Epitaxially aligned cuprous oxide nanowires for all-oxide, single-wire solar cells

As a p-type semiconducting oxide that can absorb visible light, cuprous oxide (Cu₂O) is an attractive material for solar energy conversion. This work introduces a high-temperature, vapor-phase synthesis that produces faceted Cu₂O nanowires that grow epitaxially along the surface of a lattice-matched, single-crystal MgO substrate. Individual wires were then fabricated into single-wire, all-oxide diodes and solar cells using low-temperature atomic layer deposition (ALD) of TiO₂ and ZnO films to form the heterojunction. The performance of devices made from pristine Cu₂O wires and chlorine-exposed Cu₂O wires was investigated under one-sun and laser illumination. These faceted wires allow the fabrication of well-controlled heterojunctions that can be used to investigate the interfacial properties of all-oxide solar cells.