Exploring Single Atom Substitution In Phenanthro[9,10-d]Imidazole -Based D–π–A Architectures with Fluorene and its Heteroanalogs for Non-Volatile Resistive WORM Memory Device Applications

Abstract

A series of D–π–A compounds, with fluorene and its heteroanalogs (carbazole, dibenzofuran, dibenzothiophene) as the donor units and phenanthroimidazole as the acceptor, were designed and synthesized for non-volatile memory device applications. The effect of single-atom substitution on memory behavior was examined through optical, electrochemical, and computational studies. The photophysical studies confirm a significant intramolecular charge transfer from the donor to the acceptor unit, and the electrochemical analysis shows an irreversible anodic peak (0.99–1.21 V) with an optimal band gap ranging from 2.80 to 2.88 eV. All the compounds exhibited non-volatile binary WORM memory behaviour with an ON/OFF current ratio of 105 and 103. The devices also showed excellent stability over 100 cycles and maintained a retention time of 4000 s. Notably, the compound with carbazole substitution displayed a lower threshold voltage and a higher ON/OFF current ratio of 105. Density functional theory calculations confirmed that the combined effects of charge transfer and charge trapping mechanisms are crucial to the resistive switching mechanisms observed. This work highlights the potential of single atom substitution in D–π–A systems, providing valuable insights for designing high-performance data storage devices.