Energy transfer of Eu2+→Eu3+ improves the photoluminescence properties of orange-red phosphor La2O2S:Eu

Abstract

Red phosphor with excellent performance plays an important role in improving the luminous performance of white LED(w-LEDs). In this work, a novel type of orange-red phosphors La2-xO2S:xEu(2+,3+) (0.01 ≤ x ≤ 0.08, ∆x = 0.01) for white LED were synthesized via high-temperature solid-state method, and the phase, morphology, luminescent properties, and thermal stability of the samples were systematically studied. The samples all belong to hexagonal crystal system, and the space group are all P-3m1 (164). Through XPS analysis, it was found that Eu2+ and Eu3+ coexist in La1.96O2S:0.04Eu(2+,3+) phosphor. The energy transfer between Eu2+ and Eu3+ was realized, and the fluorescence intensity increased by 418.03 %. The optimal doping concentration of Eu ions in La2-xO2S:xEu(2+,3+) phosphors is x = 0.04, and the concentration quenching mechanism is the electric quadrupole electric quadrupole (q-q) interaction. La1.96O2S:0.04Eu(2+,3+) phosphor has excellent thermal stability，the fluorescence intensity still remains 82.67 % at 418 K compared with room temperature, the activation energy Ea= 0.3961 eV, and the trap theory was used to explain the mechanism of thermal quenching. La1.96O2S:0.04Eu(2+,3+) phosphor has high luminescence quality with color purity of 87.08 %. These results show that La1.96O2S:0.04Eu(2+,3+) phosphor has certain application value in the field of white LED phosphors.