Origin of Sn(ii) oxidation in tin halide perovskites. Issue 5 (15th July 2020)

• Record Type: Journal Article
• Authors: Pascual, Jorge; Nasti, Giuseppe; Aldamasy, Mahmoud H.; Smith, Joel A.; Flatken, Marion; Phung, Nga; Di Girolamo, Diego; Turren-Cruz, Silver-Hamill; Li, Meng; Dallmann, André; Avolio, Roberto; Abate, Antonio
• Is Part Of: Materials advances. Volume 1:Issue 5(2020)
• Page Start: 1066
• Page End: 1070
• Publication Date: 2020-07-15
• Subjects: 620.11
• DOI: 10.1039/d0ma00245c
• Languages: English
• ISSNs: 2633-5409

Abstract

Abstract : Tin-halide perovskites have great potential as photovoltaic materials, but their performance is hampered by undesirable oxidation of Sn(ii ) to Sn(iv ). NMR proves DMSO to be a main cause of oxidation. Abstract : Tin-halide perovskites have great potential as photovoltaic materials, but their performance is hampered by undesirable oxidation of Sn(ii ) to Sn(iv ). In this work, we use nuclear magnetic resonance spectroscopy (NMR) to identify and describe the origins of Sn(iv ) in Sn-based perovskites, mainly focusing on direct measurements of Sn oxidation states with 119 Sn-NMR in solid-state and solution. We find that dimethylsulfoxide (DMSO), a typical solvent for Sn-based perovskites, oxidizes Sn(ii ) in acidic conditions under temperatures used for film annealing. We propose a redox reaction between DMSO and Sn(ii ), catalyzed by hydroiodic acid, with iododimethylsulfonium iodide intermediate. We find that lower temperatures and less acidic conditions abate this reaction, and we assess a range of compositions and solution components for this instability. These results suggest the need for strategies to prevent this reaction and shed light on other solution instabilities beyond Sn(iv ) that must be mitigated to achieve high-performance lead-free perovskites.