Enhancing performance of nonvolatile transistor memories via electron-accepting composition in triphenylamine-based random copolymers

With the rapid advances in organic memory, organic field-effect transistor (OFET) memory has been recognition of the value over the past few years. Although the functional polymer with the Donor-Acceptor (D-A) structure has been widely investigated, little research has been carried out to clarify the relationships among D-A structure of the polymer, capability of charge-transfer, and memory performance. Here, we report the nonvolatile memory characteristics of pentacene-based OFET memory using random copolyimides, poly[4,4-diaminotriphenylamine-hexafluoroisopropylidenediphthalimide-co-4-(N,N-bis(p-aminophenyl)amino)-4-nitroazobenzene-hexafluoroisopropylidenediphthalimide) (PI(TPA-6FDA-DACx)), with feeding ratios of DAC to TPA set as x (where x =0,10, 30,50,70,100). The OFET memory performance based on the molar ratio of DAC to TPA equal to 30:70 represents the best results with the proper charge mobility, on/off current ratio, and memory window. Intriguingly, the memory performance can be enhanced by introducing more D-A monomer in polymer electrets, yet the concomitant inferior growth of pentacene decreases the charge mobility, attributed to the intrinsically destructive arrangement of polymer backbone. Our conclusion points out the importance of polymer arrangement and capability of charge-transfer to the OFET performance and memory characteristics. The comparable results can also be applied for advanced OFET memory devices. (c) 2019 Wiley Periodicals, Inc.