All Transparent Metal Oxide Ultraviolet Photodetector

A high‐performing UV photodetector that uses large energy bandgap materials of p‐type NiO and n‐type ZnO without an opaque metal electrode is reported. A quality heterojunction is formed by large‐area applicable sputtering deposition method that has an extremely low saturation current density of 0.1 μA cm −2 . This abrupt p‐NiO/n‐ZnO heterojunction device is visible‐light transparent and shows the fastest photoresponse time of 24 ms among NiO‐based UV photodetectors, along with the highest responsivity (3.85 A W −1 ) and excellent detectivity (9.6 × 10 13 Jones) properties. Structural, physical, optical, and electrical properties of nanocrystalline NiO are systematically investigated. Mott–Schottky analyses are applied to develop the interface of NiO and ZnO by establishing energy diagrams. Defects existing inside the nanocrystalline NiO film enhance the UV detection performance by defect‐assisted carrier transportation. The results provide a solid scheme of manipulation of NiO defects for functional photoelectric device applications.