Orientation effects in self-organized, highly conducting regioregular poly(3-hexylthiophene) determined by vacuum ultraviolet spectroscopy

The performance of devices based on conducting polymers is highly dependent on the organization of the polymer chains with respect to the device structure. We present a method to probe the organization of the polymers that makes use of the σ–σ* transitions in alkyl CC and CH bonds of the conducting polymer poly(3-hexylthiophene) (P3HT).

The vacuum ultraviolet (VUV) absorption properties of these transitions are highly anisotropic due to the absorption mechanism where maximum absorption takes place when the bond vector is parallel to the electric field vector of the VUV photons. There are large differences in the VUV absorption spectra in the 120–150nm range of respectively spincoated and cast films of the polymer.

If knowledge of the polymer organization is available by other means, i.e. X-ray diffraction a simple VUV absorption spectrum can be used to determine the orientation of a given sample preparation.