Self‐Powered MXene/GaN van der Waals Heterojunction Ultraviolet Photodiodes with Superhigh Efficiency and Stable Current Outputs

A self‐powered, high‐performance Ti 3 C 2 T x MXene/GaN van der Waals heterojunction (vdWH)‐based ultraviolet (UV) photodiode is reported. Such integration creates a Schottky junction depth that is larger than the UV absorption depth to sufficiently separate the photoinduced electron/hole pairs, boosting the peak internal quantum efficiency over the unity and the external quantum efficiency over 99% under weak UV light without bias. The proposed Ti 3 C 2 T x /GaN vdWH UV photodiode demonstrates pronounced photoelectric performances working in self‐powered mode, including a large responsivity (284 mA W −1 ), a high specific detectivity (7.06 × 10 13 Jones), and fast response speed (rise/decay time of 7.55 µs/1.67 ms). Furthermore, the remarkable photovoltaic behavior leads to an impressive power conversion efficiency of 7.33% under 355 nm UV light illumination. Additionally, this work presents an easy‐processing spray‐deposition route for the fabrication of large‐area UV photodiode arrays that exhibit highly uniform cell‐to‐cell performance. The MXene/GaN photodiode arrays with high‐efficiency and self‐powered ability show high potential for many applications, such as energy‐saving communication, imaging, and sensing networks.