Ultrathin Al2O3 modifying the interface of ZnO nanorod arrays/Cu2O heterojunction for enhanced photoelectrochemical performance

The p-n heterojunctions with the built-in electric field are often adopted to promote the separation of photoexcited electron-hole pairs and enhance the photoelectrochemical (PEC) performance. However, the interface states often affect the band alignment of ZnO/Cu2O heterointerface and cause the decline of PEC performance. In this study, the ultrathin insulating Al2O3 layer was introduced to modify the interface between n-type ZnO nanorod arrays (NRA) and p-type Cu2O. Compared to that of ZnO NRA/Cu2O, the photocurrent density is significantly improved and onset potential shifts negatively for ZnO NRA-Al2O3/Cu2O. The Al2O3 ultrathin layer is deemed to suppress the photoexcited carriers trapped by the heavy interface defect states via improving the interface quality and block the recombination between electrons in the conduction band of ZnO NRA and holes in the valence band of Cu2O. This work broadens the interface modification method of p-n heterojunction and its results are favorable for photovoltaic devices, photodetection and PEC water splitting applications.