Infrared photoexcitation spectroscopy in soluble derivatives of poly(p-phenylenevinylene) and composites with C60

We report detailed photoinduced absorption spectra of soluable derivatives of poly(p-phenylenevinylene), for example MEH-PPV and BCH-PPV, and their composites with C60, from 0.05 eV to 1.3 eV. The photoinduced absorption spectra of MEH-PPV and BCH-PPV are characterized by subgap electronic absorptions and associated infrared-active vibrational (IRAV) modes. Upon adding a few percent of C60 into both polymers, the photoinduced absorption spectra are significantly enhanced in magnitude and new peaks are found at 1.15 eV and 1.25 eV. The photoinduced charge transfer from conducting polymer onto C60 enhances the quantum efficiency for photogeneration of charge carriers, resulting in the enhanced IRAV modes of the conducting polymer and the appearance of 1.15 eV and 1.25 eV signatures associated with C60.