Exploring Lead-Free (Guanidinium)BiBr Perovskite-Type Crystal toward X-Ray Detection with an Ultralow Detection Limit.

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)BiBr (GBB), which adopts a zero-dimensional (0D) inorganic perovskite-like framework. The as-grown crystals show high resistivity (3.51×10 Ω cm), low trap density (1.14×10 cm) and large carrier mobility-lifetime product (μτ=1.13×10 cm V) 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  cm, and ultralow detection limit of ~0.85 nGy s. 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.