Solvent-vapor induced self-assembly of a conjugated polymer: A correlation between solvent nature and transistor performance

A systematical investigation on solvent-vapor annealing in polymer thin film transistors is performed using a thiazolothiazole-bithiazole conjugated polymer as the active layer. Film morphology, packing order and device performance are closely related to polarity and solubility parameter of the annealing solvent and annealing time. The formation of highly ordered and closely connected fibrillar domains is realized by using a solvent with similar solubility parameter and polarity to the conjugated polymer. Field-effect transistors based on pristine polymer films exhibit a highest charge carrier mobility of 0.0067 cm(2) V-1 s(-1). After solvent vapor annealing with THF for 48 h, the mobility boosts up to 0.075 cm(2) V-1 s(-1). This correlation between solvent polarity, solubility parameter and film morphology, packing order and mobility provides a useful guideline towards high performance polymer thin film transistors with solvent-vapor annealing method. (C) 2012 Elsevier BM. All rights reserved.