Promising lanthanide-doped BiVO4 phosphors for highly efficient upconversion luminescence and temperature sensing

Abstract

The semiconductor oxide BiVO₄ has been intensively studied as a highly efficient photocatalyst. Here we attempt to adopt trivalent lanthanide (Ln³⁺)-doped BiVO₄ as a novel upconversion luminescence (UCL) material for achieving high-efficiency UCL and temperature sensing under near-infrared (NIR) irradiation. Er³⁺/Tm³⁺, Yb³⁺/Er³⁺, and Yb³⁺/Tm³⁺ ions were selected to co-dope the BiVO₄ phosphors, achieving three primary colors of red, green, and blue (RGB) with high color-purity. At an optimal doping concentration, the upconversion quantum yield of the BiVO₄:8%Yb³⁺,18%Er³⁺ phosphor reaches as high as 2.9%. Furthermore, we, for the first time, demonstrate the non-contact temperature sensing properties of a BiVO₄:Er³⁺,Tm³⁺ phosphor via employing fluorescence intensity ratio technology. The results show that the maximum absolute thermal sensitivity is ≈70 × 10^–4 K⁻¹ at 473 K under 980 nm excitation, with high and stable sensitivity of more than 60 × 10⁻⁴ K⁻¹ over a wide temperature range of 333–493 K. In addition, at a much safer wavelength of 1550 nm, this sample achieves maximum absolute sensitivity of 56 × 10⁻⁴ K⁻¹ at 453 K. Moreover, the BiVO₄:Er³⁺,Tm³⁺ phosphor presents high relative sensitivity of about 1.1% K⁻¹ under both 980 and 1550 nm excitation at 293 K. These results indicate that the BiVO₄ semiconductor oxide can be used as a novel host to achieve high UCL efficiency and promising thermal sensing performance, suggesting potential applications in the new fields of anti-counterfeiting, displays, and non-contact temperature sensors.