On the interplay of electronic and lattice screening on exciton binding in two-dimensional lead halide perovskites

Kavli Affiliate: David T. Limmer

| First 5 Authors: Rohit Rana, David T. Limmer, , ,

| Summary:

We use path integral Monte Carlo to study the energetics of excitons in
layered, hybrid organic-inorganic perovskites in order to elucidate the
relative contributions of dielectric confinement and electron-phonon coupling.
While the dielectric mismatch between polar perovskite layers and non-polar
ligand layers significantly increases the exciton binding energy relative to
their three dimensional bulk crystal counterparts, formation of exciton
polarons attenuates this effect. Dielectric confinement is well described by a
fractional dimension scaling law as a function of layer thickness. The
contribution from polaron formation is found to be a non-monotonic function of
the lead halide layer thickness, which is clarified by a general variational
theory. Accounting for both of these effects provides a description of exciton
binding energies in good agreement with experimental measurements. By studying
isolated layers and stacked layered crystals of various thicknesses, with
ligands of varying polarity, we provide a systematic understanding of the
excitonic behavior of this class of materials and how to engineer their
photophysics.

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