Effect of Temperature on Photovoltaic Solar Energy Conversion

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Abstract
Photovoltaic solar energy conversion is investigated theoretically over a temperature range of 0–400°C using semiconductor materials with band gaps varying from 0.7 to 2.4 ev. Three cases are considered. In Case I, the junction current is the ideal current. In Case II, the junction current is the ideal plus a recombination current; and in Case III, a recombination current. The best conversion performance is obtained for the ideal current; the worst, for the recombination current. The maximum conversion efficiency occurs in materials with higher band gap as the temperature is increased. GaAs is close to the optimum material for temperatures below 200°C. Experimental measurements are presented on Si, GaAs, and CdS cells. The measurements on Si and GaAs agree with theoretical expectations as far as the gross behavior is concerned. The CdS cell behaves anomalously as if it were made from a material with band gap of 1.1 ev.