Thermal-stable and high-efficient orange-red emitting orthosilicate phosphors LiGd9(SiO4)6O2:Mn2+ for n-UV-pumped w-LEDs

Abstract

Abstract A novel orange-red emitting orthosilicate phosphor LiGd9(SiO4)6:Mn2+ (LGS:Mn2+) belongs to hexagonal lattice with P63/m space group was synthesized via solid-state method and the phase composition, crystal structure as well as luminescence properties were examined for potential application in near ultraviolet (n-UV) pumped white light emitting diodes (w-LEDs). The as-prepared LGS:Mn2+ phosphor exhibits three excitation bands peaked at 273, 312 and 410 nm, which corresponds to the transitions of Gd3+ from ground state 8S7/2 to 6I7/2, 6P7/2 and Mn2+ from ground state 6A1(6S) to the individual components of the multiplets [4A1(4G), 4E(4G)], respectively. Upon excitation at 312 nm, the phosphors display an intense broad orange-red emission peaked around 594 nm, which ascribed to the typical spin-forbidden transition (4T1(4G)-6A1(6S)) of the Mn2+ ions. The concentration quenching mechanism and average separation distance in conjunction with fluorescence decay times of Mn2+ ions in LGS:Mn2+ phosphor were discussed. The indispensable parameters for application in n-UV high-powered w-LEDs, such as the thermal quenching of photoluminescence and internal quantum efficiency of LGS:Mn2+ phosphor, have also been investigated in detail. The above results indicate that LGS:Mn2+ could play a key role as an orange-red emission for potential application in n-UV-based w-LEDs.