Improving light extraction of flexible OLEDs using a mechanically robust Ag mesh/ITO composite electrode and microlens array

Abstract

In this study, we designed a highly flexible, mechanically robust Ag mesh/ITO composite transparent conducting electrode (TCE) integrated with a microlens array (MLA) to improve the light extraction of organic light-emitting diodes (OLEDs). The mechanical flexibility and durability of a flexible OLED based on a Ag mesh/ITO composite TCE were superior to those of a device with a conventional ITO electrode, retaining ∼100% initial luminance for up to 1000 cycles at a bending radius of ∼2 mm. Additionally, both experimental and theoretical characterizations suggest that the performance of a flexible OLED, such as its external quantum efficiency and angular-dependent emission, vastly improves after the incorporation of MLA due to the additional light scattering induced by the MLA. The combined use of Ag mesh and MLA is a practical way to overcome the brittleness of ITO and improve the out-coupling efficiency of flexible OLEDs (enhancement ratio of ∼1.51).