Isomer‐Dependent Modulation of Perovskite Crystallization by Methoxythioanisole for High‐Performance Inverted Solar Cells

Energy losses derived from inferior film crystalline and severe trap-assisted non-radiative recombination in the light-absorber limit the further development of high-performance perovskite solar cells (PSCs). Herein, volatile positional isomers-ortho-, meta-, and para-methoxythioanisole (o-/m-/p-MTA)-are strategically tailored to regulate the crystallization kinetics of perovskites. Among them, m-MTA optimally balances dipole moment, configuration, and multiple active sites, enabling S atoms and methoxy groups to interact with both the under-coordinated Pb²⁺ and FAI. This interaction modulates intermediate chemistry and crystallization kinetics, promoting homogeneous nucleation and extending crystallization time, thereby affording high-quality perovskites with no MTA residue in the resulting film. Consequently, target devices with m-MTA treatment deliver a champion power conversion efficiency (PCE) of 26.46% (aperture 0.09 cm²) with a minimal non-radiative voltage loss of 72 mV, and scale to a 1 cm² device with 24.75% PCE. Unencapsulated devices demonstrate great durability, retaining over 86% and 90% of their initial PCEs after 672 h at 85 °C and 1440 h of maximum power point tracking under 1-sun illumination (white LED array), respectively. The study reveals a pronounced positional isomerism effect in additive engineering and establishes volatile, multi-active-site molecules as an effective strategy for simultaneously directing crystallization, mitigating defects, and achieving efficient PSCs.