Improved Resistive Switching WORM Memory Behavior in D‑π‑A Architectures by Modifying the Terminal Donor Units

A series of D-π-A, D-π-D, and A-π-A based push–pull compounds with triarylamine and benzophenone were designed and synthesized for nonvolatile memory applications. All of the compounds showed good solubility in common organic solvents, which permits solution processability. D-π-A based compounds exhibited write-once-read-many (WORM) memory applications, and the compound with a methoxyphenyl substituent exhibited switching with a low threshold voltage of −0.82 V, an ON/OFF current ratio of 102, and a long-lasting retention time of 103 s. The effect of differently functionalized triarylamines on memory behavior was explored by optical, electrochemical, and computational studies. The highest HOMO levels of around ∼5.0 eV and irreversible anodic peaks (0.7–1.3 V) obtained for the compounds facilitate charge injection and switching behavior. Besides, electrochemical and density functional theory studies disclose the charge-transfer mechanism of the D-π-A systems, which is related to the bistability of the devices.