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

Novel Y$_{1 - x - y}$VO$_{4}$:$x$Dy$^{3 + }$, $y$Bi$^{3 +}$ ($0.01 le x le 0.05, 0 le y le 0.20$) phosphors for lightemitting diode (LED) were successfully synthesised by solid-statereaction. The calculation results of electronic structure show thatYVO$_{4}$ has a direct band gap with 3~eV at $G$. The top of thevalence band is dominated by O 2p state and the bottom of theconduction band is mainly composed of O 2p and V 3d states. Anefficient yellow emission under near-ultraviolet (365 nm) excitationis observed. Compared with the pure YVO$_{4}$:Dy$^{3 + }$ samples,the Dy$^{3 + }$, Bi$^{3 + }$ co-doped samples show a more intensiveemission peak (at 574~nm) and a new broad emission band(450--770~nm), due to the $^{4}F_{9 / 2}-{}^{6}H_{13 / 2 }$transition of Dy$^{3 + }$ and the emission of the VO$_{4}^{3 -}-$Bi$^{3 + }$ complex respectively. The optimum chromaticity indexof Y$_{1 - x - y}$VO$_{4}$:$x$Dy$^{3 + }$, $y$Bi$^{3 + }$ ($0.01 lex le 0.05, 0 le y le 0.20$) is (0.447, 0.497), which indicatesthat YVO$_{4}$:Dy$^{3 + }$, Bi$^{3 + }$ has higher colour saturationthan the commercial phosphor YAG: Ce$^{3 + }$. The effects ofconcentration of Dy$^{3 + }$, Bi$^{3 + }$, electric states and thephotoluminescence properties are discussed in details.