Red luminescence Ca1-xLa2x/3TiO3:Eu3+ phosphor with high quantum efficiency for ultraviolet-based white light-emitting diodes

Abstract

The photoluminescence properties and internal quantum efficiency (IQE) of Ca1-xLa2x/3TiO3:Eu3+ were investigated in this paper. In the excitation spectra of Ca1-xLa2x/3TiO3:Eu3+, several peaks were located from 360 to 535 nm which were attributed the 4f- 4f transitions of Eu3+. In the emission spectra, the strong emission peaks were located at 591 and 616 nm which were originated from the magnetic dipole and electric dipole transitions of Eu3+, respectively. Therefore, phosphor could be excited effectively in the near-ultraviolet light and emit a satisfactory red light. When the value of x was 0.1, the red emission intensity of Ca0.9La0.067TiO3:1 mol%Eu3+ was enhanced two times than that of CaTiO3:1 mol%Eu3+. For Ca0.9La0.067TiO3:Eu3+ (x = 0.1) phosphor, the optimal doping concentration was 5 mol%. The Ca0.9La0.067TiO3:5 mol%Eu3+ phosphor had a higher IQE compared with the Y2O2S:Eu3+ commercial phosphor (IQE: 35%) and reached as high as 83.7%. The CIE coordinates of Ca0.9La0.067TiO3:5 mol% Eu3+ were (0.636, 0.364). The electroluminescence spectrum showed the corresponding correlated color temperature (CCT) and color rendering index (Ra) values of white light-emitting diode (WLED) devices were 6295 K and 94.4, respectively. This result was much higher than the traditional WLED, which was coated with YAG:Ce3+ phosphors (CCT = 5716 K, Ra = 76). As a result, the Ca1-xLa2x/3TiO3:Eu3+ phosphor system was expected to become the red part of the WLED device.