High-Performance Photoresistors Based on Perovskite Thin Film with a High PbI₂ Doping Level.

We prepared high-performance photoresistors based on CH₃NH₃PbI₃ films with a high PbI₂ doping level. The role of PbI₂ in CH₃NH₃PbI₃ perovskite thin film was systematically investigated using scanning electron microscopy, X-ray diffraction, time-resolved photoluminescence spectroscopy, and photoconductive atomic force microscope. Laterally-structured photodetectors have been fabricated based on CH₃NH₃PbI₃ perovskite thin films deposited using precursor solution with various CH₃NH₃I:PbI₂ ratios. Remarkably, the introduction of a suitable amount of PbI₂ can significantly improve the performance and stability of perovskite-based photoresistors, optoelectronic devices with ultrahigh photo-sensitivity, high current on/off ratio, fast photo response speed, and retarded decay. Specifically, a highest responsivity of 7.8 A/W and a specific detectivity of 2.1 × 1013 Jones with a rise time of 0.86 ms and a decay time of 1.5 ms have been achieved. In addition, the local dependence of photocurrent generation in perovskite thin films was revealed by photoconductive atomic force microscopy, which provides direct evidence that the presence of PbI₂ can effectively passivate the grain boundaries of CH₃NH₃PbI₃ and assist the photocurrent transport more effectively.