Interfacial Manganese‐Doping in CsPbBr(3) 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 CsPbX(3) (X=Br, Cl) NPls. A systematic study shows that electron‐donating oleylamine acts as a shuttle ligand to transport MnX(2) 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 Mn(2+) 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.