Issue 40, 2016

Phase behaviour and composition in the formamidinium–methylammonium hybrid lead iodide perovskite solid solution

Abstract

The phase behaviour of mixed A-site cation methylammonium (MA)/formamidinium (FA) lead iodide hybrid perovskites FAxMA1−xPbI3 has been investigated using powder and variable temperature single crystal X-ray diffraction, with A site composition determined by 1H solution NMR. At room temperature, the crystal class is cubic across the composition range 0.2 ≤ x ≤ 1 but a tetragonal phase is observed for x = 0 (MAPbI3) and x = 0.1. Cooling cubic FAxMA1−xPbI3, 0.2 ≤ x ≤ 1, phases below room temperature results in a phase change to a larger unit cell with tilted [PbI6] octahedra and the temperature at which this occurs, TC→T, decreases sharply until x = 0.2 (TC→T = 257 K) before steadily increasing to TC→T = 283 K for FA0.9MA0.1PbI3. The lattice parameters and optical band gap of cubic FAxMA1−xPbI3, 0.2 ≤ x ≤ 1 at 298 K have been shown to vary in accordance with Vegard's law, though a larger band gap is observed for the tetragonal phases, 0.0 ≤ x ≤ 0.1.

Graphical abstract: Phase behaviour and composition in the formamidinium–methylammonium hybrid lead iodide perovskite solid solution

Supplementary files

Article information

Article type
Paper
Submitted
02 Aug 2016
Accepted
08 Sep 2016
First published
09 Sep 2016

J. Mater. Chem. A, 2016,4, 15375-15382

Phase behaviour and composition in the formamidinium–methylammonium hybrid lead iodide perovskite solid solution

O. J. Weber, B. Charles and M. T. Weller, J. Mater. Chem. A, 2016, 4, 15375 DOI: 10.1039/C6TA06607K

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