Pyrene-Incorporated Side Chain in π-Conjugated Polymers for Non-Volatile Transistor-Type Memory Devices with Improved Stretchability

Abstract

The direct application of a conjugated polymer as the single active layer in a field-effect transistor (FET) memory device is in high demand to integrate the conventional charge-transport and charge-storage layer. To achieve this goal, we report side-chain-engineered donor (D)-acceptor (A)-type conjugated copolymers with a D moiety of bithophene (2T) and an A moiety of diketopyrrolopyrrole (PDPP2T). Pyrene (PY)-incorporated side chains serving as electron-trapping moieties are introduced into the polymer to fulfill the charge-storage capability of PDPP2T. By controlling the PY content in the polymer, the conjugated polymer-based FET memory device documented an enhanced charge-storage capability while maintaining charge-transport performance. PY30 with the optimized PY content provides a charge-transport performance with a μh value of 0.022 cm2 V-1 s-1 and a stable charge-storage capability characterized by a δVt value of 51 V and an ION/IOFF ratio of 103. The charge-retention time can be maintained over 3 × 104 s with high data discriminability of the memory device. Collectively, the charge-storage capability can be extracted into two essential factors: (1) a suitable PY content facilitates trapping of electrons with a voltage bias. (2) The side-chain mismatch and irregular solid-state stacking give rise to the homogeneous distribution of the electron-trapping site over space. Meanwhile, the PY-incorporated side chain induces a more amorphous nature due to the mismatch between the side chains. The amorphous nature of the polymers facilitates their better stretchability and preservation in FET memory performance. With an external strain of 60%, PY30 can exhibit a μh preservation of 20% and a stable δVt value of 29 V. Our results suggest that the side-chain engineering of the conjugated polymer with the PY moiety provides a new approach to implement intrinsically stretchable conjugated polymer-based FET memory devices with simplified device fabrication procedures. ?