Encapsulation Strategies for OLEDs: From Conventional Devices to Flexible and Biointegrated Applications

Abstract Organic light‐emitting diodes (OLEDs) have rapidly evolved from rigid to flexible and stretchable displays, with applications expanding into wearable and bioelectronic devices. This expansion exposes the devices to harsh environmental conditions, including moisture, oxygen, heat, and mechanical stress. Due to these external stress factors, the need for effective encapsulation technologies has become increasingly critical to ensure long‐term device stability. his review focuses on next‐generation OLED encapsulation technologies suitable for application in wearable and bioelectronic devices. It begins by summarizing conventional encapsulation methods followed by an introduction to representative barrier performance evaluation techniques, including water vapor transmission rate (WVTR) measurements and mechanical durability testing. The review then analyzes OLED degradation mechanisms and explains how encapsulation can effectively suppress these failure pathways. Finally, thin film encapsulation (TFE) structures and design strategies are discussed in the context of their integration into flexible and bioelectronic applications. By comprehensively reviewing OLED degradation mechanisms and recent advances in encapsulation research, this review provides a valuable foundation for the design of encapsulation strategies aimed at ensuring the reliability of next‐generation flexible and bioelectronic display devices.