Green Chemistry Approach for The Synthesis of Transition Metal Sulfides based on Cu2ZnSnS4 (CZTS) and Etching of Their Impurities
2017-07
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Green Chemistry Approach for The Synthesis of Transition Metal Sulfides based on Cu2ZnSnS4 (CZTS) and Etching of Their Impurities
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2017-07
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Green Chemistry comprises a set of good practices leading to more sustainable and environmentally friendly chemical processes. In the first chapter, this dissertation introduces the Green Chemistry Principles and shows how these Principles can be applied towards the synthesis of transition metal chalcogenides. The next chapter presents results focused on the synthesis of the multinary sulfide Cu2ZnSnS4 (CZTS) using microwave as heating source. The control over the crystalline phase of CZTS was studied as a function of variations in synthetic conditions, such as source of sulfur excess, initial oxidation states of Cu and Sn sources, temperature, and time. A model explaining two different behaviors according to the sulfur excess source is proposed. The third chapter uses the concepts learned from the previous one to develop the synthesis of solid solutions between Cu2ZnSnS4 and Cu2CoSnS4, generating compounds with the formula Cu2(Zn1-xCox)SnS4. Thin films were prepared from aqueous dispersions of these Cu2(Zn1-xCox)SnS4 compounds, and the stability of the films upon annealing in sulfur atmosphere was analyzed. The fourth chapter describes the development of a milder etching solution based on a mixture of ethylenediamine and 2-mercaptoethanol to eliminate undesired copper sulfide (Cu2-XS) or copper selenide (Cu2-XS) phases from CZTS thin films. The development of this etching solution represents a viable alternative to the widely used etching methods based on potassium cyanide (KCN) use. The fifth chapter extends the application of the etching solution to etch other common undesired phases such as ZnS, SnS2, and CuxZnySnz, and a possible mechanism is proposed for the etching process based in a Lewis acid-base reaction between ethylenediamine and 2-mercaptoethanol
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University of Minnesota Ph.D. dissertation.July 2017. Major: Chemistry. Advisor: Eray Aydil. 1 computer file (PDF); xviii, 174 pages.
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Pinto, Alexandre. (2017). Green Chemistry Approach for The Synthesis of Transition Metal Sulfides based on Cu2ZnSnS4 (CZTS) and Etching of Their Impurities. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/200274.
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