Highly Efficient and Stable Self‐Powered Ultraviolet and Deep‐Blue Photodetector Based on Cs₂AgBiBr₆/SnO₂ Heterojunction

Abstract Ultraviolet (UV) photodetectors with high responsivity and fast response are crucial for practical applications. Double perovskite Cs₂AgBiBr₆ has emerged as a promising optoelectronic material due to its excellent physics and photoelectric properties. However, no work is reported based on its film for photodetector applications. Herein, an ITO/SnO₂/Cs₂AgBiBr₆/Au hole‐transport layer free planar heterojunction device is fabricated for photodetector application. The device is self‐powered with two responsivity peaks at 350 and 435 nm, which is suitable for ultraviolet‐A (320–400 nm) and deep‐blue light detecting. A high responsivity of 0.11 A W⁻¹ at 350 nm and a quick response time of less than 3 ms are obtained, which is significantly higher than other semiconductor oxide heterojunction‐based UV detectors. More importantly, the stability is significantly better than most of the hybrid perovskite photodetectors reported so far. Its photocurrent shows no obvious degradation after more than 6 months storage in ambient conditions without any encapsulation. Consequently, the utilization of Cs₂AgBiBr₆ film is a practical approach for high performance, large‐area lead‐free perovskite photodetector applications. For the mechanism, it is found that photogenerated carriers in Cs₂AgBiBr₆ film are separated at the Cs₂AgBiBr₆/SnO₂ heterojunction interface by its built‐in field. The low toxicity and high stability of this double perovskite active layer make it very promising for practical applications.