Temperature Quenching of Yellow Ce³⁺ Luminescence in YAG:Ce

TLDR

YAG:Ce is the preferred phosphor for blue‑to‑yellow conversion in white LEDs, yet its luminescence quenching temperature is believed to be low, a critical yet understudied parameter for high‑power devices. This study investigates the temperature quenching behavior of yellow Ce luminescence in YAG:Ce. The authors measured emission intensity, lifetimes, and spectral parameters across Ce concentrations from 0.033 % to 3.3 % and compared these data with ab initio calculations of the Ce³⁺ 5d excited state to elucidate quenching mechanisms. The intrinsic quenching temperature exceeds 700 K, with lower literature values attributed to concentration quenching at high dopant levels and oscillator‑strength changes at low levels, and high‑resolution spectra reveal a zero‑phonon line at 20450 cm⁻¹, a 2400 cm⁻¹ Stokes shift, a 200 cm⁻¹ phonon mode, and a Huang–Rhys parameter of 6.

Abstract

Yttrium aluminum garnet (YAG) doped with Ce3+ is the phosphor of choice for the conversion of blue to yellow light in the rapidly expanding market of white light LEDs, but it is generally thought to suffer from a low luminescence quenching temperature. The luminescence quenching temperature is an important parameter, especially in high-power LEDs, but surprisingly no systematic research has been done to measure and understand the temperature quenching of the yellow Ce luminescence in YAG:Ce. Here we report on the luminescence temperature quenching in YAG:Ce. For a wide range of Ce concentrations (between 0.033% and 3.3%) the temperature dependence of the emission intensity and the luminescence lifetimes are reported. The intrinsic quenching temperature of the Ce luminescence is shown to be very high (>700 K). The lower quenching temperatures reported in the literature are explained by thermally activated concentration quenching (for highly doped systems) and the temperature dependence of the oscillator strength (for low doping concentrations). In addition, high-resolution spectra are reported, which provide insight into the position of the zero-phonon transition (20450 cm−1), the Stokes shift (2400 cm−1), the energy of the dominant phonon mode (200 cm−1), and the Huang−Rhys parameter (S = 6). These parameters are compared with ab initio calculations on the position of and relaxation in the excited 5d state of Ce3+ in YAG, which can aid in providing a better theoretical understanding of the temperature quenching.