9,10-Ter-anthrylene-ethynylene: a new molecular architecture for solution processed anthracene-based thin film transistors

Abstract

This study deals with the properties of a new molecular architecture for organic thin film transistors obtained by introducing 10-decylanthr-9-yl-ethynyl moieties at the anthracene 9,10 positions. The resulting structure, formally a ter-anthrylene-ethynylene (D3ANT), is stable and endowed with sufficient solubility to guarantee the formation of good quality films. The molecule was characterised by ¹H NMR, mass spectrometry, IR, UV–vis and photoluminescence both in solution and in the solid state. Cyclic voltammetry measurements, combined with solution UV–vis, permitted the evaluation of HOMO and LUMO energy levels. A series of D3ANT-based OTFT devices were built both in bottom and top contact configurations by a spin coating technique. Top contact OTFT devices exhibited the best semiconducting characteristics, showing an average mobility of 1.2 × 10⁻² cm² V⁻¹ s⁻¹ with on–off ratios higher then 10⁴, while the highest mobility obtained was 0.055 cm² V⁻¹ s⁻¹. AFM thin-film characterization showed evidence of a granular structure. High-resolution STM images of D3ANT monolayers adsorbed on Au(111) and HOPG reveal highly-ordered self-organized domains with molecules lying flat on the substrates, but, remarkably, no reflections were recorded by out-of plane GIXRD of spin coated films on SiO₂.