Enhancing the Memory-Stretchability Property of π-Conjugated Polymers Using Pendant Arene Side Chains in Nonvolatile Transistor Memory

In this study, a series of arene moieties were introduced on the side chains of a diketopyrrolopyrrole (DPP)-based semiconducting polymer, including naphthalene (DPP-NA), anthracene (DPP-AN), and pyrene (DPP-PY) as an electron-trapping site for nonvolatile transistor-type memory. Therefore, the developed conjugated polymers integrate the channel and electret layers to concomitantly transport hole carriers and trap electrons. We found that the conjugations of arene moieties and their energy-level alignments to the conjugated polymer significantly influenced the memory performance. Accordingly, DPP-AN provided a good hole mobility (μh) of 0.020 cm2 V-1 s-1, a stable memory window (ΔVt) of 70 V, and an ON/OFF-state current contrast (ION/IOFF) of 4 × 103, exhibiting decent flash-type memory behaviors. To further enhance the memory-stretchability property of DPP-AN, DPPSi-AN with the octydodecyl side chain replaced by the carbosilane side chain exhibited a comparable μh of 0.029 cm2 V-1 s -1, an enhanced ΔVt of 81 V, and an ION/IOFF of 5 × 103. Notably, DPPSi-AN could achieve a high μh preservation of 53% and a stable ΔVt of 64 V at 60% tensile strain, alongside a μh preservation of 69% and a slightly decreased ΔVt of 38 V after 600 cyclic stretch tests at 60% tensile strain. The improved memory-stretchability property of DPPSi-AN could be attributed to the favorable energy levels of anthracene that are conducive to electron trapping and ameliorating hole back-trapping. In addition, the anthracene-incorporated side chain reduced the crystallinity of the polymer and the carbosilane side chain rendered more free volume over the space. The side-chain-engineered conjugated polymer can be effectively modulated with different electron-trapping moieties, which also provides facile device fabrication procedures and superior memory performance.