Ultrathin Encapsulation Structures for Skin-Attachable Quantum Dot LED

Abstract

The field of electronics has evolved from rigid and bulky components to flexible, stretchable, and skin-conformal systems that can intimately interface with the human body. Such skin-attachable electronic devices enable continuous monitoring of physiological signals, localized therapeutic stimulation, and real-time interaction with external systems. However, their direct exposure to mechanical deformation, sweat, and humidity imposes critical challenges to long-term stability and reliability. Among the various components, the encapsulation layer—which protects functional devices from the external environment while maintaining flexibility—plays a decisive role in determining device performance and lifetime. Conventional polymer encapsulants provide excellent elasticity but poor moisture barrier properties, while inorganic thin films offer superior impermeability yet insufficient stretchability. To overcome this trade-off, this study presents an ultrathin laminated hybrid encapsulation structure composed of an inorganic barrier layer, a polymeric adhesive interlayer, and a flexible PEN support film. This architecture achieves both high flexibility and low water vapor transmission rate (WVTR) by decoupling mechanical compliance and barrier performance. Furthermore, the interfacial adhesive layer minimizes stress concentration and delamination under repeated deformation, enabling stable electrical operation of skin-attachable electronics. To evaluate the environmental stability of the encapsulation, QLED devices were fabricated under identical conditions while varying only the encapsulation structure, and their operational lifetime was measured under continuous operation. The results revealed that the hybrid encapsulation composed of an inorganic barrier layer, a polymeric adhesive resin, and a PEN support film exhibited significantly improved long-term stability compared to conventional single polymer coatings. These findings confirm that the proposed hybrid architecture effectively enhances both moisture barrier performance and mechanical reliability. This study establishes a high-reliability ultrathin encapsulation design strategy applicable to next-generation wearable and skin-attachable electronic devices.