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Optical Characterization of Cesium Lead Bromide Perovskites

1
Department of Industrial Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
2
Istituto di Struttura della Materia (ISM), Consiglio Nazionale delle Ricerche CNR, Via del Fosso del Cavaliere 100, 00133 Rome, Italy
3
Istituto per la Microelettronica e i Microsistemi (IMM), Consiglio Nazionale delle Ricerche CNR, Via del Fosso del Cavaliere 100, 00133 Rome, Italy
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(6), 280; https://doi.org/10.3390/cryst9060280
Received: 3 April 2019 / Revised: 23 May 2019 / Accepted: 25 May 2019 / Published: 28 May 2019
(This article belongs to the Section Crystalline Materials)
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Abstract

CsPbBr3 and Cs4PbBr6 perovskite powders have been synthesized through a relatively simple low-temperature and low-cost method. Nanocrystalline films have also been deposited from solutions with four different molar compositions of binary salt precursors. Optical absorption, emission and excitation spectra have been performed in the UV-visible spectral range while X-ray diffraction (XRD) has been recorded to characterize the nanocrystal morphology for the different molar compositions. A preferential orientation of crystallites along the (024) crystalline plane has been observed as a function of the different deposition conditions in films growth. All the crystals show an absorption edge around 530 nm; Tauc plots of the absorption returned bandgaps ranging from 2.29 to 2.35 eV characteristic of CsPbBr3 phase. We attribute the UV absorption band peaked at 324 nm to the fundamental band-to-band transition for Cs4PbBr6. It was observed that the samples with the most ordered Cs4PbBr6 crystals exhibited the most intense emission of light, with a bright green emission at 520 nm, which are however due to the luminescence of the inclusion of CsPbBr3 nanoclusters into the Cs4PbBr6. The latter shows instead an intense UV emission. Differently, the pure CsPbBr3 powder did not show any intense fluorescent emission. The excitation spectra of the green fluorescent emission in all samples closely resemble the CsPbBr3 absorption with the peculiar dip around 324 nm as expected from density of state calculations reported in the literature. View Full-Text
Keywords: cesium lead bromide perovskites; fluorescence; Cs4PbBr6; nanocrystals cesium lead bromide perovskites; fluorescence; Cs4PbBr6; nanocrystals
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De Matteis, F.; Vitale, F.; Privitera, S.; Ciotta, E.; Pizzoferrato, R.; Generosi, A.; Paci, B.; Di Mario, L.; Pelli Cresi, J.S.; Martelli, F.; Prosposito, P. Optical Characterization of Cesium Lead Bromide Perovskites. Crystals 2019, 9, 280.

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