<p>Although perovskites are a highly alluring material in the field of solar cells and energy materials, perovskite solar cells have some instability problems. In addition to external instability factors such as humidity, temperature, and light, some instability problems occur due to the aging of the precursor solution used in cell production. With the aging of the precursor solution, phase transitions occur in the solution, and the photoactive α-phase gradually transforms into the non-photoactive δ-phase. In this study, 3,4-dibromothiophene (DBT) additive was added to the solution in order to hinder these phase transitions and to provide the stability of the precursor solution. The solutions aged at different times were coated in thin film form by the spin-coating method. XRD, UV–VIS, and AFM analyses of thin films coated with precursor solutions with and without additives were carried out. In addition, optoelectronic performance analyses of solar cells produced using these precursor solutions were carried out.</p>