Dual-Site Interface Passivation by Sulfur-Based Small Molecules for the Simultaneous Enhancement of Efficiency and Stability in Inverted Perovskite Solar Cells

Currently, in inverted perovskite solar cells, defect states at the upper interface of the perovskite layer significantly affect carrier nonradiative recombination, while the material's susceptibility to moisture limits the devices' long-term reliability. To address these issues, this study introduces 2-thiopheneethanamine hydriodide for molecular-level reconstruction of the perovskite surface. Density functional theory calculations reveal that the sulfur atom on its thiophene ring forms stable coordination with uncoordinated Pb2+ defect sites on the perovskite surface, while the amino end binds with lattice I- through N-H···I hydrogen bonds, achieving dual-site synergistic passivation. This molecular structure effectively passivates surface defects and promotes efficient charge transport, thereby enhancing electron extraction capabilities, suppressing interfacial recombination, and reducing charge accumulation. Consequently, a significant improvement in power conversion efficiency (PCE) was achieved, reaching 21.15%. In addition, the hydrophobic nature of the alkyl side chain of 2-thiopheneethylamine hydroiodide also significantly inhibits water molecule infiltration, improving the preliminary environmental stability of the devices. Unencapsulated cells retain a significantly higher efficiency than the control group after storage for 500 h in a nitrogen atmosphere at 30% humidity and 25 °C, demonstrating excellent environmental stability.