Stabilization of the trigonal high-temperature phase of formamidinium lead iodide

Binek, A., Hanusch, F. C., Docampo, P. and Bein, T. (2015) Stabilization of the trigonal high-temperature phase of formamidinium lead iodide. Journal of Physical Chemistry Letters, 6(7), pp. 1249-1253. (doi: 10.1021/acs.jpclett.5b00380) (PMID:26262982)

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Formamidinium lead iodide (FAPbI3) has the potential to achieve higher performance than established perovskite solar cells like methylammonium lead iodide (MAPbI3), while maintaining a higher stability. The major drawback for the latter material is that it can crystallize at room temperature in a wide bandgap hexagonal symmetry (P63mc) instead of the desired trigonal (P3m1) black phase formed at a higher temperature (130 °C). Our results show that employing a mixture of MAI and FAI in films deposited via a two-step approach, where the MAI content is <20%, results in the exchange of FA molecules with MA without any significant lattice shrinkage. Additionally, we show with temperature-dependent X-ray diffraction that the trigonal phase exhibits no phase changes in the temperature range studied (25 to 250 °C). We attribute the stabilization of the structure to stronger interactions between the MA cation and the inorganic cage. Finally, we show that the inclusion of this small amount of MA also has a positive effect on the lifetime of the photoexcited species and results in more efficient devices.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Docampo, Dr Pablo
Authors: Binek, A., Hanusch, F. C., Docampo, P., and Bein, T.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of Physical Chemistry Letters
Publisher:American Chemical Society
ISSN (Online):1948-7185
Published Online:16 March 2015

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