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Charge-Carrier Recombination in Halide Perovskites
journal contribution
posted on 2019-09-06, 22:13 authored by Dane W. deQuilettes, Kyle Frohna, David Emin, Thomas Kirchartz, Vladimir Bulovic, David S. Ginger, Samuel D. StranksThe success of halide
perovskites in a host of optoelectronic applications
is often attributed to their long photoexcited carrier lifetimes,
which has led to charge-carrier recombination processes being described
as unique compared to other semiconductors. Here, we integrate recent
literature findings to provide a critical assessment of the factors
we believe are most likely controlling recombination in the most widely
studied halide perovskite systems. We focus on four mechanisms that
have been proposed to affect measured charge carrier recombination
lifetimes, namely: (1) recombination via trap states, (2) polaron
formation, (3) the indirect nature of the bandgap (e.g., Rashba effect),
and (4) photon recycling. We scrutinize the evidence for each case
and the implications of each process on carrier recombination dynamics.
Although they have attracted considerable speculation, we conclude
that multiple trapping or hopping in shallow trap states, and the
possible indirect nature of the bandgap (e.g., Rashba effect), seem
to be less likely given the combined evidence, at least in high-quality
samples most relevant to solar cells and light-emitting diodes. On
the other hand, photon recycling appears to play a clear role in increasing
apparent lifetime for samples with high photoluminescence quantum
yields. We conclude that polaron dynamics are intriguing and deserving
of further study. We highlight potential interdependencies of these
processes and suggest future experiments to better decouple their
relative contributions. A more complete understanding of the recombination
processes could allow us to rationally tailor the properties of these
fascinating semiconductors and will aid the discovery of other materials
exhibiting similarly exceptional optoelectronic properties.