Facile Fabrication of Highly Stable and Wavelength-Tunable Tin Based Perovskite Materials with Enhanced Quantum Yield via the Cation Transformation Reaction

Metal halide perovskites have attracted great attention for their superior light energy conversion applications. Herein, we demonstrated a facile synthesis of zero-dimensional Sn²⁺ perovskite Cs_4-xM_xSnBr₆(M = K⁺ and Rb⁺) material through the cation transformation reaction at room temperature. Cs₄SnBr₆ NCs was mixed with pure metal bromide salts (KBr and RbBr) via the mechanochemical process to successfully synthesize Cs_4-xM_xSnBr₆ perovskite where transformation of Cs to mixed Cs/Rb and mixed Cs/K was achieved. By substituting different cations, the bright fluorescence of the Cs_4-xM_xSnBr₆ was tuned from dim green to greenish-cyan while achieving the photoluminescence (PL) quantum yield of ∼39%. The crystal structure of Sn based perovskite with the substitution of K⁺ or Rb⁺ cations was determined by X-ray diffraction (XRD). Moreover, the Cs_4-xM_xSnBr₆ demonstrated superior air stability and exhibited a better photocatalytic activity for CO₂ reduction reaction (CO₂RR) with high selectivity of CH₄ gas with a higher yield rate compared to the pristine Cs₄SnBr₆ NCs.