Energy transfer and highly thermal stability in single-phase SrY2O4:Bi3+, Sm3+ phosphors for UV-LEDs

Thermal quenching is one of the most key challenges of ultraviolet converted white light-emitting diodes (UV converted WLEDs) when they operate at high driving current, in which the phosphors are subjected to the luminescence losses resulting from non-radiative transitions with augmenting temperature. Herein, novel single-phased Bi3+,Sm3+-doped SrY2O4 (SYO) phosphors with abnormal thermal quenching property were successfully prepared applying a high-temperature solid-state strategy. X-ray diffraction, luminescent behaviors, lifetimes and temperature-dependent emission properties were employed to study the obtained powder materials. Under UV light irradiation, tunable emission from blue to red based on the energy transfer (ET) from Bi3+ to Sm3+ via a dipole-dipole mechanism is realized. Significantly, the obtained phosphors do not display thermal quenching even up to 573 K (300 degrees C). And they exhibit tiny chromaticity shift even at high temperature, indicative of excellent color stability. These phenomena may be interpreted by the ET from defect levels to Bi3+ excited states, which was identified by thermoluminescence measurements. These results indicate potential applications of SYO:Bi3+,Sm3+ in UV converted WLEDs.