Uncommon photoluminescence behavior of Fe3+ doped polyvinyl alcohol films

In this paper, pure and Fe3+ doped polyvinyl alcohol (PVA) films, using FeCl3, 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. At 300 K, the PL spectrum of pure PVA is formed by two bands I1and I2. These two bands can be connected with trap states inside the band gap. The PL intensities of I1 and I2 are found to increase with increasing the doping content. The temperature dependence of the PL intensity for neat PVA shows a decrease in the PL intensity with temperature assigned to the phonon diffusion by the photo-created electron-hole pairs. However, the PL studies of some doped samples containing an important amount of iron reveal an uncommon behavior of their PL intensity which rises with temperature. Two suggestions are given to explain such a behavior. The first is related to the change in the levels nature inside the bandgap and the second is correlated to the (I1-I2) energy.