Boosting broadband NIR luminescence in Mo4+-doped Cs2TeCl6 perovskite for toluene detection via cerium doping

Transition metal ion-activated phosphors are promising candidates for broadband near-infrared (NIR) spectroscopy applications. However, achieving high external quantum efficiency (EQE) and good thermal stability in low-dimensional halide perovskites has presented challenge. Herein, a design strategy based on cerium doping has been developed for realizing high-efficiency broadband NIR tetravalent molybdenum (Mo 4+ ) luminescence to overcome multivalent Mo-related lattice defects and self-absorption. Particularly, Ce 4+ , Mo 4+ -codoped Cs 2 TeCl 6 shows broadband NIR emissions ranging from 800–1300 nm with a full width at half-maximum of 186 nm, high EQE > 50% and good thermal stability (85%@150 °C). Experimental and theoretical studies verify the synergistic effects of breakdown of site symmetry, reduction of lattice defects and relaxation of the spin-selection rule of Mo 4+ . Moreover, gas sensing of toxic toluene with low detection limit and high sensitivity is presented due to strong molecular interaction-induced luminescence quenching. These findings provide new opportunities for broadband NIR spectroscopy applications.