High Efficiency Quasi‐2D Ruddlesden–Popper Perovskite Solar Cells

Abstract Quasi‐2D Ruddlesden–Popper perovskites (RPPs) are promising candidates for stable and efficient solar cells. Even though photovoltaic devices based on these materials are still lagging behind traditional 3D perovskites, they have experienced a dramatic increase in power‐conversion efficiency, recently reaching >20%. As knowledge develops, the toolbox of RPP researchers is steadily growing in terms of organic spacers, additives, and characterization methods. This review aims to describe the use of such a toolbox to achieve high efficiency solar cells. The use of additives, functionalized spacers, and novel fabrication techniques are explored to control morphology, crystallinity, interlayer interaction, and phase distribution. Moreover, methods to achieve the coveted phase purity in RPPs and its implications on both single‐ and multi‐junction solar cells are discussed. By describing successful cases of high efficiency solar cells combined with in‐depth knowledge of material properties, it is shown that there are still several open research questions that need exploring to further develop this fascinating class of perovskites.