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

Novel Y_1 - x - yVO_4:xDy^3 + , yBi^3 + (0.01 \le x \le 0.05, 0 \le y \le 0.20) phosphors for light emitting diode (LED) were successfully synthesised by solid-state reaction. The calculation results of electronic structure show that YVO_4 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 YVO_4:Dy^3 + samples, the Dy^3 + , Bi^3 + co-doped samples show a more intensive emission peak (at 574 nm) and a new broad emission band (450--770 nm), due to the ^4F_9 / 2-^6H_13 / 2 transition of Dy^3 + and the emission of the VO_4^3 - -Bi^3 + complex respectively. The optimum chromaticity index of Y_1 - x - yVO_4:xDy^3 + , yBi^3 + (0.01 \le x \le 0.05, 0 \le y \le 0.20) is (0.447, 0.497), which indicates that YVO_4:Dy^3 + , Bi^3 + has higher colour saturation than the commercial phosphor YAG: Ce^3 + . The effects of concentration of Dy^3 + , Bi^3 + , electric states and the photoluminescence properties are discussed in details.