Practical Interfaces for High‐Performance Perovskite Solar Cells

Perovskite solar cells (PSCs) have emerged as promising next‐generation photovoltaics, offering high power conversion efficiency (PCE) and low‐cost potential. The properties of their internal interfaces are critical determinants for device performance of both PCE and long‐term stability. This review focuses on the five core functions of interfacial layers including: (1) optimizing energy level alignment to facilitate efficient charge transport, (2) passivating defects to suppress nonradiative recombination, (3) regulating carrier dynamics to enhance charge utilization, (4) inhibiting ion migration to improve structural stability, and (5) forming environmental barriers to prevent detrimental substance exchange. We systematically discuss these functions across four key interfaces in standard layered PSCs: the transparent conductive oxide/electron transport layer (ETL), the ETL/perovskite, the perovskite/hole transport layer (HTL), and the HTL/top electrode. We emphasize the synergistic optimization of these interfaces is paramount for achieving devices with high efficiency and robust stability. Finally, we outline future research directions, highlighting the need for holistic multi‐interface engineering, the development of adaptive materials for stability, and the simplification of fabrication processes for scalable production. A concerted effort toward these goals will advance PSCs toward commercialization, fulfilling the dual requirements of high performance and long‐term stability in an environmentally benign and cost‐effective manner.