Single-Molecule Triad: 6-MCA Additive Synchronizes Defect Passivation, Morphology Control, and Moisture Blockade for Efficient and Stable Perovskite Solar Cells

Defects, humidity, and uncontrolled crystallization remain critical limitations for the perovskite photovoltaic performance. Fortunately, these issues can be addressed through additive engineering. However, it remains a challenge to develop a simple and efficient additive with the corresponding functional groups to simultaneously solve these problems. Herein, this goal was achieved by incorporating 6-maleimidocaproic acid (6-MCA) into the perovskite precursor solution. The functional groups (C═O) of 6-MCA coordinate with undercoordinated Pb 2+ ions, effectively passivating defects in the perovskite film. Concurrently, they regulate the perovskite crystallization process to improve the film morphology by suppressing pinholes, enhancing crystallinity, enlarging grain size, and lowering roughness. Additionally, the hydrophobic alkyl chain of 6-MCA improves the moisture resistance of the perovskite film. As a result, the devices modified with 6-MCA achieved a champion power conversion efficiency (PCE) of 23.74% (compared to 20.38% for the control), with a high open-circuit voltage of 1.167 V and negligible hysteresis. More importantly, the 6-MCA molecule further enhanced the light, thermal, and environmental stabilities of the devices.