Fully vacuum-free and solution-processed large-area organic solar cells (OSCs) were fabricated using a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) polymer top electrode. In addition, to evaluate the scalability of this polymer electrode toward large-scale modules, OSCs with various sized areas were fabricated, and their performance was compared with that of a metal top electrode. As a result, when we increased the area of the OSC from 0.4 to 1.6 cm2, the fill factor (FF) decreased from 40.5 % to 30.3 % and the corresponding photoconversion efficiency (PCE) decreased from 2.0 % to 1.4 % for an OSC with a polymer electrode. The FF decreased from 54.8 % to 44.1 % and essentially had no PCE degradation for the OSC with a metal electrode. Numerical calculations were also conducted to account for the FF and PCE degradation for both electrodes and to match the experimental data. Therefore, the lower FF and PCE of the OSC with a polymer electrode directly resulted from the higher sheet resistance of the polymer electrode and the corresponding higher series resistance.