Thermally stable KxCs1−xAlSi2O6:Eu2+ phosphors and their photoluminescence tuning

Abstract

Thermal quenching is one of the most crucial challenges for photoluminescence and high-power applications, in which the phosphor suffers from emission loss due to non-radiative transitions with increasing temperature. Herein, we report new isostructural solid solution phosphors, Eu²⁺-doped K_xCs_1−xAlSi₂O₆ (0 ≤ x ≤ 0.6), with abnormal thermal quenching behavior, and their asymmetric emission spectra and decay curves for two emission centers verified the presence of two kinds of Eu²⁺ centers (Eu1 and Eu2) in the lattices. The maxima of both the Eu1 and Eu2 bands exhibit a blue-shift and the emission color was tuned from blue-green with color coordinates of (0.222, 0.324) to bright blue with color coordinates of (0.172, 0.132) upon 365 nm UV excitation as a function of x. These phosphors do not exhibit thermal quenching at high temperature, and this behavior is proposed to relate to the energy transfer from defect levels to the Eu²⁺ 5d band as also verified by thermoluminescence measurements, and the result demonstrated that the reported K_xCs_1−xAlSi₂O₆:Eu²⁺ phosphors may be candidates for blue-green components in UV-pumped high power white light emitting diodes (WLEDs).