Solar cells by Germanium layer transfer on glass

We report on pn Ge solar cells grown on Ge substrates and transferred onto glass by wafer bonding. They perform similarly to cells on the native Ge substrate, whereas their energy conversion efficiency compares well with state-of-the-art stand alone Ge photovoltaic cells. We propose Germanium layer transfer and wafer bonding for the realization of effective multi-junction solar cells and versatile multi-stack engineering.