Warm White Light with a High Color-Rendering Index from a Single Gd₃Al₄GaO₁₂:Ce³⁺ Transparent Ceramic for High-Power LEDs and LDs

Abstract

Transparent ceramics (TCs) are promising for high-power (hp) white light-emitting diode (WLED) and laser diode (LD) lighting. However, comfortable warm white light has not been achieved only using a single TC in hp-WLEDs/LDs. Herein, highly transparent Gd₃Al₄GaO₁₂:Ce³⁺ (GAGG:Ce³⁺) TCs (transmittance, T = 55.9-80.2%) were prepared via a solid-state reaction. Ce³⁺ as a doped activator center in grains plays a positive role in luminescence based on the microstructural investigations by scanning electron microscopy and the cathodoluminescence system. T decreases upon increasing the Ce³⁺ concentration and/or the ceramic thickness, whereas the luminous efficacy of hp-WLEDs/LDs goes up. For blue hp-LEDs driven at 350 mA or LDs of 2 W, warm white light with a low correlated-color temperature of ∼3000 K was achieved by a single GAGG:Ce³⁺ TC, benefiting from its broad emission band (full width at half maximum, FWHM = 133-137 nm) and abundant red components (peaking at about 568-574 nm). The color-rendering index of hp-WLEDs reaches 78.9. These results are much better than the performance of the traditional Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) TC, indicating that GAGG:Ce³⁺ TCs are promising color converters for hp-WLEDs/LDs with a comfortable warm white light.