Multisite-Occupancy-Driven Intense Narrow-Band Blue Emission from Sr₅SiO₄Cl₆:Eu²⁺ Phosphor with Excellent Stability and Color Performance

Abstract

The development of an efficient blue phosphor with remarkable thermal stability required for high-quality white-lightemitting diodes (WLEDs) remains an exigent task and mainly concerned BaMgAl 10 O 17 :Eu 2+ (BAM:Eu). Despite the outstanding performance of BAM:Eu, the reduction in luminescence efficiency under long-term operation results in numerous researches on new hosts having lattice rigidity with symmetrical coordination environment. Therefore, we have synthesized a competent blue-emitting Eu 2+ -activated Sr 5 SiO 4 Cl 6 (SSC) phosphors. The admirable rigidity of these phosphors with three Sr polyhedra Sr(I)O 9 , Sr(II)O 7 , and Sr(III)O 8 assessed from Rietveld refinement indicate the dense connectivity in the crystal structure, and the ab initio calculations further support the firm electronic band structure. The broad excitation from 250 to 450 nm suitably matches the absorption band of a near-UV (n-UV) LED chip. The phosphor exhibited bright blue emission with internal quantum yield and color purity > 90% which contribute to the slender fwhm of 33 nm. The firstprinciple calculation indicates the most stable site for Eu 2+ substitution as Sr(III)O 8 , and the experimental results agreed with this fact as well. The synthesized phosphor displayed an excellent thermal stability which is superior to that of the commercial BAM:Eu phosphor. The excellent thermal stability may be owed to the highly symmetric coordination environment of Eu 2+ in the SSC host that are revealed from the distortion and charge density distribution calculation by density functional theory. The blue phosphor was further utilized for WLEDs and displayed white light with a high color-rendering index and suitable correlated color temperature, which is ideal for practical applications in warm WLEDs.

Site Occupancies, VUV-UV–vis Photoluminescence, and X-ray Radioluminescence of Eu2+-Doped RbBaPO4

“…( 7); (b) the decay curves (λex = 310 nm, λem = 407 nm) of RbBa1-xEuxPO4 (x = 0.04 and 0.08) samples at RT and fitting curves via Yokota-Tanimoto model [eqs. (8,9)].…”

“…7 The emission bands at 472, 445 and 406 nm are assigned to Eu 2+ at Sr(I)O9, Sr(III)O8 and Sr(II)O7 polyhedral sites in Sr5SiO4Cl6, respectively. 8 The blue emission peaking at 471 nm is originated from the occupancies of Eu 2+ in the monovalent cation sites Rb + , Na1 + and Na2 + in RbNa3(Li3SiO4)4. 9 Eu 2+ occupies into the LuO6 and K2O6 polyhedrons in K3LuSi2O7 with deep red emissions.…”

Ca[B8O11(OH)4] : Eu2+ – A Highly Efficient Deep Blue‐Emitting Phosphor Prepared by Low‐Temperature Self‐reduction

“…Compared with other Eu 2+ doped blue phosphors, the Ea of CBH : Eu 2+ is higher than those of Ba 3 Si 6 O 12 N 2 : Eu 2+ ( Ea =0.24 eV), [72] RbNa(Li 3 SiO 4 ) 2 : Eu 2+ ( Ea= 0.25 eV), [73] K 2 YZr(PO 4 ) 3 : Eu 2+ ( Ea= 0.25 eV), [68] Ba 3 CaK(PO 4 ) 3 : Eu 2+ ( Ea= 0.26 eV ), [70] K 2 Al 2 B 2 O 7 : Eu 2+ ( Ea =0.30 eV) [74] . But the Ea of CBH : Eu 2+ is lower than that of Sr 5 SiO 4 Cl 6 : Eu 2+ ( Ea =0.35 eV), [75] K 2 BaCa(PO 4 ) 2 : Eu 2+ ( Ea =0.51 eV), [76] and KBa 2 (PO 3 ) 5 : Eu 2+ ( Ea= 0.66 eV) [77] . The relatively high activation energy indicates that the phosphor has good thermal stability, which is an essential condition for practical applications.…”

Luminescence and energy transfer of warm white-emitting phosphor Mg2Y2Al2Si2O12:Dy3+,Eu3+ for white LEDs

“…Therefore, a white light-emitting diode (LED) is obtained by exciting single matrix uorescent powder with ultraviolet (UV) or near-UV light, and UV light will not affect white light. [1][2][3][4][5] Dy 3+ ions have blue emission peaks (480 nm, 4 F 9/2 / 6 H 15/2 ) and yellow emission peaks (575 nm, 4 F 9/2 / 6 H 13/2 ). White light can be realized by coordinating the ratio of blue light and yellow light.…”