Gas Diffusion Layers with Deterministic Structure for High Performance Polymer Electrolyte Fuel Cells.

Hydrogen-fed polymer electrolyte fuel cells (PEFCs) are promising electrochemical energy converters and a key technology for sustainable mobility and coupling energy sectors. Under operating conditions, water is produced by the oxygen reduction reaction. The gas diffusion layer (GDL) materials, interfacing the reaction sites and gas feed channels, play a key role in the water management. When water condenses in the GDL pore structure, the gas transport to the cathode catalyst layer is deteriorated, thus limiting the cell performance. State-of-the-art GDL materials are stochastic, porous media based on carbon fibers, where water and gas are transported on random, tortuous paths through the pore network. In this work, a novel approach based on a material with a deterministic structure, with a two-layered fabric, is presented. This material, with just one pore throat in the transport path, facilitates water transport and increases the effective diffusivity for gas transport through its open structure. Furthermore, the regular pattern opens up a wide range of tuning opportunities. The presented results demonstrate the improved water management, on the basis of X-ray tomographic image data, and superior cell performance of this novel class of materials, able to be adapted to the local channel geometry.

Transparent organic photodetector using a near-infrared absorbing cyanine dye.

Organic photodetectors are interesting for low cost, large area optical sensing applications. Combining organic semiconductors with discrete absorption bands outside the visible wavelength range with transparent and conductive electrodes allows for the fabrication of visibly transparent photodetectors. Visibly transparent photodetectors can have far reaching impact in a number of areas including smart displays, window-integrated electronic circuits and sensors. Here, we demonstrate a near-infrared sensitive, visibly transparent organic photodetector with a very high average visible transmittance of 68.9%. The transmitted light of the photodetector under solar irradiation exhibits excellent transparency colour perception and rendering capabilities. At a wavelength of 850 nm and at -1 V bias, the photoconversion efficiency is 17% and the specific detectivity is 10(12) Jones. Large area photodetectors with an area of 1.6 cm(2) are demonstrated.