Vacancy-engineered ZnO Nanocage-based photoelectrochemical-type optoelectronic synapse for self-powered biomimetic neuromorphic function

The development of high-performance optoelectronic synapses is paramount for artificial neuromorphic systems. However, the main optoelectronic synapses designed based on solid-state photodetectors operate in non-aqueous environments, limiting their application in liquid media to mimic biological neuromorphic functionality. Herein, a two-terminal self-powered photoelectrochemical-type (PEC) optoelectronic synapse based on metal-organic-framework-derived ZnO nanocages is constructed to operate in a liquid medium, which simulates multiple biological synaptic behaviors, encompassing paired-pulse facilitation, the transition from short-term plasticity to long-term plasticity, and learning-forgetting-relearning behaviors. The synaptic function originates from the persistent photoconductivity induced by photogenerated carrier trapping in the oxygen vacancies of ZnO nanocages. More importantly, our optoelectronic synapse successfully imitates chemically-tuned synaptic behaviors and simulates complex oxidative stress-related biological phenomena by varying the electrolyte environment. This work provides an efficient approach to constructing PEC optoelectronic synapses and demonstrates their great promise in underwater neuromorphic applications.