Abstract
Zero-dimensional (0D) inorganic perovskites have recently emerged as an interesting class of material owing to their intrinsic Pb2+ emission, polaron formation, and large exciton binding energy. They have a unique quantum-confined structure, originating from the complete isolation of octahedra exhibiting single-molecule behavior. Herein, we probe the optical behavior of single-molecule-like isolated octahedra in 0D Cesium lead halide (Cs4PbX6, X = Cl, Br/Cl, Br) nanocrystals through isovalent manganese doping at lead sites. The incorporation of manganese induced phase stabilization of 0D Cs4PbX6 over CsPbX3 by lowering the symmetry of PbX6 via enhanced octahedral distortion. This approach enables the synthesis of CsPbX3 free Cs4PbX6 nanocrystals. A high photoluminescence quantum yield for manganese emission was obtained in colloidal (29%) and solid (21%, powder) forms. These performances can be attributed to structure-induced confinement effects, which enhance the energy transfer from localized host exciton states to Mn2+ dopant within the isolated octahedra.
Highlights
0D inorganic perovskite-like Cs4PbX6 system have crystal structure in which the PbX6 octahedra are decoupled from each other by the surrounding Cs+ ions
The coexistence of 3D CsPbX3 impurity has precluded a detailed understanding on the optical properties of Cs4PbX6, leading to a growing demand for their synthesis in pure form and their phase stabilization
The synthesized samples were represented as Cs4PbX6:x% Mn, where X = (Br/Cl), Cl, and Br; and x = percentage of Mn concentration with respect to displaced lead ions
Summary
0D inorganic perovskite-like Cs4PbX6 system have crystal structure in which the PbX6 octahedra are decoupled from each other by the surrounding Cs+ ions. Nikl et al.[12] reported a UV emission band at 355 nm for Cs4PbCl6 single crystals, assigning to Pb2+ ion emission, originating from the optical transitions of 3P0,1 → 1S0 in the isolated PbCl6 octahedra, similar to Pb2+ doping in the alkali halide hosts[12]. While, Mohammed’s group[19] reported Cs4PbBr6 characteristic with two broad UV emissions at 340 nm (high-energy) and 400 nm (low-energy) attributing to Pb2+ ion and charge-transfer band denoted as “D-state”, respectively. D-state emission originates via the transfer of excited electrons from (PbBr6)4– octahedra to the Pb2+ occupying Cs sites (D-states), through their strong coupling in Cs4PbX6 host[19]. Though many reports attribute the green emission (512 nm) to the intrinsic property of Cs4PbBr6, we believe it arise from the coexistence of CsPbBr3 impurity, similar to 414 nm emission of Cs4PbCl612. As the inevitable coexistence of CsPbX3 phase represents a major drawback, new synthetic strategies are of utmost interest for obtaining pure
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