Spray-Coated Silver Nanowires as Top Electrode Layer in Semitransparent P3HT:PCBM-Based Organic Solar Cell Devices

Silver nanowire (Ag NW) thin films are investigated as top electrodes in semitransparent inverted organic solar cells. The performance of semitransparent poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) organic solar cells with Ag NW top electrode layers is found to match very closely the performance of reference devices based on thermally evaporated, highly reflective metal silver top electrodes. The optical losses of the semitransparent electrodes are investigated in detail and analyzed in terms of transmission, scattering, and reflection losses. The impact on an external back reflector is shown to increase the light harvesting efficiency of optically thin devices. Further analysis of transparent devices under illumination from the indium tin oxide (ITO) backside and through the Ag NW front electrode open the possibility to gain deep insight into the vertical microstructure related devices performance. Overall, Ag NW top electrodes are established as a serious alternative to TCO based electrodes. Semitransparent devices with efficiencies of over = 2.0% are realized.