Hybrid Seeding-Template Modulation of Sn-Pb Perovskite Crystallization for High-Efficiency All-Perovskite Tandem...

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 Sn²⁺ and Pb²⁺ 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 CsPbBr₃ 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 CsPbBr₃ 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 Sn²⁺/Pb²⁺ 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.