Self-powered 2D PbI2 Schottky photodetector for encrypted optical communication

Abstract

Two-dimensional PbI2, a layered material with atomic thickness and high carrier mobility (μe ∼ 4600 cm2/V·s, μh > 3000 cm2/V·s), shows strong potential for post-Moore optoelectronics. In this study, high-yield PbI2 was synthesized to develop photodetectors featuring both symmetric and asymmetric Schottky contacts. As a symmetric structure, the device offers superior performance under a wavelength of 405 nm, with a low dark current of 0.232 pA, a high on/off ratio of 2.67 × 105, a detectivity of 4.02 × 1012 Jones, a linear dynamic range of 108 dB, a responsivity of 1.15 A/W, an external quantum efficiency of 354%, and a rise/decay time of 32 ms/32 ms, respectively. For an asymmetric structure with an electrode width ratio of 1: 2, the device served as a self-powered photodetector driven by the non-equilibrium Schottky barrier width. At 0 V, the asymmetric PbI2 photodetector still maintains a detectivity of 7.8 × 1010 Jones, a responsivity of 0.013 A/W, an on/off ratio of 7.8 × 103, and a rise/decay time of 290 ms/299 ms. Additionally, the self-driven electric field can be modulated under a pulse illumination accompanied by a positive or negative drain–source voltage. Therefore, this architecture provides an encrypted method by integrating the opto-electric signals into binary ASCII and Morse codes, offering a potential route for developing multifunctional photodetection and optical communication in self-powered mode.