High-Performance NaK2Li[Li3SiO4]4:Eu Green Phosphor for Backlighting Light-Emitting Diodes

Narrowband green phosphors with high quantum efficiency are required for backlighting white light-emitting diode (WLED) devices. Materials from the A[Li 3 SiO 4 ] 4:Eu 2+ 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 NaK 2 Li[Li 3 SiO 4 ] 4 (NKLLSO) doped with a mixture of Eu 2+ and Eu 3+ 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 Eu 2+ sites, while Eu 3+ introduces a high concentration of vacancies that may suppress quenching from energy transfer between Eu 2+ 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.