Breaking 12% efficiency in flexible organic solar cells by using a composite electrode

The performance of flexible organic solar cells (OSCs) significantly relies on the quality of transparent flexible electrode. Here, we used silver nanowires (AgNWs) with various weight ratios to dope high-conductive poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PH1000) to optimize the optical and electronic properties of PH1000 film. A high-quality flexible composite electrode PET/Ag-mesh/PH1000:AgNWs-20 with smooth surface, a low sheet resistance of 6 Ω/sq and a high transmittance of 86% at 550-nm wavelength was obtained by doping 20 wt% AgNWs to PH1000 (PH1000:AgNWs-20). The flexible OSCs based on the PET/Ag-mesh/PH1000:AgNWs-20 electrode delivered a power conversion efficiency (PCE) of 12.07% with an open circuit voltage ( V oc ) of 0.826 V, a short-circuit current density ( J sc ) of 20.90 mA/cm 2 and a fill factor (FF) of 69.87%, which is the highest reported PCE for the flexible indium-tin oxide (ITO)-free OSCs. This work demonstrated that the flexible composite electrodes of PET/Ag-mesh/PH1000:AgNWs are promising alternatives for the conventional PET/ITO electrode, and open a new avenue for developing high-performance flexible transparent electrode for optoelectronic devices.