Synthesis and Luminescence Properties of Bi3+-Activated K2MgGeO4: A Promising High-Brightness Orange-Emitting Phosphor for WLEDs Conversion

In this article we synthesized a series of phosphors K₂MgGeO₄:Bi³⁺ with high brightness for white light-emitting diodes (WLEDs) conversion and investigated their crystal structures and luminescence properties using powder X-ray diffraction, diffuse reflectance spectra, X-ray photoelectron spectroscopy, photoluminescence spectra, and absolute quantum efficiency. K₂MgGeO₄:Bi³⁺ phosphor exhibits intense absorption in near-UV area and presents a broad asymmetric emission band with the main peak located at 614 nm, which was ascribed to the ³P₁ → ¹S₀ transition of Bi³⁺. The absolute quantum efficiency of the K₂MgGeO₄:0.01Bi³⁺ phosphor was measured to be 66.6%. Also, this orange emission with color chromaticity coordinates of (0.4989, 0.4400) has an excellent resistance to thermal quenching: its integrated intensity at 393 K still maintained ∼85% of the one at room temperature. The WLEDs devices with R_a = 93.8 were fabricated by employing K₂MgGeO₄:0.01Bi³⁺ as an orange phosphor, which contains abundant red light component in its emission spectrum. The excellent luminescent performance of K₂MgGeO₄:0.01Bi³⁺ suggests that it is a promising orange-emitting phosphor for near-ultraviolet WLEDs.