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Similar Structural Dynamics for the Degradation of CH 3 NH 3 PbI 3 in Air and in Vacuum
Author(s) -
Alberti Alessandra,
Deretzis Ioannis,
Pellegrino Giovanna,
Bongiorno Corrado,
Smecca Emanuele,
Mannino Giovanni,
Giannazzo Filippo,
Condorelli Guglielmo Guido,
Sakai Nobuya,
Miyasaka Tsutomu,
Spinella Corrado,
La Magna Antonino
Publication year - 2015
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201500374
Subject(s) - x ray photoelectron spectroscopy , tetragonal crystal system , octahedron , lattice energy , chemistry , crystallography , lattice (music) , diffraction , transmission electron microscopy , materials science , perovskite (structure) , chemical physics , analytical chemistry (journal) , chemical engineering , crystal structure , nanotechnology , physics , optics , chromatography , acoustics , engineering
We investigate the degradation path of MAPbI 3 (MA=methylammonium) films over flat TiO 2 substrates at room temperature by means of X‐ray diffraction, spectroscopic ellipsometry, X‐ray photoelectron spectroscopy, and high‐resolution transmission electron microscopy. The degradation dynamics is found to be similar in air and under vacuum conditions, which leads to the conclusion that the occurrence of intrinsic thermodynamic mechanisms is not necessarily linked to humidity. The process has an early stage, which drives the starting tetragonal lattice in the direction of a cubic atomic arrangement. This early stage is followed by a phase change towards PbI 2 . We describe how this degradation product is structurally coupled with the original MAPbI 3 lattice through the orientation of its constituent PbI 6 octahedra. Our results suggest a slight octahedral rearrangement after volatilization of HI+CH 3 NH 2 or MAI, with a relatively low energy cost. Our experiments also clarify why reducing the interfaces and internal defects in the perovskite lattice enhances the stability of the material.