Design of Novel Highly Efficient Yellow-Orange Color-Tunable Luminescence in Rb2Sr1-yCayP2O7:xEu2+ Solid Solutions for White Light-Emitting Diodes.

Traditional white light-emitting diodes (WLEDs) are limited by the energy loss due to reabsorption. Integrating binary complementary color phosphors with near-ultraviolet (n-UV) LED chips can be a good solution, and the core of it is to develop yellow-emitting phosphors. In this work, we have designed Rb2Sr1-yCayP2O7:xEu2+ solid solutions with yellow-orange color-tunable luminescence. The crystal structure, luminescence properties, and potential applications for WLEDs were explored systematically. Under n-UV light excitation, the phosphors efficiently emit broadband yellow-orange emission. The reasons and mechanisms of the variation of the PL/PLE spectra have been investigated. The optimal Rb2SrP2O7:0.5% Eu2+ sample exhibits a high quantum efficiency of 72.96% with a good color purity of 87.1%. Upon combination of the BAM:Eu2+ and Rb2SrP2O7:0.5% Eu2+ phosphors with a 380 nm n-UV chip, a WLED device is fabricated and can emit white light with good performance.