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Thermally stable and highly efficient red-emitting Eu³⁺-doped Cs₃GdGe₃O₉ phosphors for WLEDs: non-concentration quenching and negative thermal expansion.

ABSTRACT: Red phosphor materials play a key role in improving the lighting and backlit display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). However, the development of a red phosphor with simultaneous high efficiency, excellent thermal stability and high colour purity is still a challenge. In this work, unique non-concentration quenching in solid-solution Cs₃Gd_1?-?xGe₃O₉:xEu³⁺ (CGGO:xEu³⁺) (x?=?0.1-1.0) phosphors is successfully developed to achieve a highly efficient red-emitting Cs₃EuGe₃O₉ (CEGO) phosphor. Under the optimal 464?nm blue light excitation, CEGO shows a strong red emission at 611?nm with a high colour purity of 95.07% and a high internal quantum efficiency of 94%. Impressively, this red-emitting CEGO phosphor exhibits a better thermal stability at higher temperatures (175-250?°C, >90%) than typical red K₂SiF₆:Mn⁴⁺ and Y₂O₃:Eu³⁺ phosphors, and has a remarkable volumetric negative thermal expansion (coefficient of thermal expansion, ??=?-5.06?×?10^-5/°C, 25-250?°C). By employing this red CEGO phosphor, a fabricated pc-WLED emits warm white light with colour coordinates (0.364, 0.383), a high colour rendering index (CRI?=?89.7), and a low colour coordinate temperature (CCT?=?4508?K). These results indicate that this highly efficient red-emitting phosphor has great potential as a red component for pc-WLEDs, opening a new perspective for developing new phosphor materials.

SUBMITTER: Dang P

PROVIDER: S-EPMC7851390 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Thermally stable and highly efficient red-emitting Eu3+-doped Cs3GdGe3O9 phosphors for WLEDs: non-concentration quenching and negative thermal expansion.

Dang Peipei P Li Guogang G Yun Xiaohan X Zhang Qianqian Q Liu Dongjie D Lian Hongzhou H Shang Mengmeng M Lin Jun J

Light, science & applications 20210201 1

Red phosphor materials play a key role in improving the lighting and backlit display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). However, the development of a red phosphor with simultaneous high efficiency, excellent thermal stability and high colour purity is still a challenge. In this work, unique non-concentration quenching in solid-solution Cs3Gd1 - xGe3O9:xEu3+ (CGGO:xEu3+) (x = 0.1-1.0) phosphors is ...[more]

PMID: 33526788

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Project description:Eu3+-activated Ba2Y5B5O17 (Ba2Y5-x Eu x B5O17; x = 0.1-1) red-emitting phosphors were synthesized by the conventional high temperature solid-state reaction method in an air atmosphere. Powder X-ray diffraction (XRD) analysis confirmed the pure phase formation of the as-synthesized phosphors. Morphological studies were performed using field emission-scanning electron microscopy (FE-SEM). The photoluminescence spectra, lifetimes, color coordinates and internal quantum efficiency (IQE) as well as the temperature-dependent emission spectra were investigated systematically. Upon 396 nm excitation, Ba2Y5-x Eu x B5O17 showed red emission peaking at 616 nm which was attributed to the 5D0 → 7F2 electric dipole transition of Eu3+ ions. Meanwhile, the influences of different concentrations of Eu3+ ions on the PL intensity were also discussed. The optimum concentration of Eu3+ ions in the Ba2Y5-x Eu x B5O17 phosphors was found to be x = 0.8. The concentration quenching mechanism was attributed to the dipole-dipole interaction and the critical distance (R c) for energy transfer among Eu3+ ions was determined to be 5.64 Å. The asymmetry ratio [(5D0 → 7F2)/(5D0 → 7F1)] of Ba2Y4.2Eu0.8B5O17 phosphors was calculated to be 3.82. The fluorescence decay lifetimes were also determined for Ba2Y5-x Eu x B5O17 phosphors. In addition, the CIE color coordinates of the Ba2Y4.2Eu0.8B5O17 phosphors (x = 0.653, y = 0.345) were found to be very close to the National Television System Committee (NTSC) standard values (x = 0.670, y = 0.330) of red emission and also showed high color purity (∼94.3%). The corresponding internal quantum efficiency of the Ba2Y4.2Eu0.8B5O17 sample was measured to be 47.2%. Furthermore, the as-synthesized phosphors exhibited good thermal stability with an activation energy of 0.282 eV. The above results revealed that the red emitting Ba2Y4.2Eu0.8B5O17 phosphors could be potential candidates for application in near-UV excited white light emitting diodes.

Dataset Information

Thermally stable and highly efficient red-emitting Eu³⁺-doped Cs₃GdGe₃O₉ phosphors for WLEDs: non-concentration quenching and negative thermal expansion.

Publications

Thermally stable and highly efficient red-emitting Eu<sup>3+</sup>-doped Cs<sub>3</sub>GdGe<sub>3</sub>O<sub>9</sub> phosphors for WLEDs: non-concentration quenching and negative thermal expansion.

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