Design and Synthesis of Solution-Processable Donor–Acceptor Dithienophosphole Oxide Derivatives for Multilevel Organic Resistive Memories

A class of solution-processable, donor–acceptor-decorated dithienophosphole oxide derivatives has been successfully synthesized and employed to fabricate solution-processed resistive memory devices with a simple indium–tin oxide/active layer/aluminum structure. The intramolecular charge transfer (ICT) characters of the donor–acceptor dithienophosphole oxide derivatives were established from photophysical, solvatochromic, and computational studies. The number of conductance states in the organic memory devices was found to be altered by slight changes in molecular structures. The mechanism for the tristable memory property of the devices was proposed based on the correlation of the extent of ICT characters and the computed structural parameters of the compounds, current–voltage characteristics of the devices and the fitting to theoretical conduction models. These findings offer important insights for the realization of multilevel resistive memory devices through the modification of the ICT character of the active compounds.