Thermally-stable novel NaBaBi2(PO4)3: Sm3+/Dy3+ white phosphors with tunable photoluminescence

Abstract

The novel phosphors NaBaBi2(PO4)3: xDy3+ and NaBaBi2(PO4)3: 0.07Dy3+, ySm3+ were successfully synthesized using solid-state reaction method, and their microstructure, optical features and electroluminescent properties were studied. The experimental results show that the doping of Dy3+ exhibits strong yellow light emission, while Sm3+ can effectively compensate for the absent red emission in the Dy3+ emission spectrum, realize the color transition from yellow to white. In addition, the energy transfer process from Dy3+ to Sm3+ in NaBaBi2(PO4)3 was studied in details, and the light color can be adjusted by changing the ratio of Dy3+ and Sm3+, and the color temperature associated with NaBaBi2(PO4)3: 0.07Dy3+, ySm3+ can be adjusted from cool to natural. XRD and refinement results showed that Dy3+ and Sm3+ were successfully incorporated into the matrix. The morphology of NBBP: 0.07Dy3+, 0.05Sm3+ was characterized by SEM. The band gap of the NaBaBi2(PO4)3 matrix is calculated as a direct band gap by the density functional theory method, and the theoretical value (3.9534 eV) of the band gap is very similar to the experimental value (3.965 eV). By analyzing the total density of states and partial density of states, the valence band of the host is mainly composed of [PO4]. In addition, the NaBaBi2(PO4)3: 0.07Dy3+, 0.05Sm3+ phosphors have an energy transfer efficiency of 73% and exhibit excellent thermal stability, the fluorescence intensity at 428 K still maintains 81.79% of that at 303 K and has a small chromaticity shift. The correlated color temperature of the W-LEDs packaged with NaBaBi2(PO4)3: 0.07Dy3+, 0.05Sm3+ phosphor was measured as 4434K, and the color coordinates were measured as (0.3594, 0.3454). The W-LEDs driven at 3.4 V voltage and 600 mA current maintained its performance for 70 min, indicating that the packaged W-LEDs can operate continuously at high temperatures.