A series of D-π-A, D-π-D, and A-π-A based push–pull compounds with triarylamine and benzophenone were designed and synthesized for nonvolatile memory applications. All of the compounds showed good solubility in common organic solvents, which permits solution processability. D-π-A based compounds exhibited write-once-read-many (WORM) memory applications, and the compound with a methoxyphenyl substituent exhibited switching with a low threshold voltage of −0.82 V, an ON/OFF current ratio of 102, and a long-lasting retention time of 103 s. The effect of differently functionalized triarylamines on memory behavior was explored by optical, electrochemical, and computational studies. The highest HOMO levels of around ∼5.0 eV and irreversible anodic peaks (0.7–1.3 V) obtained for the compounds facilitate charge injection and switching behavior. Besides, electrochemical and density functional theory studies disclose the charge-transfer mechanism of the D-π-A systems, which is related to the bistability of the devices.
Integration of devices for their efficiency is considered to be the future goal of organic electronics. One such highly integrated device which combines the properties of both the organic field-effect transistor and organic light-emitting diodes are the organic light-emitting transistors (OLETs). These devices are exceedingly preferred for their enhanced properties/performance in terms of both mobility and luminescence. It becomes a singly stacked device enabling the integration of both a transistor and a light emitter in the same. Although it is a budding field of organic electronics, limited literature is available which keeps on increasing due to its high advantages in many applications. This review gives a brief knowledge of the OLETs being fabricated recently using different materials and the developments in device fabrications. The review looks through an organic chemist's perspective, digging into many ways through which an OLET material can be designed and characterized. It also looks through the developments made in the device architecture during the years enabling better performance through many different ways.
A series of D-A-D architectured molecules with quinoline as the central core and triarylamines (TAA) at both terminals were synthesized and studied for their memory performance. The photophysical studies exhibited...
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.
Donor-Acceptor systems are highly appreciated in the field of organic memory devices due to their efficient charge transport within the systems. In this work, we have designed and synthesized a DÀ πÀ A system constituting esterflanked quinolines and functionalized triarylamines (TAA) through a single-step cross-coupling reaction to fabricate memory devices via Write-Once Read-Many times (WORM) non-volatile memory. Structure-property relationships are reconnoitered for these conjugated DÀ πÀ A systems through a series of UV, fluorescence, XRD, DFT, and memory characterizations. The UV and CV data show efficient charge transfer with intramolecular charge transfer occurring at 407-417 nm and a short band gap of 2.56-2.65 eV. An enhancement in the resistive switching behavior of the memory devices is observed for the compounds with simple TAA-quinoline and tert-butylphenyl substituted TAA and fluorophenyl substituted quinoline due to balanced charge distribution in the compounds. This enhanced switching induces an on/off ratio of 10 3 by generating a highly ordered arrangement in the thin films. The HOMO, LUMO levels, and the ESP images together estimate a charge transfer and charge trapping as the plausible mechanism for the solution-processable WORM memory devices. The longer retention time (10 3 s) and lower threshold voltages (À 1.21-À 2.12 V) of the devices makes them intriguing compounds for memory applications.
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