Excellent thermal stability and high quantum efficiency orange-red-emitting AlPO4:Eu3+ phosphors for WLED application

Orange-red-emitting AlPO4:Eu3+ phosphors have been systematically synthesized by a co-precipitation method. Under the excitation at 394 nm these phosphor shows strong orange-red emissions with the strongest peaks at 588, 594, 685 and 700 nm. The highest PL intensity is achieved at the dopant concentration of 3 mol% and the annealing temperature of 1000 °C. Additionally, 84% of the room-temperature emission intensity is still maintained at 160 °C, indicating a good thermal stability and practicality. By a Judd-Ofelt (JO) analysis, it is demonstrated that the symmetry sites surrounding Eu3+ ions are influenced by the dopant level. The lowest value of Ω2/Ω4 ratio of 0.27 reveals the highest symmetry site at the Eu3+ concentration of 3 mol%. The CIE 1931 color chromaticity coordinates (x, y) and the activation energy of the AlPO4:3%Eu3+ phosphor are (0.5602; 0.3862) and 0.28 eV, respectively. The color coordinates of the phosphor coated on NUV LED chip and its quantum efficiency (QE) are (0.5573, 0.3253) and 38.7%, respectively. To the best of our knowledge, this is the first time that a calculated QE of AlPO4:Eu3+-based orange-red-emitting LED is reported. The obtained results show a great potential of using orange-red-emitting AlPO4:Eu3+ phosphor for WLED application.