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

doi:10.1021/acs.jpclett.0c00295

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

Research output: Contribution to journal › Article › peer-review

289 Scopus citations

Abstract

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 language	English
Pages (from-to)	2490-2496
Number of pages	7
Journal	Journal of Physical Chemistry Letters
Volume	11
Issue number	7
DOIs	https://doi.org/10.1021/acs.jpclett.0c00295
State	Published - 2 Apr 2020
Externally published	Yes

Bibliographical note

Publisher Copyright:
Copyright © 2020 American Chemical Society.

Funding

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.

Funders	Funder number
Italian ministry MIUR	CUP B88D19000160005
SAERI
Weizmann Institute’s Sustainability And Energy Research Initiative
Consiglio Nazionale delle Ricerche	CUP G66J17000350007

Access to Document

10.1021/acs.jpclett.0c00295

Cite this

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

abstract = "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.",

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AU - Mannino, Giovanni

AU - Deretzis, Ioannis

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AU - La Magna, Antonino

AU - Alberti, Alessandra

AU - Ceratti, Davide

AU - Cahen, David

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AB - 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.

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