Investigating the electrical and optical characteristics of lead-free all-inorganic Cs3Sb2Br9 single crystals

In recent years, halide perovskites have emerged as promising materials for electronic devices. While lead-based perovskites have been extensively studied, exploration of lead-free variants has been limited. Here, we highlight the innovation of observing negative photoconductivity (NPC) induced by light, followed by self-recovery, in lead-free Cs3Sb2Br9 perovskite single crystals. Our study reveals the self-trapping of holes at the V-k center, corresponding to the Br-2(-) dimer, within the midband states of this vacancy-ordered perovskite. This leads to the entrapment of photogenerated charge carriers by charged defect states denoted as V-k, creating an internal electrical field that counteracts the externally imposed field, resulting in NPC. We demonstrate the innovation through the construction of a prototype photodetector with notable sensitivity, featuring high responsivity (6.77 mA/W), detectivity (2.83 x 10(12) Jones), and a dark-to-light current ratio of approximately 10. This recognition of retroactive photocurrent in optically active perovskite materials holds promise for advancing highly sensitive detectors.