Inch-size Cs3Bi2I9 polycrystalline wafers with near-intrinsic properties for ultralow-detection-limit X-ray detection

Abstract

Lead-free perovskites are promising for next-generation bio-friendly X-ray detector materials, while it remains a challenge to fabricate high-quality wafers at a macroscopic scale using a readily scalable method. Herein, a solvent-free mechanochemical fabrication method is developed to produce inch-size lead-free perovskite Cs₃Bi₂I₉ crystalline-wafers. It is surprising to see that these polycrystalline wafers exhibit near-intrinsic properties, and more specifically, the apparent trap density is measured to be as low as 5.26 × 10⁻¹⁰ cm⁻³, essentially the same as that of their single-crystal counterparts. Therefore, the X-ray detector fabricated on the Cs₃Bi₂I₉ wafer delivers high sensitivity up to 230.46 ± 19.86 μC Gy_air⁻¹ cm⁻² and a detection limit as low as 61.25 nGy_air s⁻¹ under a 40 kV X-ray source and 40 V mm⁻¹ electric field. This research provides a readily scalable method for fabricating large perovskite wafers with near-intrinsic properties for general commercial applications.