Monolithic III‐V Nanowire Solar Cells on Graphene via Direct van der Waals Epitaxy

Novel solar cells, based on dense arrays of InGaAs nanowires, are grown directly on graphene. Here, graphene serves as the conductive back contact and growth template for van der Waals epitaxial assembly of vertical nanowires. Although far from being the optimum material, core-shell p–n junction In0.25Ga0.75As nanowire arrays demonstrate a conversion efficiency of 2.51%, representing a new record for substrate-free, III-V nanowire-based solar cells.