Thermodynamically Reinforced Dual‐Interface 1D/3D Tin‐Lead Perovskite Heterostructure for Stable All‐Perovskite Tandem Solar Cells

Tin-lead (Sn-Pb) perovskite solar cells (PSCs) remain fundamentally constrained by the intrinsic instability of Sn²⁺ oxidation and uncontrollable crystallization, critically limiting their operational reliability in tandem architectures. Herein, this study strategically introduces a π-conjugated ammonium salt, 4-aminobenzamidine dihydrochloride, which in situ directs the formation of a dual-interface one-dimensional/three-dimensional (1D/3D) perovskite heterostructure, thereby re-engineering the Sn-Pb perovskite lattice toward enhanced thermodynamic stability. The self-assembled 1D perovskitoid with intermolecular π-π stacking acts as nucleation-directing templates to relieve tensile strain and intra-/intergranular disorder. Simultaneously, the contiguous 1D perovskitoid interphases encapsulating the 3D bulk fortify the vulnerable Sn-I octahedral framework, effectively obstructing oxidative and ion-migration pathways. This dual stabilization strategy endows the Sn-Pb PSCs with unprecedented structural resilience, achieving not only a high power conversion efficiency (PCE) of 22.23% but also a T₉₈ operational lifetime beyond 1000 hours. Building upon this enhanced structural robustness, the derived 2-terminal (2T) all-perovskite tandem devices deliver a PCE of 28.50% and sustain a T₉₀ lifetime of 600 hours, underscoring the central role of lattice stabilization in advancing all-perovskite tandem photovoltaics.