Photoluminescence Properties of CsZn2B3O7∶Eu2+Broadband Green-emitting Phosphor for White Light-emitting Diodes
Near-ultraviolet pumped white light-emitting diodes(NUV-WLED),which are based on the combination of NUV LED chip with red,green and blue trichromatic phosphors,can effectively alleviate the"blue light harm"and improve the color rendering index.However,developing broadband tricolor phosphor with lower synthesis temperature is the key for large-scale application of NUV-WLED.In this study,CsZn2B3O7(hereinafter abbreviated as CZBO)with low synthesis tem-perature and multiple cationic sites was selected as the matrix material.A series of Csi-xZn2B3O7∶xEu2+(0.005≤x≤0.03,hereinafter abbreviated as CZBO∶xEu2+)broadband green phosphors were synthesized by high-temperature solid-state reac-tion method.The emission peak and full width at half maximum of CZBO∶xEu2+green phosphor are 508 nm and 109 nm,respectively.CZBO∶xEu2+phosphors exhibit a broadband absorption around 373 nm,which can be well matched with 365 nm ultraviolet LED chips.There are three Eu2+luminescence centers in the CZBO∶xEu2+phosphors,i.e.the Eu2+ions occu-pied in the Cs(1),Cs(2)and Cs(3)sites,respectively.The optimal doping concentration of Eu2+ions is 0.015,and the concen-tration quenching mechanism is dipole-dipole interaction.CZBO∶0.015Eu2+phosphor shows good chemical stability,whose emission intensity can still remain 98.7%of that of the pristine sample after being exposed to ambient atmosphere for 30 d.The color rendering index of LED device fabricated by coating CZBO∶0.015Eu2+green phosphor,commercial BaMg-Al10O17∶Eu2+blue phosphor and commercial(Ca,Sr)AlSiN3∶Eu2+red phosphor on a 365 nm ultraviolet LED chip is as high as 87.This fabricated LED device shows a stable warm white light emission under different currents(30~300 mA),and its color coordinates,color rendering index and related color temperature are almost unchanged.These results indicate that the CZBO∶0.015Eu2+green phosphor reported in this study has a potential application prospect in the field of ultraviolet LED chip driven white light emitting diode lighting.