The performance of advanced solar cells for interplanetary missions

Recent advances in space solar cell technology have produced substantial increases in Air Mass Zero (AM0) efficiency. Since these cells have been developed primarily for Earth orbiting missions, little is known of their behavior at distances far from the Sun. In order to better define the photovoltaic performance of arrays for deep space missions, JPL has completed initial measurements on a number of advanced cells under a variety of LILT (low intensity, low temperature) conditions. These include high efficiency silicon, and multi-junction III-V devices. The test results show that multi-junction cells suffer from LILT degradation and that at 5AU (approximately the solar distance of Jupiter), efficiency advantages over high efficiency silicon are minimal. Silicon cells optimized for 3-6 AU operation not only equal the efficiency available from 2 and 3 junction cells, but also tend to be more uniform