Enhancement of upconversion luminescence in Yb3+/Er3+-doped BiVO4 through calcination

Abstract

Dopant concentration is generally increased in order to enhance the emission efficiency of the upconversion phosphor materials. However, a higher doping concentration generally results in concentration quenching of the upconversion emission resulting in low upconversion efficiency. In such instances, the calcination technique can offer an alternate way of enhancing the emission efficiency of the upconversion phosphors. Here, Yb3+/Er3+-doped BiVO4 has been synthesized by microwave hydrothermal process and the as-synthesized phosphor was calcined at 900 °C in air. Yb3+/Er3+-doped BiVO4 phosphor has been systematically characterized. The elemental distribution is homogeneous. Phase change has occurred from the tetragonal BiVO4 of the as-synthesized sample to the mixture of tetragonal and monoclinic BiVO4 in the calcined sample. The bandgap of the calcined sample has been reduced by 0.52 eV as compared to the as-synthesized one. Under 980 nm excitation, the calcined sample shows ∼ 7 and 15-fold enhancement in the upconversion and downshifting emission intensity, respectively, as compared to the as-synthesized sample. The calcination is found to have increased the lifetime of all the emitting excited states resulting in enhanced emission efficiency which has been confirmed by the time-resolved photoluminescence measurements.