Vibrational Response of Methylammonium Lead Iodide: From Cation Dynamics to Phonon-Phonon Interactions.
The dynamic evolution of the vibrational interactions in the prototypical CH3NH3PbI3was studied through a comprehensive experimental and theoretical investigation with a focus on the interactions between the organic cations and the inorganic cage. To date, no clear picture has emerged on the critical and fundamental interactions between the two perovskite components, despite the relevance of phonons to the electronic properties of several classes of perovskites. For the first time, we have monitored the IR and nonresonant Raman response in the broad frequency range 30-3400 cm-1and in the temperature interval 80-360 K. Strong changes in the energies of different vibrational modes with temperature are observed and examined in the framework of phonon-phonon interactions considering a significant anharmonic contribution to the phonon relaxation process. The vibrational relaxation of the bending modes and their reorientation activation energies identify that such mechanisms are governed by medium-to-strong hydrogen bonds in the orthorhombic phase; however, any ferroelectric ordering in the orthorhombic phase is governed mostly by dipole interactions. These changes imply that charge localization mechanisms play a primary role, and our study enriches the fundamental knowledge of phonon interactions and charge transport in CH3NH3PbI3for the further development of optoelectronic applications.
Institute of Nanostructured Materials (ISMN), National Research Council (CNR), Via Gobetti 101, 40129, Bologna, Italy. t.ivanovska@bo.ismn.cnr.it.
Tanja
http://orcid.org/0000-0003-0888-3613
T
Ivanovska
Laboratory for Chemistry of Novel Materials, Universitè de Mons, Place du Park 20, 7000, Mons, Belgium. claudio.quarti@umons.ac.be.
Claudio
C
Quarti
Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Federale de Lausanne, CH-1951, Sion, Switzerland. giulia.grancini@epfl.ch.|Center for Nanoscience and Technology@Polimi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli 70/3, 20133, Milano, Italy. giulia.grancini@epfl.ch.
Giulia
http://orcid.org/0000-0001-8704-4222
G
Grancini
Center for Nanoscience and Technology@Polimi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli 70/3, 20133, Milano, Italy.
Annamaria
http://orcid.org/0000-0001-6914-4537
A
Petrozza
Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, Via Elce di Sotto, I-06123, Perugia, Italy.|D3-Computation, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy.
Filippo
http://orcid.org/0000-0003-3833-1975
F
De Angelis
Department of Chemistry, Materials and Chemical Engineering 'G. Natta', Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy.
Alberto
http://orcid.org/0000-0001-6026-5455
A
Milani
Institute of Nanostructured Materials (ISMN), National Research Council (CNR), Via Gobetti 101, 40129, Bologna, Italy.
Giampiero
http://orcid.org/0000-0001-9326-0490
G
Ruani
D002412:Cations; D007454:Iodides / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008744:Methylamines / Q000737:chemistry*; D014732:Vibration
D002412:Cations; D007454:Iodides; D008744:Methylamines; D007854:Lead; C027451:methylamine
density functional calculations; lead; perovskites; raman spectroscopy; vibrational spectroscopy