High-efficiency RbASiF6:Mn4+ (A = K, Cs) phosphors obtained by one-step green synthesis method

Red-emitting Mn 4+ -doped fluoride phosphors are recognized as promising materials for high-performance warm white light-emitting diodes (WLEDs). However, the extensive use of toxic hydrofluoric acid in traditional synthesis methods hinders their development and commercialization. Furthermore, the traditional solid-phase method often has cumbersome sintering steps, high temperature, long holding time, and certain safety hazards, so it is very necessary to develop a green synthesis method with simple steps and low energy consumption. In this study, a low-temperature solid-state method is proposed to synthesize Rb A SiF 6 :Mn 4+ ( A = K, Cs) phosphors by one step. Optimal emission intensities were observed at Mn 4+ concentrations of 1.2 % in RbKSiF 6 and 2.1 % in RbCsSiF 6 . These phosphors demonstrated high thermal stability. At 423 K, the photoluminescence intensities of RbKSiF 6 :1.2 %Mn 4+ and RbCsSiF 6 :2.1 %Mn 4+ reached 114 % and 87 % of their respective values at room temperature. Meanwhile, the chromaticity shifts were almost negligible, and high color purity was achieved for both phosphors. The electro-optical performance of WLED devices utilizing these phosphors, in combination with YAG:Ce 3+ and GaN chips, showed high color rendering indices (CRI) and low correlated color temperatures (CCT) across varying currents. Specifically, under a driving current of 20 mA, the device incorporating RbKSiF 6 :1.2 %Mn 4+ exhibited a CRI of 94 and a CCT of 3732 K, with a luminous efficacy of 61 lm/W. These findings highlight the potential of green-synthesized RASFM phosphors in advancing the application of warm WLEDs. One-step green synthesis method without HF is used to prepare Rb A SiF 6 :Mn 4+ ( A = K, Cs) phosphors with good thermal stability for white LEDs. • A low-temperature solid-state method without HF is used to prepare red phosphors. • Rb A SiF 6 :Mn 4+ phosphors shows highly luminescent efficiency and thermal stability. • The LED incorporating RbKSiF 6 : Mn 4+ exhibited a CRI of 94 and a CCT of 3732 K.