Anomalous Orange Light-Emitting (Sr,Ba)2SiO4:Eu2+ Phosphors for Warm White LEDs

Dawei Wen, Hiroki Kuwahara, Hideki Kato, Makoto Kobayashi, Yasushi Sato, Takaki Masaki, Masato Kakihana

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

Phosphors with sufficient red emission component are necessary for warm white light-emitting diodes. In this work on (Sr,Ba)2(1-x)Eu2xSiO4 phosphors, (Sr,Ba)1.5Eu0.5SiO4 achieved 75% of an internal quantum efficiency under excitation by blue light. Surprisingly, the (Sr,Ba)1.5Eu0.5SiO4 exhibited orange emission, against the well-known traditional green-yellow emission of (Sr,Ba)2SiO4:Eu2+. Moreover, the concentration quenching of Eu2+ in (Sr,Ba)2SiO4 was abnormally unobvious. With the help of calculations based on the density functional theory, it was discovered that the distinct local environment of luminescence centers rather than usual explanation such as self-absorption or intensified crystal field splitting, is responsible to the interesting red shifts in excitation and emission spectra. The refinement analysis based on X-ray diffraction revealed that the unequal distribution of Eu2+ to two crystallographic sites caused low concentration of Eu2+ at the 9-coordination site, inhibiting the concentration quenching. The (Sr,Ba)1.5Eu0.5SiO4 phosphor has warmer emission than the commercial Y3Al5O12:Ce3+. This study also promotes research on the effect of site occupancy and the local environment of luminescence centers.

Original languageEnglish
Pages (from-to)11615-11620
Number of pages6
JournalACS Applied Materials and Interfaces
Volume8
Issue number18
DOIs
Publication statusPublished - 2016 May 11

Keywords

  • color tuning
  • orange emission
  • phosphor
  • site occupancy
  • white LED

ASJC Scopus subject areas

  • Materials Science(all)

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