Based on luminescence intensity ratio (LIR) technology,
the noncontact
upconversion (UC) optical temperature sensor has aroused a great deal
of interest due to its great application prospects in some extreme
environments. However, most of the studies focused on improving its
sensitivity due to the fact that the sensitivity can be influenced
by many external field factors, such as the power density and pulse
width of pumping sources or temperature. Herein, a green-emitting
UC phosphor Sr2InF7: Yb3+, Er3+ was developed as a potential thermometer, which retained
bright green emission under 980 nm excitation with different pulse
widths and power densities or at different temperatures; the possible
mechanisms are discussed in detail. Its sensitivity almost remained
constant when using both continuous wave (c.w.) and pulsed laser or
different power densities, which meant the sensitivity of Sr2InF7: Yb3+, Er3+ was independent
of the characteristics of pumping laser. A flexible thin-film thermometer
composed of Sr2InF7: 2%Yb3+, 2%Er3+ was also fabricated to detect the temperature of microelectronic
components, which can not only accurately measure the temperature
of the working electronic circuit board but also exhibit excellent
repeatability. The results indicated that the present noncontact UC
temperature sensor showed stable green emission and thermometric sensitivity
as well as the possibility of replacing the traditional thermometers.