The charge-carrier balance strategy by interface engineering is employed to optimize the charge-carrier transport in inverted planar heterojunction perovskite solar cells. N, N-Dimethylformamide-treated poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) and poly(methyl-methacrylate)-modified PCBM are utilized as the hole and electron selective contacts, respectively, leading to a high power conversion efficiency of 18.72%.