Ultrafast Carrier Dynamics in Mn doped CsPbBr₃ Nanocrystals

Doping the semiconductor nanocrystal with transition metal ions increases the stability of the host and offers new optoelectronic functionalities. Herein, we demonstrate the influence of Mn ion doping on the carrier dynamics in CsPbBr₃ nanocrystals using ultrafast transient absorption spectroscopy. It is observed that Mn doping greatly alters and slows down the decay dynamics. Because the optical bandgap of CsPbBr₃ nanocrystals is only slightly larger than the Mn emission energy, the nonradiative energy transfer from CsPbBr₃ nanocrystals to Mn takes place. The excited carriers in Mn are known to have longer lifetime (on the order of milli seconds) and therefore act as carrier storage. However, the carrier population here decays in nanosecond timescale due to the thermal energy activation than leads to back energy transfer from Mn to CsPbBr₃ host. Nevertheless, the decay in Mn doped CsPbBr₃ is relatively retarded in comparison to undoped CsPbBr₃ nanocrystals. These rich functionalities displayed by Mn-doped CsPbBr₃ nanocrystals highlights the attractiveness of this material for future fundamental and applied research.