Photoexcitation spectroscopy of poly(3-methylthiphene): Electronic bands and vibrational modes

Abstract Photoexcitation spectroscopy, including photoluminescence, resonant Raman scattering and photoinduced absorption in the energy range 0.1eV to 2.5eV, is reported for the conjugated polymer poly(3-methylthiophene). Photoinduced electronic bands and infrared active vibrations characteristic of bipolarons were observed. Amplitude mode analysis of the Raman and photoinduced infrared modes indicates for this non-degenerate ground state system a one-dimensional gap of ⋍2.2 eV and an extrinsic component of ⋍0.22 eV . Broad cw photoluminescence band with phonon side bands are observed below the band gap and is assigned to weakly bound excitons.