Using an excellent near-UV-excited cyan-emitting phosphor for enhancing the color rendering index of warm-white LEDs by filling the cyan gap

White light-emitting diodes (LEDs) with high color rendering index (CRI) and low correlated color temperature (CCT) are desirable for next-generation solid-state lighting. In this work, we demonstrated an efficient near-UV-excited cyan-emitting phosphor based on Ce3+-doped Ca2LuHf2Al3O12 (CLHAO) garnet, which could be used to cover the cyan gap for fabricating high-CRI warm-white LEDs. We found that the CLHAO:Ce3+ samples exhibited a broad excitation band in the 300-450 nm wavelength range peaking at 400 nm, and upon 400 nm excitation they showed broad cyan emission bands in the 420-600 nm spectral region with peak positions ranging from 477 to 493 nm. The optimal CLHAO:0.02Ce(3+) sample had CIE color coordinates of (0.160, 0.255), and its internal and external quantum efficiencies were measured to be 84.3% and 60.8%, respectively. Impressively, the luminescence intensity of CLHAO:0.02Ce(3+) sample at 423 K still remained at 62% of the initial value at 303 K, and the chromaticity shift was calculated to be as low as 1.7 x 10(-2), revealing its high thermal stability and color stability at a higher temperature. Finally, a warm-white LED device (CCT = 3,194 K) was fabricated by combining CLHAO:0.02Ce(3+) cyan phosphors with commercial blue/green/red tricolor phosphors, showing bright white-light emission with a high CRI of 89.4, which was superior to that of another warm-white LED device (CRI = 83.2) fabricated without CLHAO:0.02Ce(3+) cyan phosphors. These outstanding luminescence properties of CLHAO:Ce3+ cyan phosphors illustrated that they offer a new feasible approach for the production of high-CRI warm-white LEDs toward high-color-quality solid-state lighting. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study demonstrated the efficient application of Ce3+-doped phosphors based on CLHAO garnet in the fabrication of high-CRI warm-white LEDs, showing good optical performance and thermal stability. By combining with commercial phosphors, warm-white LED devices with high CRI and superior color quality can be produced.