Exploring Lead‐Free (Guanidinium)3Bi2Br9 Perovskite‐Type Crystal toward X‐Ray Detection with an Ultralow Detection Limit

Abstract Lead‐free bismuth halogen perovskites have emerged as a promising candidate for high‐performance X‐ray detection, owing to their unique properties of bulk resistivity, significant X‐ray absorption capabilities and diminished ion migration. Herein, using the facile low‐temperature solution method, we obtained a large‐size single crystal of (guanidinium) 3 Bi 2 Br 9 ( GBB ), which adopts a zero‐dimensional (0D) inorganic perovskite‐like framework. The as‐grown crystals show high resistivity (3.51×10 12 Ω cm), low trap density (1.14×10 10 cm −3 ) and large carrier mobility‐lifetime product ( μτ =1.13×10 −3 cm 2 V −1 ) under X‐ray irradiation. Strikingly, the X‐ray detectors fabricated on GBB single crystals exhibit notable performances including low dark current drift, high sensitivity of ~1645.7 μC Gy air −1 cm −2 , and ultralow detection limit of ~0.85 nGy air s −1 . This detection limit is among the lowest level for the reported 0D perovskite X‐ray detectors. This study illuminates the prospective research into novel lead‐free hybrid perovskites for the advancement of high‐performance detectors of irradiation.