Enhancing the Performance of Perovskite/Silicon Tandem Solar Cells via Cation-π Interaction

Perovskite/silicon tandem solar cells have garnered significant attention due to their potential to surpass the Shockley–Queisser limit of single-junction solar cells. However, the fabrication of perovskite films on commercially textured silicon substrates still faces challenges, including difficulty in controlling crystal orientation, high defect density, and insufficient stability. This study innovatively introduces 5-chloro-7-azaindole (5C7A) as a functional additive in the perovskite layer. Through its unique cation-π interactions and Lewis acid–base synergistic passivation mechanism, 5C7A enables a multidimensional optimization of perovskite films. The 5C7A significantly enhances perovskite crystallinity and grain size while anchoring uncoordinated Pb²⁺ and halide vacancies, thereby reducing trap state density. Additionally, 5C7A effectively releases internal stress in the perovskite film, increases the ion migration energy barrier, and extends carrier lifetime, leading to an improvement in the power conversion efficiency of inverted single-junction devices to 23.25% along with significantly enhanced photostability. Furthermore, the fabricated perovskite/silicon tandem solar cells achieve an impressive efficiency of 30.59%. This study proposes a new paradigm for regulating perovskite films via noncovalent interactions from a molecular engineering perspective, providing a key material strategy for the industrial development of high-efficiency and stable tandem solar cells.