A novel red-emitting phosphor Mg2Y2Al2Si2O12:Ce3+/Mn2+ for blue chip-based white LEDs

Abstract

Traditional white light-emitting diodes (LEDs) (blue chip + YAG:Ce³⁺ yellow phosphor) have the limitation of red deficiency, which limits their application in the illumination field. The single cation/anion substitution or co-doping of activators can increase the red component; however, the large energy loss is attributed to the ultra-long Stokes shift and energy transfer. This work attempts to utilize the short-distance Stokes shift and a small amount of energy transfer to increase the red component in two steps. First, based on a large number of previous research results, the Mg₂Y₂Al₂Si₂O₁₂:Ce³⁺ phosphor is selected. Second, additional enhancement of the red component in the emission spectrum was achieved by ion co-doping Mn²⁺ into Mg₂Y₂Al₂Si₂O₁₂:Ce³⁺. The emission peaks for samples Mg₂Y₂Al₂Si₂O₁₂:Ce³⁺,Mn²⁺ shift from 600 to 635 nm with increase in the concentration of Mn²⁺, and the emission spectra intensity of Mg_1.97Y_1.93Al₂Si₂O₁₂:0.07 Ce³⁺,0.03 Mn²⁺ anomalously increased by ∼37%, which was attributed to the increase in the distance between Ce³⁺ ions because of the doping of Mn²⁺ ions, and reduction in the concentration of defects in the crystal, resulting in the energy loss decreases of Ce³⁺. The emission peak of Mg_1.97Y_1.93Al₂Si₂O₁₂:0.07 Ce³⁺,0.03 Mn²⁺ shifts to 618 nm and the quantum efficiency was as high as 83.07%. Furthermore, this sample has high thermal stability and the emission intensity was still 80.14% at 120 °C. As such, it has great potential in the application of white LEDs.