Manganese-Doping-Induced Quantum Confinement within Host Perovskite Nanocrystals through Ruddlesden-Popper Defects

The concept of doping Mn²⁺ ions into II-VI semiconductor nanocrystals (NCs) was recently extended to perovskite NCs. To date, most studies on Mn²⁺ doped NCs focus on enhancing the emission related to the Mn²⁺ dopant via an energy transfer mechanism. Herein, we found that the doping of Mn²⁺ ions into CsPbCl₃ NCs not only results in a Mn²⁺ -related orange emission, but also strongly influences the excitonic properties of the host NCs. We observe for the first time that Mn²⁺ doping leads to the formation of Ruddlesden-Popper (R.P.) defects and thus induces quantum confinement within the host NCs. We find that a slight doping with Mn²⁺ ions improves the size distribution of the NCs, which results in a prominent excitonic peak. However, with increasing the Mn²⁺ concentration, the number of R.P. planes increases leading to smaller single-crystal domains. The thus enhanced confinement and crystal inhomogeneity cause a gradual blue shift and broadening of the excitonic transition, respectively.