Dual Role of Sb-Incorporated Buffer Layers for High Efficiency Cuprous Oxide Photocathodic Performance: Remarkably Enhanced Crystallinity and Effective Hole Transport

The high performance of electrodeposited cuprous oxide (Cu₂O)-based photoelectrochemical (PEC) cells has been limited due to low electrical conductivity hindering effective carrier transport to electrodes and chemically unstable properties in aqueous environments, despite their several advantages such as suitable band gap, band position, and cost-effective and environmentally friend elements. To improve the fundamental photoelectrochemical properties of photocathode Cu₂O layers, particularly their photocurrent and stability, we present a simple approach using a double-layer photocathode, where the double-layer structure consists of Sb-incorporated Cu₂O (Cu₂O:Sb) and undoped Cu₂O. The Cu₂O:Sb double layer enhanced the preferred crystal growth along the [111] direction, as well as the crystallinity of the Cu₂O. This microstructural change resulted in high electrical conductivity owing to high hole mobility and the suppression of instability related to surface facets. Consequently, the introduction of Cu₂O:Sb led to the simultaneous roles of seed crystal and effective hole transport, and our double-layer photoelectrodes have shown good photocurrent without any metal photocatalysts and relatively better photostability without the help of protection layers.