Comparison of Recombination Dynamics in CH₃NH₃PbBr₃ and CH₃NH₃PbI₃ Perovskite\nFilms: Influence of Exciton Binding Energy

Abstract

Understanding carrier recombination\nin semiconductors is a critical\ncomponent when developing practical applications. Here we measure\nand compare the monomolecular, bimolecular, and trimolecular (Auger)\nrecombination rate constants of CH₃NH₃PbBr₃ and CH₃NH₃PbI₃. The monomolecular\nand bimolecular recombination rate constants for both samples are\nlimited by trap-assisted recombination. The bimolecular recombination\nrate constant for CH₃NH₃PbBr₃ is\n∼3.3 times larger than that for CH₃NH₃PbI₃ and both are in line with that found for radiative\nrecombination in other direct-gap semiconductors. The Auger recombination\nrate constant is 4 times larger in lead-bromide-based perovskite compared\nwith lead-iodide-based perovskite and does not follow the reduced\nAuger rate when the bandgap increases. The increased Auger recombination\nrate, which is enhanced by Coulomb interactions, can be ascribed to\nthe larger exciton binding energy, ∼40 meV, in CH₃NH₃PbBr₃ compared with ∼13 meV in CH₃NH₃PbI₃.