Red-shift of vanadate band-gap by cation substitution for application in phosphor-converted white light-emitting diodes

Eu3+ doped YVO4 is excellent traditional red phosphor, but shifting its efficient excitation band to a longer wavelength is necessary for application in white light-emitting diodes, and is a big challenge that calls for good solution. Following the observation that cation substitution usually is an effective way to manipulate the band-gap of phosphors, we carried out ab initio calculation for the band-gap of pure and Bi3+ doped LnVO4 (Ln = Y, Lu, and Sc). The results show that the band-gap decreases with the cationic radius from Y3+ to Sc3+, and the doping of Bi3+ further decreases their band-gaps. The experimental results on the Eu3+ doped and Eu3+, Bi3+ co-doped LnVO4 (Ln = Y, Lu, and Sc) phosphors confirm this. In particular, the excitation of Eu3+ and Bi3+ co-doped ScVO4 is shifted to approach 400 nm, which fulfills the excitation requirement of near-ultraviolet-based white light-emitting diodes, and implies that Eu3+ and Bi3+ co-doped ScVO4 should be a promising candidate as red phosphor in white light-emitting diodes.