A broadband cyan-emitting Ca2LuZr2(AlO4)3:Ce3+ garnet phosphor for near-ultraviolet-pumped warm-white light-emitting diodes with an improved color rendering index

Abstract

Finding efficient cyan phosphors with broadband absorption in the near-ultraviolet range (380–420 nm) and bright emission around 490 nm are highly important to make up for the so-called cyan gap (480–520 nm) in traditional tricolor (blue, green and red) phosphor-converted white light-emitting diodes (LEDs). Herein, we reported a new garnet phosphor, namely Ca₂LuZr₂(AlO₄)₃:Ce³⁺ (CLZA:Ce³⁺), with a cyan-emitting band, which enabled to fill the cyan gap and realize high color rendering white LEDs. The composition-optimized CLZA:1% Ce³⁺ phosphors showed an intense broad excitation band in the 370–475 nm wavelength range peaked at 408 nm and a broad asymmetric emission band at around 483 nm in the wavelength range of 414–650 nm. Importantly, the cyan-emitting CLZA:1% Ce³⁺ phosphors possessed a luminescence efficiency of 58%. Notably, the CLZA:1% Ce³⁺ cyan phosphors allowed to fill the cyan gap between the blue and green emission bands in white LEDs, and the value of color rendering index could be enhanced from 82.3 to 89.2. This study provides new insights into designing and developing suitable efficient phosphors for high-color-quality solid-state white lighting.