A star-shaped molecule as hole transporting material in solution-processed thin-film transistors

The semiconductor potentialities of a new star-shaped molecule consisting of a triphenylamine core carrying π-conjugated thiophene and thieno[3,2-b]-thiophene-C9H19 units, VM5C9, has been evaluated by its implementation as active layer in organic thin-film transistors (OTFTs). The photophysical properties of VM5C9 were previously studied by UV–vis absorption and emission spectroscopy in both dilute solutions and thin films. The latter were prepared from solutions in toluene, chloroform (CHCl3), dichloromethane (CH2Cl2) and tetrahydrofuran (THF) by spin-coating on substrates following by an annealing to a controlled temperature ranging from 60 °C to 90 °C. Thin-film morphology and structure were characterized by X-ray diffraction and scanning electron microscopy. Solution processed thin films lead to glassy films. An optimized hole mobility up to 3.8 × 10−4 cm2/V s could be reached by a fine control of the liquid-phase deposition method, the choice of solvent and post-annealing temperature.