Dual-Emission and Two Charge Transfer States in Ytterbium-Doped Cesium Lead Halide Perovskite Solid Nanocrystals

摘要： Some unusual phenomena besides near-infrared emission of Yb3+ ions have been observed in ytterbium-doped perovskite solid nanocrystals. A systematic study on doping kinetic and energy transfer processes is presented. The observed unique dual-peak PL emission of perovskite nanocrystals in the visible region can be attributed to radiative recombination in the near-surface region and the interior region of perovskite nanocrystals respectively. Insight studies based on dual-peak PL emission clarify the kinetic process of doping in perovskite nanocrystals. After dopant concentration of rare earth ions in the near-surface region is more than a certain value, dopant ions are starting to be immersed into the interior region of host nanocrystals. The unusual excitation spectra of ytterbium-doped perovskite solid nanocrystals could be explained by the presences of two charge transfer (CT) states at ~24000 cm-1 (CT1) and ~21460 cm-1 (CT2), and both of them could be observed in the near-surface region of the perovskite host. Furthermore, the lifetime of near-infrared emission of Yb3+ ions through the CT2 state is three orders faster than that through CT1 state (in millisecond) which should be fixed on the surface of perovskite nanocrystals. The results provide essential insights into the dynamic carrier behaviors and surface effects of all inorganic perovskite nanocrystals doped with rare earth ions for expanded functionality.