Switching from binary to ternary WORM memory behavior of benzothiadiazole-based D–A system

Abstract

A series of novel benzothiadiazole (BTD) derivatives was synthesized via a Pd-catalyzed Suzuki-cross-coupling reaction, encompassing compounds with D–A–D and D–A–A architectures. Devices featuring non-symmetrical structures incorporating electron-accepting cyano and nitro groups on the BTD core exhibited a non-volatile ternary WORM memory behavior. Conversely, symmetrical compounds containing di-tertiary-butyl or dimethoxy groups as donors manifested binary memory behavior. The compounds with methoxyl and cyano substitution in the D–A–A architecture displayed only binary switching behavior due to their unfavorable thin film formation and molecular packing. UV and CV data analysis revealed narrow band gaps ranging from 2.58 to 2.75 eV, facilitating charge carrier transport within the active layer. Remarkably, compounds featuring t-Bu and cyano group substitutions showcased superior performance attributes, characterized by a low threshold voltage of −0.80 V and a high ON/OFF ratio of 10². The underlying resistive switching mechanism was elucidated through analysis of HOMO, LUMO, and ESP studies, indicating a composite influence of charge transfer and charge trapping phenomena. This study highlights the significant influence of substituent modifications in D–A molecules on molecular packing, thin film morphology, and electron trap depth within the active layer. These factors profoundly impact the memory performance of organic memory devices.