Rate equation model for fluorescence and phosphoresence in Eu³⁺ doped LaAlO₃

LaAlO₃ (LAP) doped with Europium is a phosphor widely used in lighting (LED) and display technologies. The electronic transitions that emit light show two distinct lifetimes that differ by orders of magnitude. The fast decay is attributed to relaxation from the ⁵D₀ state to the ⁷F_j ground states while the slower decay comes from repopulation of the ⁵D₀ state from charges trapped in lower energy states of the host material. To understand the charge migration mechanisms, we compare the calculated energy levels of Eu³⁺ in LaAlO₃ using density functional theory with the measured emission spectrum under uv excitations and find reasonable agreement. The measured decay dynamics of the excited population after 226 nm excitation shows a strong temperature dependence with a 35% increase in the trap to ⁵D₀ transfer rate over the 78-255 K range. Results will be discussed in the context of a simple rate equation model.