Color tuning of β-Ca3(PO4)2-type phosphor with enhanced quantum efficiency via self-charge compensation for healthy and warm solid state lighting application

Phosphor with high efficiency and tunable photoluminescence is critical to solid state lighting device. Herein, three β-Ca3(PO4)2-type phosphors with improvement of quantum efficiency and tunable emission color were synthesized through the self-charge compensation method via the incorporation of Na+ or K+. The quantum efficiency and emission intensity were increased by 2.81 and 1.99 times at most due to the reduction of Eu3+ to Eu2+ in Ca10Na(PO4)7:0.01Eu2+, which was ascribed to the achievement of charge balance and cavity neutralization in Na(4) site after the incorporation of Na+ in the neighboring Ca(1), Ca(2) and Ca(3) sites. Tunable emission colors from near white to green were realized owing to the change of occupation ratio of Eu2+ at Ca(1), Ca(2) and Ca(3) sites relative to Na(4) site. Moreover, this method was applied into the Ca10-yK1+y(PO4)7:0.01Eu2+ and 0.1Ca9Y(PO4)7–0.9Ca10-zNa1+z(PO4)7:0.01Eu2+, 0.22Mn2+ systems to verify the practicability of self-charge compensation. The quantum efficiencies of the two kinds of systems were increased by 1.66 and 1.28 times, respectively, along with the decrease of blue light ratio significantly. Additionally, no blue light hazard and warm WLEDs was fabricated via the modified single-phase full visible emission 0.1Ca9Y(PO4)7–0.9Ca9.9Na1.1(PO4)7:0.01Eu2+, 0.22Mn2+ phosphor, which exhibited an excellent color rendering index of 92.9 at a correlated color temperature of 3887 K. This work illustrated that the universal self-charge compensation method could efficiently improve the multifaceted properties of phosphor to meet the needs of modern lighting.