Lead-Free Cs₃Sb₂I₉ Single Crystal with Enhanced Photodetecting Ability

Lead (Pb)-free metal halide perovskites (MHPs) have become a research hotspot to replace Pb-based optoelectronic devices, due to the toxicity of Pb, which impedes the further development and commercialization of MHPs. In this work, we report on the synthesis and properties of lead-free Cs 3 M 2 I 9 (M = Bi, Sb) perovskite single crystals (SCs) by an antisolvent recrystallization method. The obtained Cs 3 Sb 2 I 9 (CSI) SCs show superior photodetecting abilities than Cs 3 Bi 2 I 9 (CBI), demonstrating a photocurrent of 3.2 × 10 –9 A, which is 120 times higher than that of Cs 3 Bi 2 I 9 (2.5 × 10 –11 A) at a low voltage of 1 V. In addition, the CSI-based photodetector (PD) shows a responsivity of 12.2 mA/W, which is almost 94 times higher than that of CBI (0.13 mA/W). Moreover, the CSI-based PD shows a fast response speed of 46 (rise time) and 10 ms (decay time). First-principles calculations reveal that the enhanced photodetection performance of CSI over CBI originates from strong Sb-s/I-p orbital hybridization at the valence band maximum, which promotes hole delocalization and facilitates higher carrier mobility. Furthermore, the PD based on CSI SC can detect images at a distance (5 m) with clearly distinguished patterns. The results of our research can not only contribute to the discovery of better lead-free perovskite materials but also promote their application in our daily demands.