Hybrid Electrolyte-Doped OFETs for Neuromorphic Applications

Emerging applications such as brain–machine interfaces, biocompatible prosthetics, and adaptive soft robotics require artificial neuromorphic devices capable of seamlessly interfacing with biological systems. Here, we demonstrate organic field-effect transistors (OFETs) incorporating a self-doping hybrid electrolyte, 1,4-di-tert-butylbenzene-2,5-bis(1-propoxy-3-sulfonate) lithium salt (BBOPSO₃Li), as artificial synaptic devices. Incorporation of BBOPSO₃Li into poly(3-hexylthiophene) (P3HT) channels enables precise engineering of shallow trap states through the close energetic alignment between the BBOPSO₃Li energy level and the P3HT HOMO (~0.1 eV offset), resulting in tunable threshold voltage, controllable hysteresis, and enhanced carrier mobility. The doped OFETs exhibit key synaptic characteristics, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), and analog long-term potentiation and depression (LTP/LTD) with stable conductance modulation. An optimal doping concentration of 0.070 mol% provides the highest synaptic excitability, balanced temporal memory behavior, and the widest conductance window. System-level evaluations further demonstrate improved pattern recognition accuracy of up to 89.8% on MNIST-like datasets and robust time-series prediction in a physical reservoir computing framework, achieving a normalized mean square error of −32 dB. These results demonstrate that self-doping hybrid electrolytes provide a versatile strategy for engineering reversible trap states, enabling controllable synaptic plasticity and temporal dynamics in OFETs for organic neuromorphic computing.