Self-assembly of discotic molecules into mesoscopic crystals by solvent-vapour annealing

Solvent vapour annealing (SVA) is used to control the reorganization of ultrathin films of three different polycyclic aromatic hydrocarbons self-assembled on solid surfaces. To this end, two perylene-bis( dicarboximide) (PDI) derivatives exposing branched side alkyl chains with different length and a dodecyl substituted hexa-peri-hexabenzocoronene (HBC) have been used, in view of their n- and p-type semiconducting nature. For all the three molecules, nanoscopic crystals grown from solution by spin-coating and drop-casting undergo reorganization into sub-millimetric fibers, domes and needles, proving the general applicability of the SVA method. Moreover, such an approach exhibits a mass transport of the molecules on surfaces over hundreds of microns. The self-healing of the films through SVA treatment leads to a decrease of the structural defects and an increase in the lateral size of the self-assembled domains, ultimately providing an improved 3D conjugation. Therefore the SVA can be considered an important strategy with potential to enhance the performance of macroscopic organic electronic devices.