Characteristics of detachable III-V solar cells grown on porous germanium

III-V photovoltaic cells typically use germanium (Ge) as a substrate for the epitaxial growth, however, this material contributes significantly to the overall price of the multijunction solar cells. In order to reduce the environmental and economic cost of the solar cells, we have developed a porosification technique using bipolar electrochemical etching (BBE) to create a weak layer between the Ge substrate and the epitaxial layers. This approach allows the easy separation of the grown layers and the subsequent reuse of germanium. As evidence of the potential of this method, we have compared the performances of non-detached single-junction III-V solar cells grown and fabricated (without anti-reflection coating-ARC) on porosified Ge, and on bulk Ge as a reference. All the final cells show mirror-like monocrystalline III-V layers with comparable characteristics notably concerning the Voc (VocGePorous=0.862V vs VocGeBulk=0.882V) and good efficiencies (Eff.GePorous=13.03% vs Eff.GeBulk=15.96%) in comparison with current literature values on similar substrates (Vocliterature= 0.75V and FFliterature=61%). These promising results open the path toward thin III-V solar cells and multiple Ge substrates reuse.