Synergy Effect of Porphyrin Units and Alkynyl π Bridges Tunes the Memory Behavior and Threshold Voltage of Hyperbranched Polyimides

Porphyrin units are a kind of ideal electron donor units, which have large π conjugation, well-defined planar and electron-rich structures. The inserted alkynyl π bridges between porphyrin units and anhydride moieties can effectively enlarge the π-electron delocalization and molecular dimension effect, and thus enhance the electron donate ability and reduce the dipole moment in the porphyrin-based hyperbranched polyimides (HBPIs). The synergy effect of porphyrin units and alkynyl π bridges can facilitate the charge transfer (CT) formation and dissociation, realize the transformation of memory type and shorten the retention time of HBPI-TAPEPP-6FDA based memory devices. The HBPI-TAPEPP-6FDA based memory devices manifest lower threshold voltage of -2.32 and 2.42 V, higher ON/OFF current ratio up to 107 and shorter retention time about 20 s.