Boosting the Performance of Self-Powered CsPbCl-Based UV Photodetectors by a Sequential Vapor-Deposition Strategy and Heterojunction Engineering.

All-inorganic CsPbCl perovskite in ultraviolet (UV) detection is drawing increasing interest owing to its UV-matchable optical band gap, ultrahigh UV stability, and superior inherent optoelectronic properties. Almost all of the reported CsPbCl photodetectors employ CsPbCl nano- or microstructures as sensitive components, while CsPbCl polycrystalline film-based self-powered photodetectors are rarely studied on account of the terrible precursor solubility. Herein, a novel sequential vapor-deposition technique is demonstrated to fabricate CsPbCl polycrystalline film for the first time. High-quality CsPbCl films with excellent optical, electronic, and morphological features are obtained. A self-powered photodetector based on the CsPbCl film is constructed without any charge transport layer, showing a high UV detection performance. A thin p-type PbS buffer layer is further introduced to passivate the surface defects of the CsPbCl layer and decrease the interfacial energy barrier by forming a type-II heterojunction, contributing to a faster hole extraction rate and a suppressed dark current level. The best-performing device achieves an ultrafast response time of 1.92 μs, an ultrahigh on/off ratio of 2.22 × 10, and a responsivity of 0.22 A/W upon 375 nm UV illumination at 0 V bias. This comprehensive performance is the best among all of the CsPbCl photodetectors reported to date. The as-prepared photodetectors also present an eminent UV irradiation and long-term durability in ambient air. Furthermore, a large-area and uniform 625-pixel UV image sensor is fabricated and attains a prominent imaging capability. Our work opens a new avenue for the scalable production of CsPbCl-based optoelectronics.