Initial designs of singlehyphen;crystal silicon pointhyphen;contact solar cells have shown a degradation in their efficiency after being exposed to concentrated sunlight. The main mechanism appears to be an increase in recombination centers at the Si/SiO2interface due to ultraviolet light photoinjecting electrons from the silicon conduction band into the silicon dioxide that passivates the cellrsquo;s front surface. The instability of the interface is significantly worse if the oxide is grown in the presence of trichloroethane. Texturization of the surface also leads to more instability. A reasonably good resistance to ultraviolet can be created by putting a phosphorus diffusion at the surface, and can be improved further by stripping off the deposited oxide after the diffusion and regrowing a dry thermal oxide.
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