Adjustment of active protons of end-electron-withdrawing groups in small molecules for different memory characteristics

Abstract

Owing to the diverse design strategy and convenient structural modification, the small molecular organic materials have been widely applicated in the fabrication of memory devices with complex memory behavior. In this work, we successfully synthesized two asymmetric quinacridone derivatives, BQTCH and BQTCE, with the same electron donors and molecular backbone, but different terminal groups. The sandwich-structured memory devices based on BQTCH and BQTCE have also successfully been prepared via spin-coating. The optical properties, packing performances, thermal stabilities and surface morphologies of the small molecules and their corresponding films are characterized via UV–vis and emission spectra, AFM, TGA and XRD. The I–V curves indicate all the as-prepared devices exhibit excellent memory performances, and the sandwich-structured memory devices based on ITO/BQTCH/Al exhibit a ternary memory behavior (WORM type from OFF to ON1 but FLASH type from ON1 to ON2), while the memory devices based on ITO/BQTCE/Al exhibit a typical ternary memory behavior (WORM type). To explain this difference, DFT molecular simulation and the energy level diagrams of HOMO and LUMO orbitals of BQTCH and BQTCE are investigated to demonstrate the crucial role of terminal groups in influencing the memory behavior.