Highly efficient and stable blue photoluminescence from environmental-friendly double perovskites

Despite intensive explorations, lead-free, low toxicity, efficient, and stable blue fluorescent materials are still highly desirable. Cs₂NaInCl₆ double perovskite (DP) is considered as a promising candidate for solid-state lighting due to its low toxicity and good stability. In this work, Mg-doped Cs₂NaInCl₆ DPs are prepared by a solvothermal method. The Mg²⁺-doped Cs₂NaInCl₆ DPs exhibit blue photoluminescence (PL) at about 445 nm with a full-width at half maximum of 58.0 nm, which is independent of the excitation wavelength. The large Stokes shift (129.5 nm), long PL lifetime (10.44 μs), and huge Huang–Rhys factor (40.2) suggest that the blue PL originates from self-trapped excitons. After optimizing the reaction conditions and doping concentration, a high photoluminescence quantum yield of 86.98% is obtained. Moreover, the Mg-doped Cs₂NaInCl₆ DPs exhibit good resistance to irradiation and moisture, which are expected to remedy the shortage of current blue emitting materials.