Protection From Oxygen and Moisture Via Thin Oxide Barrier Coating for Organic Electronics

Protection from oxygen and moisture is crucial for organic light emitting diodes (OLED) used in flexible display applications. The surface coating is an effective way to protect the enclosed functional materials and organic substrates in order to ensure their device functionality. Parylene films, which can be vapor deposited at room temperature, are known as a superior conformal polymeric material. In fact, a few attempts have shown that the parylene can be a good barrier coating for the OLED devices. This polymer film cannot, however, provide a long-term reliability due to nature of the polymer degradation in the presence of oxygen and moisture. In order to compensate such a drawback, we have explored the ‘biomimetic’ solution processing to deposit the oxide films on the organic substrate. Oxide films can provide a better protection and more robust surface. In this study, polyethylene terephthalate (PET) commonly used for an organic substrate, is deposited with the TiO₂ films with or without the parylene underlying layer. Importantly, the oxide coating is processed at very low temperatures (< 60 °C) in aqueous solution, so the process can avoid premature failure due to high-temperature processes, and is applicable to organic structures, cheap and environment-friendly. In addition, hermeticity tests are devised to measure the moisture and oxygen permeation. Interfacial structure and mechanical properties of the resultant coatings are tested via scanning electron microscope (SEM), atomic force microscope (AFM), optical microscope (OM) and nanoindentation.