Bi₂O₃ Layer‐Integrated, Double‐Sided Responsive, Waveband‐Discriminated Perovskite Photodetector for Encrypted Optical Communication

Abstract Encrypted optical communication is a critical technology in numerous fields, including remote sensing, environmental monitoring, and homeland defense. As a core of wireless interconnect systems, the conventional photodetectors generally receive optical signals from a single direction and fail to distinguish between various wavebands, severely undermining the potential for data transfer and protection. Herein, a Bi₂O₃ layer‐integrated waveband‐discriminated perovskite photodetector is presented. By rational design of energy band and device architecture, the novel photodetector is self‐powered, double‐sided responsive, and recognizable to the short or long‐wave UV, as well as visible optical signals. Without external bias, the device exhibits a high performance with peak responsivities of 42.1 and 72.3 mA W⁻¹ in frontal and reverse incidence, respectively. Benefiting from these advantages, the photodetector is applicable to optical communication and encryption. In reverse incidence, reversible message delivery is achieved through the conversion and decoding of illumination patterns and binary digits. For a further step, the encrypted processing is fulfilled in frontal incidence. By virtue of the eight irradiation combinations, a secret key containing ten‐bit commands will generate over a billion encryption methods. This work realizes a new mode of communication and encryption that entirely relies on optical signals, offering new insights into wireless communication.