Controlling multi luminescent centers via anionic polyhedron substitution to achieve single Eu2+ activated high-color-rendering white light/tunable emissions in single-phased Ca2(BO3)1-x(PO4)xCl phosphors for ultraviolet converted LEDs

Abstract High luminous efficacy, high-color-rendering index (CRI), single-phased and single Eu 2+ doped warm white-light phosphors Ca 2 (BO 3 ) 1− x (PO 4 ) x Cl were synthesized by controlling anion substitution systematically. The anionic polyhedron substitution of PO 4 for BO 3 causes a great distortion of the host lattice, which enables the tuning of luminescent properties. An additional distinct emission peaking at 462 nm (in addition to 577 nm of Ca 2 BO 3 Cl:Eu 2+ ) was observed under the same excitation when PO 4 3− was introduced. Therefore, with the crystal structure evolution, the ratio blue/yellow was changed by adjusting the ratio of BO 3 /PO 4 , which provides a new way for developing a high CRI warm white-light phosphor. The internal quantum efficiency (IQE) of the Ca 2 (BO 3 ) 0.64 (PO 4 ) 0.36 Cl:Eu 2+ phosphor was 64.0%. The warm white light-emitting diode (w-LED) was fabricated with Ca 2 (BO 3 ) 0.64 (PO 4 ) 0.36 Cl:Eu 2+ phosphor and a 380 nm-emitting InGaN chip, which exhibited promising properties, such as the high Ra (83.4), the low correlated color temperature (3907 K) and high luminous efficacy ɳ L (30.4 lm/W). Importantly, the w-LED shows a greater R9 = 39.3 versus R9 = 14.3 of commercial YAG:Ce 3+ . These phenomenon demonstrates that Ca 2 (BO 3 ) 1− x (PO 4 ) x Cl:Eu 2+ as a warm white-light phosphor will have a great prospect of application in indoor lighting.