For organic semiconductor crystals exhibiting anisotropic charge transport along different crystallographic directions, nanoconfinement is a powerful strategy to control crystal orientation by aligning the fast crystallographic growth direction(s) with the unconfined axis(es) of nanoconfining scaffolds. Here, design rules are presented to relate crystal morphology, scaffold geometry, and orientation control in solution-processed small-molecule crystals. Specifically, organic semiconductor triisopropylsilylethynyl pyranthrene needle-like crystals with a dimensionality ofn= 1 and perylene platelike crystals withn= 2 were grown from solution within nanoconfining scaffolds comprising cylindrical nanopores with a dimensionality ofm= 1, representing one unconfined dimension along the cylinder axis, and those comprising nanopillar arrays with a dimensionality ofm= 2. Form=nsystems, native crystal growth habits were preserved while the crystal orientation inn=mdirection(s) was dictated by the geometry of the scaffold. Forn≠msystems, on the other hand, orientation control was restricted within a single plane, either parallel or perpendicular to the substrate surface. Intriguingly, control over crystal shape was also observed for perylene crystals grown in cylindrical nanopores (n>m). Within the nanopores, crystal growth was restricted along a single direction to form a needle-like morphology. Once growth proceeded above the scaffold surface, the crystals adopted their native growth habit to form asymmetric T-shaped single crystals with concave corners. These findings suggest that nanoporous scaffolds with spatially-varying dimensionalities can be used to grow single crystals of complex shapes.
ASJC Scopus subject areas
- Condensed Matter Physics