Ionogel-gated organic transistors and artificial synapses based on a composite of tosylate-doped poly(3,4-ethylenedioxythiophene) and insulating polyvinylpyrrolidone

Both ionic and electronic conductions in a channel are important factors to determine device characteristics of organic electrolyte-gated transistors (OEGTs) and artificial synaptic devices. Herein, synthesis and characterization of conducting polymer composites, based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with p-toluene sulfonate (Tos) counterions and insulating polyvinylpyrrolidone (PVP), are reported. The PEDOT:PVP ratio in the composite is easily tuned by varying the composition of the precursor solution. The PEDOT:Tos/PVP composites exhibit a higher electrical conductivity than pristine PEDOT:Tos. Ionogel-gated transistors based on the composites show good current modulation in a depletion mode. The transistors with 40% PVP by polymer weight show higher transconductance and larger hysteresis strength. Spectroscopic and electrochemical measurements reveal that addition of PVP affects the capability of doping-state modulation and the kinetics of ion conduction. With these properties, the PEDOT:Tos/PVP composite-based OEGTs exhibit good synaptic characteristics with reliable multi-level inhibitory and excitatory operations, suggesting the effectiveness of the strategy of introducing an electrically insulating polymer in conducting polymer composites to tune their charge-transport properties and device characteristics. Graphical abstract Conducting polymer composites of PEDOT:Tos/PVP are synthesized and used as a channel layer of organic electrolyte-gated transistors (OEGTs) and artificial synaptic devices. The devices with 40% PVP by polymer weight show a high transconductance and a large hysteresis strength, enabling good synaptic characteristics with reliable multi-level operations.