PbCl2 additive engineering is an effective method to decrease the charge accumulation in devices. Herein, the influence of PbCl2 additive on the charge transport properties of inverted planar MAPbI3 perovskite devices is investigated by capacitance–voltage (C–V) spectroscopy. The C–V curves show that the ΔVpeak of the MAPbI3−xClx‐based device is decreased compared to the undoped device, indicating that the introduction of chloride ions effectively mitigates charge accumulation at the interface. Simultaneously, it is proposed that the introduction of chloride ions into the perovskite lattice can decrease the trap density, which promotes charge carrier separation/transport at the electrode interfaces/absorber interface, as evidenced by photoluminescence measurements. The findings of this study clarify that trap states and charge accumulation in the MAPbI3 perovskite solar cell have a considerable influence on carrier separation/transport, enhancing the device performance to ultimately achieve power conversion efficiency (PCE) from 12.3% to 15.5%. Accordingly, this work paves the way for further improving the efficiency of perovskite solar cells.