Systematic studies on Yb Bi_1- VO₄:Tm³⁺ solid solutions: experiments and DFT calculations on up-conversion...

Compound solid solutions have attracted intensive attention due to their adjustable structure, electronic structure, and optical properties. Despite tremendous advances in compound solid solution preparations, combining a rare metal compound and a bismuth compound with the same crystal phase by forming a compound solid solution is still challenging but fascinating. For example, RE_1- Bi VO₄ with a zircon-type structure exhibits tunable band gaps and photoluminescence performance with varying RE compositions. Herein, Yb_1- Bi VO₄ solid solutions with continuous monophasic phase prepared by a facile synthesis strategy that is combined with co-precipitation and hydrothermal methods are reported. By doping a small amount of Tm³⁺, Yb Bi_1- VO₄ solid solutions can achieve a broad range up-conversion photoluminescence from UV-light to NIR-light. Combined with DFT calculations, the underlying mechanism of experimental observations is explained. In these up-conversion processes, the existence of Tm³⁺ is an essential factor. In particular, the NIR-to-UV up-conversion photoluminescence of Yb Bi_0.98- VO₄: 2 mol% Tm³⁺ solid solution is very interesting and a worthy phenomenon for further studies. As such, designing compound solid solutions may provide a new avenue for controllable up-conversion efficiencies in semiconductor nanocrystals and also a novel insight into the rational tunable up-conversion process for applications in biological labeling and imaging.