Tunable Yellow-Red Photoluminescence and Persistent Afterglow in Phosphors Ca₄LaO(BO₃)₃:Eu³⁺ and Ca₄EuO(BO₃)₃

Abstract

In most Eu activated phosphors, only red luminescence from the D is obtainable, and efficiency is limited by concentration quenching. Herein we report a new phosphor of CaLaO(BO):Eu (CLBO:Eu) with advanced photoluminescence properties. The yellow luminescence emitted from the D states is not thermally quenched at room temperature. The relative intensities of the yellow and red emission bands depend strongly on the Eu doping concentration. More importantly, concentration quenching of Eu photoluminescence is absent in this phosphor, and the stoichiometric compound of CaEuO(BO) emits stronger luminescence than the Eu doped compounds of CLBO:Eu; it is three times stronger than that of a commercial red phosphor of YO:Eu. Another beneficial phenomenon is that ligand-to-metal charge transfer (CT) transitions occur in the long UV region with the lowest charge transfer band (CTB) stretched down to about 3.67 eV (∼330 nm). The CT transitions significantly enhance Eu excitation, and thus result in stronger photoluminescence and promote trapping of excitons for persistent afterglow emission. Along with structure characterization, optical spectra and luminescence dynamics measured under various conditions as a function of Eu doping, temperature, and excitation wavelength are analyzed for a fundamental understanding of electronic interactions and for potential applications.

Tunable photoluminescence of apatite phosphor Ca5.95−xSrxLa4(SiO4)2(PO4)4O2:0.05Eu2+ and its application in light‐emitting diodes

“…Figure A displays the crystal structure of the Ca 2.95 Sr 3 La 4 (SiO 4 ) 2 (PO 4 ) 4 O 2 :0.05Eu 2+ unit cell, which was chosen to represent the series of phosphors. It clearly shows that Ca 2.95 Sr 3 La 4 (SiO 4 ) 2 (PO 4 ) 4 O 2 :0.05Eu 2+ has a layered structure and the cell contains two types of cation sites, that is, the intraformational site M(I) and the interlaminar site M(II) . Moreover, the specific coordination environments of the two cation sites are depicted in Figure B,C.…”

Delayed Concentration Quenching of Luminescence Caused by Eu3+-Induced Phase Transition in LaSc3(BO3)4

“…An alternative strategy is finding quenching-free phosphors in appropriate hosts. A higher amount of Eu 3+ in the crystal cell is expected to have more absorption, and thus, numerous highly Eu 3+ -doped phosphors have been reported, for example, Ca 8 MgLu­(PO 4 ) 7 :Eu 3+ , Ba 6 Gd 2 Ti 4 O 17 :Eu 3+ , Ca 3 Y 2 B 4 O 12 :Eu 3+ , and so on. − Being different from those cases, a polymorphism compound LaSc 3 (BO 3 ) 4 (LSBO) is selected for Eu 3+ in this work. − We find that there always are two phases, a monoclinic α-LSBO and a trigonal β-LSBO, coexisting and constantly changing with different concentration of Eu 3+ doping. The phase transition induced by the doping concentration of the activator and the changes of luminescent properties caused by the transition are then studied in detail.…”

A red-emitting Sr3La(1−x)Eux(AlO)3(BO3)4 phosphor with high thermal stability and color purity for near-UV-excited wLEDs

“…All the uorescence intensities show the trend of fast decay rst and then slow decrease. And the Eu 3+ decay curves of Sr 3 La 1Àx Eu x (AlO) 3 (BO 3 ) 4 (x ¼ 10, 20, 40, 60, 80, 100 mol%) samples can be well tted with a second-order exponential decay equation (defects in the samples might act as the channels of non-radiative relaxation) as: 32,33 IðtÞ…”