Dual-Mode ZnO/SnSe Heterojunction Devices with Integrated Bipolar Response Photodetectors and Artificial Optoelectronic Synapses for in-Sensor Computing.

Optoelectronic synapse devices (OESDs) inspired by human visual systems enable to integration of light sensing, memory, and computing functions, greatly promoting the development of in-sensor computing techniques. Herein, dual-mode integration of bipolar response photodetectors (PDs) and artificial optoelectronic synapses based on ZnO/SnSe heterojunctions are presented. The function of the fabricated device can be converted between the PDs and OESDs by modulating the light intensity. As a PD, the polarity of the output current can be switched by tuning the laser wavelength and intensity, which is attributed to the competition between the photovoltaic and photothermoelectric effects in the ZnO/SnSe heterojunction. As an OESD, the device exhibits versatile photonic synaptic characteristics at low light intensity based on the defect-dominant carrier trapping/de-trapping processes, including short/long-term plasticity and learning experience behaviors. More importantly, benefitting from the outstanding synaptic responses, logic functions including "AND" and "OR" are implemented through the in-sensor computing architecture. This work supplies a novel route to realize complex functionality in one device and offers effective strategies for developing in-sensor computing.