Visible Elimination, Ultraviolet and Near-Infrared Dual-Band Photodetector Based on Single-Crystal Perovskite Heterojunctions Toward Secure Optical Communication

Conventional photodetectors (PDs) sense either a broad waveband light or a selective narrow waveband light, which is plagued by indistinguishable diverse wavebands and is not competent for the dual task of information transfer and encryption in optical communication with an open light transmitting channel. Dual-band PDs with the ability to sense two discrete waveband lights have the potential to remedy the drawbacks of single-band PDs and realize secure optical communication with a straightforward optical encryption strategy. However, previous reports of dual-band PDs usually relied on multistacked photosensitive layers, which suffer from lattice mismatched interfaces contacting between diverse semiconductor layers and complex device fabrication processes. Herein, we propose a novel lattice-matched single-crystal perovskite heterojunction (SCPH) through a facile and low-cost liquid-phase epitaxy process. The fabricated dual-band PD with a structure of Au/MAPbCl₃/Bi-MAPbBr₃/Bi-MAPbI_2.5Br_0.5/MAPbI₃/Au senses to a broad range of ultraviolet (UV) light and a narrow range of near-infrared (NIR) light while blinding to visible lights in between. At last, a chaos-based double-encrypted secure optical communication system is built using the fabricated UV/NIR dual band SCPH PD as an efficient receiver terminal, where valid information is conveyed by UV and NIR light, respectively, and further superimposed by visible light for separately encrypted transmission. This work provides a facile method to fabricate visible-eliminating UV/NIR dual-band PDs and offers new insights into security optical communication without relying on complicated algorithms.