Nanoshuttered OLEDs: Unveiled Invisible Auxiliary Electrode

Abstract

In this study, organic light‐emitting diodes (OLEDs) with enhanced optical properties are fabricated by inserting a nanosized stripe auxiliary electrode layer (nSAEL) between the substrate and an indium tin oxide (ITO) layer. This design can avoid the shortcomings of conventional microsized layers while maintaining high optical uniformity due to the improved conductivity of the electrode. The primary advantage is that the nSAEL (submicrometer scale) is no longer visible to the naked eye. Moreover, the reflective shuttered (grating) structure of the nSAEL increases the forward‐directed light by the microcavity (MC) effect and minimizes the loss of light by the extracting the surface plasmon polariton (SPP) mode. In this study, the degree of the MC and SPP can be controlled with the parameters of the nSAEL by simply conjugating the conditions of laser interference lithography (LIL). Therefore, the current and power efficiencies of the device with an nSAEL with optimized parameters are 1.17 and 1.23 times higher than the reference device at 1000 cd/m2, respectively, and at these parameters, the overall sheet resistance is reduced to less than half (48%). All of the processes are verified by comparing the computational simulation results and the experimental results obtained with the actual fabricated device.

High‐Quality White OLEDs with Comparable Efficiencies to LEDs

“…However, WOLEDs with high luminous efficacy (LE) overcoming LEDs at high luminance are believed to be a distant goal at present even with large advances in light extraction during the last couple of decades . Those advances include scatter, low refractive index layer, micro lens array, photonic crystal, low/high refractive index grid, high refractive index substrate, corrugated structure, graded index, randomly distributed pillar array, biomimetic structure, plasmonic nanocavity, and so on. Among the proposed methods, the insertion of extraction medium between the glass and the indium tin oxide (ITO) electrode is regarded to have potential for further efficiency enhancement by extracting the waveguide mode in combination with the extraction method at the glass–air interface.…”

“…Among the proposed methods, the insertion of extraction medium between the glass and the indium tin oxide (ITO) electrode is regarded to have potential for further efficiency enhancement by extracting the waveguide mode in combination with the extraction method at the glass–air interface. However, despite the efficiency improvement due to the extraction layer, many of these methods often have limitations such as diffraction pattern and color distortion to be applied to general illumination systems and high‐performance electronic devices . To solve these problems such as the angular dependence and diffraction pattern, a random pattern is introduced, but the currently reported random patterns are obtained by using spontaneous methods which have difficulty in quantitative control of randomness and poor reproducibility .…”

P‐185: Enhanced Light Extraction of Flexible Organic Light‐emitting Diodes by Ag Nanoparticles as Scattering Layer

“…The surface roughness can increase current density because the current path become short. [10] Fig 4 (b) shows the external quantum efficiency(EQE) of fabricated OLEDs. The EQE of OLED with scattering layers exhibits a maximum of 1.8 %, while the reference device has 1.6%.…”

Toward Scalable Flexible Nanomanufacturing for Photonic Structures and Devices

“…Shim et al developed a nanosized strip auxiliary electrode layer (nSAEL) between the glass substrate and an ITO electrode via an IL process ( Figure ) . The primary advantage of this nanopatterned electrode is that high optical uniformity is maintained, with improved conductivity of the electrode.…”

“…c) Photographs of an nSAEL with fill factors of 0.30 and 0.80. Reproduced with permission . Copyright 2014, Wiley‐VCH.…”