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 Ra = 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.