Design, preparation, and optimized luminescence of a dodec-fluoride phosphor Li₃Na₃Al₂F₁₂:Mn⁴⁺for warm WLED applications

Abstract

Mn4+-activated red phosphors have attracted considerable attention as promising red components in the spectra of white light emitting diodes (WLEDs) to achieve warm white light with superior performance.

Formation mechanism and optimized luminescence of Mn4+‐doped unequal dual‐alkaline hexafluorosilicate Li0.5Na1.5SiF6

“…As exhibited in Figures and , the excitation of LNSF:Mn shows a slight red shift compared to NSF:Mn and KSF:Mn, which indicates the remote alkali metals hexa‐fluorosilicates play an influence of the optical performance of Mn 4+ . The dual alkaline ions Na + and Li + with different ionic sizes and unequal molecule ratios in LNSF lead to a low localized symmetry of Mn 4+ ions . The weaker crystal field and lower localized symmetry of Mn 4+ in LNSF:Mn lead to the stronger ZPL and higher quantum efficiency .…”

“…As observed in Figure , ZPL cannot be detectable in mission spectrum of KSF:Mn due to the high localized symmetry of Mn 4+ in KSF. The intense ZPL in both emission spectra of LNSF:Mn and NSF:Mn are beneficial to obtaining a red emission with high color‐purity and desirable CIE chromaticity coordinates that is desirable to improving the performance of lighting and displays . Particularly, the red phosphor LNSF:Mn has a stronger ZPL than NSF:Mn and KSF:Mn.…”

“…The dual alkaline ions Na + and Li + with different ionic sizes and unequal molecule ratios in LNSF lead to a low localized symmetry of Mn 4+ ions. 51,52 The weaker crystal field and lower localized symmetry of Mn 4+ in LNSF:Mn lead to the stronger ZPL and higher quantum efficiency. 53,54 As observed in Figure 5, ZPL cannot be detectable in mission spectrum of KSF:Mn due to the high localized symmetry of Mn 4+ in KSF.…”

A universal HF‐free synthetic method to highly efficient narrow‐band red‐emitting A2XF6:Mn4+ (A = K, Na, Rb, Cs; X = Si, Ge, Ti) phosphors

“…In addition, they also show high QE (~90%) and excellent thermal stability . To date, the fluoride‐based phosphors have been extended from A 2 X F 6 : Mn 4+ ( A = NH 4 , K, Na, Rb, Cs; X = Si, Ge, Sn, Ti, Zr) to A 3 B F 6 : Mn 4+ ( A = K, Na, Rb, Cs; B = Al, Ga), A 2 A ′BF 6 : Mn 4+ ( A = K, Na, Rb, Cs; A ′ = Li, Na, K; B = Al, Ga), A 2 C F 7 : Mn 4+ ( A = K, Na, Rb, Cs; C = Nb, Ta), and Li 3 Na 3 Al 2 F 12 : Mn 4+ …”

“…30,32,33 To date, the fluoride-based phosphors have been extended from A 2 XF 6 : Mn 4+ (A = NH 4 , K, Na, Rb, Cs; X = Si, Ge, Sn, Ti, Zr) to A 3 BF 6 : Mn 4+ (A = K, Na, Rb, Cs; B = Al, Ga), A 2 A′BF 6 : Mn 4+ (A = K, Na, Rb, Cs; A′ = Li, Na, K; B = Al, Ga), A 2 CF 7 : Mn 4+ (A = K, Na, Rb, Cs; C = Nb, Ta), and Li 3 Na 3 Al 2 F 12 : Mn 4+ . [34][35][36][37][38][39][40][41][42] In general, highly concentrated and toxic HF is usually used during the synthesis of Mn 4+ -activated fluoride phosphors. 30,32,[42][43][44] To get rid of damages from HF, HF-free synthetic methods need to be developed.…”