Side-Chain Engineering of Polystyrene Dielectrics Toward High-Performance Photon Memories and Artificial Synapses

The emerging applications of organic field-effect transistors (OFETs), such as photon memories and artificial synapses, require polymer dielectrics with superior charge trapping properties. Despite the introduction of high-k and fluorinated polymers in the performance optimization of OFETs, there is still a lack of widely recognized acknowledgment between molecular structures and charge trapping characteristics, as well as no general principles in designing polymeric dielectrics for electronic memory devices. Here, we propose a series of fluorinated polystyrene isomers through side-chain engineering, namely, ortho-(o-), meta-(m-), and para-fluorinated polystyrene (p-FPS). The gradually enlarged intramolecular charge separation of o-, m-, and p-FPS enhances molecular electrostatic potential, which promotes polarization and charge trapping performances, resulting in an enlarged dielectric constant, as well as more deep traps toward stable electret. Subsequently, largely improved photon memory and artificial synapse performances of p-FPS-based OFETs further suggest the dominating role of dielectric side-chain structures on memory and synapse performances, leading to a recommendation of low-k (epsilon(r) < 5) dielectric polymers with enhanced electrostatic potential for OFET-based memory devices and bionic nervous systems.