Investigating Chemistry of Metal Dissolution in Amine–Thiol Mixtures and Exploiting It toward Benign Ink Formulation for Metal Chalcogenide Thin Films

Solution processing of metal chalcogenides using elemental metals dissolved in an amine–thiol solvent mixture has recently received a great deal of attention for the fabrication of thin-film optoelectronic devices. However, little is known about the dissolution pathway for metallic precursors in such mixtures. To exploit the full potential of this method, it is essential that a detailed understanding of the dissolution chemistry be developed. In this study, we use several characterization techniques to examine these solutions and then propose reaction mechanisms for In and Cu dissolutions in a hexylamine/1,2-ethanedithiol mixture. These dissolutions are rather found to be reactions resulting in metal oxidation with coevolution of H2 forming bis(1,2-ethanedithiolate)indium(III) in the case of indium dissolution and high nuclearity Cu(I) thiolate compounds in case of copper dissolution. This understanding allowed us to address the issue of toxicity and corrosivity associated with amine–thiol solvent by util...