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

Novel Y1–x–yVO4: xDy3+, yBi3+ (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 4F9/2 – 6H13/2 transition of Dy3+ and the emission of the VO3−4–Bi3+ complex respectively. The optimum chromaticity index of Y1–x–yVO4:xDy3+, yBi3+ (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.