CsAc-Mediated Dynamic Reconstruction of Chloride Perovskite Films for High-Performance Self-Powered Near-UV Photodetectors

Methylammonium lead chloride perovskite (MAPbCl₃), with its wide bandgap of ∼3 eV, exhibits unique advantages for near-UV to UV optoelectronic devices. However, the fast crystallization kinetics and significant solubility differences of MAPbCl₃ precursors in solvents cause discontinuous films with high surface defect densities, severely limiting device performance. This study introduces a solution mediated dissolution recrystallization strategy to address the aforementioned issues, namely, employing a CsAc/methanol solution to dynamically reconstruct preformed MAPbCl₃ films. During this process, Cs⁺ doping regulates the crystallization kinetics and suppresses the formation of pinholes caused by nonequilibrium crystallization, and Ac^- anions passivate grain boundaries and surface defects through coordination. This synergistic approach yields dense, high-quality Cs₀.₃₅MA₀.₆₅PbCl₃ polycrystalline films. The resulting self-powered photodetector demonstrates exceptional performance under 405 nm laser excitation: an on/off ratio of 1.38 × 10⁶, responsivity of 0.278 A/W, detectivity of 3.49 × 10¹² Jones, and a response time of 16 μs. These metrics significantly surpass those of previously reported solution-processed counterparts. This work offers a new pathway for fabricating high-quality chloride-based perovskite films and facilitates their application in optoelectronic devices such as transparent solar cells and radiation detectors.