Directing Organic Semiconductor Crystal Orientation and Shape using Nanoconfining Scaffolds

Because optoelectronic properties can vary significantly along different crystallographic directions, directing the orientation of organic semiconductor crystals is critical. Here we demonstrate a method to dictate crystal orientation by (mis)matching the crystal dimensionality with the geometry of the nanoconfining scaffolds. Specifically, nanoconfining scaffolds that limit crystal growth in one or two dimensions were used to confine the solution-phase crystallization of 1D needlelike triisopropylsilylethynyl pyranthrene (TIPS-PY) and 2D platelike perylene. For systems in which the crystal dimensionality matched the scaffold dimensionality, control over crystal orientation was observed in one dimension for TIPS-PY and two dimensions for perylene. For systems in which the dimensionalities were mismatched, orientation control was limited to a single dimension. Intriguingly, platelike perylene crystals grown within cylindrical nanopores were found to form unconventional T-shaped single crystals with concave 90^o corners. Inside the nanopores, crystal growth was confined in two directions, forcing crystals to grow in a needlelike shape. At the scaffold surface, however, crystal growth became unrestricted and fast growth along two directions resumed.