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

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.