Two-photon Lithography for 3D Magnetic Nanostructure Fabrication

Ferromagnetic materials have been utilised as recording media within data storage devices for many decades. Confinement of the material to a two dimensional plane is a significant bottleneck in achieving ultra-high recording densities and this has led to the proposition of three dimensional (3D) racetrack memories that utilise domain wall propagation along nanowires. However, the fabrication of 3D magnetic nanostructures of complex geometry is highly challenging and not easily achievable with standard lithography techniques. Here, by using a combination of two-photon lithography and electrochemical deposition, we show a new approach to construct 3D magnetic nanostructures of complex geometry. The magnetic properties are found to be intimately related to the 3D geometry of the structure and magnetic imaging experiments provide evidence of domain wall pinning at a 3D nanostructured junction

ITO with embedded silver grids as transparent conductive electrodes for large area organic solar cells

In this work, development of semi-transparent electrodes for efficient large area organic solar cells (OSCs) has been demonstrated. Electron beam evaporated silver grids were embedded in commercially available ITO coatings on glass, through a standard negative photolithography process, in order to improve the conductivity of planar ITO substrates. The fabricated electrodes with embedded line and square patterned Ag grids reduced the sheet resistance of ITO by 25% and 40%, respectively, showing optical transmittance drops of less than 6% within the complete visible light spectrum for both patterns. Solution processed bulk heterojunction OSCs based on PTB7:[70]PCBM were fabricated on top of these electrodes with cell areas of 4.38 cm 2, and the performance of these OSCs was compared to reference cells fabricated on pure ITO electrodes. The Fill Factor (FF) of the large-scale OSCs fabricated on ITO with embedded Ag grids was enhanced by 18% for the line grids pattern and 30% for the square grids pattern compared to that of the reference OSCs. The increase in the FF was directly correlated to the decrease in the series resistance of the OSCs. The maximum power conversion efficiency (PCE) of the OSCs was measured to be 4.34%, which is 23% higher than the PCE of the reference OSCs. As the presented method does not involve high temperature processing, it could be considered a general approach for development of large area organic electronics on solvent resistant, flexible substrates. </p