Process-dependent conductivity and film homogeneity of slot-die-coated PEDOT:PSS-PVA composite films

In this study, we investigate the impact of process parameters on homogeneity and electrical conductivity of slot-die-coated PEDOT:PSS-PVA composite films that are doped with DMSO. Due to a strong correlation between conductivity and morphology of PEDOT:PSS films and the latter's dependency on the processing step itself, we apply slot die coating for maximized process control and systematically evaluate the impact of coating gap, speed, and film thickness. Since the entire coating and drying process is run in batch mode, the setup is optimized regarding steady-state conditions and high homogeneity of the films. Overall, for the films manufactured in batch mode, we obtain a reproducibility film thickness of 99% and a low deviation from the set film thickness (below 8%). In order to analyze the impact of the coating parameters, stable operating points derived from the viscocapillary model are chosen and either the dimensionless gap or the capillary number is varied. Coating gap and film thickness emerged as dominating parameters, leading to an increase in conductivity of 40% and 70%, respectively, or, when changing both simultaneously, of 157%. Only a minor impact of shear forces (increase of 10%) was found.