[10a-N303-1~11] 13.8 Optical properties and light-emitting devices

▲ [10a-N303-3] Insights into the saturation mechanism of LED phosphors

〇Jian Xu¹, Kohsei Takahashi¹, Takayuki Nakanishi¹, Takashi Takeda¹, Naoto Hirosaki¹ (1.NIMS)

Keywords:Phosphor, Time-resolved spectroscopy

Inorganic phosphors, as key components (color converters) in LEDs, their properties such as excitation/emission bands, luminescent lifetime, chemical/physical stability, directly determine the performance of LED devices. Recently, high-power solid-state lighting souces are rapidly pursued particularly used in laser projector, headlamp of automobile, etc, in which high-power-density of laser sources are employed as excitation sources instead of semiconducting diodes. However, even the best performance phosphors suffer from the emission “droop” or “saturation quenching” under high-power-density excitation, which motivates us trying to understand the mechanism of this saturation effect. Herein, three commercial LED phosphors: Y₃Al₅O₁₂ (YAG):Ce³⁺, CaAlSiN₃ (CASN):Eu²⁺ and K₂SiF₆ (KSF):Mn⁴⁺ are used as research targets, taking into account the large excited-state lifetime variation of Ce³⁺, Eu²⁺ and Mn⁴⁺. Time-resolved spectroscopy under laser excitation with different power density is investigated in detail, in order to clarify the relationship between ground-state depletion and luminescent quenching, especially under severe laser pumping.