Thermodynamically induced crystal restructuring to make CsPbCl₃ single crystal films for weak light detection

CsPbCl₃ perovskite is considered a highly promising material for ultraviolet (UV) photodetectors due to its exceptional thermal stability and excellent short-wavelength light response. However, its high lattice energy and low polarizability result in extremely low solubility in conventional solvents, making the synthesis of CsPbCl₃ single crystals a significant challenge. In this study, we propose a novel thermodynamically induced crystal restructuring (TICR) process that can transform microcrystalline films (MCFs) into single crystal films (SCFs) within a short period. This method, for the first time, has successfully achieved the synthesis of centimeter-sized CsPbCl₃ SCFs and the mechanism has been explored in depth using in-situ techniques. Furthermore, we report the first instance of a CsPbCl₃ SCF UV photodiode, which exhibits a record-breaking on/off ratio of 3.32 × 10⁷ and a detectivity of up to 1.15 × 10¹⁴ Jones under 0 V bias. It demonstrates excellent response even under weak light conditions of 10 nW·cm⁻² and maintains outstanding stability with almost no performance degradation after 15 months. This study provides a novel approach for the synthesis of perovskite single crystals and holds significant potential for advancing the development of high-performance optoelectronic devices.