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

DOI: 10.1039/D1SC03775G DOI Help

Authors: Chantalle J. Krajewska (University College London) , Seán R. Kavanagh (University College London; Imperial College London) , Lina Zhang (University College London) , Dominik J. Kubicki (University of Cambridge) , Krishanu Dey (University of Cambridge) , Krzysztof Galkowski (University of Cambridge; Nicolaus Copernicus University; Wroclaw University of Science and Technology) , Clare P. Grey (University of Cambridge) , Samuel D. Stranks (University of Cambridge) , Aron Walsh (Imperial College London; Yonsei University) , David O. Scanlon (University College London; Diamond Light Source) , Robert G. Palgrave (University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemical Science , VOL 12 , PAGES 14686 - 14699

State: Published (Approved)
Published: November 2021

Open Access Open Access

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.

Diamond Keywords: Photovoltaics; Semiconductors

Subject Areas: Chemistry, Materials, Energy


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Added On: 29/11/2021 10:42

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Discipline Tags:

Earth Sciences & Environment Sustainable Energy Systems Energy Climate Change Physical Chemistry Chemistry Materials Science Inorganic Chemistry Perovskites Metallurgy

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