Phase Behavior and Substitution Limit of Mixed Cesium-Formamidinium Lead Triiodide Perovskites
Artikel i vetenskaplig tidskrift, 2020

The mixed cation lead iodide perovskite photovoltaics show improved stability following site substitution of cesium ions (Cs+) onto the formamidinium cation sites (FA(+)) of (CH(NH2)(2)PbI3 (FAPbI(3)) and increased resistance to formation of the undesirable.-phase. The structural phase behavior of Cs(0.1)FA(0.9)PbI(3) has been investigated by neutron powder diffraction (NPD), complemented by single crystal and power X-ray diffraction and photoluminescence spectroscopy. The Cs-substitution limit has been determined to be less than 15%, and the cubic alpha-phase, Cs(0.1)FA(0.9)PbI(3), is shown to be synthesizable in bulk and stable at 300 K. On cooling the cubic Cs(0.1)FA(0.9)PbI(3), a slow, second-order cubic to tetragonal transition is observed close to 290 K, with variable temperature NPD indicating the presence of the tetragonal beta-phase, adopting the space group P4/mbm between 290 and 180 K. An orthorhombic phase or twinned tetragonal phase is formed below 180 K, and the temperature for further transition to a disordered state is lowered to 125 K compared to that seen in phase pure alpha-FAPbI(3) (140 K). These results demonstrate the importance of understanding the effect of cation site substitution on structure-property relationships in perovskite materials.


Bethan Charles

University of Bath

Mark T. Weller

Cardiff University

Sebastian Rieger

Ludwig-Maximilians-Universität München (LMU)

Lauren E. Hatcher

University of Bath

Paul Henry

Chalmers, Kemi och kemiteknik, Energi och material

Jochen Feldmann

Ludwig-Maximilians-Universität München (LMU)

Daniel Wolverson

University of Bath

Chick C. Wilson

University of Bath

Chemistry of Materials

0897-4756 (ISSN) 1520-5002 (eISSN)

Vol. 32 6 2282-2291


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