Power conversion efficiency (PCE) of phenylenevinylene-based copolymer with BF2 azopyrrole complex (PB)/modified PC70BM, that is, CN-PC70BM bulk heterojunction solar cells improves from 2.16 to 4.90% using a processing additive and drying condition. The results demonstrate that a processing additive and drying condition provides an effective means to control both the surface roughness and finer interpenetrating networks to enhance the exciton dissociation into free charge carriers, charge transportation, and collection. Taking into the account of simple device fabrication process without thermal annealing, the PCE of the polymer solar cell can further improved by chloronapthalene (CN) additive under the fast drying condition. The average carrier lifetimes extracted from the impedance spectra and found to correlate with measured PCEs. At short circuit conditions and illumination, the average charge carrier lifetime was found vary from 16.8 to 32 mu s with power conversion efficiencies ranging from 3.0 to 4.9%. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012