Published August 20, 2021 | Version v1
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Understanding thermal quenching of photoluminescence in oxynitride phosphors from first principles

  • 1. Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Chemin des étoiles 8, bte L07.03.01, B-1348 Louvain-la-neuve, Belgium
  • 2. European Theoretical Spectroscopy Facility
  • 3. MCHC R&D Synergy Center, Inc. 1000, Kamoshida-cho Aoba-ku, Yokohama, 227-8502, Japan

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Description

Understanding the physical mechanisms behind thermal effects in phosphors is crucial for white light-emitting device (WLEDs) applications, as thermal quenching of their photoluminescence might render them useless. We analyze from first-principles, before and after absorption/emission of light, two chemically close Eu-doped Ba₃Si₆O₁₂N₂ and Ba₃Si₆O₉N₄ crystals for WLEDs. The first one has an almost constant emission intensity with increasing temperature whereas the other one does not. Our results, in which the Eu-5d levels are obtained inside the band gap thanks to the removal of an electron from the 4f⁷ shell, and the atomic neighborhood properly relaxed in the excited state, attributes the above-mentioned experimental difference to an autoionization model of the thermal quenching, based on the energy difference between Eu 5d and the conduction band minimum. Our depleted-shifted 4f method can identify luminescent centers and therefore allows for effective crystal site engineering of luminescent centers in phosphors from first principles.

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References

Journal reference (Paper in which the method is described)
S. Poncé, Y. Jia, M. Giantomassi, M. Mikami, and X. Gonze, J. Phys. Chem. C 120, 4040 (2016)., doi: 10.1021/acs.jpcc.5b12361