Tunable cool to warm white emission in Ca1-xLa2x/3TiO3 coped with Dy3+ and Sm3+ for white LED application

Abstract

The luminescence properties of Ca1-xLa2x/3TiO3:Dy3+, Sm3+ phosphors were investigated in this paper. They were characterized by their photoluminescence, thermal quenching, and electroluminescence. At an excitation wavelength of 388 nm, the photoluminescence spectra of the Ca1-xLa2x/3TiO3:Dy3+ phosphors exhibited two emission peaks at 482 and 573 nm which were attributed to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. Orange-red Ca1-xLa2x/3TiO3:Sm3+ phosphors had three emission peaks at 565, 601 and 648 nm at an excitation wavelength of 404 nm due to the 4G5/2 → 6HJ/2 (J = 5, 7 and 9) transitions of Sm3+. When Dy3+ and Sm3+ were co-doped into Ca1-xLa2x/3TiO3, the phosphors achieved conversion of cool white and warm white light by varying the concentrations of Dy3+ and Sm3+. The temperature-dependent emission spectra indicated that the Ca1-xLa2x/3TiO3:Dy3+, Sm3+ phosphors exhibited good thermal stability. White light-emitting diodes (WLEDs) demonstrated that the fabricated Ca0.7La0.2TiO3:Dy3+, Sm3+ phosphors had correlated color temperature (CCT) and color rendering index (Ra) values of 6064 K and 71, respectively. They had better performances than commercial WLEDs with a combination of blue LEDs coated with yellow emitting Y3Al5O12:Ce3+ phosphors (CCT =7760 K, and Ra < 65). This study demonstrates that Ca1-xLa2x/3TiO3:Dy3+, Sm3+ phosphors can be promising candidates for NUV chip-based WLEDs.