Distortion-Free Stretchable Light-Emitting Diodes via Imperceptible Microwrinkles

Abstract

Stretchable organic light-emitting diodes (OLEDs) have been considered as a promising technology for next-generation free-form and wearable displays. However, an approach to ensure both high device performance and high resolution has not yet been suggested. While introducing a wrinkled structure in the active pixel areas is a decent method, the formation of out-of-plane macroscopic wrinkles having a wavelength of a few hundred mu m has caused distortion in the shape of the pixel, which is a critical drawback for a matrix-configured display demanding a sharp pixel definition. Herein, microwrinkled OLEDs are fabricated to define a distortion-free pixel by direct deposition of OLEDs on biaxially prestretched elastomeric substrate, being feasible by a low-temperature-based solution process. The total thickness of the device can be significantly reduced up to 350 nm, producing the imperceptible microwrinkles having a wavelength under 20 mu m. The microwrinkled OLEDs show a luminance over 8000 cd m(-2) and maximum current efficiency of 7.76 cd A(-1), which is comparable to the device without wrinkled structure. Finally, a stretchable 4 x 4 OLED pixel array with a microwrinkled structure is demonstrated showing sharply defined square-patterned emission, proving the potential in the future high-resolution stretchable display.