High-Performance Near-Infrared Perovskite Single-Crystal Photodetectors Enabled by Multifunctional Additive Engineering for Image Encryption

Iodide-based metal halide perovskite single crystals are promising candidates for near-infrared photodetection because of their favorable bandgaps and outstanding optoelectronic characteristics. However, iodide oxidation during crystallization deteriorates precursor stability, crystal quality, and device performance. Herein, potassium formate is introduced as a multifunctional additive that simultaneously suppresses iodide oxidation, passivates vacancy-related defects, and inhibits ion migration. As a result, the optimized crystal achieves an ultralow trap-state density of 5.23 × 108 cm-3, approaching the best values reported for perovskite single crystals. The corresponding photodetector shows a narrowband response centered at 800 nm, a specific detectivity of 1.14 × 1011 Jones, and a wide linear dynamic range of 146 dB. It also enables reliable image encryption with strong resistance to visible-light interference, a capability that is difficult to realize with conventional broadband photodetectors. These findings provide a practical route toward stable near-infrared photodetection for secure optical information processing.