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Published online by Cambridge University Press: 01 February 2011
The morphology and organic field effect transistor (OFETs) properties of two component blends of semicrystalline 6,13-bis(triisopropylsilylethinyl)pentacene (TIPS-pentacene) with selected amorphous and semi-crystalline low permittivity side chain aromatic insulating binders deposited at room temperature under vacuum from a good solvent are reported. When blended with an amorphous binder there is evidence from XPS for strong interaction between TIPS-pentacene and binder in the solidified film giving rise to twisted TIPS-pentacene crystals containing dislocations. Due to this strong interaction we see no evidence of segregation of TIPS-pentacene towards the active interface and hence we observe a rapid fall off in saturated hole mobility at a active concentration less than 50 wt-%. When blended with a crystalline binder there is no evidence from XPS of any interaction between TIPS-pentacene and binder in the solidified film. We propose that when a crystalline binder is used, which crystallizes more slowly from solution than TIPS-pentacene, we observe stratification of the active material to both interfaces and as a result an increase of saturated hole mobility to 0.4 cm2/Vs at 20 wt-% in isotactic poly(vinylbisphenyl). The potential application of the approach are in the formulation of low cost organic semiconductors whose solution and solid state properties can be fine tuned by careful binder selection.