide beneath the polysilicon resulted in a small additional improvement. It is suspected that the saturation current of the best cells is dominated by the base component. Open circuit voltages of 645 to 650 mV were obtained on 0.17 ..cap omega..-cm float zone cells using contacts with a 2000 A layer of polysilicon and an interfacial oxide grown by RCA clean. Contact resistance values of 1 to 5 x 10/sup -4/..cap omega..-cm/sup 2/ were typical for polysilicon contacts doped by diffusion. Values as low as 5 x 10/sup -5/ ..cap omega..-cm/sup 2/ were obtained using rapid thermal annealing.
- Research Organization:
- SERA Solar Corp., Santa Clara, CA (USA); Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6822876
- Report Number(s):
- SAND-86-7051; ON: DE87005619
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
ANNEALING
CHEMICAL COATING
CHEMICAL VAPOR DEPOSITION
CONCENTRATOR SOLAR CELLS
CRYSTALS
DEPOSITION
DIRECT ENERGY CONVERTERS
ELECTRIC CONTACTS
ELECTRICAL EQUIPMENT
EQUIPMENT
FABRICATION
HEAT TREATMENTS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
POLYCRYSTALS
RECOMBINATION
SILICON SOLAR CELLS
SOLAR CELLS
SOLAR EQUIPMENT
SURFACE COATING