The development of printed electronics made with organic (carbon-based) semiconductor materials has resulted in several promising technologies including organic light emitting diodes for displays, solid state lighting, and organic photovoltaics. The advantages of organic electronic materials are their relatively low cost and availability compared with inorganic semiconductor materials. However, in general, the active layers and electrodes used in organic electronics can be susceptible to chemical reactions with water vapor and/or oxygen during use, thereby reducing their lifetime, efficiency, and overall performance. There is a critical need to develop advanced permeation barriers for assembling these devices given the role the packaging has in the reliability of the organic electronics and the ever-increasing demand for these products. These barrier films must also be mechanically robust (resist cracking) when large applied strains are imposed during use. This award supports fundamental research to provide knowledge for the processing of mechanically reliable, ultrathin polymer barrier films processed with the atomic layer deposition technique. Additionally, summer enrichment programs are planned for high school students to encourage their interest in pursuing education and careers in STEM fields.
The overarching goal of the proposed research is to provide a fundamental understanding of mechanical reliability of ultra-barrier films made by atomic layer deposition for application to flexible printed electronics. The experimental protocol will explore the relationship between processing conditions, onset failure strain, and material composition/structure failures to elucidate the factors that impact the reliability of atomic-layered-deposited barriers used in flexible electronics. These films differ from most atomic-layered-deposited film in that they are processed at temperatures below 100°C for compatibility with low cost substrates and/or sensitive organic electronic devices. Thus, the stoichiometry of these atomic-layered-deposited films can be quite different than those processed at higher temperatures, resulting in properties that are not fully characterized or understood. This research will provide a systematic scientific study to understand, predict and minimize cracking of low-temperature coatings, with a specific focus on the effects of processing conditions (temperature, chemical functionalization of the polymer substrates) on their barrier performance and mechanical properties. This will be enabled by coupling state-of-the-art mechanical testing with surface science and multi-scale modeling studies that will provide the link between the stoichiometry of the atomic-layered-deposited coatings, their hydrogen content, and the analyzed mechanical behavior.
