Tuning the crystal structure of contorted hexabenzocoronene thin films for transistors applications

Though the structure of organic semiconductors in the active channels of thin-film transistors is known to impact device performance, controlling such structure has been a long-standing challenge. We demonstrate the ability to fine-tune the crystal packing of semiconducting contorted hexabenzocoronene (HBC) thin films via solvent-vapor annealing. Solvent-vapor annealing with weakly hydrogen-bonding solvents having large molar volumes preferentially yields the P21/c crystal structure of HBC. Annealing with solvent vapors having smaller molar volumes and stronger tendencies to hydrogen-bond coaxes HBC films to adopt a previously-unpublished crystal structure that is similar to that of the Pbcn structure. Elucidating the structures of HBC thin films when they are exposed to a myriad of solvent vapors has allowed us to produce a processing diagram, with which we have been able to predictively access different crystal structures for thin-film transistor applications.