Enhanced Interfacial Contact Enables Stable MA-free Perovskite-Silicon Tandem Photovoltaics.

Despite rapid efficiency gains in perovskite-silicon tandem solar cells (P/Si TSCs), state-of-the-art devices continue to rely heavily on methylammonium (MA)-containing wide-bandgap (WBG) perovskites, where MA facilitates crystallization but intrinsically accelerates thermal degradation and halide segregation. Achieving efficient, thick (>700 nm), MA-free WBG perovskites on textured silicon remains an unresolved challenge. Here, a coordination network coupled with π-π stacking work is designed to synchronize kinetics in MA-free FACs-based perovskite and promote conformal integration with textured silicon. A compact heterocyclic molecule simultaneously forms hydrogen-bonds with FA cations and coordinates with the Pb-I framework, while engaging in π-π stacking with underlying self-assembled monolayers. This multi-interaction synergy regulates nucleation and drives vertical crystal growth, yielding void-free buried interfaces and columnar grains spanning the full film thickness. The reconstructed interface exhibits reduced trap density and favorable energy-level alignment, enabling efficient hole extraction and suppressing electron back-transport and mixed-halide segregation. Consequently, the 1.68 eV MA-free perovskite device achieves an efficiency of 24.04%. Monolithic P/Si TSCs reach 33.04% efficiency, maintaining >90% initial performance after 1600 h of maximum power point tracking. This work establishes a generalizable strategy to decoupling crystallization control from MA incorporation, enabling durable and high-performance tandem photovoltaics.