Dual color tuning in Ce³⁺‐doped oxyfluoride ceramic phosphor plate for white LED application

Abstract

Ceramic phosphor plates of cerium (Ce3+)‐doped oxyfluoride were fabricated by the solid‐state reaction method. These phosphors exhibit efficient emission, with the novel feature of color tuning by varying both the doping concentration and excitation wavelength. As the Ce3+ concentration increases, the excitation spectrum broadens by a factor of 1.6, and the excitation peak wavelength shifts from 390 to 435 nm, and there is a variation in excitation energy of ~ 10%. Luminescence spectrum of low Ce3+ concentration samples is tuned from blue to green with the change of excitation wavelength. The emission peak exhibits a shift of 58 nm into the red spectral region, varying the Ce3+ concentration from 0.05 to 0.1 mol%; whereas this shift is only 6 nm when Ce3+ content changes from 0.25 to 1 mol%. Photoluminescence (PL) quantum yield has achieved 76%. The crystal structure was examined using X‐ray diffraction to explain its possible influence on the redshift luminescence. A proof of concept of white LED was constructed using a 450 nm blue LED chip with an oxyfluoride phosphor plate, showing a luminous efficacy (LE) of 64 lm/W with a color rendering index of 74.

Spectrum regulation of YAG:Ce/YAG:Cr/YAG:Pr phosphor ceramics with barcode structure prepared by tape casting

“…To avoid these problems, thermally robust phosphor plates, such as phosphor in glass (PiG), phosphor glass–ceramics, and especially phosphor ceramics, are used for high‐power LED/LD lighting 1,12,16–23 . Among these phosphor plates, ceramics are increasingly valued due to their high thermal conductivity, reproducibility, and reduced degradation 24–29 …”

“…1,12,[16][17][18][19][20][21][22][23] Among these phosphor plates, ceramics are increasingly valued due to their high thermal conductivity, reproducibility, and reduced degradation. [24][25][26][27][28][29] For YAG:Ce phosphor ceramics, the non-negligible drawbacks are low color rendering and high correlated color temperature (CCT) due to the lack of red spectral components. To solve this problem, many efforts have been made to exploit novel compositions or structures to enrich the red spectral component in phosphor ceramics.…”

Governing the crystallographic sites for tuning Eu2+ emission in an apatite oxyfluoride host to be applied for superior white light emitting diodes

“…12 For the recently reported oxyfluorides, the presence of multiple crystallographic sites was able to provide versatile cationic environments for Ce 3+ or Eu 2+ ions, which are effective in generating broad emissions from these ions. 13 Eventually, an appropriate cationic replacement can drive the luminescent centers to produce emission wavelength shifts very effectively. Arunkumar et al recently reported a broad-band-emitting Ca 4 F 2 Si 2 O 7 :Ce 3+ phosphor based on the occupation of Ce 3+ ions at multiple crystallographic sites in the host under n-UV excitation.…”