We demonstrate a flexible, transparent, and conductive composite electrode comprising silver nanowires (Ag NWs), and indium-doped zinc oxide (IZO) layers. IZO is sputtered onto an Ag NW layer, with the unique structural features of the resulting composite suitable as a flexible, transparent, conductive electrode. The IZO buffer layer prohibits surface oxidation of the Ag NW, and is thereby effective in preventing undesirable changes in electrical properties. The newly designed composite electrode is a promising alternative to conventional ITO films for the production of flexible and transparent electrodes to be applied in next-generation flexible electronic devices.
Fabrication of junction-free Ag fiber electrodes for flexible organic light-emitting diodes (OLEDs) is demonstrated. The junction-free Ag fiber electrodes are fabricated by electrospun polymer fibers used as an etch mask and wet etching of Ag thin film. This process facilitates surface roughness control, which is important in transparent electrodes based on metal wires to prevent electrical instability of the OLEDs. The transmittance and resistance of Ag fiber electrodes can be independently adjusted by controlling spinning time and Ag deposition thickness. The Ag fiber electrode shows a transmittance of 91.8% (at 550 nm) at a sheet resistance of 22.3 Ω □ , leading to the highest OLED efficiency. In addition, Ag fiber electrodes exhibit excellent mechanical durability, as shown by measuring the change in resistance under repeatable mechanical bending and various bending radii. The OLEDs with Ag fiber electrodes on a flexible substrate are successfully fabricated, and the OLEDs show an enhancement of EQE (≈19%) compared to commercial indium tin oxide electrodes.
The progress in 3D printing research has led to significant developments ranging from customized printing to rapid prototyping. However, the 3D printing of electrodes, especially stretchable electrodes for the fabrication of 3D printable electronic devices, is challenging due to the inherent weakness with respect to the printing material. A novel preparation method is reported for a 3D printable conductive ink with a self‐wiring effect during heat treatment, which pushes the silicone rubber outward and results in the accumulation of the conductors within the wire. This effect results in the formation of a polymer shell around the conductor, thus yielding conductors with larger stretchability and soft passivation characteristics. The conductive ink is prepared via the following steps: i) mixing of conductive filler, silicone rubbers, and solvent; followed by ii) soft heat treatment for soft curing and solvent evaporation. Furthermore, a capacitive sensor is fabricated using this dielectric polymer layer. As a demonstration, a mouse controller is fabricated using a capacitive sensor array prepared using the conductors developed in this study.
This paper reports organic light-emitting diodes (OLEDs) with improved light extraction fabricated by embedding an extremely low-index photonic crystal (LIPC) layer. The LIPC layer increases the optical efficiency through the reduced wave-guide mode between the substrate and anode both by increased light resonance and by a strengthened diffraction effect from an extremely low-refractive-index medium, specifically a line structure composed of a vacuum gap. As a result, the current efficiency and power efficiency of the LIPC-OLEDs are 1.51 and 1.93 times higher, respectively, than the reference device at 1000 cd m(-2). Because most of the light extraction is significant, especially in the forward direction, at the specific wavelengths satisfying the Bragg's diffraction equation, it is possible to calculate the anomalous spectrum of the LIPC-OLED through the finite-difference time domain (FDTD) method.
We demonstrated light extraction improvement by applying a scattering layer of Ag nanoparticles physically synthesized through a low-temperature annealing process to flexible organic light-emitting diodes (OLEDs). In general, increasing the size of Ag nanoparticles is preferred to increase light scattering, but a high-temperature annealing process (∼400 °C) is required to produce them. However, flexible substrates generally cannot withstand high-temperature processes. In this study, we formed Ag nanoparticles at a low temperature of ∼200 °C by inserting a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate buffer layer, thus promoting Ag dewetting. As a result, the scattering layer of enlarged Ag nanoparticles formed at low temperatures increased the external quantum efficiency by 24% in a flexible OLED compared to a reference device.
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