A solar cell design for the Bepi Colombo high intensity — High temperature mission

An extensive set of environmental tests revealed that the standard solar cell design incorporated in the typical photovoltaic array configuration performs less than expected in the high intensity high temperature environment (HIHT) of the Bepi Colombo mission, characterized by temperatures between 200 and 230 °C and an incident irradiance of up to 11 times the air mass zero spectrum. Fill factor driven performance degradations of up to 20 % were observed. With the help of electroluminescence imaging and a set of root cause tests with limited material combinations, the degradation mechanism was identified. A new cell design was developed based on these results and verified in a 1500 actual test hour UV test. Despite a cell temperature of 230 °C and 11 solar constant irradiance, the cell performance remained unaffected. This shows the general suitability of this design for HIHT missions.