Degradation analysis of InGaP/GaAs/Ge triple-junction solar cells in high-temperature and high-light-intensity environments by luminescence techniques

This paper demonstrates results of durability tests and photoluminescence spectroscopy of InGaP/GaAs/Ge triple-junction solar cells for Japan's inner planetary missions. Degradation of the solar cells under high-light intensity and high temperature environments was evaluated by a forward current injection test and a continuous operation test. These tests revealed that the forward current application possibly causes more degradation than the actual solar cell operation. We diagnosed the solar cells in more detail by photoluminescence spectroscopy. The intensity of the band-edge emission decreased excessively after the forward current injection test, but did not decrease after the continuous operation test. This result agreed well with the change in the electrical property. No new deep level emissions were detected after the tests.