Achieving Antithermal Quenching Orange Photoluminescence in Sb³⁺-Doped CsCd₅Cl₁₁ All-Inorganic Halides

Owing to the outstanding photoluminescent (PL) characteristics including the broadband emission and high PL quantum yield, metal halides with robust crystal structures have promising applications in information anticounterfeiting and encryption, optical temperature sensing, optoelectronic devices, etc. However, their intrinsic luminescent thermal quenching severely limits their practical applications at high temperatures. Herein, a novel three-dimensional all-inorganic metal halide CsCd₅Cl₁₁ with the distorted octahedra was successfully synthesized. Upon doping with Sb³⁺, the CsCd₅Cl₁₁:Sb³⁺ halides exhibit antithermal quenching orange PL over the temperature range of 260-440 K. Their integrated PL intensity at 440 K can reach approximately 610% and 320% of those at 260 and 300 K, respectively. Structure and thermoluminescence analysis indicates that the luminescent antithermal quenching originates from the intrinsic structural rigidity of the octahedra in the structure and the trapped excitons absorbing thermal energy to escape from the shallow traps, thereby compensating for the thermally induced nonradiative transition losses of excitons. Moreover, the CsCd₅Cl₁₁:Sb³⁺ underlying PL luminescence mechanism was systematically elucidated by first-principles calculations. Enlightened by the adaptable optical properties, the platform of the developed halides for high-temperature visualization and anticounterfeiting is demonstrated. This work not only presents a new halide material with antithermal quenching but also broadens versatile applications in optoelectronic fields.