Large-area InSe nanofilm for artificial optoelectronic synapses with ultra-low energy consumption

Optoelectronic synaptic devices based on two-dimensional (2D) materials hold great promise for the development of energy-efficient artificial neural visual systems (ANVSs), owing to their strong light–matter interactions and atomic thickness. 2D indium selenide (InSe) with the outstanding gate control capability and high sensitivity has tremendous application potential in photonic neuromorphic computing. Here, a simplified two-terminal (2 T) photonic synapse device with ultralow energy consumption based on solution-processed 2D InSe is proposed for the first time. An electrochemical intercalation method is employed to prepare 2D InSe nanosheets while simultaneously introducing Se vacancies, which act as defect centers to efficiently trap photogenerated carriers. Large-scale (2 ×2 cm²) InSe nanofilms are fabricated via facile spin-coating, and the resulting 5 × 6 2 T optoelectronic synaptic device array successfully simulates advanced synaptic functions, including excitatory postsynaptic currents, paired-pulse facilitation, and the transition from short-term memory to long-term memory. More importantly, the device achieves ultra-low energy consumption of ∼0.51 fJ per event, which is one order of magnitude lower than that of biological synapses and surpasses most photoelectric synaptic devices based on 2D materials. Spectrum-dependent synaptic responses further enhance the tunability of synaptic behavior, which can be utilized to simulate human learning and memory processes under various emotional states. This work presents a facile method for fabricating high-performance optoelectronic synapses, thereby expanding the potential of solution-processed 2D materials for applications in advanced optoelectronic devices.