Rare-Earth-Free High-Efficiency Narrow-Band Red-Emitting Mg3Ga2GeO8:Mn4+ Phosphor Excited by Near-UV Light for White-Light-Emitting Diodes

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• 作者：Xin Ding ; Ge Zhu ; Wanying Geng ; Qian Wang ; Yuhua Wang
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：January 4, 2016
• 年：2016
• 卷：55
• 期：1
• 页码：154-162
• 全文大小：662K
• ISSN：1520-510X

文摘

A series of novel red emission Mg₃Ga₂GeO₈ (MGG):Mn⁴⁺ phosphors under near-UV (NUV) excitation are synthesized successfully by traditional high-temperature solid-state reaction. The structure of Mg₃Ga₂GeO₈ is investigated by high-resolution transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction (XRD) Rietveld refinement. It has one octahedral site and one tetrahedral site in the crystal structure. According to XRD and photoluminescence (PL) property analysis, Mn⁴⁺ can occupy an octahedral (Mg²⁺/Ga³⁺) site. The PL properties are investigated by diffuse-reflectance, emission, excitation, and temperature-dependent spectroscopy and decay curves. It can emit red light peaking at 659 nm under NUV excitation. The critical quenching concentration of Mn⁴⁺ was about 0.5 mol %. The concentration quenching mechanism could be a d–d interaction for the Mn⁴⁺ center. The CIE chromaticity coordinates and full-width at half-maximum are (0.295, 0.677) and 24 nm, respectively. It demonstrated that MGG:Mn⁴⁺ has high color purity. The PL intensity of MGG:0.5% Mn⁴⁺ drops to 72% when the temperature is raised up to 150 °C. Furthermore, MGG:0.5% Mn⁴⁺ exhibits outstanding quantum efficiency (64.7%). By tuning of the weight ratio of blue, green, and red phosphors, the fabricated white-light-emitting diodes using a 405 nm GaN NUV chip combined with a blend of blue phosphor BAM:Eu²⁺, green phosphor Sr₂SiO₄:Eu²⁺, and red-emitting phosphor MGG:Mn⁴⁺ driven by 40 mA current can get white light with chromaticity coordinates (0.316, 0.375) and CCT = 3340 K. This demonstrates that MGG:Mn⁴⁺ is a potential red phosphor matching NUV LED chips to get white light.