Stable Lead-Free Silver Bismuth Iodide Perovskite Quantum Dots for UV Photodetection

Perovskites are known for their high yield photoluminescence and higher photovoltaic conversion efficiencies. To make them practically useful, the toxicity and stability issues need to be addressed. Herein, we report a less toxic and stable silver bismuth iodide quantum dot system, prepared by a modified ligand assisted reprecipitation (LARP) method. Three types of phase structures such as AgBiI4, Ag2BiI5, and AgBi2I7 were obtained, and their structural and photophysical properties were investigated. By replacing lead (Pb), the toxicity would be reduced considerably and the optical properties persisted for more than six months at ambient conditions. The as-prepared silver bismuth iodide QDs were then used to construct photodetector devices, and the device performances were studied. The constructed photodetector devices have generated the photocurrent values of (AgBi2I7 ∼ 0.12 and 0.32 mA), (Ag2BiI5 ∼ 0.87 and 1.6 μA), and (AgBiI4 ∼ 0.16 and 0.61 mA) at different biasing voltages of 0.1 and 0.2 V, respectively, under visible light irradiation. The AgBi2I7 QD system generated higher photocurrent value and exhibited a better ON/OFF ratio of (Ion /Ioff = 6.5 × 104). The silver bismuth iodide QDs based photodetectors are promising for ultraviolet photodetection.