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Issue 10, 2020

Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopy

Author affiliations

Abstract

Lead halide perovskite semiconductors providing record efficiencies of solar cells have usually mixed compositions doped in A- and X-sites to enhance the phase stability. The cubic form of formamidinium (FA) lead iodide reveals excellent opto-electronic properties but transforms at room temperature (RT) into a hexagonal structure which does not effectively absorb visible light. This metastable form and the mechanism of its stabilization by Cs+ and Br incorporation are poorly characterized and insufficiently understood. We report here the vibrational properties of cubic FAPbI3 investigated by DFT calculations on phonon frequencies and intensities, and micro-Raman spectroscopy. The effects of Cs+ and Br partial substitution are discussed. We support our results with the study of FAPbBr3 which expands the identification of vibrational modes to the previously unpublished low frequency region (<500 cm−1). Our results show that the incorporation of Cs+ and Br leads to the coupling of the displacement of the A-site components and weakens the bonds between FA+ and the PbX6 octahedra. We suggest that the enhancement of α-FAPbI3 stability can be a product of the release of tensile stresses in the Pb–X bond, which is reflected in a red-shift of the low frequency region of the Raman spectrum (<200 cm−1).

Graphical abstract: Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopy

Supplementary files

Article information


Submitted
04 Dec 2019
Accepted
31 Jan 2020
First published
26 Feb 2020

This article is Open Access

Phys. Chem. Chem. Phys., 2020,22, 5604-5614
Article type
Paper

Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopy

J. Ibaceta-Jaña, R. Muydinov, P. Rosado, H. Mirhosseini, M. Chugh, O. Nazarenko, D. N. Dirin, D. Heinrich, M. R. Wagner, T. D. Kühne, B. Szyszka, M. V. Kovalenko and A. Hoffmann, Phys. Chem. Chem. Phys., 2020, 22, 5604 DOI: 10.1039/C9CP06568G

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