Understanding heterogeneous nucleation in binary, solution-processed, organic semiconductor thin films

Heterogeneous nucleation is often the precursor to crystallization in solution-processed organic semiconductor thin films. Here, we study the efficacy of a series of nine small-molecule organic semiconductor additives in seeding the crystallization of solution-processable triethylsilylethynyl anthradithiophene (TES ADT). By systematically varying the concentrations of the additives in TES ADT thin films, we found the tendency of the additives to crystallize, their solubility in the casting solvent, and their similarity in chemical structure to TES ADT, to determine the nucleation and resulting density of nuclei. Tracking the crystallization process further yields information about the mechanism of nucleation. While pure TES ADT nucleates instantaneously at the onset of crystallization, nucleation transitions to a distributed process occurring throughout crystallization with the incorporation of increasing amounts of additives.