Influence of Shape on Carrier Relaxation Dynamics of CsPbBr3 Perovskite Nanocrystals
Lead halide perovskite nanocrystals (NCs) have recently emerged as a new class of functional materials for designing efficient light harvesting systems because of their unique photophysical properties. Here, we report the influence of different shapes on the relaxation dynamics of perovskite nanocrystals. The structural transformation of CsPbBr3 NCs from cubic shape to rod shape is done with changing the solvent from toluene to dichloromethane (DCM). Rietveld analysis reveals that the crystallinity along with preferred orientation (PO) of the orthorhombic phase plays vital role for the unidirectional growth of rod shaped CsPbBr3 NCs in DCM. The time-resolved emission spectroscopy and ultrafast transient absorption spectroscopy are being used to understand the photoinduced relaxation processes. The global and target analysis of femto second transient absorption kinetics has been done to understand the individual excited-state species. Analysis reveals that trap sates play an important role in the carrier relaxation dynamics of cubic and rod shaped NCs. The lifetime of the swallow trap (ST) changes from 25 ps to 45 ps and the lifetime of deep trap (DT) states changes from 163 ps to 303 ps with changing the shape of nanocrystals from cubic to rod. This work highlights the tuning the crystal phase, shape and the exciton dynamics of CsPbBr3 NCs that would be beneficial for designing efficient photovoltaic devices.