Self-calibrated multi-mode optical thermometry in up-converting phosphor Cs2NaErCl6: Yb3+

With the development of temperature measurement technology, people put forward higher requirements for the accuracy and precision of temperature measurement. However, most of the current luminescent thermometers use a single optical signal for temperature detection, which has a certain range of temperature insensitivity, resulting in inaccurate temperature measurement. Here, an all-inorganic rare-earth halide double perovskite Cs2NaErCl6: Yb3+ (CNEC: Yb3+) phosphor was synthesized, which not only expressed triple-mode thermometric properties based on thermally coupled levels (TCLs), non-thermally coupled levels (N-TCLs) and lifetime (FL), but also capable of providing self-referencing and high-sensitivity temperature measurements under excitation at 980 nm. Benefiting from the low phonon energy of the matrix, high doping concentration and the excellent internal up-conversion quantum efficiency (UCQY) about 6.52% of optimal composition CNEC: 40%Yb3+, all modes exhibit superior sensitivities, reversibility and thermal resolution under 980 nm irradiation. In addition, a flexible thin film thermometer composed of CNEC: 40%Yb3+ was prepared to realized multi-mode thermal monitoring of local hot spots of electronic components. The excellent three-mode temperature measurement results indicated that CNEC: Yb3+ phosphors have great potential in temperature sensing.