Nano-sized indium-free MTO/Ag/MTO transparent conducting electrode prepared by RF sputtering at room temperature for organic photovoltaic cells

As an alternative to indium-tin oxide (ITO), MTO/Ag/MTO (MAM) multilayer transparent electrodes with a nano-sized Ag thin film embedded between Mn-doped tin oxide (MTO) layers were prepared. The MTO/Ag/MTO thin films were deposited on a glass substrate by RF sputtering at room temperature to evaluate their characteristics as transparent electrodes for organic photovoltaic cells (OPVs). Optical and electrical properties of the single layer MTO were investigated at various working pressures and oxygen partial pressures. Based on the optimal condition, the MTO/Ag/MTO multilayer electrode showed a sheet resistance of 10.1-10.6 Ω/sq and transmittance of 80.1-85.4% in the visible range (λ=380-780 nm). Their values are compatible with commercial indium-tin oxide (ITO). Conventional-type bulk hetero-junction organic photovoltaic cells (BHJ-OPVs) using the MTO/Ag/MTO multilayer electrode show an open circuit voltage (VOC) of 0.62 V, a short circuit current (JSC) of 7.12 mA/cm2, a fill factor (FF) of 0.62, and a power conversion efficiency (PCE) of 2.73%. This PCE is comparable with a commercial ITO electrode (3.17%). This suggests that the MTO/Ag/MTO multilayer electrode is a new promising transparent conducting electrode for BHJ-OPVs.