Interfacial Energetics in Metal Halide Perovskite Solar Cells.

Controlling the energetic landscape of metal halide perovskite solar cells is crucial for optimizing device efficiency and stability, as well as enabling new architectures beyond conventional layered designs. While band alignment criteria are key determinants of performance in organic photovoltaic devices, they are often insufficient for perovskites due to their high charge carrier density, mobile ions, and soft lattice structure. A deep understanding of the electronic structure of the perovskite and the contacting layers remains an active area of research and requires expertise in the characterization techniques. In this review, we analyze how interfacial energetics influence charge extraction, the formation of energy barriers, interfacial recombination, and ion migration, highlighting the unique challenges posed by the soft ionic lattice of metal halide perovskites. To this end, we provide a comprehensive overview of experimental techniques for probing energetic alignment, emphasizing their operating principles, limitations, and emerging in situ variants. Building on these insights, we discuss strategies for controlling the interfacial energetics of perovskite solar cells, ranging from interfacial layers and dipolar modifiers to electrical doping. Finally, we explore the device architectures that eliminate the need for charge-selective layers. Together, these insights establish a framework for understanding and engineering the energetic landscape of metal halide perovskite-based devices, linking fundamental semiconductor physics with practical strategies for future perovskite technologies.