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Main Title: Vibrational dynamics in lead halide hybrid perovskites investigated by Raman spectroscopy
Author(s): Ibaceta-Jaña, Josefa
Muydinov, Ruslan
Rosado, Pamela
Mirhosseini, Hossein
Chugh, Manjusha
Nazarenko, Olga
Dirin, Dmitry N.
Heinrich, Dirk
Wagner, Markus R.
Kühne, Thomas D.
Szyszka, Bernd
Kovalenko, Maksym V.
Hoffmann, Axel
Type: Article
Language Code: en
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support our results with the study of FAPbBr3 which expands the identification of vibrational modes to the previously unpublished low frequency region (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).
Issue Date: 26-Feb-2020
Date Available: 22-Apr-2020
DDC Class: 540 Chemie und zugeordnete Wissenschaften
Subject(s): low frequency region
Raman spectroscopy
vibrational modes
Sponsor/Funder: TU Berlin, Open-Access-Mittel - 2020
DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelemente
BMWi, 0324095H, Verbundvorhaben: speedCIGS - Rechnerunterstützte Optimierung des CIGS-Depositionsprozesses in der industriellen Umsetzung; Teilvorhaben: Transparent leitende Schichten und Perowskit Absorber Schichten für Tandem Konzepte mit CIGS Absorber
Journal Title: Physical Chemistry Chemical Physics
Publisher: RSC Publishing
Publisher Place: London
Volume: 22
Publisher DOI: 10.1039/C9CP06568G
Page Start: 5604
Page End: 5614
EISSN: 1463-9084
ISSN: 1463-9076
Appears in Collections:FG Technologie für Dünnschicht-Bauelemente » Publications

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