Reducing hot carrier cooling rate in metal halide perovskites through lead vacancies: time-domain ab initio analysis

Abstract

Hybrid organic–inorganic perovskites are promising for optoelectronic applications, yet the impact of intrinsic defects on hot carrier dynamics remains poorly understood. Here, we investigate hot carrier dynamics in methylammonium lead triiodide (MAPbI₃) perovskite containing Pb vacancies, a prevalent defect type, using ab initio nonadiabatic molecular dynamics. We observe pronounced slower hot carrier cooling in Pb vacancy-containing MAPbI₃ compared to pristine system. In particular, the hot hole cooling in the Pb vacancy system is approximately an order of magnitude slower than that of pristine perovskite for states situated ∼0.5 eV below the top of the valence bands. This deceleration arises primarily from reduced nonadiabatic couplings due to charge state localization and suppressed fluctuations of the inorganic sub-lattice, facilitated by the enhanced rotational disorder of MA cations in the presence of Pb vacancies. Additionally, Pb vacancies introduce intraband defect states capable of trapping photogenerated hot holes, further delaying the hot carrier cooling process. The absence of trap-assisted hot carrier cooling dynamics in hybrid perovskite is consistent with the well-established consensus of defect tolerance in these materials. Our findings provide crucial insights into defect-mediated hot carrier dynamics in hybrid perovskites, holding significant implications for advancing the development of perovskite solar cells and related devices through defect engineering.