Efficient violet-light-excitable blue-cyan-emitting Ca2YHf2GaAl2O12:Ce3+ garnet phosphors enable high-color-rendering full-spectrum warm-white LEDs

High-color-rendering full-spectrum warm-white light-emitting diodes (LEDs) are in great demand in the field of high-end solid-state white lighting. However, the so-called cyan gap (480-520 nm) in conventional white LEDs always limits their color rendering index (CRI) values, and thus there is a pressing need for cyan phosphors to fabricate full-spectrum white LEDs. Herein, we report on an efficient violet-excited blue-cyan-emitting Ca2YHf2GaAl2O12:Ce3+ 2 YHf 2 GaAl 2 O 12 :Ce 3 + (CYHGA:Ce3+) 3 + ) garnet phosphor, which is capable of realizing full-spectrum warm-white LEDs with superior CRI (Ra = 98.2, R12 = 96, R9 = 95) and low correlated color temperature (CCT) of 3735 K. Importantly, when excited at 398 nm, the optimal CYHGA:2%Ce3+ 3 + sample exhibits a strong broadband blue-cyan emission (emission peak: 473 nm; emission bandwidth: 92 nm) with high luminescence efficiency (internal quantum efficiency: 69.9 %; external quantum efficiency: 43.3 %), which perfectly covers both blue and cyan spectral region and enables to close the so-called cyan gap. The fabricated warm-white LED device based on CYHGA:2%Ce3+ 3 + blue-cyan phosphor generates bright warm-white lights with ultra-high CRI values (Ra >= 96.5; R12 >= 94; R9 >= 93) and low CCT values (3674-3845 K) upon 20-320 mA driving currents. Thus, blue-cyan- emitting CYHGA:Ce3+ 3 + garnet phosphors possess a bright application prospect in high-quality full-spectrum LED lighting.