ABSTRACT
Highly crystalline thin films of organic semiconductors offer great potential for fundamental material studies as well as for realizing high-performance, low-cost flexible electronics. The fabrication of these films directly on inert substrates is typically done by meniscus-guided coating techniques. The resulting layers show morphological defects that hinder charge transport and induce large device-to-device variability. Here, a double-step method for organic semiconductor layers combining a solution-processed templating layer and a lateral homo-epitaxial growth by a thermal evaporation step is reported. The epitaxial regrowth repairs most of the morphological defects inherent to meniscus-guided coatings. The resulting film is highly crystalline and features a mobility increased by a factor of three and a relative spread in device characteristics improved by almost half an order of magnitude. This method is easily adaptable to other coating techniques and offers a route toward the fabrication of high-performance, large-area electronics based on highly crystalline thin films of organic semiconductors.
ABSTRACT
A model that describes solvent evaporation dynamics in meniscus-guided coating techniques is developed. In combination with a single fitting parameter, it is shown that this formula can accurately predict a processing window for various coating conditions. Organic thin-film transistors (OTFTs), fabricated by a zone-casting setup, indeed show the best performance at the predicted coating speeds with mobilities reaching 7 cm2 V-1 s-1 .
