Voltage-Switchable MoO3/ZnO Heterojunction Enabling Dual-Mode Optical Encryption and Brain-Inspired Vision.

The functional integration of photodetectors (PDs) and neuromorphic visual sensors (NVS) holds promise for developing advanced intelligent optoelectronic devices. However, the integration is challenged by the substantial difference in their operating mechanisms. In this work, we demonstrate multifunctional MoO3/ZnO heterojunction devices capable of voltage-tunable switching between PD and NVS modes within a single device. Under zero external bias, the fabricated heterojunction exhibits a unique four-stage photoresponse arising from the pyroelectric effect, featuring a broad spectral response ranging from 355 to 1550 nm, high on-off ratios up to 1.4 × 105, and ultrafast photoresponse speed with a rise/fall time of 20/60 ms. When an external bias is applied, the heterojunction shows persistent photoconductive behaviors (PPC) caused by the defect trapping and detrapping processes, thereby successfully emulating the key synaptic functions of the human visual system, mainly including short-term plasticity (STP), long-term plasticity (LTP), and learning-memory behaviors. Importantly, the heterojunctions realize the multifunctional integration of optical encryption communication and image recognition with memory functions, corresponding to the PD and NVS modes, respectively. This work not only provides deep insight into an interfacial coupling effect in oxide heterojunction systems, but also offers effective strategies for developing reconfigurable optoelectronic devices beyond conventional functional boundaries.