Abstract: A hydrogen passivated photovoltaic device such as a solar cell comprises a lattice mismatched substrate such as Ge or Si, and a hydrogen passivated heteroepitaxial layer such as InP grown on the substrate. The hydrogen passivated heteroepitaxial III-V photovoltaic device is produced by exposing a sample of a heteroepitaxial III-V material grown on a lattice-mismatched substrate to reactive hydrogen species at elevated temperatures. Reactive hydrogen forms bonds with dangling bonds along dislocations defined in the sample. The electrical activity in the dislocations is passivated as a result of the hydrogenation process.