Pinhole-free CsCu2I3 thin films by I2-modification for solar-blind ultraviolet photodetector and application to free-space optical communication

Recently, copper-based lead-free perovskites have emerged as a promising material due to their unique physical properties, abundance on earth, and lower toxicity. Among them, CsCu ₂I ₃ has received extensive attention for optoelectronic device applications due to its excellent air stability and stable self-trapped exciton-based yellow emission. However, the inherent one-dimensional crystal structure of CsCu ₂I ₃ -based perovskite makes it difficult to control the morphology during the synthesis process, which results in a high density of pinhole defects on the thin films. Here, we reported a strategy to obtain a high-quality and pinhole-free CsCu ₂I ₃ thin film by modifying growth kinetics by adding I ₂ during synthesis. The I ₂-modified CsCu ₂I ₃ film improved surface morphology while preserving crystalline and optical properties. Therefore, the ultraviolet (UV) photodetector based on the I ₂-modified CsCu ₂I ₃ film showed enhanced performances in the solar-blind waveband, including a high responsivity of 1.74 μA/W and fast response and recovery times of 0.684 and 0.686 s, respectively. Finally, the solar-blind UV photodetector based on the I ₂-modified CsCu ₂I ₃ thin film exhibited outstanding demonstration in optical communication systems without ambient interference, indicating its potential for various optoelectronic applications.