Fully Vacuum-Free Fabrication of Bi-Directional Polymer Light-Emitting Diodes Based on a Hybrid Lamination Top Electrode

Abstract

This study investigates a hybrid lamination electrode based on a silver nanowire and a conductive polymer for the top electrode of bi-directional polymer light-emitting diodes (PLEDs). Through a vacuum-free hot-press lamination step, the proposed hybrid electrode employed a complete and concrete electrical contact with the underlying emissive polymer layer. In addition, by inserting a hole injecting poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer to increase the level of work function, the bi-directional PLED device with a laminated top electrode showed a more competitive device performance such as an operating voltage, a current efficiency, and a total external quantum efficiency compared to the counterpart device with a multilayered electrode of MoO 3 /Ag/MoO 3 by the vacuum thermal evaporation method. An analysis carried out on the angular characteristics of bi-directional PLEDs including the variation of color coordinates and change in luminance values according to emission angles confirmed that the hybrid lamination electrode provided a more uniform angular distribution regardless of the direction of emission without any optical micro-cavity effect. Detailed optical and electrical analyses were also performed to evaluate the compatibility of the hybrid lamination electrode for the low-cost fabrication of efficient PLEDs.