Tuning crystal polymorphs of a π-extended tetrathiafulvalene-based cruciform molecule towards high-performance organic field-effect transistors

It is a common phenomenon for organic semiconductors to crystallize in two or more polymorphs, leading to various molecular packings and different charge transport properties. Therefore, it is a crucial issue of tuning molecular crystal polymorphs (i.e., adjusting the same molecule with different packing arrangements in solid state) towards efficient charge transport and high performance devices. Here, the choice of solvent had a marked effect on controlling the growth of α-phase ribbon and β-phase platelet during crystallization for an indenofluorene (IF) π-extended tetrathiafulvalene (TTF)-based cruciform molecule, named as IF-TTF. The charge carrier mobility of the α-phase IF-TTF crystals was more than one order of magnitude higher than that of β-phase crystals, suggesting the importance of reasonably tuning molecular packing in solid state for the improvement of charge transport in organic semiconductors.