Synthesis, optical properties and application of Y7O6F9:Er3+ for sensing the chip temperature of a light emitting diode

Abstract

Submicron-sized Er³⁺ doped Y₇O₆F₉ phosphors were synthesized via the precipitation method and a subsequent annealing process. The influence of the Er³⁺ doping concentrations and the heating temperature on the luminescence of Y₇O₆F₉:Er³⁺ was investigated under the excitation of the Er^{3+ 4}G_11/2 level at 378 nm. Upon raising the Er³⁺ doping concentration, both the intensity and lifetime of the Er³⁺ green emission at 547 nm originating from ⁴S_3/2 → ⁴I_15/2 decrease, which is proved to be caused by energy transfer via cross relaxation between two neighboring Er³⁺ ions. The thermal sensing properties of Y₇O₆F₉:Er³⁺ were evaluated using the temperature dependent intensity ratio between the ²H_11/2–⁴I_15/2 and ⁴S_3/2–⁴I_15/2 transitions of Er³⁺ under 378 nm excitation. The experimental results show that the thermal sensitivity decreased with an increase in the Er³⁺ doping content, which is caused by the increased energy transfer probability among Er³⁺. The increased energy transfer of Er³⁺ reduces the thermalized population of Er³⁺ in the ²H_11/2 levels, which in turn decreases the thermal sensitivity. The applicability of Er³⁺ doped Y₇O₆F₉ as a thermal sensor was demonstrated by measuring the chip temperature of a 1 W InGaN type near-ultraviolet light emitting diode (n-UV LED).