We quantified the chemical species present at polycrystalline cesium tin bromide perovskite, CsSnBr3 and cesium titanium bromide antifluorite, Cs2TiBr6. For CsSnBr3, experiments utilized the orthogonal reactivity of the Cs+ cation, the Sn2+ cation, and the Br– halide anion. Ambient- pressure exposure to BF3 solutions probed the reactivity of interfacial bromines. Reactions with p-trifluoromethylanilinium chloride probed the exchange reactivity of the Cs+ cation. A complex-forming ligand, 4,4’-bis(trifluoromethyl)-2,2’-bipyridine, probed for interfacial Sn2+- site cations. For Cs2TiBr6, both BF3 and (C6F5)3B probed the reactivity of interfacial bromines. Fluorine features in x-ray photoelectron spectroscopy (XPS) quantified reaction outcomes for each solution-phase species. XPS indicated adsorption of BF3 on CsSnBr3 and (C6F5)3B on Cs2TiBr6 indicating surface-available halide anions on both surfaces. For CsSnBr3, temperature- programmed desorption (TPD) quantified a ~215 kJ mol–1 desorption energy of BF3 on the surface. Adsorption of the fluorinated anilinium cation included no concomitant adsorption of chlorine as revealed by the absence of Cl 2p features within the limits of XPS detection. The bipyridine ligand demonstrated adsorption to CsSnBr3. We discuss the present results in the context of interfacial stability, passivation, and reactivity for solar-energy conversion devices.
| Identifer | oai:union.ndltd.org:wpi.edu/oai:digitalcommons.wpi.edu:etd-theses-2343 |
| Date | 13 July 2018 |
| Creators | Gao, Weiran |
| Contributors | Ronald Grimm, Advisor, Aaron Deskins, Committee Member, Pratap M. Rao, Committee Member, Michael Timko, Committee Member |
| Publisher | Digital WPI |
| Source Sets | Worcester Polytechnic Institute |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Masters Theses (All Theses, All Years) |
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