New triarylamines with high mobility have been identified for p-channel OFET applications: their high ON/OFF ratio proves them to be a promising candidate for circuits and switches.
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.
A series of π-extended
quinolines with D−π–A–D
and D−π–A–A architectures were designed
and synthesized via the Sonagashira cross-coupling reaction to serve
as ambipolar organic semiconductors for use in C–FET. Ambipolar
mobilities were observed for methoxy- and tert-butyl
group-substituted compounds. Among the molecules studied, π-extended
methyl 2-(4-methoxyphenyl)-6-((4-methoxyphenyl)ethynyl)quinoline-4-carboxylate
with D−π–A–D architecture exhibited high
ambipolar transistor characteristics with hole and electron mobilities
of 0.10 and 0.05 cm2/V s, respectively. The good charge
carrier mobilities are supported by an electron-donating methoxy group
with high highest occupied molecular orbital (HOMO) and lowest unoccupied
molecular orbital (LUMO) levels, extensive π-conjugation, and
better self-assembly. Organic field-effect transistor (OFET) devices
were fabricated using the spin-coating technique with BGTC configuration.
By employing the postannealing technique, self-assembled crystalline
films were obtained as depicted by scanning electron microscopy (SEM).
These compounds can find potential applications in organic light-emitting
transistors, sensors, and logic circuits.
A series of phenanthroline functionalized triarylamines (TAA) has been designed and synthesised to evaluate their OFET characteristics. Solution processed OFET devices have exhibited p-channel/ambipolar behaviour with respect to the substituents.
Facile and efficient solution-processed bottom gate top contact organic field-effect transistor was fabricated by employing the active layer of picene (donor, D) and N,N′-di(dodecyl)-perylene-3,4,9,10-tetracarboxylic diimide (acceptor, A). Balanced hole (0.12 cm2/Vs) and electron (0.10 cm2/Vs) mobility with Ion/off of 104 ratio were obtained for 1:1 ratio of D/A blend. On increasing the ratio of either D or A, the charge carrier mobility and Ion/off ratio improved than that of the pristine molecules. Maximum hole (µmax,h) and electron mobilities (µmax,e) were achieved up to 0.44 cm2/Vs for 3:1 and 0.25 cm2/Vs for 1:3, (D/A) respectively. This improvement is due to the donor phase function as the trap center for minority holes and decreased trap density of the dielectric layer, and vice versa. High ionization potential (− 5.71 eV) of 3:1 and lower electron affinity of (− 3.09 eV) of 1:3 supports the fine tuning of frontier molecular orbitals in the blend. The additional peak formed for the blends at high negative potential of − 1.3 V in cyclic voltammetry supports the molecular level electronic interactions of D and A. Thermal studies supported the high thermal stability of D/A blends and SEM analysis of thin films indicated their efficient molecular packing. Quasi-π–π stacking owing to the large π conjugated plane and the crystallinity of the films are well proved by GIXRD. DFT calculations also supported the electronic distribution of the molecules. The electron density of states (DOS) of pristine D and A molecules specifies the non-negligible interaction coupling among the molecules. This D/A pair has unlimited prospective for plentiful electronic applications in non-volatile memory devices, inverters and logic circuits.
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