Open AccessSensitivity of Nitrogen K-Edge X-ray Absorption to Halide Substitution and Thermal Fluctuations in Methylammonium Lead-Halide Perovskites
Author(s) -
Cody M. Sterling,
C. Kamal,
Gabriel Man,
Pabitra K. Nayak,
Konstantin A. Simonov,
Sebastian Svanström,
Alberto GarcíaFernández,
Thomas Huthwelker,
Ute B. Cappel,
Sergei M. Butorin,
Håkan Rensmo,
Michael Odelius
Publication year - 2021
Publication title -
journal of physical chemistry. c./journal of physical chemistry. c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.401
H-Index - 289
eISSN - 1932-7455
pISSN - 1932-7447
DOI - 10.1021/acs.jpcc.1c02017
Subject(s) - halide , triiodide , perovskite (structure) , chemistry , absorption edge , spectral line , absorption spectroscopy , absorption (acoustics) , electronic structure , chemical physics , analytical chemistry (journal) , band gap , crystallography , materials science , inorganic chemistry , computational chemistry , optics , physics , optoelectronics , electrode , astronomy , dye sensitized solar cell , electrolyte , chromatography , composite material
The performance of hybrid perovskite materials in solar cells crucially depends on their electronic properties, and it is important to investigate contributions to the total electronic structure from specific components in the material. In a combined theoretical and experimental study of CH 3 NH 3 PbI 3 -methylammonium lead triiodide (MAPI)-and its bromide cousin CH 3 NH 3 PbBr 3 (MAPB), we analyze nitrogen K-edge (N 1s-to-2p*) X-ray absorption (XA) spectra measured in MAPI and MAPB single crystals. This permits comparison of spectral features to the local character of unoccupied molecular orbitals on the CH 3 NH 3 + (MA + ) counterions and allows us to investigate how thermal fluctuations, hydrogen bonding, and halide-ion substitution influence the XA spectra as a measure of the local electronic structure. In agreement with the experiment, the simulated spectra for MAPI and MAPB show close similarity, except that the MAPB spectral features are blue-shifted by +0.31 eV. The shift is shown to arise from the intrinsic difference in the electronic structure of the two halide atoms rather than from structural differences between the materials. In addition, from the spectral sampling analysis of molecular dynamics simulations, clear correlations between geometric descriptors (N-C, N-H, and H···I/Br distances) and spectral features are identified and used to explain the spectral shapes.