Controlling the morphology of the MAPbI_3-xCl_x active layer has remained a challenge towards advancing perovskite solar cells (PvSCs). Here, we demonstrate that a low temperature additive dripping (AD) treatment step, using diphenyl ether (DPE), can significantly improve the power conversion efficiency (PCE), compared to the control device using chlorobenzene (CB), by 15% up to 16.64%, with a high current density (J_SC) of 22.67 mA/cm². We chose DPE for its small and appropriate dipole moment to adjust the solubility of the MAPbI_3-xCl_x precursor during the formation of the intermediate phase and the MAPbI_3-xCl_x phase. The low DPE vapor pressure provides a longer processing window for the removal of residual dimethylformamide (DMF), during the annealing process, for improved perovskite formation. Imaging and X-ray analysis both reveal that the MAPbI_3-xCl_x film exhibits enlarged grains with increased crystallinity. Together, these improvements result in reduced carrier recombination and hole trap-state density in the MAPbI_3-xCl_x film, while minimizing the hysteresis problem typical of PvSCs. These results show thatthe AD approach is a promising technique for improving PvSCs.