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Disorder to order : how halide mixing in MAPbl₃₋ₓBrₓ perovskites restricts MA dynamics

Title data

Fykouras, Kostas ; Lahnsteiner, Jonathan ; Leupold, Nico ; Tinnemans, Paul ; Moos, Ralf ; Panzer, Fabian ; de Wijs, Gilles A. ; Bokdam, Menno ; Grüninger, Helen ; Kentgens, Arno P. M.:
Disorder to order : how halide mixing in MAPbl₃₋ₓBrₓ perovskites restricts MA dynamics.
In: Journal of Materials Chemistry A. Vol. 11 (2023) Issue 9 . - pp. 4587-4597.
ISSN 2050-7496

Official URL: Volltext

Project information

Project financing: Deutsche Forschungsgemeinschaft

Abstract in another language

Mixed-halide lead perovskites are of particular interest for the design of tandem solar cells currently reaching record efficiencies. While halide phase segregation upon illumination of mixed perovskites is extensively studied, the effect of halide disorder on A cation dynamics is not well understood, despite its importance for charge carrier diffusion and lifetime. Here, we study the methylammonium (MA) reorientational dynamics in mixed halide MAPbI3−xBrx perovskites by a combined approach of experimental solid-state NMR spectroscopy and molecular dynamics (MD) simulations based on machine-learning force-fields (MLFF). 207Pb NMR spectra indicate the halides are randomly distributed over their lattice positions, whereas PXRD measurements show that all mixed MAPbI3−xBrx samples are cubic. The experimental 14N spectra and 1H double-quantum (DQ) NMR data reveal anisotropic MA reorientations depending on the halide composition and thus associated disorder in the inorganic sublattice. MD calculations allow us to correlate these experimental results to restrictions of MA dynamics due to preferred MA orientations in their local Pb8I12−nBrn “cages”. Based on the experimental and simulated results, we develop a phenomenological model that correlates the 1H dipolar coupling and thus the MA dynamics with the local composition and reproduces the experimental data over the whole composition range. We show that the dominant interaction between the MA cations and the Pb–X lattice that influences the cation dynamics is the local electrostatic potential being inhomogeneous in mixed halide systems. As such, we generate a fundamental understanding of the predominant interaction between the MA cations and the inorganic sublattice, as well as MA dynamics in asymmetric halide coordinations.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Chair Experimental Physics II - Optoelectronics of Soft Matter
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Inorganic Chemistry III
Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Research Centres > Bayreuth Center for Material Science and Engineering - BayMAT
Research Institutions > Research Centres > Nordbayerisches Zentrum für NMR-Spektroskopie - NMR-Zentrum
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
500 Science > 540 Chemistry
600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 08 Mar 2023 08:17
Last Modified: 08 Mar 2023 08:17