Inverted perovskite solar cells (IPSCs) have witnessed an impressive development in recent years. However, their efficiency is still significantly behind theoretical limits, and device instabilities hinder their commercialization. Two main obstacles to further enhancing their performance via one-step deposition are: 1) the unsatisfactory film quality of perovskite and 2) the poor surface contact. To address the above issues, 4-butanediol ammonium Bromide (BD) is utilized to passivate Pb defects by forming PbN bonds and fill vacancies of formamidinium ions at the buried surface of perovskite. The wettability of poly [bis (4-phenyl) (2,4,6-triMethylphenyl) amine] films is also improved due to the formation of hydrogen bonds between PTAA and BD molecules, resulting in better surface contacts and enhanced perovskite crystallinity. As a result, BD-modified perovskite thin films show a significant increase in the mean grain size, as well as a dramatic enhancement in the PL decay lifetime. The BD-treated device exhibits an efficiency of up to 21.26%, considerably higher than the control device. Moreover, the modified devices show dramatically enhanced thermal and ambient stability compared to the control ones. This methodology paves the way to obtain high-quality perovskite films for fabricating high-performance IPSCs.