Surface reconstruction and defect healing of MAPbI3 perovskite microcrystalline thick films for sensitive and self-powered X-ray detectors

Abstract

Metal halide perovskite microcrystalline thick films with large grain size are promising for X-ray-based imaging due to their merits of large-area preparation, controlled thickness and optoelectronic properties comparable to single crystals. However, they usually possess a discontinuous surface and high trap density at grain boundaries, which makes it challenging to achieve sensitive X-ray detectors. Herein, we report the preparation of smooth methylammonium lead triiodide (MAPbI₃) microcrystalline thick films with a maximum grain size of 200 μm by MA-induced surface reconstruction. Subsequently, butylamine bromide (BABr) modification was used for defect healing at the surface and grain boundaries, resulting in enhanced carrier transport properties, reduced dark noise and suppressed nonradiative recombination. Finally, self-powered X-ray detectors with the high sensitivity of 3.55 × 10⁴ μC Gy_air⁻¹ cm⁻² and low detection limit of 4.35 nGy_air s⁻¹ were achieved, which enabled clear imaging at the ultra-low dose rate of 480 nGy_air s⁻¹ under zero bias. More importantly, all experimental conditions of the crystal growth and post-treatment are compatible with the commercial thin-film transistor (TFT) backplanes, which promotes the practical imaging application of perovskite X-ray detectors.