Synthesis and photoluminescence properties of octahedral K2(Ge,Si)F6:Mn4+ red phosphor for white LED

Abstract

AbstractA novel red-emitting K2(Ge,Si)F6:Mn4+ phosphor with uniform morphology was synthesized by co-precipitation method. The pure K2GeF6 phase with P63mc space group other than P3m1 space group was affirmed just by incorporation of Si in K2GeF6 at room temperature according to XRD characterization. SEM images showed lamellar and octahedron grain morphology for K2GeF6:Mn4+ and K2(Ge,Si)F6:Mn4+ phosphors, respectively. It was also found that the photoluminescence excitation (PLE) and photoluminescence (PL) showed slight displacement in K2GeF6:Mn4+ and K2(Ge,Si)F6:Mn4+ system. And the zero-phonon line (ZPL) of the PL spectrum of K2GeF6:Mn4+ with Si showed a strong peak. Meanwhile crystalline field surrounding Mn4+ changes could affect the decay time in this fluoride system. The color gamut of the LED devices based on K2(Ge,Si)F6:Mn4+ and K2GeF6:Mn4+ reached up to 94.58% NTSC (National Television Standards Committee) and 94.386% NTSC, respectively, that was much higher than that based on nitride red phosphors. All these original characteristics in K2(Ge,Si)F6:Mn4+ phosphor are desirable for potential applications as a red phosphor for improving lighting and display quality of conventional white LEDs.