Synergistic Crystallization and Defect Passivation Induced by a Multifunctional Additive for >20% Efficient Carbon-Based Perovskite Solar Cells

The integration of multifunctional molecular additives into perovskite formulations offers a promising pathway toward more efficient and stable solar cells. Here, we investigate the use of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), a monomer with amide and sulfonic acid functionalities, as an additive to simultaneously modulate crystallization, passivate defects, and suppress ion migration in carbon-based perovskite solar cells (C-PSCs), enabling enhanced crystallinity, increased grain size, and prolonged photoluminescence lifetimes. Density functional theory (DFT) calculations and spectroscopic analyses confirm strong interfacial binding between AMPS and both Pb- and FA-terminated surfaces, with preferential Pb-SO₃H coordination driving defect passivation. Devices fabricated with optimized AMPS content achieve a champion power conversion efficiency of 20.2%, along with an improved fill factor from 0.70 to 0.72, charge extraction from 1.18 to 1.28 V, and recombination resistance from 39.9 to 52.7 Ω. Furthermore, reduced ion migration (from 15 × 10¹⁸ cm^-3 to 7 × 10¹⁸ cm^-3), a lower ideality factor (from 1.34 to 1.20), and superior operational stability (retaining 95% of initial power conversion efficiency (PCE) compared to the control device at 85% of initial PCE) under illumination and ambient relative humidity (∼45%) over 1000 h highlight the role of the additive in stabilizing the perovskite lattice. This study unveils AMPS as a low-cost, solution-processable, and multifunctional additive tailored for C-PSC architectures, offering a scalable strategy for next-generation, stable, and efficient perovskite photovoltaics.