Fabrication of an oxide/metal/oxide structured electrode integrated with antireflective film to enhance performance in flexible organic light-emitting diodes

Abstract

Flexible organic light-emitting diodes (OLEDs) are used widely in optoelectronic devices, with possible new applications, including foldable/rollable displays. Unique features of flexible OLEDs included high brightness, low power consumption, and flexibility. The performance of a flexible OLED is frequently hindered by refractive index difference between the air and the flexible substrate medium, leading to inefficient light outcoupling. To address this issue, we developed a mechanically robust oxide/metal/oxide (OMO) structured transparent conducting electrode (TCE), integrated with silica nanoparticles-based antireflective (AR) film, to improve the light extraction efficiency of flexible OLEDs. The AR-OMO structures were prepared on polyethylene terephthalate substrates using a combination of plasma enhanced chemical vapor deposition and magnetron sputtering. Our results show that an OLED device based on AR-OMO TCE exhibits higher luminance efficiency (LE) and total external quantum efficiency (EQE(tot)) than devices based on pristine OMO or an indium tin oxide structure due to the presence of AR film that suppresses waveguided-mode light loss at the air-substrate interface. The champion AR-OMO-based flexible OLED devices achieved an LE of 12.3 cd/A and an EQE(tot) of 5.0%. The AR-OMO device also demonstrated outstanding mechanical flexibility, retaining 100% of its initial luminance up to a bending radius of 6 mm. (C) 2021 Elsevier Ltd. All rights reserved.