Atomistic Surface Passivation of CH₃NH₃PbI₃ Perovskite Single Crystals for Highly Sensitive Coplanar-Structure X-Ray...

Organic-inorganic halide perovskites (OIHPs) are recognized as the promising next-generation X-ray detection materials. However, the device performance is largely limited by the ion migration issue of OIHPs. Here, we reported a simple atomistic surface passivation strategy with methylammonium iodide (MAI) to remarkably increase the ion migration activation energy of CH₃NH₃PbI₃ single crystals. The amount of MAI deposited on the crystal surface is finely regulated by a self-assemble process to effectively suppress the metallic lead defects, while not introducing extra mobile ions, which results in significantly improved dark current stability of the coplanar-structure devices under a large electric field of 100 V mm^-1. The X-ray detectors hence exhibit a record-high sensitivity above 700,000 μC Gy_air ^-1 cm^-2 under continuum X-ray irradiation with energy up to 50 keV, which enables an ultralow X-ray detection limit down to 1.5 nGy_air s^-1. Our findings will allow for the dramatically reduced X-ray exposure of human bodies in medical imaging applications.