Bipolar-ResponsePerovskite Photodetector Controlledby the Ferroelectric Depolarization Field for Secure Optical Communication

Traditional optical communication systems are constrained by fixed photoresponse values and light intensity, significantly impairing the potential for data transmission and protection. Here, a single-band bipolar-response perovskite self-powered photodetector is demonstrated on the (PEA)₂PbI₄/BaTiO₃/Si heterojunction. By employing BaTiO₃ as the intrinsic layer, the device demonstrates a low dark current on the order of 10^–12 A at a 5 V bias. When BaTiO₃ functions as the ferroelectric layer, the variation in the depolarization field not only achieves multilevel modulation of the photoresponse magnitude but also reverses the sign. Leveraging the bipolar characteristics of the device, a secure optical communication system has been developed, featuring a dual-channel optical signal reception specifically designed for information transmission. One channel is designated for receiving encrypted information, while the other channel receives key information. The device only needs to identify the positive and negative values of the input signals with arbitrary light intensity without distinguishing the strength of the signal values. The accurate retrieval of transmitted information is contingent upon the application of an encryption algorithm, thereby enhancing the security of the communication system. This work provides novel perspectives for the realization of more secure and reliable encrypted optical communication systems.