This review discusses defects and defect passivation in perovskite solar cells (PSCs). Perovskite solar cells have shown rapid improvements in power conversion efficiency (PCE), but challenges remain in terms of photoelectric conversion efficiency and long-term stability. Defects in perovskite materials significantly affect film quality and performance. Defect passivation using additives is an effective approach to improve PSC performance. The review covers the types of defects in perovskite materials, including point, one-dimensional, two-dimensional, and three-dimensional defects, and their effects on performance. It also discusses various types of additives used in PSCs, such as ionic compounds, organic molecules, and polymers. The review provides guidance for the development of more sustainable and effective additives to enhance PSC performance. The review highlights the role of ionic compounds in passivating defects in perovskite films. Cations such as cesium (Cs⁺) and rubidium (Rb⁺) are effective in passivating defects by forming ion bonds with defect sites. Anions such as halide ions (I⁻, Br⁻, Cl⁻) are also used to passivate defects with positive charges. Organic molecules, including organic ammonium salts, are also effective in passivating defects in perovskite films. Lewis acids and Lewis bases are used to passivate electron-rich and electron-poor defects, respectively. The review also discusses the use of functional groups such as N and S in Lewis acids and bases for defect passivation. The review emphasizes the importance of passivating defects in perovskite films to improve the performance and stability of PSCs. Various methods, including interface engineering, additive engineering, molecular design, and composition regulation, are used to passivate defects in perovskite films. The review provides a systematic introduction to defect passivation in PSCs, including the effect of defects on devices and the influence of different types of additives on PCE. This work offers relevant guidance for the design and enhancement of PCE through the utilization of additives.This review discusses defects and defect passivation in perovskite solar cells (PSCs). Perovskite solar cells have shown rapid improvements in power conversion efficiency (PCE), but challenges remain in terms of photoelectric conversion efficiency and long-term stability. Defects in perovskite materials significantly affect film quality and performance. Defect passivation using additives is an effective approach to improve PSC performance. The review covers the types of defects in perovskite materials, including point, one-dimensional, two-dimensional, and three-dimensional defects, and their effects on performance. It also discusses various types of additives used in PSCs, such as ionic compounds, organic molecules, and polymers. The review provides guidance for the development of more sustainable and effective additives to enhance PSC performance. The review highlights the role of ionic compounds in passivating defects in perovskite films. Cations such as cesium (Cs⁺) and rubidium (Rb⁺) are effective in passivating defects by forming ion bonds with defect sites. Anions such as halide ions (I⁻, Br⁻, Cl⁻) are also used to passivate defects with positive charges. Organic molecules, including organic ammonium salts, are also effective in passivating defects in perovskite films. Lewis acids and Lewis bases are used to passivate electron-rich and electron-poor defects, respectively. The review also discusses the use of functional groups such as N and S in Lewis acids and bases for defect passivation. The review emphasizes the importance of passivating defects in perovskite films to improve the performance and stability of PSCs. Various methods, including interface engineering, additive engineering, molecular design, and composition regulation, are used to passivate defects in perovskite films. The review provides a systematic introduction to defect passivation in PSCs, including the effect of defects on devices and the influence of different types of additives on PCE. This work offers relevant guidance for the design and enhancement of PCE through the utilization of additives.