Preparation and optical properties of Eu²⁺ doped CaGa₂S₄–CaS composite bicolor phosphor for white LED

Abstract

In the present paper, we report the optical properties of the bicolor composite phosphor on the base of CaS and Ga2S3 and study the possibility using this composite to obtain a white light LED. In particular, the energy transfer between the green and red emission bands of the bicolor composite phosphor activated by Eu2+ ions was studied. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Luminescence in Sulfides: A Rich History and a Bright Future

“…As the quantum efficiency of CaGa 2 S 4 :Eu and Sr 2 Ga 2 S 5 :Eu was reported to be similar to that of YAG:Ce [174], the thiogallates recently attracted attention as color conversion phosphor as well [174,175,176,177,178,179]. The emission band width is considerably smaller than in YAG:Ce, which necessitates the use of at least a second, red-emitting phosphor to produce white light starting from a blue LED.…”

“…The emission band width is considerably smaller than in YAG:Ce, which necessitates the use of at least a second, red-emitting phosphor to produce white light starting from a blue LED. Several authors reported the combination of CaS:Eu and CaGa 2 S 4 :Eu [175,177,179], even with a ‘one pot synthesis’ based on the observation that a CaS:Ga 2 S 3 starting ratio higher than 1:1 leads to a mixture of CaS:Eu and CaGa 2 S 4 :Eu. Taking into account that CaS:Eu has a much more severe concentration quenching behavior compared to CaGa 2 S 4 :Eu, it is questionable whether this synthesis approach is optimal in terms of overall quantum efficiency of the mixture.…”

Impact of hydrostatic pressure on the crystal structure and photoluminescence properties of Mn4+-doped BaTiF6red phosphor

“…[6][7][8][9][10] Currently, a rare-earth activator is the most promising approach for energy efficient red phos-phors for fluorescent lamps and WLEDs. The most successful materials are rare-earth-doped sulfates and (oxy)nitrides, [11][12][13][14][15][16][17][18] such as Eu 2+ -doped CaS, Eu 3+ -doped Y 2 O 2 S and Eu 2+ -doped CaAlSiN 3 . Nevertheless, the poor chemical stability and critical syntheses conditions of these air-and moisture-sensitive sulfides/nitrides make them unfavorable as competitive candidates for advanced WLEDs.…”

The red luminescence of Sr4 Al14 O25 :Mn4+ enhanced by coupling with the SrAl2 O4 phase in the 3SrO · 5Al2 O3 system

“…This is because the nitride red phosphors, such as MAlSiN 3 :Eu 2+ and M 2 Si 5 N 8 :Eu 2+ (M = Ca, Sr, Ba), that have been popularly applied in WLEDs are very costly, despite of their excellent performance in luminescent efficiency and thermal stability . Nevertheless, the sulfate red phosphors, such as CaS:Eu 2+ , Sr(S,Se):Eu 2+ , (Sr,Ca)Ga 2 S 4 :Eu 2+ , or (Y,La) 2 O 2 S:Eu 3+ , are chemically unstable when exposed to a humid environment . Furthermore, the Ni/Ag electrodes of an LED chip tend to react with sulfur to form black compounds, which prominently affect the extraction of emitted photons.…”