In situ Studies on the Kinetic Controlled Morphology Development of Conjugated Polymer Films Processed by Blade Coating

Abstract

The thin-film morphology of conjugated polymers regulated by coating conditions can significant impact on electrical properties in organic field-effect transistors. Here, we analyze thin-film morphology of blade-coated poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)) thin-films varying with the solvent and coating temperature. In order to achieve P(NDI2OD-T2) thin-films revealing large polymer domain, elongated packing structure and predominant face-on orientations, the consideration of pre-aggregation of P(NDI2OD-T2) in solution and the amount of thermal energy from coating temperature is crucial during film formation. The direct investigation of evolution of film formation is highly desirable with in situ measurements. By combining in situ UV-Vis spectroscopy and in situ grazing incidence wide angle X-ray scattering, we observed five stages which appear during blade coating. The insight will offer fundamental understanding of the relationship between film morphologies and charge transport properties as well as a potentially powerful method to control film microstructure of various organic electronics.