Abstract

Electronicproperties of organic semiconductor (OSC) thin films are largely determined bytheir morphologies and crystallinities. However, solution-processed conjugatedsmall-molecule OSC thin films usually exhibit abundant grain boundaries andimpure grain orientations because of complex fluid dynamics during solutioncoating. Here, a novel methodology, water-surface drag coating, is demonstratedto fabricate high-quality OSC thin films with greatly enhanced charge transportproperties. This method utilizes the water surface to alter the evaporation dynamicsof solution to enlarge the grain size, and a unique drag-coating process toachieve the unidirectional growth of organic crystals. Using 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene(Dif-TES-ADT)

asan example, thin films with millimeter-sized single-crystal domains and purecrystallographic orientations are achieved, revealing a significant enhancement(4.7 times) of carrier mobility. More importantly, the resulting film can bedirectly transferred onto any desired flexible substrates, and

flexibletransistors based on the Dif-TES-ADT thin films show a mobility as high as 16.1cm² V^-1 s^-1, which represents the highestmobility value for the flexible transistors reported thus far. The method isgeneral for the growth of various high-quality OSC thin films, thus opening upopportunities for high-performance organic flexible electronics.

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