Rubbing effects on the structural and optical properties of poly(3-hexylthiophene) films

Steady state photoconductivity and x-ray diffraction combined with optical and electronic spectroscopies were applied to study spin coated poly(3-hexylthiophene) (P3HT) films mechanically rubbed using a teflon bar. As expected, photoconductivity evidenced a strong increase in the photo-response along the rubbing direction. But, while rubbing during annealing at a temperature of 70 °C resulted in a sizeable photocurrent anisotropy along the direction parallel or perpendicular to the rubbing, the samples rubbed at room temperature (RT) showed an isotropic and comparatively stronger enhancement of absorption and photoconductivity spectral features. According to these observations, rubbing at RT resulted in a significant increase in local order and macroscopic alignment of the film, while a higher degree of global order but with a relaxed local structure was obtained after rubbing at 70 °C.