Organic Synaptic Transistors Exhibiting Interface Photoisomerizable Effect with Enhanced UV-NIR Response and Bidirectional Modulation for Neuromorphic Vision

Neuromorphic devices are pivotal for surpassing von Neumann architecture constraints, advancing neuromorphic computing and multifunctional simulations. Light-stimulated organic field-effect transistors (OFETs) are promising platforms for this purpose. However, most synaptic transistors are limited to single-wavelength response, and achieving bidirectional (excitatory/inhibitory) light modulation in unipolar devices remains challenging. Here, we fabricate an organic synaptic transistor using a spiropyran (SP) and poly(4-vinylphenol) (PVP) blended interface modification layer. This device achieves enhanced broadband responsivity from ultraviolet (UV) to near-infrared (NIR) with ultralow electrical energy consumption (0.104 fJ/spike), enabling applications in diverse functional simulations, as well as multispectral image perception, memory, processing, and color-mixed handwritten digit recognition. The enhancement stems from a collective effect: zwitterion-dipole-induced hole accumulation within the channel following SP photoisomerization and surface-trap-mediated photogenerated electron capture. Furthermore, we demonstrate bidirectional synaptic modulation in a unipolar transistor with an SP interface modification layer via gate voltage control. This exploits the voltage-dependent functionality of photogenerated zwitterions: hole induction at small negative fields (excitatory) and hole capture at high negative fields (inhibitory), applied to dynamic image encryption. This work demonstrates an easily accessible strategy for developing organic synaptic transistors with enhanced broadband responsiveness and bidirectional optical modulation.