Molecular Cross-Linking of Perovskites by Boronic Acid for Ambient-Air Fabrication of Stable and Scalable MA-Free Solar Cells.

The ambient-air fabrication of thermally stable, methylammonium-free (MA-Free) perovskite solar cells (PSCs) is pivotal for achieving low-cost and durable photovoltaics. However, the acute ambient moisture sensitivity of MA-Free perovskites severely hinders the formation of high-quality absorbing layers. Here, we propose 1,4-benzenediboronic acid (DBPA) as a versatile additive to modulate crystallization and film formation under ambient conditions. DBPA's multifunctional boronic groups simultaneously passivate lattice and interfacial defects by coordinating with undercoordinated Pb2+ and forming hydrogen bonds with halide ions. Furthermore, the hydrophobic aromatic backbone crosslinks adjacent grains, reinforces adhesion to charge transport layers. Besides, the hydrophobic aromatic backbone offers favorable moisture resistance of the perovskite film. As a result, DBPA-modified PSCs achieve a PCE of 23.95% under ambient preparation, outperforming the control (21.80%). Importantly, this strategy broadens the processing humidity window, ensuring good reproducibility across a wide humidity range and enabling a PCE of 19.52% (13.02% for control) even at 90% RH. Following ISOS-L-1 protocols, the DBPA device retained 94.2% of its initial PCE after 700 h of MPPT operation. This work highlights DBPA as a distinctive additive candidate for high-efficiency and durable MA-Free PSCs, offering a scalable strategy for practical perovskite photovoltaics.