First-principles calculations of oxygen vacancies and cerium substitution in lutetium pyrosilicate

Cerium-doped lutetium pyrosilicate (LPS:Ce) has attracted much attention for its extensive applications. However, oxygen vacancies will lower its luminescent efficiency. The charge transfer transition between cerium ions and neighboring oxygen vacancies has a long decay time. First-principles calculations on oxygen vacancies, cerium substitution and their complexes in LPS have been performed to research their influence on luminescence. The bridging-oxygen vacancy has the lowest formation energy among oxygen vacancies. We discuss the process of luminescence quenching due to oxygen vacancies. The cerium substitution is less favorable in the oxygen-rich condition. The defect complex of the cerium substitution and bridging-oxygen vacancy has the lowest formation energy among defect complexes. The charge transfer transition between cerium ions and neighboring oxygen vacancies is not related to it but to other two defect complexes. All defect complexes have high formation energies in oxygen-rich condition. We discuss the density of states of perfect and defective crystals. - Highlights: → Bridging-oxygen vacancy is dominant among all the oxygen vacancies. → Ce substitution decreases with the increase of the oxygen abundance. → Bridging-oxygen vacancy and Ce substitution complex is the dominant defect complex. → The charge transfer transition can be suppressed under oxygen-rich condition.