A novel yellow-green garnet phosphor to narrow the cyan gap for high-color-rendering full-spectrum WLEDs

The pursuit of full-spectrum white light-emitting diodes (WLEDs) with high color rendering is often hampered by the “cyan gap”, a spectral deficiency that compromises light quality. Herein, we narrow this gap by developing a novel yellow-green-emitting Y 2- x CaScAl 3 SiO 12 :0.06Ce 3+ (YCSASO:0.06Ce 3+ ) garnet phosphor. A series of YCSASO: x Ce 3+ ( x  = 0.01-0.16) garnet phosphors is synthesized and systematically studied. Structural analysis confirms that all phosphors crystallize in a pure cubic garnet structure, with Ce 3+ ions occupying the dodecahedral sites of Y 3+ and leading to a slight lattice expansion. Upon 450 nm excitation, the YCSASO: x Ce 3+ phosphors exhibit a wide asymmetric band characteristic of the Ce 3+ emission (5d 1 →4f). The tunability of the emission color across the green-to-yellow region is achieved through variation of Ce 3+ concentration, because of enhanced crystal field splitting and resonant energy transfer. YCSASO:0.06Ce 3+ as the optimal composition effectively narrows the cyan gap, exhibiting a broad emission band centered at 549 nm with a full width at half maximum (FWHM) of 124 nm, an internal quantum efficiency (IQE) of 56.3%, and an external quantum efficiency (EQE) of 28.4%. First-principles calculations indicate that incorporating Ce 3+ 5d states narrows the host bandgap, facilitating efficient electron transitions. This phosphor achieves stable thermal performance by maintaining 59% of its initial intensity at 423 K and remarkable color stability with a chromaticity shift as low as Δ E  = 5.1 × 10 −3 . A prototype WLED based on this yellow-green phosphor, a 455 nm blue LED chip, and a red-emitting CaAlSiN 3 :Eu 2+ phosphor maintains excellent stability for at least 12 h and generates high-quality warm white light, achieving a color rendering index (Ra = 92.2), a correlated color temperature (CCT = 3490 K), and a luminous efficacy of 52.6 lm/W. This work validates the strategic use of the yellow-green YCSASO:0.06Ce 3+ phosphor to narrow the cyan gap, paving the way for advanced full-spectrum lighting.