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Size Isn’t Everything - Compositional Variation in Hybrid Organic-Inorganic Lead Halide Perovskites: Kinetically- versus Thermodynamically-controlled Synthesis

preprint
submitted on 08.02.2021, 08:39 and posted on 09.02.2021, 10:33 by Jiyu Tian, Eli Zysman-Colman, Finlay Morrison

The formation and study of a partial solid solution Az1-xFAxPbBr3, using ‘similar’ sized cations azetidinium (Az+) and formamidinium (FA+), was explored via mechanosynthesis and precipitation synthesis. The composition and lattice parameters of samples from both syntheses were analysed by 1H NMR and Rietveld refinement of the powder X-ray diffraction. A clear mismatch in the composition of the perovskite was found between the precipitated samples and the corresponding solutions. Such a mismatch was not observed for samples obtained via mechanosynthesis. The discrepancy suggests products are kinetically-controlled during precipitation, compared to thermodynamically-controlled mechanosynthesis. Furthermore, the cell volume as a function of composition in both 6H (Az-rich) and 3C (FA-rich) solid solutions suggests that FA+ is actually smaller than Az+, contradicting the literature. In the 3C (Az-poor) solid solutions, the extent of Az1-xFAxPbBr3 is unexpectedly smaller than Az1-xMAxPbBr3, again in contradiction to the expectation based on the reported cation sizes. These results indicate that other factors, as yet unidentified, must also contribute to the solid solution formation of organic-inorganic hybrid perovskites, not simply the relative sizes of the A-site cations.

Funding

201603780020

History

Email Address of Submitting Author

eli.zysman-colman@st-andrews.ac.uk

Institution

University of St Andrews

Country

United Kingdom

ORCID For Submitting Author

0000-0001-7183-6022

Declaration of Conflict of Interest

The authors declare no conflict of interest

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