Monolithic III–V nanowire PV for photoelectrochemical hydrogen generation

Nanowires have attracted a lot of interest for PV applications benefiting from their high aspect ratio geometry. Core-shell structure is ideal for nanowires PVs where the light absorption direction and minority carrier transport direction are decoupled, but the high quality core-shell p-n junction is hard to grow due to the high surface defect density. In this paper, we studied III-V nanowires for photoelectrochemical hydrogen generation where p-n core-shell structure growth is not necessary. A junction is naturally formed between the semiconductor nanowire and liquid electrolyte to extract the photogenerated carriers in nanowires. The wide tunable bandgap of III-V materials are promising for photoelectrochemical hydrogen generation application that requires an energy between 1.7-2.2 eV for reasonable efficiency. GaP nanowires were grown on Si substrates by MOCVD using gold nanoparticles as catalyst. The cathodic and anodic photocurrents were both observed for the GaP nanowires in acidic solution. The stable cathodic photocurrent was believed to be caused by hydrogen evolution while the unstable anodic photocurrent was caused by nanowire degradation.