A novel yellow emitting phosphor Dy3+, Bi3+ co-doped YVO4 potentially for white light emitting diodes

Novel Y1-x-yVO4:xDy(3+), yBi(3+) (0.01 <= x <= 0.05, 0 <= y <= 0.20) phosphors for light emitting diode (LED) were successfully synthesised by solid-state reaction. The calculation results of electronic structure show that YVO4 has a direct band gap with 3 eV at G. The top of the valence band is dominated by O 2p state and the bottom of the conduction band is mainly composed of O 2p and V 3d states. An efficient yellow emission under near-ultraviolet (365 nm) excitation is observed. Compared with the pure YVO4:Dy3+ samples, the Dy3+, Bi3+ co-doped samples show a more intensive emission peak (at 574 nm) and a new broad emission band (450-770 nm), due to the F-4(9/2) - H-6(13/2) transition of Dy3+ and the emission of the VO43- -Bi3+ complex respectively. The optimum chromaticity index of Y1-x-yVO4:xDy(3+), yBi(3+) (0.01 <= x <= 0.05; 0 <= y <= 0.20) is (0.447, 0.497), which indicates that YVO4:Dy3+, Bi3+ has higher colour saturation than the commercial phosphor YAG: Ce3+. The effects of concentration of Dy3+, Bi3+, electric states and the photoluminescence properties are discussed in details.