During my postdoctoral stay at the Physics Institute of BUAP one of my duties is the deposition of thin-film semiconductors. At this laboratory IFUAP-205, I have been doing chemistry activities like the preparation of precursors solutions. In Fig.1, I want to show you three vials with solutions of different molar concentrations used for copper sulfide thin-film deposition: Copper chloride (CuCl2), Sodium hydroxide (NaOH) and Thiourea (NH2CSNH2). These solutions were dissolved in deionized water and stirred using a magnetic plate. What I have learned here is that solutions should be prepared one day before or in the moment of the chemical…