Enhancement of photovoltaic performance by two-step dissolution processed photoactive blend in polymer solar cells

based on poly(3-hexylthiophene):[6,6]-phenyl-C-61-butyric acid methyl ester (P3HT:PC61BM) and polythieno[3,4-b]-thiophene-co-benzodithiophene:[6,6]-phenyl-C-71-butyric acid methyl ester (PTB7:PC71BM) photovoltaic systems, by a two-step dissolution treatment of photoactive blends. Optical and morphological characterization revealed that the composition of the ordered polymer and donor/acceptor phase structure in the photoactive layer can be optimized using a two-step dissolution treatment. In addition, time-resolved photoluminescence indicated that exciton dissociation efficiency could be increased using this method. Current density-voltage (J-V) measurements showed that power conversion efficiencies (PCE) of the two-step dissolution treated devices were higher than those of one-step treated devices by 24% and 8% for P3HT:PC61BM and PTB7:PC71BM systems, respectively. Therefore, this two-step dissolution treatment further optimizes the performance of polymer solar cells.