Post-Synthetic Doping and Ligand Engineering of Cs2AgInCl6 Double Perovskite Nanocrystals

Lead-free double perovskite (DP) nanocrystals (NCs) have emerged as a promising class of perovskite nanomaterials with potential applications in various optical and optoelectronic domains. Meanwhile, doping impurity ions into perovskite structures represents a unique and effective means to tailor and optimize the properties of perovskite materials. Herein, we introduce a postsynthetic doping approach to the fabrication of Mn2+-doped Cs2AgInCl6 DP NCs with enhanced optical characteristics. We demonstrate that, in the postsynthetic reaction, the initial surface-doped Mn2+ ions undergo a gradual inward migration process within the NCs, resulting in homogeneous Mn2+ doping with a maximum photoluminescence (PL) quantum yield (QY) of 5.2%. This PL QY value can be further improved to 8.2% through codoping with Na+ ions and careful engineering of the NC surface state. In-depth studies involving conventional one-dimensional proton and two-dimensional NMR spectroscopic techniques unveil the pivotal role played by the surface ligands and their states. Based on our findings, we propose a comprehensive postsynthetic doping mechanism. Our study not only presents an accessible doping technique for lead-free perovskite NCs but also offers valuable insights into the dopant dynamics and ligand engineering for perovskite-type nanomaterials in a broader context.