Inner-shell excitation studies of conducting organic polymers: selenophene, 3-methyl selenophene, and their polymers

Inner-shell electron energy loss spectra (ISEELS) of gaseous selenophene and 3-methylselenophene in the regions of Se 3d, Se 3p, Se 3s, and C 1s are presented and analyzed. The ISEELS spectra are compared to the C 1s near-edge X-ray absorption fine structure (NEXAFS) spectra of the corresponding polymers deposited electrochemically onto Pt, both with and without doping, to form the electrically conducting state. Methyl substitution at the 3-position of the selenophene ring is found to have little effect on the intensity of the C 1s → π* transition, suggesting that the π manifold is relatively unaffected. The C 1s NEXAFS of thin polyselenophene and poly-3-methylselenophene films confirms that (1) the polymeric chain is composed of the same structural units as the monomers and (2) doping enhances electrical conductivity via a narrowing of the π–π* band gap. Keywords: core excitation, ISEELS, NEXAFS, conducting polymers.