Donor-acceptor conjugated polymers of arylene vinylene with pendent phenanthro[9,10-d]imidazole for high-performance flexible resistor-type memory applications

We report the synthesis and resistive memory device characteristics of new donor-acceptor (D-A) conjugated poly(arylene vinylene) polymers, PVC-PI, PVT-PI, and PVTPA-PI, consisting of carbazole (C), thiophene (T), and triphenylamine (TPA) with pendent phenanthro[9,10-d]imidazole (PI). PVC-PI, PVT-PI, and PVTPA-PI synthesized by Stille coupling reaction have the optical band gaps of 2.86, 1.68, and 2.58 eV, respectively. These polymers possess similar HOMO energy levels (-5.08 to -5.18 eV), but different LUMO energy levels (-2.24, -3.40, and -2.60 eV for PVC-PI, PVT-PI, and PVTPA-PI, respectively). The PVC-PI flexible device with the sandwich configuration of PEN/Al/polymer/Al reveals the volatile static random access memory (SRAM) characteristic while the PVTPA-PI device exhibits the nonvolatile write-once-read-many-times (WORM) switching behavior. The above two devices could operate at low voltages (less than 2.5 V) with high ON/OFF current ratios (over 10(4)) and exhibit excellent durability upon repeated bending tests. However, the PVT-PI device only shows a diode-like electrical behavior. The polymer conformation affects the strength of D-A electrical polarization and charge trapping ability, leading to the variation of the volatility of the memory devices. The present study demonstrates that the prepared vinylene-based donor-acceptor conjugated polymers have excellent memory characteristics with reproducibility and reliability for advanced flexible organic electronics.