Enhancement in crystallinity of poly(3‐hexylthiophene) thin films prepared by low‐temperature drop casting

Abstract

AbstractLow‐temperature casting of high molecular weight (HMW > 40 kDa) regioregular poly(3‐hexylthiophene) (P3HT) is demonstrated to yield highly crystalline P3HT thin films with well defined and preferentially edge‐on oriented [(100) contact plane] nanocrystallites on the pure and silanized Si/SiO2 substrates. Transmission electron microscopy and X‐ray diffraction provide evidence for the increase in preferential edge‐on orientation of P3HT‐conjugated backbone while decreasing the film preparation temperature below room temperature. The optimum growth temperature is about −12°C for the given concentration (2 mg/mL in CHCl3). The reduced evaporation rate of the solvent results in a better selection of the thermodynamically stable orientation of nanocrystallites onto the substrate. The degree of preferential orientation and size of the crystallites can be further increased on n‐octadecyltrichlorosilane‐treated SiO2 substrates as well as by annealing the films at 200°C for 1 h. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012