Using Organic Light-Emitting Electrochemical Thin-Film Devices To Teach Materials Science

Light-emitting thin films provide an excellent opportunity to learn about principles of electrochemistry, spectroscopy, microscopic structure of the solid state, basic circuits, and engineering design. There is currently strong interest in academic and industrial engineering research centering on developing organic light-emitting devices for applications in flat panel displays. In this educational module, designed for high school or introductory undergraduate courses, students learn how to make a ruthenium-based thin-film device. In the process, they learn about the solid-state electrochemistry at work in the film, as well as the electroluminescence that results when current passes through the device. Solutions containing a [Ru(bpy)₃]Cl₂ and polyvinyl alcohol are mixed to produce an even distribution of the ruthenium complex in a polymer matrix. Students build a small machine to spin-coat this mixture as a thin layer onto a conducting indium-tin-oxide electrode on a glass substrate. A gallium-indium eutectic is used as the second electrode. Students learn about the simple electric circuits required to operate both the spin-coater and the light-emitting device. They then follow the engineering design process in testing modifications to the original procedure to improve device performance and investigate the mechanisms involved in the electroluminescence.