High-performance narrow-band green-emitting phosphor enabled by substituting Na with Rb

Exploring green phosphors with satisfactory peak position (525–535 nm) and full width at half-maximum (FWHM) to replace the commercial narrow-band green β-SiAlON:Eu 2+ phosphor (λ em = 540 nm, FWHM = 54 nm) is crucial for realizing wide-gamut full-color liquid crystal display (LCD) devices. Here, taking the UCr 4 C 4 -type tetragonal phase RbNa 3 (Li 3 SiO 4 ) 4 :3%Eu 2+ (RN 3 (LSO) 4 :Eu 2+ ) blue phosphor as starting model, we substitute Na + with Rb + to synthesize a series of Rb 1+x Na 2.97-x (Li 3 SiO 4 ) 4 :3%Eu 2+ (0.1 ≤ x ≤ 2.5) (R 1+x N 2.97-x (LSO) 4 :Eu 2+ ) phosphors that exhibit tunable emission from blue to green. We demonstrate that Rb + -substitution triggers tetragonal-to-monoclinic phase transition, making Eu 2+ ions enter two new, cuboid-like Rb and Na sites and resultant green emission. With optimized content of Rb + , Rb 3 Na(Li 3 SiO 4 ) 4 :3%Eu 2+ (R 3 N(LSO) 4 :Eu 2+ ) green phosphor not only shows appropriate peak position (∼526 nm) and FWHM (∼43 nm) compared to β-SiAlON:Eu 2+ phosphor, but also high internal quantum efficiency (IQE) of 90.2% and superior thermal stability (integrated emission intensity at 150 °C is 105.7% of room-temperature performance). Using the green R 3 N(LSO) 4 :Eu 2+ phosphor, white light-emitting diode prototype shows a wide-color-gamut (111.2% National Television System Committee, NTSC). This work demonstrates that as-prepared green R 3 N(LSO) 4 :Eu 2+ phosphor has a potential application in LCD backlight display, and may stimulate more researches on exploring high-performance narrow-band UCr 4 C 4 -type phosphors. • Achieving high-performance narrow-band green Rb 3 Na(Li 3 SiO 4 ) 4 :Eu 2+ phosphor by substituting Na with Rb that not only exhibits appropriate peak position (526 nm) and FWHM (43 nm) but also high IQY of 90.2%. • Rb 3 Na(Li 3 SiO 4 ) 4 :Eu 2+ green phosphor shows good thermal stability properties with an integrated emission intensity of 105.7% at 150 °C. • Using the green Rb 3 Na(Li 3 SiO 4 ) 4 :Eu 2+ phosphor, high-quality WLED can cover 111.2% of the color space of NTSC.