Interfacial Manganese-Doping in CsPbBr₃ Nanoplatelets by Employing a Molecular Shuttle

Mn-doping in cesium lead halide perovskite nanoplatelets (NPls) is of particular importance where strong quantum confinement plays a significant role towards the exciton–dopant coupling. In this work, we report an immiscible bi-phasic strategy for post-synthetic Mn-doping of CsPbX₃ (X=Br, Cl) NPls. A systematic study shows that electron-donating oleylamine acts as a shuttle ligand to transport MnX₂ through the water–hexane interface and deliver it to the NPls. The halide anion also plays an essential role in maintaining an appropriate radius of Mn²⁺ and thus fulfilling the octahedral factor required for the formation of perovskite crystals. By varying the thickness of parent NPls, we can tune the dopant incorporation and, consequently, the exciton-to-dopant energy transfer process in doped NPls. Time-resolved optical measurements offer a detailed insight into the exciton-to-dopant energy transfer process. This new approach for post-synthetic cation doping paves a way towards exploring the cation exchange process in several other halide perovskites at the polar–nonpolar interface.