Effect of sheet resistance of Ag-nanowire-based electrodes on cell-performances of ITO-free organic solar cells

This study examined the effects of a sheet resistance of silver nanowire (AgNW)-based electrode on the cell-performances in indium tin oxide (ITO)-free organic solar cells (OSCs) fabricated with AgNWs and highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) bilayer electrodes (AgNWs/hcPEDOT). The transmittance and sheet resistance (R_sh) of AgNWs/hcPEDOT electrodes were controlled by varying the spin-coating cycle of AgNW films. Variations in cell-performances including the power conversion efficiency (PCE), the short-circuit current density (J_sc), and the fill factor (FF) that resulted from varying the R_sh of AgNW-based films were systematically studied. With reducing R_sh of transparent electrodes, the FF and the series resistance were continuously improved, but the OSC with the highest FF showed a low J_sc value due to the decrease in transmittance with increasing AgNW density. As a result, an optimum OSC showed a PCE of 2.699%, which is a slightly low PCE value compared with ITO-based OSCs. These results indicate that the cell-performance of OSCs is highly dependent on R_sh of the AgNW-based electrode and that a trade-off between R_sh and transmittance of transparent electrodes should also be considered to perfectly replace the conventional ITO and to achieve higher device-efficiency. (paper)