Curvature-Conforming Nanostructured Encapsulation for Washable and Mechanically Reliable Fiber OLEDs

Reliable encapsulation of fiber-based organic light-emitting diodes (OLEDs) remains a primary bottleneck for wearable optoelectronic textiles, as cylindrical geometry and repeated deformation couple environmental ingress with mechanical damage in ways that planar barrier strategies do not address. Here, a fiber-specific encapsulation architecture is presented, combining an Al₂O₃/ZnO nanolaminate barrier grown by low-temperature atomic layer deposition with a mechanically compliant Parylene-C overlayer. During alternating deposition cycles, process-induced reorganization within the nanolaminate─including crystallinity suppression that eliminates grain-boundary diffusion pathways, interfacial oxygen exchange that passivates vacancy-associated defect states in ZnO, and selective Zn depletion that generates internal nanostructured heterogeneities─simultaneously enhances environmental sealing and crack tolerance on curved substrates. X-ray reflectivity analysis confirms that this reorganization produces an interdiffused architecture whose structural compactness is largely preserved despite internal restructuring, while nanoindentation reveals a reduced elastic modulus-to-hardness ratio consistent with improved resistance to crack initiation. Device-level validation is performed on monorail-structured fiber OLEDs under two complementary, fiber-relevant stress frameworks: a washing-mimetic multistep protocol sequentially imposing water exposure, wet-state deformation, constrained handling stress, and thermal incubation; and a hinge-based pure bending configuration providing strain-validated cyclic loading without buckling artifacts. Encapsulated devices retain electroluminescence after 1000 bending cycles at 1.8% tensile strain, exceeding the strain tolerance of the unencapsulated counterpart, indicating that the barrier actively extends the mechanical operating window, and remain emissive under full water submersion. Operational lifetime is preserved after combined bending and washing preconditioning at an initial luminance of 2000 cd·m^-2, confirming poststress stability under conditions relevant to practical textile integration.