Fabrication and characterization of combined metallic nanogratings and ITO electrodes for organic photovoltaic cells

• Gold nanowire gratings for organic photovoltaic cells were fabricated on, within and below ITO electrodes.
• The nanogratings have been fabricated by e-beam lithography and nano imprint lithography.
• The gratings were analyzed by SEM, AFM and GISAXS measurements.
• The tuneability of the plasmon resonance has been shown by white light extinction spectroscopy.

Organic photovoltaic devices are interesting alternatives to conventional silicon based photovoltaic cells, due to potentially lower material costs and energy consumption during the fabrication process. However, the energy conversion efficiency of organic photovoltaic cells may still be improved. One possible approach is a combination with metallic nanostructures to improve light absorption properties in the active layer. We report on the fabrication and characterization of metallic nanogratings integrated with an indium tin oxide (ITO) electrode to be combined with small-molecule organic photovoltaic cells. With respect to geometry and extinction properties gratings fabricated by two different fabrication methods, conventional electron beam lithography and nanoimprint lithography, are presented. Furthermore, gratings fabricated on top of ITO are compared to gratings integrated both below and within ITO electrodes. Fabricating structures below or within electrodes is advantageous for organic thin film techniques to avoid compromising the crystallinity of the organic thin film and short-circuiting across the thin layer.

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