Mixed‐Cation MA_<i>x</i>Cs_1−<i>x</i>PbBr₃ Perovskite Single Crystals with Composition Management for High‐Sensitivity X‐Ray Detection

Abstract

High‐sensitivity X‐ray detection is widely applied in medical imaging, environmental monitoring, and scientific research. Perovskite single crystals have been demonstrated to be a kind of potential material in X‐ray detection because of their large X‐ray attenuation coefficient, low crystal growth cost, and excellent photoelectric properties. In this study, a successful method to grow mixed‐cation MA x Cs 1− x PbBr 3 single crystals with the assistance of an antisolvent and a highly sensitive X‐ray detector with symmetrical sandwich structure is reported. The analysis of absorption spectra of these crystals indicates the bandgap is tunable from 2.25 to 2.16 eV with increasing methylammonium (MA) compositions. Through the space‐charge‐limited current measurement, these mixed‐cation crystals achieve significantly improved electronic properties involving trap density, mobility, and conductivity, compared with the MAPbBr 3 and CsPbBr 3 crystals. The optimized electronic properties enable a high‐sensitivity X‐ray detector and a systematical analysis of crystal composition and detection performance. The X‐ray detectors based on mixed‐cation crystals exhibit a higher sensitivity and lower detection limit. The MA 0.6 Cs 0.4 PbBr 3 ‐based detector achieves a sensitivity of up to 2017 μC Gy air −1 cm −2 and a detection limit of 1.2 μGy air s −1 under an applied voltage of 1 V, which is much better than our prepared MAPbBr 3 ‐ and CsPbBr 3 ‐based detectors.