Highly Reliable and Ultra-Flexible Wearable OLEDs Enabled by Environmentally and Mechanically Robust Hybrid Multibarrier Encapsulation Layers

Thin-film encapsulation is a core technology that determines the reliability of next-generation displays, including wearable and stretchable displays. However, the encapsulation technologies developed to date are highly vulnerable to mechanical stress and harsh hygrothermal environments. Therefore, the degradation of their original encapsulation performance (as determined by mechanical and environmental reliability tests) is a major limitation. This paper describes a novel inorganic/organic multibarrier encapsulation method based on structural and material design to overcome the reliability problems of freeform displays. The highly reliable mechanical properties of the encapsulation system are verified using the tensile-testing-on-water method, which is the most reliable method for thin films with thicknesses of tens to hundreds of nanometers. The optimal encapsulation system developed herein achieves an unprecedented elongation of 2.8% in its freestanding form, surpassing the elastic limit of traditional inorganic materials, and maintains a notable elongation of 1.43% after being exposed to harsh environments for 30 h (85 degrees C and 85% relative humidity). The inorganic/organic hybrid encapsulation system designed through systematic analysis in this study is expected to increase the lifetime of devices and facilitate high outdoor usability in applying ultraflexible wearable organic light-emitting diodes. Not only structural rules for an inorganic/organic encapsulation with an elongation of 2.8%, but also material design rules that maintain an elongation of 1.43% even after 30 h of exposure to a harsh environment are presented. The proposed encapsulation system is expected to extend device lifetimes while enabling high outdoor usability for wearable organic light-emitting diodes. image