Synthesis of imidazole derivatives and study of the ON-based different memory performances

Design of Triphenylamine-based D-π-A Systems for Efficient Ternary WORM Memory Devices

The impact of various substituent moieties on the molecular framework of a conjugated D-A system in resistive switching memory property has been scrutinized through an array of novel D-π-A molecules. The synthesized molecules with triphenylamine (TPA) as the electron donor and dicyanovinylindanone (IC) as the electron acceptor demonstrated substantial non-volatile WORM (Write-Once Read-Many) memory behaviour with appreciable ON/OFF current ratios up to 105 and a lowest recorded threshold voltage of -0.80 V. The well-balanced combination of these potent electron donating and accepting units culminated in exceptional intramolecular charge transfer interactions and minimal band gap values (1.82-2.31 eV) for the molecules, as demonstrated by photophysical and electrochemical investigations. These factors, coupled with the thin-film morphological studies, corroborated the superior performance of the fabricated devices. A longer retention time of 2000s and an endurance of 100 cycles mark the substantial stability of the memory devices. Moreover, conversion from binary to ternary WORM memory was achieved by the effective tuning of the electronic properties of the D-A systems by various substituent moieties. Molecular simulation studies revealed that the resistive switching phenomenon arises from a synergistic interplay of charge transfer and charge trapping processes within these D-A systems.

Effect of terminal substituent of iso-indigo-based materials on the intermolecular stacking and memory performance

Attributed to the characteristics of narrow band gap structural units and full spectral response, iso-indigo is often used as an electron acceptor in organic electronic materials. Organic molecules with large conjugated surfaces and strong intermolecular forces can form ordered stacked structures through self-assembly. In this paper, the self-assembly performances of IDCF3 and IDCN are regulated by changing the end groups. The effects of terminal groups on the resistive memory behaviours and reproducibility are investigated. The properties of IDCF3 and IDCN devices are characterized by UV-VIS spectroscopy, cyclic voltammetry and DSC diffraction. The results show that when the end groups with different steric hindrance are introduced into the ends of the molecules with good backbone plane, the conjugated surfaces of the molecules will bend due to the different steric hindrance of the end groups in the form of cambium and layer-ordered packing, which will affect the threshold voltage and device reproducibility.

Improving Memory Performances by Adjusting the Symmetry and Polarity of O-Fluoroazobenzene-Based Molecules

Three O-fluoroazobenzene-based molecules were chosen as memory-active molecules: FAZO-1 with a D-A2-D symmetric structure, FAZO-2 with an A1-A2-A1 symmetric structure, and FAZO-3 with a D-A2-A1 asymmetric structure. Both FAZO-1 and FAZO-2 had a lower molecular polarity, whereas FAZO-3 had a higher polarity. The fabricated indium-tin oxide (ITO)/FAZO-1/Al (Au) and ITO/FAZO-2/Al (Au) memory devices both exhibited volatile static random access memory (SRAM) behavior, whereas the ITO/FAZO-3/Al (Au) device showed nonvolatile ternary write-once-read-many-times (WORM) behavior. It should be noted that the reproducibility of these devices was considerably high, which is significant for practical application in memory devices. In addition, the different memory performances of the three active materials were determined to be attributable to the stability of electric-field-induced charge-transfer complexes. Therefore, the switching memory behavior could be tuned by adjusting the molecular polarity.