Altmetric

Direct observation of dynamic symmetry breaking above room temperature in methylammonium lead iodide perovskite

File Description SizeFormat 
acsenergy_notcubic_16.pdfPublished version2.71 MBAdobe PDFDownload
Title: Direct observation of dynamic symmetry breaking above room temperature in methylammonium lead iodide perovskite
Author(s): Beecheri, AN
Semonin, OE
Skelton, JM
Frost, JM
Terban, MW
Zhai, H
Alatas, A
Owen, JS
Walsh, A
Billinge, SJL
Item Type: Journal Article
Abstract: Lead halide perovskites such as methylammonium lead triiodide (CH3NH3PbI3) have outstanding optical and electronic properties for photovoltaic applications, yet a full understanding of how this solution-processable material works so well is currently missing. Previous research has revealed that CH3NH3PbI3 possesses multiple forms of static disorder regardless of preparation method, which is surprising in light of its excellent performance. Using high energy resolution inelastic X-ray (HERIX) scattering, we measure phonon dispersions in CH3NH3PbI3 and find direct evidence for another form of disorder in single crystals: large-amplitude anharmonic zone edge rotational instabilities of the PbI6 octahedra that persist to room temperature and above, left over from structural phase transitions that take place tens to hundreds of degrees below. Phonon calculations show that the orientations of the methylammonium (CH3NH3+) couple strongly and cooperatively to these modes. The result is a noncentrosymmetric, instantaneous local structure, which we observe in atomic pair distribution function (PDF) measurements. This local symmetry breaking is unobservable by Bragg diffraction but can explain key material properties such as the structural phase sequence, ultralow thermal transport, and large minority charge carrier lifetimes despite moderate carrier mobility. From the PDF we estimate the size of the fluctuating symmetry broken domains to be between 1 and 3 nm in diameter.
Publication Date: 21-Sep-2016
Date of Acceptance: 21-Sep-2016
URI: http://hdl.handle.net/10044/1/44227
DOI: http://dx.doi.org/10.1021/acsenergylett.6b00381
ISSN: 2380-8195
Publisher: American Chemical Society
Start Page: 880
End Page: 887
Journal / Book Title: ACS Energy Letters
Volume: 1
Issue: 4
Copyright Statement: © 2016 The Authors.This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html), which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
Keywords: AUGMENTED-WAVE METHOD
HALIDE PEROVSKITES
SOLAR-CELLS
PHASE-TRANSITIONS
HIGH-PERFORMANCE
ORGANIC CATIONS
SCATTERING
SPECTROSCOPY
CH3NH3PBI3
CRYSTAL
cond-mat.mtrl-sci
cond-mat.mtrl-sci
Publication Status: Published
Appears in Collections:Faculty of Engineering
Materials



Items in Spiral are protected by copyright, with all rights reserved, unless otherwise indicated.

Creative Commons