Diketopyrrolopyrrole-Based Dual-Acceptor Copolymers to Realize Tunable Charge Carrier Polarity of Organic Field-Effect Transistors and High-Performance Nonvolatile Ambipolar Flash Memories

Abstract

Incorporation of dual acceptors into the copolymer backbone can effectively improve the electron affinity to achieve ambipolarity for use in specific electronic devices, for example, organic field-effect transistors (OFETs) and flash memories. Herein, two diketopyrrolopyrrole (DPP)-based copolymers, pDPPy-BTz and pDPPy-ffBTA, are developed by introducing dialkoxybithiazole and difluorobenzotriazole, respectively. Upon evaluating their electrical properties in OFETs, the polarity of dominant carriers in the OFET channel is found to be tuned by the monomer structures and measurement atmosphere. Specifically, the device based on pDPPy-BTz exhibits a p-type dominant ambipolar character with a μh/μe of 5.3 in air, whereas the electron mobility is enhanced by removing the oxygen and water (vacuum condition), resulting in a charge carrier polarity change to display an n-type dominant feature with the μh/μe decreasing to 0.3. Owing to the electron-donating property of thiophene groups, the pDPPy-ffBTA polymer exhibits a p-type unipolar performance in air and balanced ambipolar (μh/μe = 0.8) charge carrier transport under vacuum. On account of the well-defined ambipolar behavior, the polymers are used in nonvolatile memory devices. High performance is obtained with both polymers with memory windows of 10–16 V, stable data retention of over 105 s, and high reliability during >500 programming and erasing cycles. Overall, this study demonstrates a charge carrier polarity change in OFETs fabricated with DPP-based dual-acceptor copolymers by incorporating various acceptors into the polymer backbone and reports a high-performance nonvolatile ambipolar flash memory.