Steric-Hindrance-Engineered 1D/3D Heterojunction Unlocks Atomic-Level Matched Buried Interface for Efficient Perovskite Solar Cells

Solving the interfacial stability of perovskite solar cells (PSCs) is an inevitable requirement to achieve their long-term stability as well as commercial applications. Low-dimensional/three-dimensional perovskite heterojunctions (1D/3D or 2D/3D) have emerged as a promising architecture for efficient PSCs. Here, symmetric sulfonium-based molecules with tunable alkyl spacers are introduced to construct a heterojunction buried interface, achieving atomic-scale lattice matching between the perovskite film and the adjacent layer underneath. The interface, based on a one-dimensional (1D) spacer molecule with suitable steric hindrance and characterized by a higher degree of compatibility, functions as a template to facilitate uniform crystallization and effectively alleviates stress during the initial stages of crystallization. This, in turn, enhances the quality of the overlying perovskite film, prolongs the carrier lifetime, and optimizes the stress state. The 1D/3D PSCs fabricated using this interface design not only demonstrate high efficiency and stability but also exhibit excellent reproducibility, achieving a remarkable power conversion efficiency of 25.03% under standard AM 1.5 G one-sun illumination. After aging in an ambient air environment with a relative humidity of 55% for 1400 h, 94% of the initial efficiency is maintained for 1D/3D PSC.