La ³⁺ –Al ³⁺ cosubstitution and enhanced luminescence in the green SrAl ₂ Si ₂ O ₈ :Mn ²⁺ for liquid crystal display backlights

Abstract Mn 2+ ‐activated green phosphors have attracted extensive attention due to narrow emission band and high color purity, which are expected to be applied in white light‐emitting diodes (LEDs) backlight for ultrahigh color gamut liquid crystal display. However, due to the d–d forbidden transition of Mn 2+ , its luminescence intensity is greatly limited. Herein, considering the optimization principles of matrix structure, we have designed a new strategy to modify the SrAl 2 Si 2 O 8 (SASO) host that La 3+ –Al 3+ ions substitute for Sr 2+ –Si 4+ and synthesized a series of Sr 1 − x La x Al 2 + x Si 2 − x O 8 :Mn 2+ (SL x ASO:Mn 2+ ) phosphors by the high‐temperature solid‐state reaction. In comparison to La/Al monodoping, the codoping modification of matrix structure can optimize the local crystal structure surrounding the luminescence center. Under excitation at 450 nm, a green emission peaks at 516 nm with full‐width at half‐maximum (FWHM) of 29.3 nm. The effects of La 3+ –Al 3+ cosubstitution on crystal structure and luminescence properties have been discussed by the fluorescence decay curves, diffuse reflectance spectra and polyhedron distortion. The luminescence intensity is greatly enhanced with the increase of La 3+ –Al 3+ cosubstitution and reaches the maximum value at x = 0.2, which is up to 15 times as the undoped sample. This paper provides a feasible new method for improving the luminescence performance of Mn 2+ ‐activated aluminosilicate green phosphor.