Mu-Huai Fang et al.RU-SHI LIU2021-08-032021-08-0320218974756https://www.scopus.com/inward/record.uri?eid=2-s2.0-85103508904&doi=10.1021%2facs.chemmater.1c00180&partnerID=40&md5=f032e225047f9907f7f41932f4d74118https://scholars.lib.ntu.edu.tw/handle/123456789/575846Narrowband green phosphors with high quantum efficiency are required for backlighting white light-emitting diode (WLED) devices. Materials from the A[Li3SiO4]4:Eu2+ family have recently been proposed as having superior properties to industry-standard β-SiAlON green phosphors. Here, we show that a cheap, easily synthesized host NaK2Li[Li3SiO4]4 (NKLLSO) doped with a mixture of Eu2+ and Eu3+ is an outstanding narrowband green phosphor, with an external quantum efficiency of 51% and superb thermal stability (97.1% of room-temperature performance at 150 °C). Structural studies reveal that green emission occurs from two Eu2+ sites, while Eu3+ introduces a high concentration of vacancies that may suppress quenching from energy transfer between Eu2+ sites. A WLED package constructed using our NKLLSO phosphor shows extremely high color vividness, competitive with a β-SiAlON comparator. This work will stimulate further research on efficient green phosphors for practical WLED devices. ? 2021 American Chemical Society.Energy transfer; Green manufacturing; Light emission; Light emitting diodes; Phosphors; Silicon; External quantum efficiency; Green emissions; Green phosphor; High quantum efficiency; Industry standards; Structural studies; Temperature performance; White light emitting diodes; Quantum efficiency[SDGs]SDG7journal article10.1021/acs.chemmater.1c001802-s2.0-85103508904