Near-Infrared Emission Properties and LED Applications of Y2Ti2O7:Cr3+/Nd3+ Phosphors Improved by Doping with Ce3+ Ions

Near infrared (NIR) Y₂Ti₂O₇:Ce³⁺/Cr³⁺/Nd³⁺ phosphors were synthesized using a solid-state reaction technique. NIR luminescent performance of Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors was improved by doping with Ce³⁺ ions. The emission intensity of Y₂T₂O₇:Cr³⁺/Nd³⁺/Ce³⁺ phosphors is significantly higher than that of Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors. The external quantum efficiency and internal quantum efficiency of Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺/1.5% Ce³⁺ are 16 and 22.8%, respectively. The luminescent mechanisms of the Y₂Ti₂O₇:Cr³⁺/Nd³⁺ and Y₂T₂O₇:Cr³⁺/Nd³⁺/Ce³⁺ phosphors were investigated. As a result, the effective energy transfer process from Cr³⁺ to Nd³⁺ ions exists in Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors, while the effective energy transfer process from Ce³⁺ to Cr³⁺ and Nd³⁺ ions exists in Y₂T₂O₇:Cr³⁺/Nd³⁺/Ce³⁺ phosphors. NIR emission intensities of LED devices assembled with Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺/1.5% Ce³⁺ phosphors are better than those of LED devices assembled with Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺ phosphors at different work currents. In addition, the temperature-sensitive behavior of Y₂Ti₂O₇:Cr³⁺/Nd³⁺ phosphors was also studied. Their LIR and S_a values monotonically increase in the temperature range of 303–393 K. The maximum S_a values of Y₂Ti₂O₇:0.5% Cr³⁺/0.5% Nd³⁺, Y₂Ti₂O₇:0.5% Cr³⁺/0.7% Nd³⁺, Y₂Ti₂O₇:0.5% Cr³⁺/1.0% Nd³⁺, Y₂Ti₂O₇:0.5% Cr³⁺/2.0% Nd³⁺ samples are 0.79 × 10^–2, 0.88 × 10^–2, 1.24 × 10^–4, and 2.53 × 10^–3 K^–1, respectively.