Using an excellent near-UV-excited cyan-emitting phosphor for enhancing the color rendering index of warm-white LEDs by filling the cyan gap. (June 2021)

• Record Type: Journal Article
• Authors: Zhang, Zongjie; Devakumar, Balaji; Wang, Shaoying; Sun, Liangling; Ma, Nan; Li, Wei; Huang, Xiaoyong
• Is Part Of: Materials today chemistry. Volume 20(2021)
• Publication Date: 2021-06
• Subjects: Ce3+ ions -- Ca2LuHf2Al3O12 -- Garnet phosphors -- Solid-state lighting -- Photoluminescence -- LED devices; Chemistry -- Periodicals; Materials -- Research -- Periodicals; Materials science -- Periodicals; Chemistry; Materials -- Research; Electronic journals; Periodicals; 660.282
• DOI: 10.1016/j.mtchem.2021.100471
• Languages: English
• ISSNs: 2468-5194

Abstract

Abstract: 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 Ce 3+ -doped Ca2 LuHf2 Al3 O12 (CLHAO) garnet, which could be used to cover the cyan gap for fabricating high-CRI warm-white LEDs. We found that the CLHAO:Ce 3+ 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 × 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:Ce 3+ 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. Graphical abstract: The near-UV-excitable Ca2 LuHf2 Al3 O12 :0.02Ce 3+ cyan phosphors with IQE = 84.3% and EQE = 60.8% were verified to be useful to cover the cyan gap and realize high-color-rendering white LEDs. Image 1 Highlights: Ce 3+ -doped Ca2 LuHf2 Al3 O12 cyan-emitting garnet phosphors were prepared. Their excitation spectra covered the wavelength range from 300 to 450 nm. Under 400 nm excitation, they can emit bright cyan luminescence with peaks around 477–493 nm. Ca2 LuHf2 Al3 O12 :0.02Ce 3+ phosphors showed high photoluminescence efficiency of IQE = 84.3% and EQE = 60.8%. The CRI value of white LED can be improved from 83.2 to 89.4 using Ca2 LuHf2 Al3 O12 :0.02Ce 3+ phosphors.