Self-Powered UV Dual-Band Photodetector Based on Cs₃BiCl₆/GaN Heterojunction for Logical Operation and Encrypted...

Dual-band photodetectors have huge potential for application in secure optical communication, multicolor imaging, and logical operation. However, the majority of currently documented dual-band photodetectors suffer from high energy consumption and poor photoresponse performance; especially, the dual-band photodetectors targeted at the UV region have yet not been reported. In this study, for the first time, a self-powered UV dual-band photodetector based on Cs₃BiCl₆/GaN heterojunction is designed and fabricated through a dual-source co-evaporation technique. Experiments and theoretical simulations confirm that the unique dual-band absorption characteristics of Cs₃BiCl₆ and the strong surface-charge recombination near the Cs₃BiCl₆ surface are the primary factors enabling the achievement of UV dual-band photodetection. Importantly, owing to the well-matched energy band alignment of Cs₃BiCl₆ and GaN, the photodetectors exhibit ultra-high I_on/I_off ratio (1 × 10⁷), large specific detectivity (1.23 × 10¹² Jones), and ultrafast response speed (τ_r/τ_f = 28 µs/190 µs). Finally, utilizing the UV dual-band characteristics of the fabricated device, the logical operation and encrypted photo-communication applications are successfully demonstrated. The obtained results suggest that the lead-free perovskite Cs₃BiCl₆ is potentially an attractive candidate for the manufacture of high-performance UV dual-band photodetectors that can be employed in advanced encryption technology.