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.

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.