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Understanding of Luminescence Properties Using Direct Measurements on Eu 2+ ‐Doped Wide Bandgap Phosphors
Author(s) -
Amin Muhammad Ruhul,
Strobel Philipp,
Qamar Amir,
Giftthaler Tobias,
Schnick Wolfgang,
Moewes Alexander
Publication year - 2020
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.202000504
Subject(s) - phosphor , luminescence , materials science , spectroscopy , band gap , excited state , photoluminescence , doping , europium , analytical chemistry (journal) , direct and indirect band gaps , optoelectronics , atomic physics , chemistry , physics , quantum mechanics , chromatography
Abstract Recent developments in solid‐state lighting lead to a demand for new phosphors with excellent thermal stability, exhibiting large bandgaps for highly efficient emission. A detailed characterization of the luminescent material AELi 2 Be 4 O 6 :Eu 2+ (AE = Ba, Sr) is presented using soft X‐ray absorption spectroscopy, X‐ray emission spectroscopy, X‐ray excited optical luminescence (XEOL) spectroscopy, and density functional theory (DFT) calculations. The experimental indirect bandgap for both BaLi 2 Be 4 O 6 :Eu 2+ (BLBO:Eu) and SrLi 2 Be 4 O 6 :Eu 2+ (SLBO:Eu) is found to be 6.5 ± 0.3 eV, which agrees well with the DFT calculations (6.8 eV for BLBO:Eu and 7.4 eV for SLBO:Eu). The crucial Eu 2+ 5d to conduction band energy separation is determined to be 0.21 ± 0.10 and 0.25 ± 0.10 eV for BLBO:Eu and SLBO:Eu, respectively, using resonant inelastic X‐ray scattering. These measured values are in good agreement with the thermal quenching measurements (0.20 ± 0.03 eV for BLBO:Eu and 0.26 ± 0.03 eV for SLBO:Eu). Finally, the XEOL measurement confirms the Eu 2+ 5d 1 4f 6 → 4f 7 transition, which is responsible for the ultranarrow band (full width at half‐maximum: 25 nm) blue optical luminescence at 455–457 nm for both compounds. With these measurements and calculations, deep insights are gained into the key properties of those two phosphors.