We investigated the effect of the drying time on the active layer based on a regioregular poly(3-hexylthiophene) (RR-P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), as well as the performance of polymer-based organic photovoltaic (OPV) devices. The devices were fabricated with different combinations of spin speed and solution concentration at a fixed thickness of the active layer. These conditions varied the properties of the active layer in terms of the polymer crystallinity and the phase separation in the blend. We identified distinct differences for different drying times of the solvent during the spin-coating process. The active layers were characterized by using analysis methods such as X-ray diffraction (XRD), ultraviolet-visible (UV-visible) spectroscopy and atomic force microscopy (AFM). The qualitative property of the active layer and the highest power conversion efficiency were obtained with the slowest coated active layer with the lowest solution concentration under AM 1.5 G spectral illumination of 100 mW/cm2.