Tunable emission in Sr₉LiY_0.667(PO₄)₇: Eu²⁺, Mn²⁺ phosphor via energy transfer for pc-LEDs application

A novel tunable emitting phosphor of Sr₉LiY_0.667(PO₄)₇ (SLYP): Eu²⁺, Mn²⁺ was synthesized via a high-temperature solid-state reaction. The broad photoluminescence excitation band observed within the 250–450 nm region revealed the applicability of the SLYP: Eu²⁺, Mn²⁺ phosphor for both ultraviolet and near-ultraviolet excitation. The photoluminescence spectrum of SLYP: Eu²⁺, Mn²⁺ exhibited green emitting of Eu²⁺ at 520 nm and orange-red emitting of Mn²⁺ at 610 nm. Owing to the energy transfer (ET) process of Eu²⁺→Mn²⁺, the SLYP: Eu²⁺, Mn²⁺ sample exhibited a tunable polychromatic emission color ranging from green to red by adjusting Mn²⁺ concentration, achieving an ET efficiency as high as 69.89%. The SLYP: 3%Eu²⁺, 20%Mn²⁺ sample also demonstrated an exceptional internal quantum efficiency value of 71.53% under 345 nm excitation. The luminescent intensity of SLYP: 3%Eu²⁺, 20%Mn²⁺ phosphor remained at 76.53% at 423 K compared to room temperature, with only minor chromaticity changes at elevated temperatures, further confirming its excellent thermostability. These findings suggest that the tunable polychromatic emitting color phosphor of SLYP: Eu²⁺, Mn²⁺ has potential applications in phosphor-converted light-emitting diodes.