Water Splitting Exceeding 17% Solar-to-Hydrogen Conversion Efficiency Using Solution-Processed Ni-Based Electrocatalysts and Perovskite/Si Tandem Solar Cell.

Various noble metal-free electrocatalysts have been explored to enhance the overall water splitting efficiency. Ni-based compounds have attracted substantial attention for achieving efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts. Here, we show superior electrocatalysts based on NiFe alloy electroformed by a roll-to-roll process.

Extremely flat metal films implemented by surface roughness transfer for flexible electronics.

We present an innovative approach to fabricate an extremely flat (EF) metal film which was done by depositing metal on an extremely flat mother substrate, then detaching the metal from the substrate. The detached flexible metal films had a roughness that was within 2% of the roughness of the mother substrate, so EFs with < 1 nm could be fabricated using the surface roughness transfer method. With quantitative analysis using synchrotron XPS, it was concluded that the chemical reaction of oxygen atoms with the metal film played a critical role in designing a peel-off system to get extremely flat metal films from the mother substrate.

Wavelength-Scale Structures as Extremely High Haze Films for Efficient Polymer Solar Cells.

Wavelength-scale inverted pyramid structures with low reflectance and excellent haze have been designed for application to polymer solar cells (PSCs). The wavelength-scale structured haze films are fabricated on the back surface of glass without damages to organic active layer by using a soft lithographic technique with etched GaN molds. With a rigorous coupled-wave analysis of optical modeling, we find the shift of resonance peaks with the increase of pattern's diameter.

Role of ultrathin metal fluoride layer in organic photovoltaic cells: mechanism of efficiency and lifetime enhancement.

Although rapid progress has been made recently in bulk heterojunction organic solar cells, systematic studies on an ultrathin interfacial layer at the electron extraction contact have not been conducted in detail, which is important to improve both the device efficiency and the lifetime. We find that an ultrathin BaF2 layer at the electron extraction contact strongly influences the open-circuit voltage (Voc ) as the nanomorphology evolves with increasing BaF2 thickness. A vacuum-deposited ultrathin BaF2 layer grows by island growth, so BaF2 layers with a nominal thickness less than that of single-coverage layer (≈3 nm) partially cover the polymeric photoactive layer.

Nano-branched transparent conducting oxides: beyond the brittleness limit for flexible electrode applications.

Although the performance of transparent conducting oxides based on bixbyite In(2)O(3) (Sn doped In(2)O(3): ITO) and wurtzite ZnO (Al, In, and Ga doped ZnO) is sufficient in conventional optoelectronic devices, their flexibility remains insufficient for demands in mobile and foldable electronics generation. A lot of alternative materials such as metallic nanowires and carbon based nano-structures have been tried for transparent flexible electrodes, but poor thermal stability of metal nanowires and limits in conductivity of carbon based nano-structures are still waiting for permanent solutions. Here, we show that the cross-linked ITO nano-branches have superior mechanical flexibility compared to ITO bulk film without any cracks even with a bending radius of 0.

Three-dimensional nanobranched indium-tin-oxide anode for organic solar cells.

A nanostructured three-dimensional (3D) electrode using transparent conducting oxide (TCO) is an effective approach for increasing the efficiency of optoelectronic devices used in daily life. Tin-doped indium oxide (ITO) is a representative TCO with high conductivity and a high work function for anode applications. This paper reports the fabrication of a large-area ITO nanostructure with a branch shape using an electron beam evaporation process at temperatures as low as 80 °C, which was free of any carrier gas and catalyst.

Highly reflective Ag-Cu alloy-based ohmic contact on p-type GaN using Ru overlayer.

We report on a metallization scheme of high reflectance, low resistance, and smooth surface morphology ohmic contact on p-type GaN. Ag-Cu alloy/Ru contact showed low contact resistivity as low as 6.2 x 10(-6) Ohms cm(2) and high reflectance of 91% at 460 nm after annealing at 400 degrees C in air ambient.