Author

Weiran Gao

Faculty Advisor or Committee Member

Ronald Grimm, Advisor

Faculty Advisor or Committee Member

Aaron Deskins, Committee Member

Faculty Advisor or Committee Member

Pratap M. Rao, Committee Member

Faculty Advisor or Committee Member

Michael Timko, Committee Member

Identifier

etd-071318-135124

Abstract

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.

Publisher

Worcester Polytechnic Institute

Degree Name

MS

Department

Chemical Engineering

Project Type

Thesis

Date Accepted

2018-07-13

Accessibility

Unrestricted

Subjects

perovskite, surface chemistry, TPD, XPS

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