Self-Powered Bipolar Photodetectors Based on Dye-Modified Lead-Free Perovskites for Encrypted Optical Communication

Self-powered photodetectors (SPPDs) have attracted considerable attention due to their low power consumption, low cost, and small size. However, traditional SPPDs typically possess a unipolar photoresponse, which adds complexity to the processing of optical signals. Here, self-powered bipolar photodetectors (SP-BPDs) with a structure of ITO/In2O3/CsBi3I10-IR813/C are fabricated by modifying CsBi3I10 using a near-infrared (NIR) organic dye (IR813, p-toluenesulfonate). The photodetector not only broadens its absorption to the NIR range but also generates a reverse current under illumination with wavelengths exceeding 675 nm. The reversal of the photocurrent polarity is attributed to the competition between the photovoltaic effect of the heterojunction and the photothermoelectric effect of IR813 under different wavelengths of light. The current state of the SP-BPD can be effectively modulated by precisely regulating the wavelength and power density of the incident light. Therefore, five basic all-optical logic gates ("OR", "AND", "NOT", "NOR", and "NAND") and encrypted optical communication can be realized in the SP-BPD. This study presents a simple and practical strategy for designing SP-BPDs.