High Mobility and ON/OFF Ratio of Solution-Processable p-Channel OFETs from Arylacetylene End-Capped Alkoxyphenanthrenes.

New arylacetylene end-capped alkoxyphenanthrenes were synthesized and demonstrated as the best active layer for solution-processable p-channel organic field-effect transistors. The alkoxy chain embedded compounds exhibited enhanced solubility and induced non-covalent interactions resulting in effective molecular packing. The 'Lewis soft' heteroatoms direct the most stable conformation with dihedral angles possible for molecular interactions, and energy levels. DFT studies supported the fine-tuning of FMOs, with high HOMO levels ∼-5.2 eV ensuring a low barrier for charge injection. OFET devices exhibited a maximum charge carrier mobility up to 1.30 cm2 /Vs with the highest ON/OFF ratio of 107 . The strong π-π interactions and the crystallinity of the films are well supported by GIXRD and SEM analysis.

Butterfly-Like Triarylamines with High Hole Mobility and On/Off Ratio in Bottom-Gated OFETs.

Highly π-extended butterfly-shaped triarylamine dyads with aryleneethynylene spacer were constructed using an efficient synthetic route. These aryleneethynylene-bridged dyads are highly fluorescent and exhibited high HOMO levels, and low bandgaps, which are suitable for high-performance p-type OFETs. The field-effect transistors were fabricated through a solution-processable method and exhibited promising p-type performance with field-effect mobility up to 4.3 cm2 /Vs and high Ion/off of 108 under ambient conditions.

Tunable Charge Transport Using Heterocycles-Flanked Alkoxyphenanthrenes for High-Performing OFETs.

A series of new heterocycles-flanked alkoxyphenanthrenes with D'-D-D' and A-D-A architecture was synthesized for high-performance solution-processable p-channel, n-channel, and ambipolar organic field-effect transistors. The impact of electron-donating and -accepting abilities of the sulfur- and nitrogen-containing heteroaromatics on photophysical, electrochemical, and semiconducting properties was analyzed. The presence of heteroaryl rings improves the extended conjugation, two-dimensional lattices of π-π stacks, and increased molecular interaction of the functionalized phenanthrenes (PN) to allow better self-assembly. The electronically dynamic PN self-assembles into continuous microdomains, forming percolation channels for holes, electrons, or both reliant on functionalization. The low-lying LUMO levels of the compounds enabled ambipolar transport and reduced energy levels for charge injections. Spin-coated devices fabricated using functionalized PN with sulfur-containing heteroaryl substituted PN exhibited the highest hole mobility of 0.85 cm2/(V s) with 108 on/off current ratio. Compounds with A-D-A architecture showed n-channel/ambipolar charge transport, especially napthalimide acceptor substituted PN exhibited n-channel electron mobility of 0.78 cm2/(V s) and an on/off ratio of 106. X-ray diffraction and scanning electron microscopy studies further delineate the impact of efficient packing in the film. Quantum chemistry calculations combined with Marcus-Hush electron transfer theory interpret the transport parameters, and heteroatoms are established to impact the charge mobility intensely.

Hexaarylbenzene based high-performance p-channel molecules for electronic applications.

Hexaarylbenzene-based molecules find potential applications in organic electronics due to wider energy gap, high HOMO level, higher photoconductivity, electron-rich nature, and high hole-transporting property. Due to the unique propeller structure, these molecules show low susceptibility towards self-aggregation. This property can be tailored by proper molecular engineering by the incorporation of appropriate groups. Therefore, hexaarylbenzene chromophores are widely used as the materials for high-efficiency light-emitting materials, charge transport materials, host materials, redox materials, photochemical switches, and molecular receptors. This review highlights the diverse structural modification techniques used for the synthesis of symmetrical and unsymmetrical structures. Also, the potential applications of these molecules in organic light-emitting diodes, organic field-effect transistors, organic photovoltaics, organic memory devices, and logic circuits are discussed.

Picene and PTCDI based solution processable ambipolar OFETs.

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.