A yellow-green-emitting phosphor K3LaSi2O7:Eu2+ with superior thermal stability for solid-state lighting

Abstract

Yellow-green-emitting phosphors with good thermal stability when excited by ultraviolet (UV) light are relatively less common compared to blue and red phosphors. In this study, a serial of K3LaSi2O7:xEu2+ (KLSO: xEu2+) phosphors with hexagonal structure (P63/mcm space group) were successfully synthesized. Under 360 nm excitation, KLSO: xEu2+ exhibits yellow-green luminescence peaked at 540 nm. Additionally, sharp emission peaks at 592 and 614 nm are observed when excited at 390 nm, indicating a small amount of Eu3+ ions still exist. The Eu2+ ions are found to occupy both La3+ and K+ sites in the KLSO host, resulting in two luminescent centers at 535 and 592 nm based on Gaussian fitting of the emission spectrum. The optimal Eu2+-doping concentration is verified at KLSO:0.05Eu2+. The thermal stability tests indicate that its luminescence intensity at 150 °C maintains 90.01 % of that at room-temperature. Meanwhile, the component substitution of Na+ ions for K+ ones is beneficial for the enhancement of luminescence, achieving a quantum efficiency of 40.62 %. Finally, this phosphor is applied to white LED, which shows a correlated color temperature (CCT) of 4164 K, a color rendering index (CRI) of 86.6, and CIE color coordinate of (0.3604,0.3174). It indicates that K3LaSi2O7:xEu2+ is a promising candidate for solid-state lighting.