Preparation and luminescence properties of Ba0.92-xSrxAl2Si2O8:0.08Eu2+ blue-cyan phosphors for white light LEDs

Abstract

Currently, there is a cyan gap in white light-emitting diodes (LEDs) manufactured by combining near-ultraviolet (NUV) chips with tricolour (blue/green/red) phosphors, resulting in a poor colour rendering index (Ra). Broadband blue-cyan phosphors contain blue, cyan and green luminescent components that complement the cyan gap. In this paper, feldspar-structured Ba0.92-xSrxAl2Si2O8:0.08Eu2+ (x = 0–0.5) phosphors were prepared by a high-temperature solid-phase method and a cation substitution strategy. A phase transition was achieved by varying the concentration of x, which resulted in the formation of two luminescent centres and a 10.33-fold enhancement of the luminescence intensity for Ba0.92Al2Si2O8:0.08Eu2+. The colour of the emission changed from the original green to blue-cyan, and the strongest emission peak with a half-height width of 94.5 nm was observed at a Sr2+ concentration of 0.3 (30%) and covered the blue, cyan and green wavelength ranges (390–600 nm). The experimental value of the optical band of the substrate is 5.71 eV, and the luminous intensity of the Ba0.62Sr0.3Al2Si2O8:0.08Eu2+ sample at 150 °C was 91.3% of that at room temperature. Ba0.62Sr0.3Al2Si2O8:0.08Eu2+, (Ca, Sr) AlSiN3:Eu2+ and 365 nm NUV chips were successfully packaged into white LED devices. The colour rendering index (Ra) of the prepared white LED devices was 87, R9 was 89, the colour coordinates were (0.3763, 0.3382), and the colour temperature was 3759 K, which effectively solves the problem of the lack of cyan luminescent components in white LED devices and simplifies the manufacturing process of white LEDs.