Bright tunable white-light emissions from Bi3+/Eu3+ co-doped Ba2Y5B5O17 phosphors via energy transfer for UV-excited white light-emitting diodes

Abstract

Single-phased tunable white-emitting inorganic phosphors are important for fabricating high-performance white light-emitting diodes. Herein, we reported on the realization tunable white emissions from Bi3+ and Eu3+ ions co-doped Ba2Y5B5O17 phosphors by controlling the energy transfer process from Bi3+ to Eu3+ ions. In this paper, Bi3+ singly doped Ba2Y5B5O17 and Bi3+/Eu3+ co-doped Ba2Y5B5O17 phosphors were synthesized through the conventional high-temperature solid-state reaction method. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental mapping, photoluminescence (PL), and CIE color coordinates. Upon excitation by ultraviolet (UV) light at 345 nm, Bi3+ singly doped Ba2Y4.995Bi0.005B5O17 phosphors showed a broadband cyan emission with a maximum at 503 nm and a shoulder at 410 nm, due to 3P1→1S0 transition of Bi3+ ions. Concentration-dependent PL intensity study revealed that the Ba2Y5-xBixB5O17 phosphors had highest emission intensity at x = 0.005. In contrast, the Eu3+ singly doped Ba2Y4.2Eu0.8B5O17 phosphors exhibited dominant sharp red emission lines around 616 nm upon 396 nm UV excitation. Interestingly, efficient energy transfer from Bi3+ to Eu3+ ions was observed in Bi3+/Eu3+ co-doped Ba2Y4.995-yEuyBi0.005B5O17 phosphors. Consequently, after excitation at 345 nm into the Bi3+1S0→3P1 transition, the Ba2Y4.995-yEuyBi0.005B5O17 phosphors showed intense sharp red emissions around 611 nm of Eu3+ ions together with a broad cyan emission band centered at 410 nm and 503 nm due to Bi3+ ions. By changing the Eu3+/Bi3+ concentration ratio, tunable white emissions were achieved in Ba2Y4.995-yEuyBi0.005B5O17 phosphors. The corresponding CIE chromaticity coordinates of Ba2Y4.995-yEuyBi0.005B5O17 phosphors were tuned from cyan color (0.226, 0.350) to near white (0.309, 0.354) and ultimately to red color (0.640, 0.341) by gradually increasing the doping concentration of Eu3+ ions. Our results demonstrated that these as-prepared Bi3+/Eu3+ co-doped Ba2Y5B5O17 phosphors had promising application potential in UV-excited white light-emitting diodes.