The Photoluminescence of Poly(methylphenylsilylene): The Origin of the Long-Wavelength Broad Band

The photoluminescence of poly(methylphenylsilylene) consists of a relatively sharp band at 350 nm and a significantly broad band in the 400-500-nm region. The luminescence behavior is investigated at low temperatures in an effort to identify the origin of the long-wavelength broad emission. The excitation spectra differ for the sharp and the broad emission bands: The broad emission band is more enhanced when the excitation is carried out at the π,π* absorption band of the phenyl substituent as compared to the excitation at the σ,σ* absorption band of the silicon skeleton. The lifetimes are of the order of picoseconds for both the sharp and the broad bands. The intensity of the broad emission monotonically decreases as the temperature increases from 4.2 K to ~180 K, whereas the intensity of the sharp emission remains nearly constant. From these experiments together with the previous theoretical considerations we conclude that the broad emission band is an emission from the intrapolymer skeleton σ to pendant π* charge transfer state.