Design considerations for high-intensity solar cells

Abstract

The factors affecting the efficiency of a solar cell change when the solar cell is subjected to concentrated sunlight. In this paper, we examine the effects of high solar intensities on Si and GaAs solar cells. It is shown that the current-collection efficiency in Si solar cells increases at intermediate levels but may be reduced at very high solar intensities due to plasma recombination. Methods to avoid the degradation of efficiency are suggested. The open-circuit voltage increases with concentration, and the rate of increase is faster in Si than in GaAs. The fill factor also increases with concentration, again at a faster rate in Si than in GaAs. Consequently, the efficiency in a Si solar cell under concentration may increase faster than in a GaAs solar cell. The effect of increased temperature is also examined. It is shown that the increase in temperature degrades the efficiency of Si faster than in GaAs. Thermal analysis shows that it is possible to limit the temperature rise to a low value (25 °C) even under 1000 sun concentration by using simple designs of heat sinks. Consequently, there is no significant advantage of GaAs solar cells over Si solar cells for high-intensity operation, except when high temperatures are desired for a complementary thermal system.