Solution-phase growth of organic single-crystal arrays

We have successfully developed a method for directly forming organic single-crystal thin films at designated locations on a substrate by solution-phase growth. An original micropattern, in which small rectangular regions were connected to a large rectangular region, was designed. The small regions and the large region were used as nucleation control regions (NCRs) and a growth control region (GCR), respectively. The key to success was to vary local supersaturation of a solution droplet by making a large difference in solvent evaporation between a NCR and a GCR. We found that the NCR played a very important role in forming a single nucleus and in investigating the possibility of control of the crystal orientation. By using the developed micropattern and controlling the solvent vapor pressure during growth, we fabricated single-crystal arrays of a stable organic semiconductor, 3,9-bis(4-ethylphenyl)-peri-xanthenoxanthene (C2Ph-PXX).