The thin-film morphology, degree of crystallinity, as well as the electrical properties of triisopropylsilyl (TIPS) pentacene organic thin- film transistors (OTFTs) were significantly influenced by the solvent used for spin- coating a TIPS pentacene layer. The TIPS pentacene films spin- coated from solvents having high boiling points (chlorobenzene and xylene) showed dendritelike morphology and a higher degree of crystallinity, while TIPS pentacene spin- coated from solvent having a low boiling point (chloroform) showed amorphous- like morphology and a lower degree of crystallinity. The field-effect mobility of OTFTs fabricated from chlorobenzene was 4 x 10(-2) cm(2)/V s, whereas mobility of 10(-4) to 10(-5) cm(2)/ V s was achieved when using chloroform. This implies that the morphology, crystallinity, as well as the electrical properties of TIPS pentacene have a strong dependence on the solvent used for spin- coating. (c) 2007 The Electrochemical Society.