We investigated the optical properties of a dielectric-metal-dielectric multilayer for the transparent top cathode in top-emitting organic light emitting diodes (TOLEDs). The optical transmittance of the metal layer was enhanced by depositing a dielectric material which had a high refraction index n below and above the metal (Ag) layer. Due to multiple reflections and interferences, the Ag layer sandwiched between dielectric materials with a high value of n can show improved transmittance. Because the WO 3 had a high value of n (>2.0), a thin WO 3 layer could fulfill the optimum zero-reflection condition with an Ag metal layer. Thus, a WO 3 /Ag/WO 3 multilayer should have high transmittance with a low sheet resistance. The optimum thicknesses of both Ag and WO 3 to obtain the best transmittance value were determined by theoretical calculation, and they agreed well with the experimental results. The best results were obtained for the thermally evaporated WO 3 (300 Å)/Ag (120 Å)/WO 3 (300 Å) structure, a high transmittance of ∼93.5% and a low sheet resistance about ∼7.22 ohm/sq were obtained. When the top Al cathode was replaced with the WO 3 /Ag/WO 3 multilayer, the maximum luminance value (J = 220 mA/cm 2 ) increased from 8400 to 11700 cd/m 2 , and the power efficiency increased about 26%. To improve the electron injection efficiency at the cathode region, a 20-Å thick Al layer was introduced as an electron injection interlayer between the organic materials and the WO 3 /Ag/WO 3 cathode. Using the Al interlayer decreased the operation voltage at J = 10 mA/cm 2 by 6.9 V. Thus, a WO 3 /Ag/WO 3 with an Al interlayer could promote the transparency of the top cathode and lower the electron injection barrier, enhancing the electroluminescent properties of TOLED.

The use of three-dimensional (3D) hierarchical indium tin oxide (ITO) branches of electrochromic devices (ECDs) is an effective approach for increasing the optical properties via localized surface plasmon resonance compared with two-dimensional nanostructured electrodes. ECDs with 3D branches were designed to operate in transparent, mirror and black states. Finite-difference time-domain simulation was used to find the electrical field distributions in three types of ECD: glass/ITO with Ag film, glass/ITO branches and glass/ITO branches with Ag nanoparticles. The ECDs had an optical transmittance of 73.76% in the transparent state, a reflectance of 79.77% in the mirror state and a reflectance of 8.78% in the black state. We achieved an ECD with high stability that can show ∼ 10 000 switching cycles among the three states. NPG Asia Materials (2017) 9, e362; doi:10.1038/am.2017.25; published online 17 March 2017 INTRODUCTION Electrochromic devices (ECDs) can exhibit reversible color changes induced by electric energy and the resulting electrochemical redox reactions of materials. 1,2 The changes in optical states are consequences of a change in the electronic state as a result of electron transfer between the electrochromic (EC) material and an electrode. ECDs offer many advantages over conventional displays, including a low operating voltage (V OP ), memory effects, color variations and visibility in sunlight. [3][4][5][6][7] Therefore, ECDs are expected to achieve applications in information displays or in light-modulating devices such as smart windows, switchable mirrors, electronic papers and chemical sensors. [8][9][10][11][12] Conventional ECDs are composed of a non-metal (NM) EC material (for example, poly(ethylene oxide), poly(methyl methacrylate), polyvinylidene difluoride, WO 3 , MoO 3 , Ir(OH) 3 , NiO). [13][14][15][16][17] In particular, WO 3 , which is the most widely known EC material, has attracted considerable attention because of its broad applications such as in ECDs, photocatalysis and sensing devices. 3 However, the use of NM-ECD encounters two drawbacks. (1) It has low optical transmittance when in the transparent state because of the inherent color and high extinction coefficient (k) of the NM materials compared with the metal ions in the electrolyte of the transparent state. [13][14][15][16][17][18] (2) The NM-ECD cannot exhibit a mirror state. Because free electrons are rarely generated in NM materials, an electric field easily penetrates the NM materials. Therefore, most of the incident energy is absorbed or transmitted. As a result, NM-ECDs are not suitable for use in displays and windows.Silver (Ag) has been used as an EC material because of its superior optical properties. Because Ag readily assembles into nanoparticles

Top-illuminated flexible organic solar cells with a high power conversion efficiency (≈6.75%) are fabricated using a dielectric/metal/polymer (DMP) electrode. Employing a polymer layer (n = 1.49) makes it possible to show the high transmittance, which is insensitive to film thickness, and the excellent haze induced by well-ordered nanopatterns on the DMP electrode, leading to a 28% of enhancement in efficiency compared to bottom cells.

Flexible organic light‐emitting diodes with a high light‐extraction efficiency are demonstrated using O2 plasma treatment on the back side of a PET substrate. The plasma‐treated PET substrate extracts the confined waveguided electroluminescence wave in the structure, confirmed by finite‐difference time‐domain simulations. This leads to the enhancement of light extraction to air and thereby improvement of luminance by 70%.

Implementing nanostructures on plastic film is indispensable for highly efficient flexible optoelectronic devices. However, due to the thermal and chemical fragility of plastic, nanostructuring approaches are limited to indirect transfer with low throughput. Here, we fabricate single-crystal AgCl nanorods by using a Cl2 plasma on Ag-coated polyimide. Cl radicals react with Ag to form AgCl nanorods. The AgCl is subjected to compressive strain at its interface with the Ag film because of the larger lattice constant of AgCl compared to Ag. To minimize strain energy, the AgCl nanorods grow in the [200] direction. The epitaxial relationship between AgCl (200) and Ag (111) induces a strain, which leads to a strain gradient at the periphery of AgCl nanorods. The gradient causes a strain-induced diffusion of Ag atoms to accelerate the nanorod growth. Nanorods grown for 45 s exhibit superior haze up to 100% and luminance of optical device increased by up to 33%.