Toward robust stretchable OLEDs: Unifying light extraction and mechanical compliance via random micro-/nanostructuring

The advancement of flexible and stretchable optoelectronics has long been limited by two fundamental challenges. The first is inefficient light extraction caused by photon trapping in waveguide modes, and the second is the inherent trade-off between optical performance and mechanical durability. Here, we report a cost-effective and scalable elastomeric substrate with randomly distributed micro-/nanostructures fabricated by a sandpaper-templated replication process. These substrates achieve high optical transmittance (>91%) with widely tunable haze. Their randomly distributed structures reduce internal reflection and generate a near-Lambertian emission profile, thereby significantly enhancing light outcoupling. When integrated into flexible white organic light-emitting diodes (OLEDs), the optimized substrates improved light extraction efficiency by 48%, attaining a peak current efficiency of 127.5 cd/A. Moreover, the devices exhibit robust mechanical and environmental stability, retaining more than 90% of their initial luminance after 2500 bending cycles and 30 min of water immersion. Intrinsically stretchable OLEDs fabricated on these substrates maintain stable operation under 50% strain, satisfying application needs that demand extensibility beyond conventional flexibility. The proposed strategy offers a scalable route to wearable and implantable optoelectronics with improved optical, mechanical, and environmental robustness.