ESR and LESR X-band study of morphology and charge carrier interaction in blended P3HT–SWCNT and P3HT–PCBM–SWCNT solid thin films

An electron spin resonance (ESR) X-band study of regio-regular poly(3-hexylthiophene) (RR-P3HT) and RR-P3HT/PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) composites blended with a low concentration (∼0.1–1%) of single wall carbon nanotubes (SWCNT) is presented. The substantial line-width broadening of polaron and PCBM anion radical ESR spectra was registered after SWCNT incorporation. The possibility of an electron spin exchange interaction between SWCNT conductive electrons and polymer polarons in the RR-P3HT:SWCNT blend without light illumination and between SWCNT conductive electrons and polymer polarons and PCBM anion radical electrons in the RR-P3HT:PCBM:SWCNT blend under light illumination is discussed. In addition, the unusually significant RR-P3HT film morphology (dominant crystalline phase orientation) is substantially altered, in particular a rotation of up to 90° of the P3HT crystalline phase relative to the film plane, due to SWCNT annexation in the polymer, is registered by the ESR spectra external magnetic field angular dependences.

► An electron exchange between SWCNT conductive electrons and P3HT polarons.
► The exchange rate of ∼0.02 μs is comparable with the T2 of the P3HT polaron at 77 K.
► The P3HT aromatic ring is parallel to the film plain in the metallic SWCNT:P3HT film.