Water-soluble Ag2S QD modified CsPbI2Br heterojunction photodetector with ultra-low dark current and ultra-fast response speed

Mixed halide inorganic perovskite CsPbI3-xBrx has attracted attention in the field of optoelectronics. As a desirable photoactive material, the application of CsPbI2Br in the field of photodetector (PD) remains to be explored. The synergistic passivation strategy based on Ag2S quantum dot (QD) aqueous solution improves the morphology of the CsPbI2Br perovskite film. At the same time, Ag2S/CsPbI2Br bulk heterojunction optimizes the energy level arrangement between perovskite and Au electrode, improves the carrier transmission and collection capacity, and thus improves the performance of PD. Ag2S/CsPbI2Br bulk heterojunction PD has an ultra-low dark current of 7.74 pA, an ultra-fast response speed of 2.95/3.07 μs, and a high switching ratio of 7.67 × 105. This work provides a method for the preparation of high-quality mixed halide perovskite materials and a strategy for the development of high-performance perovskite PDs based on bulk heterojunction.