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Lookup NU author(s): Dr James DawsonORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2019 American Chemical Society.Lattice compression through hydrostatic pressure has emerged as an effective means of tuning the structural and optoelectronic properties of hybrid halide perovskites. In addition to external pressure, the local strain present in solution-processed thin films also causes significant heterogeneity in their photophysical properties. However, an atomistic understanding of structural changes of hybrid perovskites under pressure and their effects on the electronic landscape is required. Here, we use high level ab initio simulation techniques to explore the effect of lattice compression on the formamidinium (FA) lead iodide compound, FA1-xCsxPbI3 (x = 0, 0.25). We show that, in response to applied pressure, the Pb-I bonds shorten, the PbI6 octahedra tilt anisotropically, and the rotational dynamics of the FA+ molecular cation are partially suppressed. Because of these structural distortions, the compressed perovskites exhibit band gaps that are narrower (red-shifted) and indirect with spin-split band edges. Furthermore, the shallow defect levels of intrinsic iodide defects transform to deep-level states with lattice compression. This work highlights the use of hydrostatic pressure as a powerful tool for systematically modifying the photovoltaic performance of halide perovskites.
Author(s): Ghosh D, Aziz A, Dawson JA, Walker AB, Islam MS
Publication type: Article
Publication status: Published
Journal: Chemistry of Materials
Print publication date: 11/06/2019
Online publication date: 14/05/2019
Acceptance date: 02/04/2019
Date deposited: 15/01/2020
ISSN (print): 0897-4756
ISSN (electronic): 1520-5002
Publisher: American Chemical Society
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