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Optical Properties of Layered Hybrid Organic–Inorganic Halide Perovskites: A Tight-Binding GW-BSE Study

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posted on 02.10.2019, 19:14 by Yeongsu Cho, Timothy C. Berkelbach
We present a many-body calculation of the band structure and optical spectrum of the layered hybrid organic–inorganic halide perovskites in the Ruddlesden–Popper phase with the general formula A2An–1MnX3n+1, where n controls the thickness of the primarily inorganic perovskite layers. We calculate the mean-field band structure with spin–orbit coupling, quasi-particle corrections within the GW approximation, and optical spectra using the Bethe–Salpeter equation. The model is parametrized by first-principles calculations and classical electrostatic screening, enabling an accurate but cost-effective study of large unit cells and corresponding n-dependent properties. A transition of the electronic and optical properties from quasi-two-dimensional behavior to three-dimensional behavior is shown for increasing n, and the nonhydrogenic character of the excitonic Rydberg series is analyzed. For methylammonium lead iodide perovskites with butylammonium spacers, our n-dependent 1s and 2s exciton energy levels are in good agreement with those from recently reported experiments, and the 1s exciton binding energy is calculated to be 302 meV for n = 1, 97 meV for n = 5, and 37 meV for n = ∞ (bulk MAPbI3). A calculation for an exfoliated n = 1 bilayer predicts a very large 1s exciton binding energy of 444 meV.

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