Optimizing and adjusting the photoluminescence of Mn-doped fluoride phosphors via forming composite particles.

Nowadays, Mn4+-doped red phosphors are widely used in white LEDs to improve the color rendering index and decrease the correlated color temperature. Great efforts have been made to enhance the luminous efficiency. In this work, new composite particles containing two fluorides with similar structures K2LiAlF6 and K2NaAlF6 were developed to improve the emission intensity. The composite particles contain K2LiAlF6 and K2NaAlF6 phases with an increase of Na content. The particle sizes of the products were in the nanoscale and the element distribution was investigated. Importantly, the as-prepared composite particles had higher emission intensity than simple mixtures. Structural and optical characterization studies were systematically carried out to understand the enhancement mechanism. Finally, a white LED device was fabricated by combining the synthesized red phosphor and YAG:Ce on a blue chip.