High-impurity precursor based CH3NH3PbI3 (MAPbI(3)) perovskite thin films are fabricated by using the one-step spin-coating method with an anti-solvent mixture-mediated nucleation (ASMEN) process under various dropping times. The structural, optical and excitonic properties of the resultant perovskite thin films are characterized through the X-ray diffractometer, absorbance spectrometer, photoluminescence spectrometer and Raman scattering spectrometer. The experimental results show that the dropping time and the use of 10% dicloromethane (DCM) in the ASMEN process strongly influences the formation of point defects in the resultant MAPbI(3) thin film, which dominates the current-hysteresis behavior in the current density-voltage curves of solar cells. In addition, this investigation helps further understand the effects of toluene/DCM anti-solvent mixture on the formation of point defect-free MAPbI(3) thin films.