Synergistic Effect of PC71BM and F4TCNQ as Multifunctional Passivation Layer for High-Efficiency Perovskite Solar Cells with Superior Stability

The migration of iodide ions and the inefficient interfacial charge transport continue to pose significant challenges to power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). In this study, we innovatively introduce a multifunctional passivation method that involves doping the P-type material 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) into the fullerene derivative (6,6)-Phenyl C71-butyric acid methyl ester (PC71BM). The introduction of F4TCNQ not only enhances the ability of PC71BM to passivate uncoordinated Pb2+ ions but also promotes a uniform distribution of the passivation layer. Results indicate that this passivation layer effectively immobilizes iodide ions, preventing their random movement within the PVK films and reducing iodine-related defects. Additionally, by raising the Fermi level and enhancing the P-type characteristics, it improves hole extraction and transport, thereby reducing nonradiative recombination in the target device. Consequently, the n-i-p PSCs with the mixed passivation layer achieved a champion PCE of 25.87%, with a higher open-circuit voltage (1.182 V) and a remarkable fill factor (84.64%). Notably, in large-scale manufacturing, n-i-p mini-modules reached a commendable PCE of 22.34%. Furthermore, these devices demonstrated superior stability, maintaining over 95% of their initial efficiency after 900 h of maximum power point (MPP) tracking under ISOS-L-1 standards.