Manipulating the sublattice distortion induced by Mn2+ doping for boosting the emission characteristics of self-trapped excitons in Cs4SnBr6

Abstract

The fundamental photophysics involved in the doping effect of zero-dimensional (0D) lead-free tin-halide perovskites (Cs₄SnX₆, X = Br and I), especially the dynamics of self-trapped excitons (STEs), is crucial for their practical applications. Here, we proposed the use of Mn²⁺ doping to realize efficient emission from the STEs in Cs₄SnBr₆. The Mn²⁺-doped Cs₄SnBr₆ exhibits an enhanced photoluminescence (PL) quantum yield of up to ∼75.8%, a broadened emission spectrum, and improved thermal stability. The experimental observations combined with first-principles calculations reveal that the significant PL enhancement originates from the enhanced electron–phonon coupling and the increased binding energies of STEs, as a consequence of the large distortion of [SnBr₆]⁴⁻ octahedra induced by Mn²⁺ doping. In addition, it was verified that the color tuning of Mn²⁺-doped Cs₄SnBr₆ is achieved by the competitive transfers of free excitons to STE states and Mn²⁺ sites based on time-resolved and temperature-dependent PL measurements. The Mn²⁺-doped Cs₄SnBr₆ assembled into commercial UV-LED chips exhibits strong white light emission with a color temperature of 6346 K. Our findings not only provide deep insight into the dynamics of STEs in Mn²⁺-doped Cs₄SnBr₆ but also open new horizons for manipulating and optimizing the emission of STEs in 0D perovskites, thereby laying a foundation for developing white LEDs based on 0D perovskites.