Crystallization regulation of solution-processed two-dimensional perovskite solar cells

Two-dimensional (2D) perovskites have gained tremendous research interest in optoelectronic applications thanks to their structural diversity and superior environmental stability. The advancement of perovskite solar cells (PSCs) using 2D perovskites is necessarily accompanied by an in-depth understanding of the crystallization kinetics for thin-film formation. The manipulation of crystalline orientation and ordered quantum well (QW) arrangement have emerged as two main factors to achieve high-quality 2D perovskite deposition. This review aims to provide guidelines on crystallization control in 2D perovskites and inspires the development of simple and compatible optimization methods for different 2D perovskite systems. First, we summarize the archetypes of 2D perovskites that have been incorporated into high-performance PSCs and review the essential crystal nucleation and growth mechanisms. We then provide our insights into the state-of-the-art strategies used to manipulate the crystallization kinetics of 2D perovskites with an emphasis on their functionalities of optimized film properties and cell performance. Finally, we focus on the remaining challenges and prospects of 2D PSCs to further optimize the device performance for practical applications.