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

Abstract

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, CsCu2I3 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 CsCu2I3-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 CsCu2I3 thin film by modifying growth kinetics by adding I2 during synthesis. The I2-modified CsCu2I3 film improved surface morphology while preserving crystalline and optical properties. Therefore, the ultraviolet (UV) photodetector based on the I2-modified CsCu2I3 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 I2-modified CsCu2I3 thin film exhibited outstanding demonstration in optical communication systems without ambient interference, indicating its potential for various optoelectronic applications.