Stabilizing Perovskite Fabrication in Ambient Air
Perovskite-based solar cells have advanced rapidly due to their high efficiency potential, low-cost processing, and flexible fabrication routes. While silicon solar cells remain the dominant commercial technology, combining perovskites with silicon in tandem architectures offers a clear pathway to exceed the efficiency limits of single-junction devices. By pairing perovskite's tunable absorption with silicon's proven performance, perovskite–silicon tandem solar cells open new opportunities for high-efficiency photovoltaics. Yet translating these advances from laboratory demonstrations to scalable manufacturing remains a major challenge. A central obstacle lies in fabricating high-quality perovskite films under ambient conditions. Moisture in air directly interferes with perovskite crystallization, leading to disordered crystal growth, surface degradation, and the accumulation of non-ideal secondary phases. Although thermal annealing is often used to improve crystallinity, the combined effects of heat and humidity can instead accelerate irreversible degradation when processing in air. Together, these factors make crystallization control under ambient conditions particularly difficult, underscoring the need for new strategies that can stabilize film formation without relying on tightly controlled environments. Previous studies have explored several approaches to optimize perovskite film fabrication in ambient air, such as solvent engineering and longitudinal homogeneous intermediates in hybrid sequential deposition, as well as techniques like the P1.5 process that introduce a diffusion barrier layer. However, challenges persist, particularly in achieving the same performance as films fabricated in controlled environments. Now, writing in Joule, Tan et al. tackle this challenge with a novel approach that intervenes in the wet-film stage to stabilize the crystallization process. Instead of relying on environmental controls to eliminate moisture, the authors introduce an additive, n-butylammonium thiocyanate (nBASCN), to regulate crystallization dynamics. Implemented as part of the hybrid sequential deposition process, this wet-film intervention modifies the crystallization pathway, preventing premature nucleation and promoting uniform growth. The key innovation lies in the use of nBASCN to decouple diffusion from crystallization, enabling uniform crystallization and improving film quality under ambient conditions. This intervention not only improves film quality but also enhances device performance, with nBASCN-treated devices achieving higher power conversion efficiency (PCE) compared to untreated controls. Beyond improving single-junction perovskite solar cells, this approach is also effective for tandem solar cells, demonstrating the strategy's applicability to more complex multi-junction devices. This marks a crucial step toward achieving scalable, high-efficiency tandem solar cells.
