KCa4(BO3)3:Ln3+ (Ln = Dy, Eu, Tb) phosphors for near UV excited white–light–emitting diodes

Abstract

A series of doped KCa 4 (BO 3 ) 3 :Ln 3+ (Ln: Dy, Eu and Tb) compositions were synthesized by solid-state reaction method and their photoluminescent properties were systematically investigated to ascertain their suitability for application in white light emitting diodes. The X-ray diffraction (XRD) and nuclear magnetic resonance (MAS-NMR) data indicates that Ln 3+ -ions are successfully occupied the noncentrosymmetric Ca 2+ sites, in the orthorhombic crystalline phase of KCa 4 (BO 3 ) 3 having space group Ama2, without affecting the boron chemical environment. The present phosphor systems could be efficiently excitable at the broad UV wavelength region, from 250 to 350 nm, compatible to the most commonly available UV light-emitting diode (LED) chips. Photoluminescence studies revealed optimal near white-light emission for KCa 4 (BO 3 ) 3 with 5 wt.% Dy 3+ doping, while warm white-light (CIE; X = 0.353, Y = 0.369) is obtained at 1wt.% Dy 3+ ion concentration. The principle of energy transfer between Eu 3+ and Tb 3+ also demonstrates the potential white-light from KCa 4 (BO 3 ) 3 :Eu 3+ ,Tb 3+ phosphor. Whereas, single Tb 3+ and Eu 3+ -doped systems showed bright green (Tb 3+ ) and red (Eu 3+ ) emissions, respectively. Having structural flexibility along with remarkable chemical/thermal stability and suitable quantum efficiency these phosphors can be promising candidates as white-light-emitter for near UV LEDs.

Tunable photoluminescence properties and energy transfer in oxyapatite-based Ca2Tb8(SiO4)6:Eu3+ phosphors for UV-LEDs

“…Such high thermal stability is good enough for LED applications. The activation energy (E a ) is obtained using the equation [38,40]:…”

Structural and luminescence properties of tunable white-emitting Sr0.5Ca0.5Al2O4:Eu2+, Dy3+for UV-excited white-LEDs

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