Effect of Al3+ ions on excitation energy transfer from fluorescent polyvinyl alcohol to Tb3+ ions

Abstract

The investigation of fluorescent polymers doped with various rare earth ions, particularly when sensitized by ultraviolet and visible radiation, is vital for improving the efficiency of photonic devices. In the present work, steady-state and time-domain photoluminescence measurements of fluorescent polyvinyl alcohol (PVA) films doped with Tb³⁺ and Al³⁺ ions were carried out to understand how the co-doping of Al³⁺ ions affects the optical properties of Tb³⁺ ions doped in the polymer matrix. A decrease in the intensity of the PVA fluorescence (450 nm) and phosphorescence (470 nm) emission bands, along with a corresponding reduction in decay times in the presence of Tb³⁺ ions, indicating energy transfer from PVA to Tb³⁺ with an efficiency of 41 %. With Al³⁺ ions, co-doping the PL intensity of the PVA fluorescence band increased, while the ⁵D₄ → ⁷F₆,_5,4 transition of the Tb³⁺ ion decreased, along with a reduction in decay time. These findings suggest that the presence of Al³⁺ ions reduces energy transfer by decreasing cross-relaxation processes and increasing the diversity of Tb³⁺ ion sites. This preliminary study highlights the potential for developing brighter, cost-effective optical materials with high photon flux control.