Perovskite solar cells have demonstrated remarkable progress in recent years. However, their widespread commercialization faces challenges arising from defects and environmental vulnerabilities, leading to limitations in energy conversion efficiency and device stability. To overcome these hurdles, passivation technologies have emerged as a promising avenue. These passivators are strategically applied at the interface between perovskite absorbers and charge transport layers to mitigate the adverse effects of defects and environmental factors. While prior reviews have predominantly focused on experimental observations, a comprehensive theoretical understanding of the passivators has been lacking. This review focuses on recent advancements in first-principles density functional theory studies that delve into the fundamental properties of passivators and their intricate interactions with perovskite materials and charge transport layers. By exploring the atomic-level roles of passivators, this review elucidates their impact on critical parameters such as open circuit voltage (Voc), short circuit current density (Jsc), fill factor, and the overall stability of perovskite solar cells. The synthesis of theoretical insights from these studies can serve as guidelines for the molecular design of passivators with the ultimate objective of advancing the commercialization of high-performance perovskite solar cells.