Green synthesis, luminescent properties and application for WLED of flower-like K2LiAlF6:Mn4+ phosphor

Chrysanthemum-like K2LiAlF6:Mn4+ phosphors were synthesized by simple co-precipitation method without using HF. The K2LiAlF6:Mn4+ phosphor can be effectively excited through blue light at 465 nm, then produces sharp red-light emission near 634 nm. The luminescence quenching of Mn4+ is caused by the d-d interaction between Mn4+ ions. The effects of surfactant and lithium source on the luminescent properties of K2LiAlF6:Mn4+ phosphors were discussed. Mn4+ is located in a strong crystal field environment in the K2LiAlF6 matrix and its emission mechanism is discussed. Warm white light emitting diode (WLED) device, which is fabricated by coating a certain proportion mixture of yellow YAG:Ce3+ phosphor and red K2LiAlF6:5%Mn4+ phosphor on the blue GaN chip, has low correlation color temperature (CCT = 3588 K), high color rendering index (Ra = 90.8) and good electroluminescence stability under different currents. These properties illustrate that K2LiAlF6:5%Mn4+ phosphor is a promising red light emitting material.