Application of Ionic Liquids in Enhancing the Performance of All‐Inorganic Perovskite Solar Cells

All‐inorganic perovskite solar cells (IPSCs) have emerged as a research hotspot in clean energy due to their excellent thermal stability and photovoltaic potential. However, issues including perovskite defects, poor interfacial compatibility, and environmental instability have severely hindered the enhancement of their power conversion efficiency. Ionic liquids (ILs), featuring low volatility, high ionic conductivity, and structural designability, offer a promising solution to these challenges. This review systematically summarizes the fundamental properties and molecular structures of ILs, analyzes the structural instability and defect types of inorganic perovskites, and highlights the core roles of ILs in IPSCs as additives, solvents, and interface modifiers. Notably, ILs enable the fabrication of large‐grain, dense, and defect‐free perovskite films by inducing stable intermediate phases and regulating crystallization kinetics. Defects are precisely passivated through the synergistic effect of cations and anions, thereby suppressing non‐radiative recombination of charge carriers. The energy‐level alignment between perovskite and charge transport layers (or carbon electrodes) can also be optimized. Moreover, the hydrothermal stability of IPSCs is enhanced by forming a hydrophobic barrier on the perovskite film surface. Finally, the future research directions of ILs are proposed, providing guidance for the industrial development of high‐efficiency, stable, and low‐cost IPSCs.