Highly Sensitive X‐Ray Detector Made of Large Lead‐Free Perovskite Cs3Bi2I9 Single Crystals with Anisotropic Response

Abstract Direct X‐ray detectors require high‐quality and large‐size materials to reduce radiation hazards. As an all‐inorganic lead‐free perovskite, Cs 3 Bi 2 I 9 has good prospects for research and applications in the field of X‐ray detection. A refined evaporation method is proposed for the growth of Cs 3 Bi 2 I 9 single crystals (SCs), and a high‐quality SC with a size of 18 × 20.5 × 3 mm 3 is obtained. Due to the anisotropy of Cs 3 Bi 2 I 9 SCs, two different device structures, vertical and coplanar, are designed. The coplanar device has a higher sensitivity of 59 464.4 µC Gy air −1 cm −2 , while the vertical device performs better on the limit of detection (LoD), with an LodD as low as 1.27 nGy air s −1 .