Recent Progress of Two-step Spin-coated Formamidinium Lead-based Perovskite Solar Cells

In recent years, perovskite solar cells (PSCs) have gained much attention due to their superior photoelectric conversion performance, and the photoelectric conversion efficiency (PCE) of the perovskite solar cells prepared in laboratories up to 26%. However, despite these advancements, the scaling-up process often leads to significant efficiency losses, which limits its further commercialization. It is crucial to develop an affordable, scalable, and controllable production method. The most commonly used preparation methods for perovskite films are the one-step method and the two-step method. Unfortunately, the one-step method suffers from a narrow processing window and environmental concerns as it requires the addition of an anti-solvent, which leads to poor reproducibility and hinders the scaling-up process. In contrast, the two-step method exhibits high reproducibility and friendliness to operators and the environment as perovskite films' growth is divided into two parts. In addition, the two-step spin coating solution method stands out for its easy fabrication, good repeatability, and high operability. It is conducive to the controllable preparation of high-quality large-area perovskite films and has great potential in commercial applications. Based on the characteristics that the preparation of perovskite is divided into two steps, the two-step solution method has more regulatory directions, and a lot of research work has been reported. In this review, the recent progress and the problems of the two-step spin coating solution method in additive engineering, interface modification, solvent engineering, and other engineering are described in detail, and the challenges and future research prospects of the two-step spin coating solution method are also analyzed. Additive engineering involves incorporating additives into inorganic components, organic components, and charge transport layers. Interface modification encompasses electron transport layer perovskite interface as well as perovskite-hole transport layer interfaces. The purpose of this review is to provide insight into the research of large-area and high-performance perovskite solar cells.