Spectral engineering of ultrathin germanium solar cells for combined photovoltaic and photosynthesis

In densely populated areas, ground mounted photovoltaic power plants compete with agriculture for cultivable land. Agrivoltaic systems allow the combination of these two forms of land use by deliberately designed light sharing. In this contribution, we present a spectrally selective solar cell, for use in agrivoltaic systems, greenhouses, and photo-bioreactors. Our concept benefits from a solar cell with a transmission spectrum which can be easily tuned for the specific absorption requirements of algae and plants. This is achieved by a Fabry-Perot-type multilayer resonator as a back reflector, which determines the transmission and absorption spectrum of the solar cell. We demonstrate the extent of how this transmission spectrum can be engineered by varying the layer thicknesses of the reflector and we show how the reflecting metal layers in the back reflector influence the transmission and photocurrent generation of the spectrally selective solar cell. Finally, we analyze the optical loss mechanisms of the solar cell layer stack to address further optimization potential. Our work offers a spectrally selective solar cell which can be easily adjusted for the requirements of combining photovoltaic and photosynthesis