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.
| Original language | Undefined/Unknown |
|---|---|
| Pages (from-to) | 2077-2084 |
| Number of pages | 8 |
| Journal | Chemistry of Materials |
| Volume | 21 |
| Issue number | 10 |
| Publication status | Published - 2009 |