Effect of Surface Termination on Carrier Dynamics of Metal Halide Perovskites: Ab Initio Quantum Dynamics Study

Abstract

Metal halide perovskites (MHPs) have attracted considerable attentions as promising candidates for next-generation optoelectronic devices, such as light-emitting diode (LED), owing to their outstanding photophysical properties. Nanostructuring is considered an essential approach to facilitate the bright emission of MHPs, which entails an increase in the surface domain that can directly affect the carrier dynamics. However, a comprehensive understanding of the surface termination effect on the photodynamic properties of MHPs is still lacking. Herein, we systematically investigate the effect of surface termination on the carrier recombination dynamics of CsPbBr3 using ab-initio non-adiabatic molecular dynamics simulations. We found separate localizations of electron and hole carriers in the vicinity of the more and less coordinated inorganic polyhedral, respectively, which can be explained by the energy level changes associated with the modifications in Pb-Br bond lengths and their anharmonicity. This leads to the spatial separation of charge carriers, which retards the radiative kinetics more than the non-radiative one, reducing the photoluminescence quantum yield (PLQY). We further found that the homogenous linewidth is broadened upon introduction of surface terminations. Thus, our study suggests a possible LED-performance degradation mechanism due to surface termination, and thereby proposes guidelines for enhancing the light-emission properties of nanostructured MHPs.