Boosting the charge injection of polymer electrets for light-stimulated artificial synaptic transistors

Abstract

Semiconductor/polymer electret constructions are extensively utilized in organic field-effect transistors, memories, and artificial synapses. The challenge of exciton separation efficiency and charge injection from semiconductors into insulating polymers persist due to their disparate energy levels. In this work, we propose an effective method to enhance charge injection efficiency, thereby improving the optical response, by incorporating N,N′-dioctyl-3,4,9,10-perylenetetracarboxylic diimide (C₈-PTCDI) between the p-type semiconductor and the electret layer. For example, the 40 nm 2,7-diocty[1]benzothieno[3,2-b]benzothiophene (C₈-BTBT)/2 nm C₈-PTCDI/polymer electret-based synaptic transistors show a superior photosensitivity of 5.6 × 10⁶, compared with other transistors. C₈-PTCDI not only acts as an electron acceptor to improve the exciton dissociation and increase the photo-induced charge concentration, but also provides an electron transport layer in the channel for electron injection into PS. To verify its universality, 40 nm C₈-BTBT/2 nm [6,6]-phenyl-C71-butyric acid methyl ester (PC₇₁BM)/polymer electret synaptic transistors were also prepared with a photosensitivity of up to 1.4 × 10⁶. Moreover, utilizing a configuration of C₈-BTBT/C₈-PTCDI/polymer electrets, light-stimulated artificial synaptic transistors were fabricated and employed in “pup” picture learning, neural network computing and image recognition tasks (achieving a recognition rate of up to 98.3%).