1. Enhanced visible light absorption in layered Cs3Bi2Br9 through mixed-valence Sn(ii)/Sn(iv) doping
- Author
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Lina Zhang, Seán R. Kavanagh, Samuel D. Stranks, Robert G. Palgrave, Clare P. Grey, Dominik J. Kubicki, David O. Scanlon, Krishanu Dey, Krzysztof Galkowski, Aron Walsh, Chantalle J Krajewska, Grey, Clare [0000-0001-5572-192X], Stranks, Samuel [0000-0002-8303-7292], and Apollo - University of Cambridge Repository
- Subjects
Materials science ,INITIO MOLECULAR-DYNAMICS ,Band gap ,Chemistry, Multidisciplinary ,CS3SB2I9 ,BAND-GAP ,02 engineering and technology ,Intervalence charge transfer ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,ENERGY ,CHARGE-TRANSFER ,X-ray photoelectron spectroscopy ,Perovskite (structure) ,3403 Macromolecular and Materials Chemistry ,Science & Technology ,Valence (chemistry) ,34 Chemical Sciences ,Doping ,OPTICAL-PROPERTIES ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,3. Good health ,3402 Inorganic Chemistry ,Chemistry ,Crystallography ,PEROVSKITES ,Physical Sciences ,LUMINESCENCE ,PHASE-TRANSITION ,3406 Physical Chemistry ,PHOTOLUMINESCENCE ,Density functional theory ,03 Chemical Sciences ,0210 nano-technology ,Visible spectrum - 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.
- Published
- 2021