Synergistic Effect of BMIMBF ₄ Passivator and MASCN Vapor for the Fabrication of High‐Performance MAPbI ₃ Wafer X‐Ray Detector

Abstract Polycrystalline perovskite wafers have attracted considerable attention for their potential in the reliable fabrication of X‐ray detectors. However, the high defect density and numerous grain boundaries in perovskite wafers result in severe ion migration and degraded optoelectronic properties. Herein, an innovative method utilizing the synergistic effect of defect passivation and grain growth is proposed by introducing 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF 4 ) passivator and methylammonium thiocyanate (MASCN) vapor during the fabrication of MAPbI 3 wafers. The treated wafers demonstrate an ion activation energy ( E a ) of 0.59 eV, a dark current drift ( I drift ) of 8.72 × 10 −5 nA cm −1 s −1 V −1 , and a mobility‐lifetime product ( µτ ) of 9.63 × 10 −4 cm 2 V −1 , all indicative of superior performance. These characteristics enable MAPbI 3 wafer detectors to achieve an exceptional sensitivity of 30360 µC Gy air −1 cm −2 , a low detection limit (LoD) of 19.2 nGy air s −1 , and a high spatial resolution of 6.38 lp mm −1 . Additionally, these detectors maintain outstanding operational stability after 3600 s of continuous X‐ray exposure (total dose: 381.6 mGy air ) and following 45 days of storage at 60% RH. Therefore, the synergistic approach of defect passivation and grain growth provides a promising strategy for advancing the fabrication of high‐performance polycrystalline perovskite wafer X‐ray detectors.