ITO-free large-area flexible organic solar cells with an embedded metal grid

We report on ITO-free large-area flexible organic solar cells with embedded thick metal grids. Embedded thick metal grids on flexible substrates allow uniform spin coating of thin layers of PEDOT:PSS (PH1000) semitransparent electrodes and organic semiconductor layers. A transparent SU8 photo-patternable polymer is used as a flexible substrate. Electroplated copper metallic grids, up to 15 mu m thick, defined by photolithography, produce a shadow area of 5.5% of the active area. Inverted solar cells with an active area of 9.3 +/- 0.2 cm(2), exhibited a fill factor of 0.53 +/- 0.06, and an open-circuit voltage of 808 +/- 5 mV and a short-circuit current density of 5.5 +/- 0.5 mA/cm(2), yielding a power conversion efficiency of 2.4 +/- 0.4% under 100 mW/cm(2) air mass 1.5G illumination. The fill-factor and open circuit voltage values of large-area solar cells are comparable to values reported on small-area solar cells. (C) 2015 Elsevier B.V. All rights reserved.