This study is aiming primarily at improving cuprous oxide based photovoltaic devices by identifying and overcoming performance-limiting loss mechanisms. It is focused mainly on the fundamental optimization of the cuprous oxide thin films and the device by tuning the deposition process and the device design by a choice of the heterojunction partner material. The device performance-limiting effect of the conduction band offset is explained and experimentally addressed by the choice of aluminum gallium nitride as the window layer. The successful attempt to passivate defects in the sputtered cuprous oxide thin films by hydrogen is demonstrated. Further investigation unveiled a hydrogen induced passivation of defects, that are located at the polycrystalline material s grain boundaries. The limiting mechanism of strong interface recombination was diminished by modifying the sputter deposition by introducing a semi-transparent electrode reducing the sputter deposition induced damage. Finally, the ability to vastly increase the conductivity up to the degeneracy of cuprous oxide by extrinsic doping with nitrogen is demonstrated.
