Photoinduced photoluminescence enhancement in CdSe quantum dot-polyvinyl alcohol composites

The effect of thermal annealing at 100 °C under irradiation by LED's light of 409 nm on the photoluminescence (PL) of polymer films of polyvinyl alcohol (PVA) and PVA films with embedded CdSe quantum dots (QDs) was investigated. X-ray diffraction study revealed that annealing increases a degree of crystallinity of the PVA matrix in the both films studied. In the PL spectra of the annealed QD-PVA composite, both an increase (up to thirteen-folds at room temperature) of the QD-related PL band and a small spectral shift toward the red spectrum region were found. The PL intensity at low temperatures and the activation energy of the PL thermal quenching also increased. In the PL spectra of pure PVA, a small decrease in the PL intensity and a red shift of the PL band were observed. The color of the composite film changed from yellow to slightly reddish with no changes in the PVA film transparency. The effect of PL enhancement in CdSe QD-PVA composite is ascribed to the improvement of QD surface defect passivation by the functional groups or the polymer chain fragments of PVA matrix caused by photochemical transformations in the polymer.