During the process of the low-temperature solution fabrication, it always leads to high defects density at the grain boundaries and the interfaces, which are great barriers toward excellent solar cells. Different polar molecules of solvents are brought in to modify the surface composition by tuning the nucleation densities to obtain perovskite films with high crystallization quality. In this work, with efficiently exchanging intramolecular mechanism, high-quality MAPbI₃-based perovskite films had been conveniently fabricated. Two kinds of polar molecules of dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) were added to the dimethylformamide (DMF) solvent to result in perovskite films with high quality. As a result, the device with NMP solvent treatment outputs improved efficiency of 18.5% at the short-circuit current (J_sc) of 23.3 mA cm^–2, with an open-circuit voltage (V_oc) of 1.075 V and a fill factor of 77.1% under standard AM 1.5 solar illumination. This method of solvent engineering might provide a convenient way for the application of perovskite-based photovoltaic devices.