Active control of evaporative solution deposition by modulated infrared illumination

We designed and built a highly adaptive and flexible system based on modulated infrared irradiation for the active control of evaporative material deposition suitable for solution processing of organic electronic materials. We performed systematic experiments using thick layers of a high molecular weight aqueous dispersion of poly(3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) nanoparticles as well as thin layers of light-emitting polymers in an organic solvent. We identified two complementary deposition modes, where material accumulates either in the illuminated or the nonirradiated regions, depending on the molecular weight of the solute and the solution layer thickness. We developed numerical models that account for heat transfer due to infrared illumination, solvent evaporation into the gas phase, and solute redistribution in the liquid layer. The computational results agree well with the experimental observations regarding the solute depletion and accumulation behavior.