Energy transfer induced color tunable photoluminescence in Tb3+/Sm3+ co-doped Y2O3 nano-phosphor for warm white LEDs

Abstract

In this work, the Tb3+/Sm3+ doped and co-doped Y2O3 nano-phosphors have been prepared by solution combustion method. The structural and morphological analyses of Y2O3 nano-phosphors confirm its nano-crystalline structure. The EDS spectra reveal the evidence of Y, Sm, Tb and O elements in the co-doped phosphor. The excitation spectrum of the Tb3+/Sm3+ co-doped nano-phosphor contains the excitation bands due to Tb3+ and Sm3+ ions. The Tb3+ doped nano-phosphor gives intense green (541 nm) and slightly weak blue (483 nm) emissions upon 292 nm excitation. The critical distance and PL intensity per activator ion were calculated to identify the factor responsible for quenching the PL intensity. The PL intensity of green and blue emission bands decreases regularly via doping of Sm3+ ion. This occurs due to energy transfer from Tb3+ to Sm3+ ions. The energy transfer leads to improve the PL intensity of the orange red emission band of Sm3+ ion. The energy transfer has been verified by the lifetime measurements and the energy transfer efficiency is found to increase via doping of Sm3+ ion. The CIE diagrams show wide color tunability from the greenish yellow to reddish orange regions and the color purity of Tb3+ doped nano-phosphor also changes accordingly via Sm3+ doping. The CCT analysis of Tb3+/Sm3+ co-doped nano-phosphors indicates a warm nature of the emitted light. Therefore, the Tb3+/Sm3+ co-doped Y2O3 nano-phosphor may be applied in the field of display devices, color tunable devices and warm white LEDs.