A general strategy for manufacturing flexible synaptic transistors with high mechanical stability

Flexible organic synaptic transistors (FOSTs) have attracted considerable attention owing to their flexibility, biocompatibility, ease of processing, and reduced complexity. However, FOSTs rarely maintain the mechanical stability of their synaptic properties while meeting the device deformation requirements. Here, we experimentally found that bending deformation had a greater influence on the synaptic performance (i.e., the excitatory postsynaptic current (EPSC) value) of FOSTs than on the on-state current. Moreover, through formula derivation, we proved that the density of bending-induced defect states generated near the channel considerably influences the synaptic performance. We propose a general approach to tune the stable segment of the device using an encapsulation layer. The EPSC value of the ordinary FOSTs without a regulated stable segment decreased by nearly 1.5–2 orders of magnitude after bending. In contrast, the designed flexible synaptic device exhibited relatively stable EPSC. Moreover, the designed FOST exhibited stable paired-pulse facilitation, long-term potentiation, and optical synaptic performance. Furthermore, neuromorphic computational simulations based on our device before and after 500 bending cycles were performed using a handwritten artificial neural network. The device showed stable recognition accuracy after 50 learning cycles (91.55% in the initial state and 90.43% after 500 bending cycles). The successful application of a stable segment in flexible synaptic transistors provides a convenient and simple idea for fabricating flexible neuromorphic electronics with mechanical stability.