Precise Ligand Tuning Emission of Mn-Doped CsPbCl3 Nanocrystals by the Amount of Sulfonates

Using Mn-doped CsPbCl₃ nanocrystals (Mn:CsPbCl₃ NCs) to improve perovskite's properties is becoming an important strategy. Here, we demonstrate a modified supersaturated recrystallization route to synthesize high-quality Mn:CsPbCl₃ NCs at room temperature. Unprecedentedly, sulfonate ligands with various concentrations are shown to successfully tune the dual-color emission of Mn:CsPbCl₃ NCs. Ultrafast transient absorption studies reveal that the host-to-dopant internal energy-transfer process involves the mediated traps. Interestingly, the dual-color emission is tuned via stabilizing mediated traps with a small amount of ligand (band edge (BE) emission reduces and Mn²⁺ emission increases), passivating the deep traps with a large amount of ligand (Mn²⁺ emission increases), and destroying Mn:CsPbCl₃ NCs with too much ligand (both BE and Mn²⁺ emission is quenched). Furthermore, the ligand tuning Mn²⁺ emission exhibits quenching for Cu²⁺ with high sensitivity and selectivity. Our work provides a new strategy to tune the optical properties of Mn:CsPbCl₃ NCs and presents its potential application in an optical detector.