Photoluminescence investigations and thermal activation energy evaluation of Fe3+-doped PVA films

In this work, we study the inclusion mechanism of Fe3+ ions in a polyvinyl alcohol (PVA) matrix. Pure and Fe3+-doped PVA films, using FeCl3 solution, are prepared by a solution casting method. The effect of Fe3+ doping on the photoluminescence (PL) behavior of PVA is investigated in the temperature range from 10 to 300 K. The PL intensity is found to decrease as the temperature increases for the samples slightly doped. This behavior is attributed to the phonon diffusion by the photo-created electron–hole pairs. However, this behavior is completely inverted when the content of Fe3+ increases. The first author has already published a work discussing the possible explanations of such a behavior where the PL intensity increases with temperature. This paper is devoted to study the thermal activations energy and its variation with doping. Therefore, the PL integrated intensity as a function of 1/T is simulated by the Arrhenius model for the samples whose PL intensity decreases with temperature. However, for the other samples, a model of two activation energies is used. The gap energy values and the PL spectra of all samples at 300 K were used to justify the suggested transitions.