We report a nearly twofold increase of short circuit current: from Isc ∼ 10 mA/cm2 to Isc = 16–20 mA/cm2 in P3HT/PCBM solar cells (SC) employing freshly prepared regio-regular poly(3-hexylthiophene) (RR-P3HT) without special purification. The power conversion efficiency is enhanced to η≥ 4% as compared to our best η=3.8% in SC with commercial polymer despite the decreased filling factor (FF= 0.42, as compared to best FF = 0.59). We used our earlier found  procedures with optimal post heat treatment temperatures and time for our polymer SC. We also discovered a strong correlation between the device preparation procedures and performance. The optimal phase separation of PCBM and RR-P3HT into a bi-continuous network structure occurs after quite long solution stirring times (enhanced homogenization) and surprisingly very short annealing time at optimal temperature. We also found that the optimal concentration of PCBM in a RR-P3HT matrix is rather low, only c∼35 wt%, contrary to high c∼80 wt% in PPV based SC.