Importance of the electrode conductivity in organic photovoltaic solar cells

Realization of performing large area flexible organic photovoltaic cells needs highly conductive and transparent electrode. In the present manuscript we show that it is possible to improve the power conversion efficiency of organic solar cells deposited onto PET/ITO anode by improving the conductivity of the anode. When covered with a thin, 12 nm, metal bilayer, Cu/Ag, itself covered by a refractory metal oxide, MoO₃ or WO₃, it is possible to significantly decrease the sheet resistance of the ITO anode, while its transmission is only slightly reduced, which result in a figure of merit as high as 32 × 10⁻³ Ω⁻¹. Moreover, the flexibility of these multilayer structures is better than that of ITO alone. In the case of PET substrates, when these optimized anodes are introduced in photovoltaic cells based on the planar heterojunction CuPc/C₆₀, the power conversion efficiency of these cells is higher than that of the cells using ITO alone. This improvement becomes more significant and useful for larger areas devices that are needed for practical applications. The best results are obtained with ITO/Cu/Ag/WO₃ anodes.