Fine structure of thermoluminescence assisted by molecular vibrations in disordered organic semiconductors

The article deals with the issue of the influence of a separate mode of molecular vibrations on the formation of the thermoluminescence from disordered systems with quasi-continuous spectra of localized carriers. The contribution of vibrations is noticeable if the energy of their quanta is close to the depth of some localized carriers and the transition of the carrier into the conductive region occurs via absorption of these quanta. At some value of a carrier-vibration interaction, the effect manifests itself in the appearance of a fine discrete structure on the generally smooth thermoluminescence curve. The thermoluminescence of polymers is calculated using the model of non-adiabatic transitions, in which the carrier-vibrational interaction is determined by the displacements of nuclei in the presence of the carrier. The dependence of the arising discrete structure of the thermoluminescence curve on a number of parameters of the system like the magnitude of the carrier-vibration interaction, the width of vibrational levels, the parameters of the conductive region is investigated. The processes with participation of multiple quanta of vibrations are investigated and the formation of repetitive structures on the thermoluminescence curve has been shown owing to the absorption of several vibrational quanta. Analysis of a number of experiments is presented using the suggested theory.