Solutal‐Marangoni‐Flow‐Mediated Growth of Patterned Highly Crystalline Organic Semiconductor Thin Film Via Gap‐Controlled Bar Coating

Abstract Application‐oriented patterned growth of organic semiconductor (OSC) thin films with single crystalline domains is crucial for fabricating sophisticated high‐performance organic‐electronic and optoelectronic devices; however, fabricating these patterned nanometer‐thick crystals in a simple, fast, and effective manner is a difficult task with a roll‐to‐roll printing process. Here, a simple bar‐coating approach to form an array of single‐crystal‐like OSC thin‐film patterns at a rate of a few millimeters per second is introduced. To this end, the processing parameters of a gap‐controlled bar‐coating method is optimized, including coating speed, crystal nucleation, and solution fluidics, which allow a high degree of morphological control of bar‐coated OSC films in an area of several centimeters. In particular, it is demonstrated that the solutal‐Marangoni flow induced by a suitable solvent additive can considerably improve molecular mass transport and induce favorable vertical phase separation. Thus, organic transistors based on the OSC patterns fabricated with the additive‐assisted bar coating show a field‐effect mobility of up to 20 cm 2 V −1 s −1 and superior operational stability. The proposed bar coating method will facilitate an industry‐level application of organic electronics.