Electrohydrodynamic-Mediated Molecular Coordination for Stabilizing α-Phase Perovskite Solar Cells

Abstract Formamidinium-rich perovskite solar cells (PSCs) have achieved remarkable efficiencies, yet their phase purity is often compromised by the competitive nucleation of the nonperovskite δ-phase during rapid processing. Herein, we demonstrate an electrohydrodynamic (EHD)-mediated chemical strategy to bypass this kinetic trap using a multifunctional molecular, tetramethylthiourea (TeMTU). By precision tuning of the surface tension-Coulombic repulsion balance, TeMTU orchestrates the EHD-driven microdroplet evolution, effectively locking the in-flight precursor into a critically supersaturated state that fundamentally suppresses δ-phase nucleation. Beyond macroscopic fluid dynamics, molecular-level investigations reveal that TeMTU forms robust coordination complexes with the lead halide framework. This chemical intervention significantly elevates the activation energy barrier for the α-to-δ phase transition by 42%, as corroborated by Density Functional Theory and variable-cell double-ended surface walking analysis. The resulting α-phase FA-based films exhibit exceptional crystallinity and a minimized defect density, enabling electrospray-fabricated PSCs to achieve an impressive power conversion efficiency (PCE) of 26.24% (0.05 cm2) and 25.39% (1.0 cm2). Furthermore, the chemically stabilized lattice demonstrates operational durability, retaining 95% of its initial PCE after 3000 h of continuous maximum power point tracking at 65 °C.