Stability of GaAs/Ge solar cells with standard front contacts after long-term, high-temperature exposure

A series of accelerated high-temperature soak tests has been performed on GaAs/Ge solar cells with standard front contacts in order to determine their ability to operate on space missions that require the solar array to operate at temperatures up to 250°C for long periods of time. Four soak tests were performed: one at 300°C for 1000 h, one at 300°C for 500 h, and two at temperatures up to 370°C for up to 260 h. The tests used GaAs/Ge solar cells with etch-through front contacts and GaAs/Ge solar cells with a GaAs cap front contact structure. The solar cells in the 300°C soak tests showed no significant degradation. In the other tests, the solar cells showed severe degradation in open-circuit voltage, and maximum power. Results of these tests show that these solar cells should be able to operate in temperatures up to 180°C for long periods of time (eight years). If the solar cells are required to operate above 180°C for long periods of time, new contact systems must be developed