Solvent effects on chain orientation and interchain π-interaction in conjugated polymer thin films: Direct measurements of the air and substrate interfaces by near-edge X-ray absorption spectroscopy

Near-edge x-ray absorption fine-structure spectroscopy (NEXAFS) was applied to investigate polymer structures and show that NEXAFS band shapes and intensities are also insensitive to the intermolecular π-interaction in regioregular poly(3-hexylthiophene) films. Delamination was used to expose the substrate interface and it was found that the interchain π-interaction was dependent on the deposition solvent quality. Direct imaging by friction-mode atomic force microscopy (AFM) revealed the expected presence of a mosaic surface morphology with a finer length scale than surface topography. The ability to directly measure chain segmental orientation and interaction at the interfaces could lead to a systematic optimization for even higher device performance. The results show that a strong modification of the NEXAFS spectra was observed and related to π-π interactions between chain segments.