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Small-molecule-based multilevel memory devices have attracted increasing attention because of their advantages, such as super-high storage density, fast reading speed, light weight, low energy consumption, and shock resistance. However, the fabrication of small-molecule-based devices always requires expensive vacuum-deposition techniques or high temperatures for spin-coating. Herein, through rational tailoring of a previous molecule, DPCNCANA (4,4'-(6,6'-bis(2-octyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)-9H,9'H-[3,3'-bicarbazole]-9,9'-diyl)dibenzonitrile), a novel bat-shaped A-D-A-type (A-D-A=acceptor-donor-acceptor) symmetric framework has been successfully synthesized and can be dissolved in common solvents at room temperature. Additionally, it has a low-energy bandgap and dense intramolecular stacking in the film state. The solution-processed memory devices exhibited high-performance nonvolatile multilevel data-storage properties with low switching threshold voltages of about -1.3 and -2.7 V, which is beneficial for low power consumption. Our result should prompt the study of highly efficient solution-processed multilevel memory devices in the field of organic electronics.

To simplify the conventional donor–acceptor molecular scaffold design, we report the synthesis of two simple donor (TCz) and acceptor (PI) semiconductors via brief synthetic routes. The film formed from solution process through the simple blending of TCz and PI revealed a compacted, continuous, and smooth morphology. The optical and electrochemical properties of the blend films with various blend proportions were characterized by UV–vis absorption spectra and cyclic voltammograms. The as-fabricated ITO/TCz:PI/Al sandwiched devices exhibited both volatility and reversibility dually tunable electrical data storage performance as the blend ratio varying. From these observations we demonstrate a very simple but powerful strategy to obtain organic memory devices with good performance.

By introducing a coplanar fluorenone into the center of an azo molecule, the turn-on voltages of the ternary memory devices are significantly decreased to lower than -2 V due to the improved crystallinity and the reduced charge injection barrier. The resulting low-power consumption devices will have great potential applications in high-performance chips for future portable nanoelectronic devices.

Two conjugated small molecules with different molecular length, DPAPIT and DPAPPD, in which an electron donor dimethylamino moiety and an electron acceptor phthalimide core unit are bridged by another electron-accepting azobenzene block, were designed and synthesized. DPAPIT molecule with longer conjugation length stacked regularly in the solid state and formed uniform nanocrystalline film. The fabricated memory devices with DPAPIT as active material exhibited outstanding nonvolatile ternary memory effect with the current ratio of ∼1 : 101.7 : 104 for “0”, “1” and “2” states and all the switching threshold voltages lower than −3 V. In contrast, the shorter molecule DPAPPD showed amorphous microstructure and no obvious conductive switching behavior was observed in the device. The crystallinity and surface roughness of DPAPIT thin films were significantly improved as the annealing temperature increased, lowering the switching threshold voltages which are highly desirable for low-power consumption data-storage devices. It is worth noting that the tristable memory signals of DPAPIT film could also be achieved by using conductive atomic force microscopy with platinum-coated probe, which enables fabrication of nano-scale or even molecular-scale device, a significant progress for the ultra-high density data storage application. Mechanism analysis demonstrated that two charge traps with different depth in the molecular backbone were injected by charge carriers progressively as the external bias increased, resulting in the formation of three distinct conductive states (OFF, ON1 and ON2 states).

A series of conjugated donor–acceptor (D–A) molecules with the electron-rich unit triphenylamine (TPA) as donor and azobenzene chromophore and/or cyano group as acceptors were successfully synthesized. Acceptors varying in number and electron-withdrawing strength were incorporated into the molecular backbone to investigate the impact on device switching behavior. It is found that the data storage states and memory effects are highly dependent on the number and strength of the electron-deficient groups. The devices based on the D–π–A1–π–A2 molecule with two electron-withdrawing groups exhibited excellent ternary memory behavior, while those based on the D–π–A1 or D–π–A2 molecule containing one electron-accepting moiety showed binary memory characteristics. In addition, the bistable memory effects of TPAVC 2 and TPAAH 3-based data storage devices varied from WORM to flash when the acceptor changed from a cyano group to an azobenzene chromophore. Therefore, tunable multilevel memory device performance has been achieved by adjusting the number and electron-withdrawing strength of acceptor moieties in the molecular backbone, offering guidance for the rational design of superior D–A molecules for high density data storage (HDDS) applications.