The synergistic role of azeotropic solvent mixtures and atactic polystyrene on the morphology, crystallization and field effect mobility of thin film 6,13-bis(triisopropylsilylethynyl)-pentacene based semiconductors

The effect of anisole/decane binary solvent mixture and the subsequent addition of low wt% aPS on 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) thin film morphology is investigated by optical microscopy, AFM and UV–Vis measurements. We show that, over the composition range anisole/decane of 96/4 to 85/15 wt%, the solution maintains an azeotropic composition with the boiling point of the binary mixture remaining constant at 152 °C, and the solvent composition remaining constant during evaporation and drying. It was found that addition of up to 20 wt% decane has little impact on micro-scale crystal morphology but has a significant influence on the growth mode and terrace roughness. The formation of large crystals is explained in terms of the change in solvent, increase in decane content, weakening the solute–solvent interactions and promoting efficient nucleation of the favoured H-aggregates of TIPS-pentacene. The effect of the TIPS-pentacene—aPS ratio up to 20 wt% for drop-cast thin film was similarly investigated. It is found that addition of aPS has a significant effect on both macroscopic crystal properties such as surface coverage, unity of orientation and long range order. It also changes the surface morphology and layer ordering on the nano-scale.