Flux-assisted cyan emission enhancement in Sr8Si4O12Cl8:Eu2+ for high color rendering index white light-emitting diodes

Phosphors featuring cyan emissions (480-520 nm) are highly demanded to obtain high-quality white light-emitting diodes (WLEDs). However, current cyan phosphors suffer from unsatisfactory luminescence efficiency, which limits their practical use. Herein, we report flux-assisted enhancement of cyan emission in Sr 8 Si 4 O 12 Cl 8 :Eu 2+ (SSOC:Eu 2+ ) through deliberate optimization of the flux species and amount. The introduction of H 3 BO 3 into this cyan phosphor facilitates crystallization and increases Eu 2+ ammount in the host, resulting in an enhancement of emission intensity. The optimized flux-assited (1.5 wt% H 3 BO 3 ) SSOC:4%Eu 2+ ( λ em  = 489 nm) exhibits an emission intensity 2.39 times higher than that of the SSOC:Eu 2+ preapred without flux, together with high internal quantum efficiency (IQE, 84.4%) and external quantum efficiency (EQE, 45.2%) under 365 nm excitation. Moreover, the PL intensity of this cyan phosphor keeps 85.7% and 58.6% of its room-temperature value at 423 and 623 K, respectively. A high-quality WLED with both color rendering index (CRI) and R9 values of 91, was fabricated by combining the cyan phosphor with commercial green and red phosphors, demonstrating the great potential of H 3 BO 3 -assited SSOC:Eu 2+ in full-visible-spectrum WLEDs. This work provides an effective strategy for substantially improving the emission intensity of phosphors by regulating the microenvironment of the host.