The three-year “TOP” project addresses the central topic of energy supply in Germany and Europe: Approx. 20 million m² glass surfaces are installed in Europe every year for building facades. These surfaces are thus available for alternative energy generation, without requiring additional separate areas. So far, these surfaces have not been accessible or only been available to a restricted extent using conventional photovoltaic technologies. A solution seems to be possible with dimensionable solar foils that can be easily integrated on large surfaces and are available as transparent version. Fraunhofer ISE investigates the topics of reliability and understanding the degradation mechanisms within the project.