Designing Light-Sensitive Organic Semiconductors with Azobenzenes for Photoelectrochemical Transistors as...

Organic neuromorphic electronics aim to emulate the adaptive behavior of biological synapses using soft, biocompatible materials capable of analog and stimulus-responsive modulation. While azobenzene-based semiconductors provide reversible light-induced switching, their application in mixed ionic-electronic conductors for neuromorphic systems remains largely unexplored. In this study, photoresponsive organic photoelectrochemical transistors (OPECTs) are engineered by functionalizing PEDOT:PSS with azobenzene derivatives bearing nitro or fluorine substituents. These modifications alter the electronic structure and surface properties of the gate, enabling systematic tuning of interfacial capacitance, a critical parameter governing photogating and neuromorphic response. Optical and electrochemical measurements, supported by DFT calculations reveal that substituent-dependent modulation of bulk and interfacial capacitance directly impacts gating efficiency. Devices exhibit reversible, analog conductance changes under optical and electrical co-stimulation, emulating both short- and long-term synaptic plasticity. These results establish a structure-capacitance-function relationship and provide a chemically tunable platform for the development of light-responsive neuromorphic interfaces in adaptive bioelectronics.