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

Abstract

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 MAPbI₃ 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 cm² V⁻¹. These optimized MAPbI₃ 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.