Dielectric Screening and Charge-Transfer in 2D Lead-Halide Perovskites for Reduced Exciton Binding Energies

Aaron Forde; Sergei Tretiak; Amanda J Neukirch

doi:10.1021/acs.nanolett.3c03320

Dielectric Screening and Charge-Transfer in 2D Lead-Halide Perovskites for Reduced Exciton Binding Energies

Nano Lett. 2023 Dec 27;23(24):11586-11592. doi: 10.1021/acs.nanolett.3c03320. Epub 2023 Dec 8.

Authors

Aaron Forde^{1

2}, Sergei Tretiak^{1

3}, Amanda J Neukirch¹

Affiliations

¹ Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
² Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
³ Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.

Abstract

Layered lead-halide perovskites have shown tremendous success as an active material for optoelectronics. This is attributed to the electronic structure of the inorganic sublattice and large exciton binding energies due to quantum and dielectric confinement. Expanding functionalities for applications that depend on free-carrier generation requires new material design routes to decrease the binding energy. Here we use electronic structure methods with model Bethe-Salpeter equation (BSE) to examine the contributions of the dielectric screening and charge-transfer excited-states to the exciton binding energy of phenylethylammonium (PEA₂PbBr₄) and naphthlethylammonium (NEA₂PbBr₄) lead-bromide perovskites. Our model BSE calculations show that NEA introduces hole acceptor states which impose charge-transfer character on the exciton along with larger dielectric screening. This substantially decreases the exciton binding compared to PEA. This result suggests the use of organic cations with high dielectric screening and hole acceptor states as a viable strategy for reducing exciton binding energies in two-dimensional halide perovskites.

Keywords: Binding Energy; Charge Transfer; Dielectric; Exciton; Perovskite.