Indoor photovoltaics use the artificial light indoors to generate electricity. This technology is particularly useful for devices that cannot be constantly charged, such as many components in IoT systems. “Various photovoltaic technologies can be used for this purpose,” explains Dr. Henning Helmers, Head of Department at Fraunhofer ISE. “Solar cells based on III-V semiconductors currently have the highest material costs, but are also the most efficient, especially under artificial (LED) light.”

In their study, the researchers optimized gallium indium phosphide (GaInP) solar cells, as their band gap is almost ideal for converting visible light into electricity. "We investigated how well the solar cells with different architectures work under low light conditions", summarizes Malte Klitzke, lead author of the study and scientist at Fraunhofer ISE. "It was shown, that the n-doped GaInP cell, performs significant better than the p-doped cell N-doped GaInP cells generate more charge carriers and produce more electricity, even under very weak light. This enabled us to achieve very high efficiencies with them in our experiments when converting weak indoor light into usable power."

The research result combines findings from several research projects: “50Percent”, funded by the Federal Ministry of Economics and Climate Protection (BMWK), "H2Demo", funded by the Federal Ministry of Education and Research (BMBF) and “SMART”, supported by AZUR SPACE Solar Power and the German Space Agency (DLR).