Temperature-Dependent Optical Band Gap in CsPbBr3, MAPbBr3, and FAPbBr3 Single Crystals

Giovanni Mannino, Ioannis Deretzis, Emanuele Smecca, Antonino La Magna, Alessandra Alberti, Davide Ceratti, David Cahen

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184 Scopus citations


Single crystals represent a benchmark for understanding the bulk properties of halide perovskites. We have indeed studied the dielectric function of lead bromide perovskite single crystals (MAPbBr3, CsPbBr3 and for the first time FAPbBr3) by spectroscopic ellipsometry in the range of 1-5 eV while varying the temperature from 183 to 440 K. An extremely low absorption coefficient in the sub-band gap region was found, indicating the high optical quality of all three crystals. We extracted the band gap values through critical point analysis showing that Tauc-based values are systematically underestimated. The two structural phase transitions, i.e., orthorhombic-tetragonal and tetragonal-cubic, show distinct optical behaviors, with the former having a discontinuous character. The cross-correlation of optical data with DFT calculations evidences the role of octahedral tilting in tailoring the value of the band gap at a given temperature, whereas differences in the thermal expansion affect the slope of the band gap trend as a function of temperature.

Original languageEnglish
Pages (from-to)2490-2496
Number of pages7
JournalJournal of Physical Chemistry Letters
Issue number7
StatePublished - 2 Apr 2020
Externally publishedYes

Bibliographical note

Publisher Copyright:
Copyright © 2020 American Chemical Society.


This activity was partially supported at CNR by the national project BEYOND NANO Upgrade (CUP G66J17000350007). CNR also gratefully acknowledges the project PON entitled “Tecnologia per celle solari bifacciali ad alta Efficienza a 4 terminali per utility scale”, called BEST-4U, financed by the Italian Ministry MIUR (CUP B88D19000160005). At the Weizmann Institute this work was supported by a research grant from the YOTAM project. D.R.C. acknowledges support from the Weizmann Institute’s Sustainability And Energy Research Initiative, SAERI.

FundersFunder number
Italian ministry MIURCUP B88D19000160005
Weizmann Institute’s Sustainability And Energy Research Initiative
Consiglio Nazionale delle RicercheCUP G66J17000350007


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