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 µm 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 µm. 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 × 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.

Highly efficient, heat dissipating, stretchable organic light-emitting diodes based on a MoO3/Au/MoO3 electrode with encapsulation

“…Incorporation of OLEDs into wearable 2 , epidermal 3 , and stretchable electronics 4,5 , with color stability, and high brightness under intensely strained bending/stretching has been of major interest. This interest has led to various studies on electrodes as a replacement of poly (3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) 6 , and indium tin oxide (ITO) [7][8][9] , which included a graphene-based electrode 10 , a highly transparent metal-grid 11 and polymer with silver nanowires (AgNWs) 12,13 . Even though these approaches provide considerable enhancements for flexible/stretchable electronics, there is still scope for further improvement in terms of device stability and efficiency 6,8,9,[12][13][14] .…”

Structures and Materials in Stretchable Electroluminescent Devices

“…This problem may be addressed according to a recent report of directly depositing PLED on prestretched substrate to improve the predictability of the 2D wrinkles. [52]…”

Emerging Biomedical Applications of Organic Light‐Emitting Diodes

“…[40,[48][49][50][51][52] Additionally, stretchable OLEDs have gained a lot of attention and are extremely promising for wearable devices, which usually experience both bending and tensile strain. [48,[52][53][54][55][56][57][58] Despite the great promise in achieving highly flexible lightemitting devices, the use of OLEDs in medicine typically requires device lifetimes ranging from few hours in case of plaster-type wearables up to years when used as implants. In addition, for many applications the devices have to withstand harsh environmental conditions, in particular high humidity and/or immersion into water.…”