Speaker
Description
White light-emitting diodes (WLEDs) have become ubiquitous in modern society because they last longer and use less energy than their predecessors. There are two popular approaches to achieving white light in LEDs: combining a blue LED with a yellow phosphor ($YAG:Ce³⁺$) or using a UV-LED with blue, green, and red (RGB) phosphors. Unfortunately, the blue LED and $YAG:Ce³⁺$ combination exhibits poor color rendering and high color-correlated temperature (CCT), while the UV-LED with RGB phosphors suffers from re-absorption. A single-activator phosphor that simultaneously emits blue, green/yellow, and red light to produce white light would address these challenges. In this work, single-activated warm-white-emitting phosphors were achieved. Garnet-type $Ca₂YZr₂Al₃O₁₂:Dy³⁺$ phosphors that absorb n-UV radiation were synthesized using the high-temperature solid-state reaction method. They adopt to a cubic crystal structure consisting of dodecahedral $Ca/YO_8$, octahedral $ZrO_6$, and tetrahedral $AlO_4$ frameworks. $Dy³⁺$ ions preferentially occupy the low symmetry $Ca/Y$ site. The $Ca/YO_8$ dodecahedron consists of two types of bond lengths, $Ca/Y-O_1$ and $Ca/Y-O_2$, causing the site to deviate from inversion symmetry (i.e., a non-centrosymmetric site). Because $Dy³⁺$ occupies this non-centrosymmetric site, a dominant yellow ($^4F_{9/2}\rightarrow^6H_{13/2}$, 580 nm) electric-dipole transition and a less dominant blue ($^4F_{9/2}\rightarrow^6H_{15/2}$, 481 nm) magnetic-dipole transition are observed, resulting in warm white emission with a low CCT < 3500 K. Our results demonstrate that n-UV excitable $Ca₂YZr₂Al₃O₁₂:Dy³⁺$ warm-white emitting phosphors have strong potential for application in WLEDs.
| Apply for student award at which level: | PhD |
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| Consent on use of personal information: Abstract Submission | Yes, I ACCEPT |