A First‐Principles Study of the Energy Level Distributions of Oxygen Vacancy Defects in Eu‐Doped SrAl₂O₄

Abstract

Strontium aluminate doped with the europium(II) ion (SrAl₂O₄:Eu²⁺) is a versatile material with phosphor mechanoluminescent applications and static electricity‐induced luminescence properties. Oxygen vacancies play a crucial role in the mechanism governing the luminescence of SrAl₂O₄:Eu²⁺. The present study uses first‐principles calculations to estimate the energy level distribution of oxygen vacancies in europium‐doped strontium aluminate while considering the valence states of the luminescent Eu²⁺ and Eu³⁺ centers in the emission process. The results indicate that the energy levels of the oxygen vacancies are distributed ≈ 2.5 eV for Eu²⁺ and above 2.5 eV for Eu³⁺. Regardless of the charge states of the oxygen vacancies, their energy levels exhibit a relatively broad distribution owing to structural relaxation. The energy levels ε(0/1+) and ε(0/2+) of the oxygen vacancies shift toward the conduction band for Eu³⁺ relative to Eu²⁺. This finding is valuable for understanding the re‐excitation of electrons trapped in oxygen vacancies through external stimuli, such as thermal, mechanical, or electrical effects.