Universal selection rule for surfactants used in miniemulsion processes for eco-friendly and high performance polymer semiconductors

Abstract

Commercial interest in the environmentally friendly processing of polymer semiconductors is on the rise. To reduce noxious solvent use and to realize water-borne colloids of polymer semiconductors, we developed a universal and eco-friendly miniemulsion process to satisfy four essential criteria: (1) efficient emulsification for synthesizing small and uniform polymer semiconductor particles, (2) efficient coalescence of particles to yield high quality thin films with low roughness and high fill-factors, (3) efficient removal of residual surfactants, and (4) high ordering of polymers within particles. We screened various surfactants to find conditions that satisfied the suggested selection rules regardless of the charge polarity and molecular structure of the polymer semiconductor. Our universal method can be applied to first-generation polythiophene derivatives as well as to the latest p-type, n-type and ambipolar polymers with planar backbones and high charge carrier mobility. Using these results, we fabricated for the first time a high-performance complementary inverter and a photodiode using water as a processing solvent.