2024-03-29T00:39:00Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/2104172021-08-18T09:46:50Zcom_10261_46com_10261_3col_10261_299
Phase Diagram of Methylammonium/Formamidinium Lead Iodide Perovskite Solid Solutions from Temperature-Dependent Photoluminescence and Raman Spectroscopies
Francisco López, Adrián
Charles, Bethan
Alonso Carmona, M. Isabel
Garriga Bacardi, Miquel
Campoy Quiles, Mariano
Weller, Mark T.
Goñi, Alejandro R.
Ministerio de Ciencia, Innovación y Universidades (España)
Generalitat de Catalunya
Halide perovskites
Optical-properties
Single-crystals
Organic cations
Formadinium
The complete phase diagram of organic-cation solid solutions of lead iodide perovskites [FAxMA1–xPbI3, where MA stands for methylammonium, CH3NH3, and FA for formamidinium, CH(NH2)2] with compositions x ranging from 0 to 1 in steps of 0.1 was constructed in the temperature range from 10 to 365 K by combining Raman scattering and photoluminescence (PL) measurements. The occurrence of phase transitions was inferred from both the temperature-induced changes in the optical emission energies and/or the phonon frequencies and line widths, complementing X-ray and neutron scattering literature data. For MA-rich perovskites (x ≤ 0.2), the same structural behavior as for MAPbI3 was observed with decreasing temperature: cubic Pm3̅m → tetragonal-I I4/mcm → orthorhombic Pnma. As the FA molecule is larger and more symmetric but less polar than MA, a tetragonal crystal structure is favored at low temperatures and FA compositions x > 0.4, to the detriment of the orthorhombic phase. As a consequence, with decreasing temperature, the phase transition sequence for FA-rich compounds is cubic Pm3̅m → tetragonal-II P4/mbm → tetragonal-III. The latter presumably belongs to the P4bm symmetry group, according to neutron scattering data. Strikingly, the isostructural (tetragonal-to-tetragonal) transformation, which occurs between 200 and 150 K, exhibits a kind of critical point for x = 0.7. For intermediate FA contents, the perovskite solid solution transforms close to 250 K directly from the cubic phase to the tetragonal-III phase. The latter is characterized by a nonmonotonic dependence of the band-gap energy on temperature. We ascribe such behavior to a substantial tilting of the PbI6 octahedra in the tetragonal-III phase. In this way, we established important links between crystal-phase stability and the electronic as well as vibrational properties of mixed organic-cation halide perovskites, which might impact the current search for more stable best-performing optoelectronic materials.
The Spanish Ministerio de Ciencia, Innovación y Universidades is gratefully acknowledged for its support through Grant No. SEV-2015-0496 in the framework of the Spanish Severo Ochoa Centre of Excellence program and through Grants MAT2015-70850-P (HIBRI2) and PGC2018-095411-B-100 (RAINBOW). We also thank the Catalan agency AGAUR for grant 2017-SGR-00488. AFL acknowledges an FPI fellowship (BES-2016-076913) from the Spanish Ministerio co-financed by the European Social Fund and the Ph.D. programme in Materials Science from Universitat Autònoma de Barcelona in which he is enrolled. B.C. thanks the EPSRC for Ph.D. studentship funding via the CSCT CDT (EP/G03768X/1).
Peer reviewed
2020-05-05T08:18:14Z
2020-05-05T08:18:14Z
2020-02-13
artículo
http://purl.org/coar/resource_type/c_6501
Journal of Physical Chemistry C 124(6): 3448-3458 (2020)
1932-7447
http://hdl.handle.net/10261/210417
http://dx.doi.org/10.13039/501100002809
en
#PLACEHOLDER_PARENT_METADATA_VALUE#
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info:eu-repo/grantAgreement/MINECO/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/SEV-2015-0496
info:eu-repo/grantAgreement/MINECO/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/MAT2015-70850-P
MICIU/ICTI2017-2020/PGC2018-095411-B-100
Postprint
http://dx.doi.org/10.1021/acs.jpcc.9b10185
Sí
open
American Chemical Society