Despite consistently falling launch costs, the mass budget for power systems remains a strong limiting factor in spacecraft design. Here, the high power per mass ratio of organic solar cells offers a great potential for future applications, as it can lead to significant weight and thus cost reductions. Yet, validating and testing materials for organic solar cells within the scope of space missions cannot keep up with the rapid development of new compounds in this field. In previous experiments, not only were organic solar cells shown to be able to withstand well the UV radiation present in an unfiltered AM0 solar radiation in a laboratory environment [1], but organic cells have also been successfully launched on a suborbital rocket into space [2].

We report the development of a small, lab-scale thermal vacuum chamber, allowing the investigation of organic and various other novel solar cell technologies in a realistic space environment simulation adhering to typical standards for space industry such as ECSS. In addition, a way to relate previous space experiments to laboratory experiments is given with the newly established set-up. The test environment is contained within a high vacuum pressure vessel, with the cold background of space being simulated by a thermal vessel flushed with liquid nitrogen with a highly absorbing surface coating. To imitate thermal radiation from Earth for low Earth orbit simulations, an electrically heated thermal plate can also be additionally inserted. Heating from solar radiation can either be simulated by means of an AM0 sun simulator, with an irradiance of 136.7 mW/cm², or by heating the entire thermal vessel to the desired temperature. This allows a performance analysis of the solar cells under the most realistic space-like conditions. To recreate the high thermal stresses most satellites are subjected to, the thermal vacuum chamber allows for continuous cycling between simulating the direct illumination from the Sun and the cold environment in Earth's shadow. By controlling atmospheric composition, pressure, and temperature inside the thermal vacuum chamber, alien environments such as the Martian surface can also be simulated.

This approach allows us to quickly identify and further optimize promising materials for organic solar cells for space applications, that then can be further investigated in the framework of spaceflight missions.