Despite the continuous improvement of bulk heterojunction solar cell performance, their power conversion efficiency lags far behind inorganic counterparts. A better understanding of underlying mechanisms that limit the device performance allows the development of strategies to improve the power conversion efficiency of the devices. Of particular importance is the dynamics of charge carriers (generation, transportation, collection, and recombination) within the bulk heterojunction or at interfaces with electrodes. Within this body of work, charge carrier dynamics of bulk heterojunction solar cells were investigated as a function of (i) the use of electron transport layer poly[(9,9-bis(3՜-(N,N-dimethylamino)-propyl)-2,7-fluorene)-alt-2,7- (9,9-dioctyl)-fluorene] (PFN), (ii) altering dielectric constant by considering Clausius-Mossotti relation, and (iii) the appearance of the S-shaped current density-voltage curve
