Self-Powered Bipolar Photodetector Based on the MoO_<i>x</i>/CdSe/SnTe Structure Toward the Application in Secure Optical Communication

Bipolar photodetectors, characterized by their ability to reverse output current polarity in response to external illumination, have garnered significant research attention in recent years. This study presents a self-powered bipolar photodetector based on a MoO_<i>x</i>/CdSe/SnTe heterostructure, emphasizing its potential application in secure optical communication systems. The device employs a back-to-back diode configuration, leveraging on the photovoltaic effect, to facilitate the separation and transportation of photogenerated charge carriers. The MoO_<i>x</i>/CdSe and CdSe/SnTe junctions are instrumental in establishing the built-in potential, leading to the generation of a negative photocurrent under short-wavelength illumination and a positive photocurrent under long-wavelength illumination, exhibiting response times within the microsecond range. The device's swift response and precise control make it highly suitable for secure communication systems. Employing the bipolar photodetector as a light signal receiver, a secure optical communication system was demonstrated, wherein the 735 nm light, serving as a positive valid signal, was effectively masked by the 405 nm light negative interference signal. This investigation provides valuable insights into the fabrication and performance optimization of wavelength-dependent bipolar photodetectors featuring a wide-narrow bandgap back-to-back diode heterostructure.