Enhanced luminescence performance of CaO:Ce3+,Li+,F− phosphor and its phosphor-in-glass based high-power warm LED properties

Abstract

To obtain white light-emitted diodes (wLEDs) with a low correlated color temperature (CCT) and a high color rendering index (CRI), red-emission is indispensable in their emission spectra. Herein, CaO:Ce³⁺,Li⁺,F⁻ yellow phosphors with more red spectral component have been prepared via a high temperature solid-state reaction. As compared to the F⁻ undoped samples, CaO:Ce³⁺,Li⁺,F⁻ phosphor have lower critical doping concentration of Ce³⁺ and show stronger luminescence. At the critical concentration, a quantum efficiency of 66.4% and enhanced thermal and chemical stability were obtained in CaO:Ce³⁺,Li⁺,F⁻. Furthermore, a CaO:Ce³⁺,Li⁺,F⁻-based phosphor-in-glass (PiG) using the red-emitting glass system with the composition of SiO₂–Na₂CO₃–Al₂O₃–CaO:Eu³⁺ as the host material was constructed and used for high-power white LED applications. Such PiG samples with different phosphor doping concentrations can satisfy various light color demands and display higher reliability than the CaO:Ce³⁺,Li⁺,F⁻ phosphor. An optimal PiG-based wLED exhibits color coordinates of (0.3769, 0.3386), a CCT of 3774 K, a CRI of 82.5 and a LE of 73.1 when the mass ratio of phosphor to glass matrix was 7 : 50 in PiG. Moreover, such PiG-based wLED also showed acceptable color stability under different drive currents. All the above results demonstrate that CaO:Ce³⁺,Li⁺,F⁻ can be expected to be a potential alternative yellow phosphor for blue light excited PiG based warm wLEDs, particularly for high-power devices.