Significant enhancement of out-coupling efficiency for yarn-based organic light-emitting devices with an organic scattering layer

Abstract

Yarn-based organic light-emitting devices (YOLEDs) have emerged as candidates for potential applications in electronic textiles and wearable electronics. However, the efficiency of YOLEDs is lower than that of conventional OLEDs based on glass substrates because of the loss of light in the interface between the yarn and the organic layers. This paper reports an enhanced out-coupling efficiency when Norland Optical Adhesive 63 (NOA63): Bathophenanthroline (Bphen) particles are used as an organic scattering layer (OSL) for applications in high-efficiency YOLEDs. The RMS roughness of the yarn/OSL/PEDOT:PSS structures (4.3 nm) is drastically reduced in comparison with that of yarn (19.7 nm). Furthermore, the transmittance intensities at 515 nm of yarn with and without an OSL containing Bphen particles are 87% and 82%, respectively, and the luminance of YOLEDs with Bphen particles in the OSL (194.1 cd/cm2) is 41.7 cd/cm2 larger than that without Bphen particles (152.4 cd/cm2) due to the scattering of light from those particles. Moreover, at 515 nm, the electroluminescence (EL) intensity of YOLEDs with Bphen particles in the OSL is 1.3 times larger than that of the YOLEDs without the particles. This successful demonstration of enhanced luminescence and enhanced EL for YOLEDs based on an OSL containing Bphen particles indicates a potential for applications of YOLEDs in next-generation wearable display systems.