Hybrid Parylene-C/Al2O3-TiO2 Nanolaminate Barriers for Reliable Freestanding OLED Photopatches

Skin-attachable light-emitting patches are attracting increasing attention as wearable phototherapeutic platforms for photobiomodulation, wound healing, and skin treatment. However, the practical implementation of organic light-emitting diode (OLED) patches remains challenging because OLEDs require highly reliable encapsulation against moisture and oxygen, whereas body-conformal operation demands an ultrathin, mechanically compliant form factor. Here, we present a direct-delamination-based fabrication strategy for freestanding OLED photopatches designed for single-use-compatible skin-attachable phototherapy. The device is constructed using a vertically symmetric architecture in which the OLED stack is positioned near the mechanical neutral plane between top and bottom hybrid encapsulation layers. Each encapsulation layer consists of Parylene-C organic buffers and atomic-layer-deposited Al2O3/TiO2 nanolaminate (ATN) barriers, enabling defect-decoupled moisture blocking and mechanical stress relaxation. The optimized 2-dyad Parylene-C/ATN structure achieves a water-vapor transmission rate on the order of 10-6 g m-2 day-1 while maintaining mechanical robustness under severe bending. The encapsulated OLED exhibits a 19-fold improvement in operational lifetime compared with an unencapsulated device and retains stable performance after hygrothermal exposure, water immersion, and biofluidic media exposure. The final freestanding RGB OLED patches operate reliably under bending, folding, rolling, underwater immersion, and post-delamination conditions. This work provides a simple and potentially scalable route toward ultraflexible and environmentally reliable OLED photopatches for temporary skin-attachable phototherapy and wearable healthcare applications.