Tunable white light and energy transfer of Eu²⁺‐Tb³⁺‐Eu³⁺ tri‐activated glasses synthesized in air

Abstract

An ever increasing demand for white light‐emitting diodes (W‐LEDs) results in the gradual growth of research on functionalized luminescent glasses. In this paper, single‐composition tunable white‐emitting Eu2+‐Tb3+‐Eu3+ tri‐activated glasses were synthesized by melt quenching method without additional reducing atmosphere. The coexistence of Eu2+ and Eu3+ was confirmed by ultraviolet‐visible transmission spectra, photoluminescent spectra, fluorescence decay curves, and X‐ray photoelectron spectroscopy. Tb3+ can act as bridge to connect Eu2+‐Eu3+ luminescent centers by energy transfer. Tone‐tunable white light can be achieved by coupling the emission centered at 412, 541, and 612 nm contributed from Eu2+, Tb3+, and Eu3+, respectively. By adjusting the relative content of Eu2+/Tb3+/Eu3+, ideal chromaticity coordinates of (0.33, 0.33) can be achieved under excitation of ultraviolet light. High thermal stability and tiny chromaticity shift were exhibited in samples. These results suggest that Eu2+‐Tb3+‐Eu3+ tri‐activated glasses have great potential application in ultraviolet‐driven W‐LEDs.

Self‐reduction of Eu3+ to Eu2+ in europium‐doped Li2B4O7 glass prepared in air

“…Obviously, the emission intensity of the broadband of Eu 2+ ions, ascribed to the transition of 5d → 4f levels of Eu 2+ ions, gets stronger and stronger with increasing y values, the enhancement of Eu 2+ ions is associated with the higher concentration of Eu 2+ ions induced by the partial replacement of B 2 O 3 with BN. However, the emission intensity of Eu 3+ ion at 613 nm is considerably weak, which may result from the energy transfer from Eu 2+ to Eu 3+ ions in our glass, the similar result has been verified in other glass system . Furthermore, the position of the broadband emission of Eu 2+ ions, with increasing y values, shows a tendency of redshift from 414 ( y = 0%), 434 ( y = 0.5%), 436 ( y = 1.0%), 442 nm ( y = 1.5%) to 452 nm ( y = 2.0%), respectively.…”

“…With increasing y values, the concentration of Eu 2+ gets higher, the distance among Eu 2+ ions becomes shorter, which attributes to the stronger interaction between Eu 2+ ‐Eu 2+ ions. That is, the ligand field strength surrounding Eu 2+ ions is strengthened, promoting the excited state close to the ground state . Thus, the shortened distances among Eu 2+ ions may produce red shift, as observed in both the transmittance and excitation spectra.…”

“…However, the emission intensity of Eu 3+ ion at 613 nm is considerably weak, which may result from the energy transfer from Eu 2+ to Eu 3+ ions in our glass, the similar result has been verified in other glass system. 34,36 Furthermore, the position of the broadband emission of Eu 2+ ions, with increasing y values, shows a tendency of redshift from 414 (y = 0%), 434 (y = 0.5%), 436 (y = 1.0%), 442 nm (y = 1.5%) to 452 nm (y = 2.0%), respectively. The observed redshift is related to the higher concentration of Eu 2+ ions induced by the partial replacement of B 2 O 3 with BN.…”

“…strengthened, promoting the excited state close to the ground state. 34 Thus, the shortened distances among Eu 2+ ions may produce red shift, as observed in both the transmittance and excitation spectra. Figure 3C,D show the excitation-wavelength-dependent emission spectra of europium-doped Li 2 B 4 O 7 glasses excited by the 394 and 375 nm, respectively.…”

Influence of Optical Basicity on Cu+ Luminescence in Aluminosilicate Oxyfluoride Glasses

“…In particular, they present as free of epoxy resin in encapsulation (Dong et al, 2015;Meza Rocha et al, 2016;Kapoor et al, 2017;Ghosh et al, 2018;Li et al, 2019). Much research about white light-emitting glasses has been performed via doping co-activators including Eu 2+ /Eu 3+ /Tb 3+ (Fu et al, 2012;Guo et al, 2019), Ce 3+ /Tb 3+ /Mn 2+ (Ghosh et al, 2017), Ag/Eu 3+ (Li et al, 2012), Bi 3+ /Mn 2+ (Liu et al, 2016), Sb 3+ /Mn 2+ (Guo et al, 2012b;Ming et al, 2013).…”