Hybrid Seeding‐Template Modulation of Sn–Pb Perovskite Crystallization for High‐Efficiency All‐Perovskite Tandem Solar Cells

ABSTRACT Narrow‐bandgap (NBG) Sn–Pb perovskites are indispensable for achieving high‐efficiency all‐perovskite tandem solar cells (TSCs). However, the pronounced disparity in the Lewis acidity of Sn 2+ and Pb 2+ often causes asynchronous nucleation and uncontrolled crystallization, severely limiting the device performance. Here, we propose a hybrid heterogeneous seeding and growth‐template strategy that integrates CsPbBr 3 quantum dots (QDs) with porous UiO‐66 metal–organic frameworks (MOFs) through grafted poly(4‐vinylpyridine) (P4VP) to achieve homogenous Sn–Pb perovskite films. Specifically, the embedded CsPbBr 3 QDs act as abundant nucleation centers, lowering the energy barrier and providing an epitaxial growth template, while the carbonyl (C═O) groups of UiO‐66 ligands and the imine (C═N) moieties of P4VP coordinate with Sn 2+ /Pb 2+ to finely regulate crystallization kinetics. Moreover, the UiO‐66‐P4VP framework functions as a scaffold to promote uniform film growth, resulting in Sn–Pb perovskite films with homogeneous composition and reduced defect density. As a result, the optimized single‐junction NBG perovskite solar cell achieves a fill factor exceeding 81% and a power conversion efficiency (PCE) of 23.32%. Furthermore, the two‐terminal all‐perovskite tandem device delivers a PCE of 29.18% and retains 80% of its initial efficiency after 500 h of continuous maximum power point tracking under simulated sunlight, demonstrating remarkable operational stability.