Tailoring the Resistive Switching WORM Memory Behavior of Functionalized Bis(triphenylamine)

Abstract

To better understand the structure–property relationship and the significance of the donor–acceptor (D–A) system in resistive memory devices, a series of new organic small molecules with A-π-D-π-A- and D-π-D-π-D-based architecture comprising a bis(triphenylamine) core unit and ethynyl-linked electron donor/acceptor arms were designed and synthesized. The devices with A-π-D-π-A structures exhibited write-once-read-many memory behavior with a good retention time of 1000 s while those based on D-π-D-π-D molecules presented only conductor property. The compound with nitrophenyl substitution resulted in a higher ON/OFF current ratio of 104, and the fluorophenyl substitution exhibited the lowest threshold voltage of −1.19 V. Solubility of the compounds in common organic solvents suggests that they are promising candidates for economic solution-processable techniques. Density functional theory calculations were used to envision the frontier molecular orbitals and to support the proposed resistive switching mechanisms. It is inferred that the presence of donor/acceptor substituents has a significant impact on the highest occupied molecular orbital–lowest unoccupied molecular orbital energy levels of the molecules, which affects their memory-switching behavior and thus suggests that a D–A architecture is ideal for memory device resistance switching characteristics.

A metastable small organic molecule for secure memory devices

“…41 Considering that small organic molecules display tunable properties and designable structures; we are interested in introducing special stimuli-responsive small organic molecules as active materials into organic electrical memory devices that are more likely to simultaneously achieve data storage and secure memory devices. 42–44…”

ZnO Nanoparticle-Induced Performance Enhancement of a Coumarin-Based Nonvolatile Memory Device

“…22,23 Molecules with such structure ensure intermolecular and intramolecular charge transfer. 22,23 Moreover, the donor−acceptor groups present in the molecular scaffold serve as trap centers for the injected charges from the electrodes. 22 These trap centers can hold up the charges for a long period of time which may enhance the data retention capability of the device.…”

“…22,23 Moreover, the donor−acceptor groups present in the molecular scaffold serve as trap centers for the injected charges from the electrodes. 22 These trap centers can hold up the charges for a long period of time which may enhance the data retention capability of the device. 22 In this regard, the coumarin scaffold, with its versatile physicochemical properties, can serve as an excellent molecular backbone for designing small organic molecules that are ideal for use in organic resistive switching devices.…”

“…22 These trap centers can hold up the charges for a long period of time which may enhance the data retention capability of the device. 22 In this regard, the coumarin scaffold, with its versatile physicochemical properties, can serve as an excellent molecular backbone for designing small organic molecules that are ideal for use in organic resistive switching devices. Coumarin derivatives are abundantly found in many naturally occurring substances and are a widely researched class of molecules due to their widespread applications in disease therapeutics.…”

“…Apparently, the blue region, located over the coumarin scaffold, can serve as an open channel for charge carrier transport along the molecular framework. 22 Moreover, the red regions, mostly located over the oxygen atoms, can act as traps in the molecular structure. 64 Besides, intermolecular and intramolecular CT in the excited state can induce stability in the trapped charges which promotes a prolonged ON state.…”