Novel cyan‐emitting KBaScSi₂O₇:Eu²⁺ phosphors with ultrahigh quantum efficiency and excellent thermal stability for WLEDs

Abstract

Owing to the conventional phosphor‐converted white LEDs (pc‐WLEDs) generally suffer from blue‐green cavity, thus, developing an appropriate phosphors covering both the blue and green regions in their emission spectra are very urgent. Herein, a novel Sc silicate phosphor, KBaScSi2O7:Eu2+ (KBSS:Eu2+), has been successfully designed and prepared via a solid‐state reaction. The crystal structure, luminescent properties, thermal quenching, quantum efficiency as well as its application in UV‐pumped WLEDs have been investigated systematically. The KBSS:Eu2+ phosphor exhibits a strong and broad excitation band ranging from 290 to 450 nm, and gives a sufficient cyan emission of 488 nm with a full‐width half‐maximum (FWHM) of 70 nm, which filled the blue‐green cavity. Importantly, the optimized KBSS:Eu2+ phosphor possesses an ultrahigh quantum efficiency (QE) up to 91.3% and an excellent thermal stability retaining 90% at 423 K with respect to that measured at room temperature. Finally, the as‐fabricated UV‐based WLEDs device, with only coupled the mixture of KBSS:Eu2+ cyan phosphor and CaAlSiN3:Eu2+ red ones to a commercial 365nm UV chip, exhibits a satisfactory color‐rendering index (Ra = 88.6), correlated color temperature (CCT = 3770K), and luminous efficiency (LE = 21 lm/W).

Local Structure Modulation-Induced Highly Efficient Red-Emitting Ba2Gd1–xYxNbO6:Mn4+ Phosphors for Warm WLEDs

“…The emission spectra of Ba 2 GdNbO 6 :Mn 4+ and Ba 2 YNbO 6 :Mn 4+ present a multiple-peak profile with the strongest peaks situated at 688 and 690 nm, respectively, which are attributed to a spin-forbidden 2 E g → 4 A 2g transition. Noteworthily, the emission-band position slightly shifted from 688 to 690 nm, which is mainly attributed to the imparity between 4 A 2g and 2 E g levels in Ba 2 GdNbO 6 :Mn 4+ and Ba 2 YNbO 6 :Mn 4+ . Besides, different emission profiles are primarily originating from the interaction of lattice vibrations, lattice distortion, and 2 E g → 4 A 2g transition.…”

“…Additionally, the redshift (∼2 nm) of the PL spectra also occurs with Y 3+ ions replacing Gd 3+ ones in Ba 2 GdNbO 6 (Figure 3d), originating from enhanced covalent interaction between Mn 4+ and O 2− ions giving the lower energy of the 2 E g → 4 A 2g transition. 14,21 However, the redshift range from 688 to 690 nm is small, mainly originated from the fine distinction between 4 A 2g and 2 E g levels. 25 To further investigate the impact of the Y 3+ -doping contents on lifetime, the luminescence decay curves excited by 355 nm were measured and are depicted in Figure 3e.…”

“…However, there are still weaknesses of high correlated color temperature (CCT) and low color rendering index (CRI) in the existing commercial WLEDs coupling Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce 3+ ) phosphors with blue InGaN chips. 4,5 Significantly, the introduction of red luminescence phosphors is an effective and available strategy to solve the above problems. 6,7 Various red-emitting phosphors have been developed so far, such as Eu 3+ -/Sm 3+ -/Eu 2+ -/Ce 3+doped phosphors.…”

Thermally Stable Phosphor KBa2(PO3)5:Eu2+ with Broad-Band Cyan Emission Caused by Multisite Occupancy of Eu2+

“…19 Wang and co-workers found that the broad emission band of K 2 HfSi 3 O 9 :Eu 2+ excited at 400 nm is a combination of two Gaussian components at 462 and 494 nm, which resulted from two crystallographically distinct K + atom sites in the host lattice. 20 Because the crystal-field strength (D q ) is proportional to 1/R 5 23 Ca 2 (BO 3 ) 1−x (PO 4 ) x Cl:Eu 2+ , 24 Li 2 BaSiO 4 :Eu 2+ , 25 KBaSc-Si 2 O 7 :Eu 2+ , 26 and so on.…”

Novel blue-emitting KBaGdSi2O7:Eu2+ phosphor used for near-UV white-light LED

“…The blue emission of Eu 2+ and Ce 3+ doped KBaYSi2O7 have been reported by Feng et al [19] and Zhang et al [20] respectively. Moreover, other members of KMReSi2O7 family, KSrScSi2O7 and KBaScSi2O7 have been reported as the host for Eu 2+ doping and exhibited a blue emission peaked at ~ 436 nm and cyan emission peaked at ~ 488 nm [21][22].…”