Photoexcited Defects In Poly(3-Methylthiophene) - Light-Induced Electron-Spin-Resonance And Photoinduced Absorption

Light induced electron spin resonance (LESR) and photoinduced absorption (PA) are reported for poly(3-methylthiophene) (P3MT). The LESR is composed of a single line at g congruent-to 2 whose position, width and intensity are dependent on the exciting photon energy, h-omega-L. The LESR line intensity shows a sharp peak at 2.05 eV, where the line is the narrowest and it has the smallest g. The PA spectrum is composed of infrared active vibrations (IRAV) absorption bands and two midgap electronic bands, at 0.39 and 1.28 eV. The intensity of these three features as a function of h-omega-L is similar to each other and shows a sharp peak at 2.10 eV. Based on these observations, the possible spin-charge relationships for the photoinduced defects are discussed.