Enhancing Efficiency and Stability of Perovskite Solar Cells via Mixed Cation Passivation with GAI/BDAI on the 3D Perovskite Layer

Effective defect passivation is a crucial factor in the performance of perovskite solar cells (PeSCs). Dimensional engineering is a highly promising method for efficiently passivating nonradiative recombination pathways on the surface of PeSCs, enhancing their overall performance and stability. Here, we report a passivation method using a special combination of guanidinium iodide (GAI) and butane diammonium iodide (BDAI) cations for the perovskite/electron transport layer interface. The dual-cation passivation layer, consisting of GAI and BDAI, significantly improves PeSC performance. This modified layer PeSC achieves a fill factor of 83.4% and a power conversion efficiency of 22.1%, surpassing single-cation passivation layers in both efficiency and effectiveness. The mixed cation passivation layer forms a Ga+/BDA+/3I– perovskite film on top of the 3D perovskite structure. Compared to the control film, this layer creates a smoother and more hydrophobic surface, which decreases nonradiative recombination and improves electron transport characteristics. The enhanced film of the adapted device remarkably maintained over 83% of its original efficiency for over 500 h, suggesting the possibility of producing robust and effective PeSCs for long-term renewable energy solutions.