Concentration quenching inhibition and fluorescence enhancement in Eu-doped molybdate red phosphors with two-phase mixing.

Red phosphor plays a crucial role in improving the quality of white light illumination and backlight displays. However, significant challenges remain to enhance red emission intensity in different matrix materials. Herein, a class of two-phase mixing red phosphors of NaIn(MoO):Eu (NIMO:Eu) has been successfully prepared by the traditional high-temperature solid-state reaction method. The coordination environment, phase structure, excitation and emission spectra, fluorescence kinetics, and temperature-dependent luminescence properties of the system have been studied comprehensively. It is worth mentioning that the red emission intensity continues to increase with the increased Eu doping concentration, and the fluorescence lifetimes remain unchanged. These extraordinary phenomena mainly stem from the special concentration quenching mechanism in such two-phase mixing material, namely, the increased lattice interface barriers from Eu six-coordinated units and Eu eight-coordinated units can effectively block the non-radiation by enlarging the average distance between luminescent centers. The improved fluorescence thermal stability and suppressed non-radiative transition rate in NIMO:40%Eu sample are further proving regulatory role of lattice interface barriers. In addition, a warm white light-emitting diode (LED) is successfully fabricated, exhibiting Commission Internationale de l'Eclairage (CIE) coordinates of (0.343, 0.335), a color rendering index (CRI) of 92.1, and a correlated color temperature (CCT) of 5013 K, showing significant application prospects for high-quality lighting devices.