Enhanced visible light absorption in layered Cs3Bi2Br9 through mixed-valence Sn(II)/Sn(IV) doping

Chantalle J. Krajewska; Seán R. Kavanagh; Lina Zhang; Dominik J. Kubicki; Krishanu Dey; Krzysztof Gałkowski; Clare P. Grey; Samuel D. Stranks; Aron Walsh; David O. Scanlon; Robert G. Palgrave

doi:10.1039/D1SC03775G

Enhanced visible light absorption in layered Cs₃Bi₂Br₉ through mixed-valence Sn(ii)/Sn(iv) doping†

Chantalle J. Krajewska,^a Seán R. Kavanagh,

^abc Lina Zhang,^a Dominik J. Kubicki,^dj Krishanu Dey,^d Krzysztof Gałkowski,^def Clare P. Grey,

^j Samuel D. Stranks,

^dg Aron Walsh,

^ch David O. Scanlon

^abi and Robert G. Palgrave

*^a

Author affiliations

* Corresponding authors

^a Department of Chemistry, University College London, 20 Gordon Street, London, UK
E-mail: r.palgrave@ucl.ac.uk

^b Thomas Young Centre, University College London, Gower Street, London WC1E 6BT, UK

^c Department of Materials, Imperial College London, Exhibition Road, London SW72AZ, UK

^d Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK

^e Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, 87-100 Toruń, Poland

^f Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland

^g Department of Chemical Engineering & Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK

^h Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Korea

ⁱ Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK

^j Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK

Abstract

Lead-free halides with perovskite-related structures, such as the vacancy-ordered perovskite Cs₃Bi₂Br₉, are of interest for photovoltaic and optoelectronic applications. We find that addition of SnBr₂ to the solution-phase synthesis of Cs₃Bi₂Br₉ leads to substitution of up to 7% of the Bi(III) ions by equal quantities of Sn(II) and Sn(IV). The nature of the substitutional defects was studied by X-ray diffraction, ¹³³Cs and ¹¹⁹Sn solid state NMR, X-ray photoelectron spectroscopy and density functional theory calculations. The resulting mixed-valence compounds show intense visible and near infrared absorption due to intervalence charge transfer, as well as electronic transitions to and from localised Sn-based states within the band gap. Sn(II) and Sn(IV) defects preferentially occupy neighbouring B-cation sites, forming a double-substitution complex. Unusually for a Sn(II) compound, the material shows minimal changes in optical and structural properties after 12 months storage in air. Our calculations suggest the stabilisation of Sn(II) within the double substitution complex contributes to this unusual stability. These results expand upon research on inorganic mixed-valent halides to a new, layered structure, and offer insights into the tuning, doping mechanisms, and structure–property relationships of lead-free vacancy-ordered perovskite structures.

This article is part of the themed collection: 2021 EES Lectureship winner: Sam Stranks

Chemical Science

Enhanced visible light absorption in layered Cs₃Bi₂Br₉ through mixed-valence Sn(ii)/Sn(iv) doping†

Abstract

Supplementary files

Article information

Download Citation

Permissions

Enhanced visible light absorption in layered Cs₃Bi₂Br₉ through mixed-valence Sn(II)/Sn(IV) doping

Social activity

Search articles by author

Spotlight

Advertisements

Chemical Science