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

详细信息    查看全文

• 作者：Dawei Wen ; Hiroki Kuwahara ; Hideki Kato ; Makoto Kobayashi ; Yasushi Sato ; Takaki Masaki ; Masato Kakihana
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：May 11, 2016
• 年：2016
• 卷：8
• 期：18
• 页码：11615-11620
• 全文大小：427K
• 年卷期：0
• ISSN：1944-8252

文摘

Phosphors with sufficient red emission component are necessary for warm white light-emitting diodes. In this work on (Sr,Ba)_2(1–x)Eu_2xSiO₄ phosphors, (Sr,Ba)_1.5Eu_0.5SiO₄ achieved 75% of an internal quantum efficiency under excitation by blue light. Surprisingly, the (Sr,Ba)_1.5Eu_0.5SiO₄ 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)_1.5Eu_0.5SiO₄ 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.