Highly Efficient Blue Emission from Self-Trapped Excitons in Stable Sb3+-Doped Cs2NaInCl6 Double Perovskites

Highly efficient blue-emitting three-dimensional (3D) lead–free halide perovskites with excellent stability have attracted worldwide attention. Herein, a doping route was adopted to incorporate Sb3+ ions into the Cs2NaInCl6 for decorating the electronic band structure. Due to the moderate electron–phonon coupling, the Sb3+-doped Cs2NaInCl6 double perovskites showed a narrow and relatively unusual blue emission of self-trapped excitons (STEs). Density functional theory (DFT) calculation indicated that the doped Sb3+ ions could break the parity-forbidden transition rule and modulate the density of state (DOS) population effectively to boost the PLQY of STEs drastically. The optimized Sb3+:Cs2NaInCl6 exhibited a PLQY of up to 75.89% and excellent stability under the consecutive illumination of 365 nm UV light for 1000 h. This kind of highly efficient lead-free Sb3+-doped Cs2NaInCl6 double perovskites may overcome the bottlenecks of severe toxicity and insufficient stability and therefore have an extensive application in the scarce blue photonic and optoelectronic fields.