Homoepitaxial Seed-Mediated Growth for High-Efficiency FAPbI₃ Perovskite Solar Cells.

Seed-mediated growth has emerged as a pivotal strategy for fabricating high-efficiency perovskite solar cells (PSCs), particularly when perovskite nanocrystals (PNCs) with identical structural configurations are utilized as the seeds. Although homogenous seed-mediated growth is recognized as a feasible and effective strategy, research on high-quality PNCs serving as seeds remains limited, largely constrained by the inherent poor stability of iodine-based perovskite PNCs. To address this challenge, we incorporate cyclohexylamine (CA) molecules to enhance the stability and optical properties of FAPbI₃ and CsPbI₃ PNCs, thereby enabling their utilization as alternative seed candidates for fabricating FAPbI₃ perovskite films. The PNCs sharing the same composition (FAPbI₃ PNCs) facilitate fully lattice-matched homogeneous growth, thereby promoting the fabrication of high-quality perovskite films featuring larger grain sizes, reduced defect densities, and more favorable energy level alignment. Consequently, the power conversion efficiency (PCE) of the resultant PSCs is boosted from 22.35% to 25.55%. Furthermore, the stability of the fabricated PSCs has been elevated, retaining 92.4% of their initial efficiency after 3 months of storage in an ambient atmosphere. This strategy not only facilitates the fabrication of high-quality perovskite films but also provides a promising alternative for designing high-performance seed-induced growth systems in the field of perovskite photovoltaics.