Accurate Solar Cell Measurements at Low Temperatures using a Cryostat

Calibrated measurements of solar cells at low temperatures are of specific interest for various space missions, for example to Mars and Jupiter. In the past 15 years, several hundred triple-junction and component solar cells have been measured at the solar cell calibration laboratory at Fraunhofer ISE (CalLab PV Cells), mainly in the frame of the European Space Agency (ESA) programs ExoMars and JUICE. To allow for measurements at temperatures as low as 123 K a specially developed cryostat setup is being used. This paper summarizes the main challenges and findings in respect to measurement procedures and calibration of solar cells under low temperature conditions, including the mounting of the solar cells, control of the correct solar cell temperature, and definition of the correct illumination spectrum and intensity.