Lanthanide-doped lead-free double perovskite La2MgTiO6 as ultra-bright multicolour LEDs and novel self-calibrating partition optical thermometer

The infinite potential of lanthanide in optoelectronic research has triggered the search for ideal host materials. Herein, based on the excellent lanthanide compatibility of double perovskite La2MgTiO6, light-responsive multifunctional phosphors with four modes were successfully constructed (Modes I–IV: Tm–Yb; Er–Yb; Ho–Yb; Er/Tm–Yb). After systematically exploring the internal mechanism of high-purity and brightness upconversion (UC) photoluminescence behind the four modes, intense green, blue and near-white lighting-emitting diodes (LEDs) were fabricated. Besides, aiming at the different emission energy levels of the monitored bands, the temperature-sensing performance of Modes I–IV was strictly evaluated utilizing thermally coupled or non-thermally-coupled luminescence intensity ratio (LIR) techniques. All the modes demonstrate excellent temperature measurement potential, stability and repeatability. Especially in Mode IV, a novel self-calibrating partition thermometer with dual-emitting centers originating from Er/Tm was designed successfully, which can provide specific LIR for three regions of low temperature, medium temperature and high temperature, and finally achieve high relative sensitivity over an ultra-wide temperature range. The results testify that the as-synthesized multifunctional phosphors break through the limitation of lanthanide doping types in a single material, which can realize the diversification of application functions and launch a new chapter for the design of advanced multifunctional materials.