A depth behavioral understanding for each layer in perovskite solar cells (PSCs) and their interfacial interactions as a whole has been emerged for further enhancement in power conversion efficiency (PCE). Herein, NiO@Carbon was not only simulated as a hole transport layer but also as a counter electrode at the same time in the planar heterojunction based PSCs with the program wxAMPS (analysis of microelectronic and photonic structures)-1D. Simulation results revealed a high dependence of PCE on the effect of band offset between hole transport material (HTM) and perovskite layers. Meanwhile, the valence band offset (?Ev) of NiO-HTM was optimized to be?0.1 to?0.3 eV lower than that of the perovskite layer. Additionally, a barrier cliff was identified to significantly infl uence the hole extraction at the HTM/absorber interface. Conversely, the ?Ev between the active material and NiO@Carbon-HTM was derived to be ?0.15 to 0.15 eV with an enhanced efficiency from 15％to 16％.