Band-Gap Tuning in All-Inorganic CsPb x Sn1- xBr3 Perovskites

Heidi A Schwartz; Hannah Laurenzen; Asma Marzouk; Manuel Runkel; Kai Oliver Brinkmann; Detlef Rogalla; Thomas Riedl; Sahel Ashhab; Selina Olthof

doi:10.1021/acsami.0c20285

Band-Gap Tuning in All-Inorganic CsPb _x Sn_{1- x}Br₃ Perovskites

ACS Appl Mater Interfaces. 2021 Jan 27;13(3):4203-4210. doi: 10.1021/acsami.0c20285. Epub 2021 Jan 12.

Authors

Heidi A Schwartz¹, Hannah Laurenzen¹, Asma Marzouk², Manuel Runkel³, Kai Oliver Brinkmann³, Detlef Rogalla⁴, Thomas Riedl³, Sahel Ashhab², Selina Olthof¹

Affiliations

¹ Department of Chemistry, University of Cologne, Greinstrasse 4-6, 50939 Cologne, Germany.
² Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, P.O. Box 34110, Doha 122104, Qatar.
³ Institute of Electronic Devices and Wuppertal Center for Smart Materials & Systems, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany.
⁴ RUBION, University of Bochum, Universitätsstr. 150, 44801 Bochum, Germany.

PMID: 33435668
DOI: 10.1021/acsami.0c20285

Abstract

We investigate all-inorganic perovskite CsPb_xSn_1-xBr₃ thin films to determine the variations in the band gap and electronic structure associated with the Pb/Sn ratio. We observe that the band gap can be tuned between 1.86 eV (x = 0) and 2.37 eV (x = 1). Intriguingly, this change is nonlinear in x, with a bowing parameter of 0.9 eV; furthermore, a slight band gap narrowing is found for low Pb content (minimum x ∼ 0.3). The wide tunability of the band gap makes CsPb_xSn_1-xBr₃ a promising material, e.g., for a wide-gap subcell in tandem applications or for color-tunable light-emitting diodes. Employing photoelectron spectroscopy, we show that the valence band varies with the Pb/Sn ratio, while the conduction band is barely affected.

Keywords: UPS; XPS; all-inorganic perovskite; band gap; crystal structure; density functional theory; halide perovskite; photoelectron spectroscopy.