A donor-acceptor copolymer, poly[(2,5-bis(2-hexyldecyloxy)-phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]-thiadiazole)] (PPDT2FBT), was used as a hole-transport layer (HTL) in mesoporous-type perovskite solar cells. To suppress carrier recombination, we introduced a passivation layer between the perovskite-HTL interface. As a result, the fill factor for the PPDT2FBT-based device was greatly improved to 0.81 and a power conversion efficiency of 18.4% was achieved.