Structure-Guided Additive Engineering for Efficient and Stable Perovskite Solar Cells

The use of functional additives to passivate defects in the perovskite active layer has become an effective strategy for enhancing the performance of perovskite solar cells (PSCs). Consequently, the judicious selection of additive structures is critical for optimizing the device performance. In this study, we examined the defect-passivating properties of the conjugated molecule 4-aminobenzylphosphonic acid (4-ABzPA) through comparative analysis with the structurally similar nonconjugated molecule 2-aminoethylphosphonic acid (2-AEPA). Our investigation provides a comprehensive assessment of the roles of conjugated molecules in various key areas including defect passivation, crystallization enhancement, energy-level alignment, and long-term stability. These results demonstrate that compared to 2-AEPA, the conjugated molecule 4-ABzPA exhibits unique electron delocalization properties. Leveraging this characteristic, the P=O groups within 4-ABzPA display stronger coordination with Pb²⁺, while the NH₂groups exhibit enhanced capability to suppress halide vacancy. This synergistic passivation effectively reduces the defect density, leading to the formation of high-quality perovskite films. Furthermore, the conjugated molecule optimizes energy-level alignment and establishes effective pathways for charge transport. PSC devices based on 4-ABzPA achieved a champion efficiency of 24.01% and demonstrated exceptional stability under various conditions.