Efficient and Anti‐Thermal Quenching Luminescence of Ce ³⁺ Sensitized Rare‐Earth‐Based Double Perovskite Cs ₂ NaHoCl ₆ Single Crystals for Versatile Photoelectric Applications

ABSTRACT Lead‐free halide double perovskites (DPs) have attracted growing attention owing to their eco‐friendly composition and remarkable optoelectronic performance. However, it remains a challenge to develop DPs that simultaneously achieve high photoluminescence quantum yield (PLQY), excellent stability, and multifunctional applications. Herein, rare‐earth‐based DPs Cs 2 NaHoCl 6 single crystals are successfully synthesized, which achieve the optimized red and near‐infrared (NIR) emissions of Ho 3+ through doping Ce 3+ ions. Benefiting from strong absorption of Ce 3+ and efficient energy transfer to Ho 3+ under 340 nm excitation, the PLQY remarkably increases from 3.67% to 92.56%, which are confirmed by experimental analyses and density functional theory calculations. Meanwhile, taking advantage of abnormal anti‐thermal quenching luminescence of Ho 3+ and highly efficient thermal response capability of Stark levels of 5 F 5 within the temperature range of 80–500 K, the prepared DPs provide a distinctive platform for luminescence thermometer with a superior relative sensitivity value of 5.19% K −1 at 80 K and red‐NIR light‐emitting diode. These results not only establish Ce 3+ as a generalizable strategy for optimizing luminescence in rare‐earth‐based DPs, but also open new avenues for their multiple potential applications in solid‐state lighting, temperature sensing, night vision imaging as well as plant growth illuminating.