Stretchable platforms incorporating layers with very low Young’s modulus for realization of efficient stretchable organic light emitting diodes

Abstract

Wearable electronics that can be attached to the human body have recently received a lot of attention. To adapt to the human body's curvature and movement, wearable electronic devices are desired to exhibit adequate stretchability [1-2]. Various methods have thus been proposed for realization of stretchable electronics. However, there are many hurdles in realizing stretchable organic light emitting diodes (OLEDs) unlike rigid or flexible OLEDs. In particular, the scarcity of intrinsically stretchable transparent electrodes (TEs) is of concern as TEs are a component indispensable to optoelectronic devices including OLEDs. In this work, to reach the high performance simultaneously with high degree of stretchability, novel platforms are proposed that consist of elastomers as a substrate, multiple of photo-patternable hard islands, and a stress-relief layer based on materials with an extremely low Young’s modulus. The rigid islands are then connected with stretchable serpentine interconnectors so that each of the islands are electrically connected to one another. When this platform is stretched, rigid islands where OLEDs are deposited do not deform, but the serpentine interconnector stretches and maintains electrical connections with adjacent islands. Our theoretical modeling shows that the stress and strain applied to interconnectors due to the stretching are further reduced as the Young’s modulus of the bottom layer is lowered [3]. In this work, elastomer with a very low Young’s modulus (≈3.0 kPa) is thus used to greatly relieve the applied stress of the interconnectors. Electrodes deposited on this stretchable platform show very low resistant variation even if interconnectors are stretched until 140% to 5000 times. Stretchable OLEDs also can be stretched 140% with virtually negligible degradation in brightness and electrical characteristics.