MASCN Vapor-Assisted Fabrication of Compact and Large-Grain MAPbI3 Polycrystalline Wafer for X-Ray Detection and Imaging

Lead halide perovskite wafers, which have adjustable size and thickness, are promising for the tailored fabrication of X-ray detectors. However, common voids and grain boundaries, acting as carrier traps in polycrystalline wafers, present a major challenge to achieving optimal optoelectronic properties. Herein, an innovative approach is adopted by introducing methylammonium thiocyanate (MASCN) vapor into the hot-pressing environment of MAPbI 3 wafers, promoting perovskite grain merging and growth. The resulting compact wafers with larger crystal grains display an extended average carrier lifetime ( τ avg ) of 31.61 ns, a high ion activation energy ( E a ) of 0.47 eV, a reduced dark current drift ( I drift ) of 4.11 × 10 −4 nA cm −1 s −1 V −1 , and an improved mobility-lifetime product ( µτ ) of 8.26 × 10 −4 cm 2 V −1 . These optimized MAPbI 3 wafer-based detectors achieve a high sensitivity of 16611 µC Gy air −1 cm −2 , a low detection limit (LoD) of 47.5 nGy air s −1 , and robust operational stability in X-ray detection. Furthermore, these detectors exhibit excellent X-ray imaging capability, achieving a high spatial resolution of 5.64 lp mm −1 . Therefore, the deployment of volatile thiocyanate salt during hot pressing provides a novel strategy for engineering high-quality polycrystalline perovskite wafers, propelling forward the field of X-ray detection.