Effects of Evaporation Velocity and Film Thickness on Poly(3-Hexylthiophene) Thin Films Processed from Aggregate Dispersions in Binary Solvent Mixtures

Aggregate dispersions of P3HT in two series of solvent mixtures, chloroform: dichloromethane and toluene: dichloromethane, are used to study the impact of the evaporation velocity and film thickness on the P3HT films processed using two spin-coating speeds (1000 rpm and 2000 rpm). The structural order and surface morphology were investigated with UV/Vis absorption spectroscopy and atomic force microscopy techniques. There is no evidence that the characteristics of the liquid phase P3HT dispersions impact the structures of the films, which is in agreement with a previous study of drop cast P3HT films that were dried over much longer time periods. An association is observed between the extent of aggregation in the liquid phase and the thickness and surface roughness parameters of the films. However, the structural order does not correlate with the thickness of the films, which was previously reported for polymer films processed from amorphous polymer solutions in pure organic solvents. (C) 2016 Wiley Periodicals, Inc.