Solution-processed perovskite thin-films: the journey from lab- to large-scale solar cells

In the last decade, the power conversion efficiency (PCE) of solution-processed perovskite solar cells (PSCs) in the lab-scale has reached an incredible level of 25.5%. Generally, PSCs are composed of a stack consisting of a perovskite thin-film sandwiched between an electron transporting layer (ETL) and a hole transporting layer (HTL). Although the quality of the ETL and HTL interfaces with the perovskite thin-film is important, the quality of the perovskite thin-film is also critical to achieving high-performance PSCs. Low-temperature deposition of organic–inorganic perovskite thin-films by simple solution processes is one of the significant advantages of PSCs compared to other well-developed semiconductors for manufacturing solar cells. However, growing highly uniform and crystalline solution-processed perovskite thin-films is very challenging due to multiple phenomena during film formation, including solvent evaporation, wetting effects, inhomogeneous film stress and uncontrolled nucleation and growth. Therefore, understanding the different stages of perovskite crystallization is critical for achieving high-quality films and realizing higher PCEs. On the other hand, switching to large-scale solar modules leads to a substantial loss in performance, decreasing the chance of commercialization of this technology. Therefore, developing large-scale deposition techniques for reliable perovskite crystallization is very vital for scaling up PSCs. So far, several solution-processed methods such as anti-solvent and two-step processes have been developed for lab-scale perovskite thin-films deposition. However, these methods are not applicable for large-scale perovskite deposition. This review explores various scalable solution-processed perovskite deposition techniques. Moreover, different solvent quenching techniques as the most critical step of large-scale perovskite crystallization are discussed to provide a comprehensive view for achieving high-quality perovskite thin-films with large areas. Finally, the existing challenges and opportunities to push forward the commercialization of PSCs are discussed.