Adjustment of conformation change and charge trapping in ion-doped polymers to achieve ternary memory performance

Abstract

Ion-doped poly(4-vinylpyridine) derivatives (P4VPCz), where in the pendant chains the electron-withdrawing pyridine moiety and acceptor carbazole moiety are linked by a flexible alkyl spacer were designed and synthesized. Sandwiched ITO/P4VPCz/Al devices, made through simple spin-coating processes have shown that they could be tuned from a binary to ternary memory performance, by increasing the carbazole content. P4VPCz2 with a 20% mole ratio of the carbazole moiety shows a binary performance according to the charge trapping of the pyridine acceptor in the polymer, while P4VPCz5 which contains a 50% mole ratio of carbazole in the pendant chains, exhibits a ternary data storage ability, probably induced by double mechanisms (i.e. a conformational change and charge trapping). Interestingly, as the carbazole mole ratio reached 80%, the polymer P4VPCz8 has a high conductivity state, with no switching behavior, because of the large amount of doped ions improving the charge transfer mobility. Thus, we hope can offer a guideline to achieve a high-performance multilevel memory material, via combining different mechanisms as well as doping ions.