Structure–Function Coupling in Pyridyl Triazole Copolymers for Neuromorphic Synaptic Transistors

Organic ferroelectric transistors are excellent candidates as low-cost alternatives for synaptic devices. Specifically, interfaces with donor–acceptor semiconducting polymers and copolymers of poly(vinylidene fluoride) (PVDF) are attractive for mimicking synaptic responses. By tailoring the linking unit between the pyridyl triazole (PyTr) acceptors and thiophene donors, three copolymers are synthesized incorporating selenium-substituted thiophene, benzothiadiazole, and fluorine-substituted thiophene linkers. Using the hexafluoropropylene copolymer of PVDF (PVDF-HFP) as the dielectric layer, the three PyTr semiconductors show p-type transport in transistor architectures with carrier mobilities between 0.1 and 0.2 cm² V^–1 s^–1. The synaptic plasticity is investigated by applying long-term pulsed voltages at the gate electrode to emulate potentiation and depression processes. To assess their neuromorphic functionality, the synaptic responses of the devices are tested for image recognition in a multilayer perceptron neural network. The copolymer with the benzothiadiazole linker achieved recognition accuracy close to 80%, whereas the one with a fluorine-substituted thiophene linker shows no synaptic behavior, highlighting the critical role of the semiconductor–dielectric interface. A detailed study of the interface trap density and morphology is performed to identify how interfacial properties directly influence synaptic device performance.