Molecular vibrations, activation energies of trapped carriers and additional structure in thermoluminescence of organic polymers

Abstract

Manifestations of optical vibrations in thermoluminescence of organic polymers were observed. Thermoluminescence curves and Raman spectra of the polymers which have different degrees of ordering: poly(di-n-hexylsilane), poly(methylphenylsilane) and poly(di-n-penthylsilane) were measured and the features on thermoluminescence curves were observed. Activation energies of localized charge carriers were found by the fractional thermally stimulated luminescence in the 5–50K temperature range. The shape of the thermoluminescence curve was calculated in the model which assumed that the release of carriers from traps may be activated via the energy transfer from the vibrations to the carriers. The model explained the appearance of the features on thermoluminescence curves and the coincidence of the carriers’ activation energies with the vibration quanta. Thermoluminescence shows (and the calculations support this claim) that the decrease of the degree of the polymer ordering causes a decrease of the number the discrete values of activation energies and of the number of the features on thermoluminescence curves.