F63.00004. Peculiar Defects Behavior in Charge Recombination of Metal Halide Perovskites

Presented by: Weibin Chu


Abstract

Metal halide perovskites have attracted great attention due to their high and rapidly rising power efficiencies, as well as many other important advantages. Since the low-cost solution-based synthesis of the perovskites invariably introduces defects, a strong defect tolerance should exist in these materials. However, it is usually believed that those defects would form Shockley-Read-Hall (SRH) electron-hole recombination centers that decrease solar conversion efficiency. Herein we investigate the non-radiative recombination processes in both MAPbI3 and CsPbI3 using ab initio non-adiabatic molecular dynamics within real-time time-dependent Kohn-Sham formalism and surface-hopping framework. Regardless of whether the defects introduce a shallow or deep state in the band structure, we find that charge recombinations in these perovskites are not enhanced which contrary to predictions of the SRH theory. We show that the strong tolerance of electron-hole recombination against defects is explained due to the combination of having low-frequency lattice phonons and weakly overlapping electron and hole states. Both factors significantly decrease the non-adiabatic coupling and inelastic electron-phonon interactions. The previous SRH models that work for the conventional semiconductors, fails for the metal halide perovskites because they do not explicitly include the electron-phonon coupling. Thus, we propose that other “soft” semiconductors, in particular, a small bulk modulus should exhibit defects properties similar to those of the perovskites.

Authors

  • Weibin Chu
  • Wissam Saidi
  • Jin Zhao
  • Oleg Prezhdo


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