Synergistic effect of multifunctional MXene-nanosheet and naphthoquinone sulfonate toward high-performance perovskite solar cells and modules

Interface defect passivation strategies play a vital role in the design of efficient, and stable perovskite solar cells (PSCs). Presently, we combine MXene-nanosheets with a 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQSNa) which function as novel and multifunctional passivators to modify and enhance the performance of the pre-buried tin oxide (SnO₂)/perovskite interface for n-i-p PSCs. It was observed that the surface terminals of the MXene nanosheets effectively interact with the undercoordinated Sn and the terminal-hydroxyl (OH_T) groups while also passivating the oxygen vacancies in the SnO₂ film. Moreover, although the two naphthoquinone groups in NQSNa are electron-withdrawing groups, they are more prone to keto-enol tautomerism resulting in a stronger electron-donating character compared to the –NH₂ group in sodium 4-amino-1-naphthalenesulfonate (NASNa). Therefore, naphthoquinone groups of NQSNa promote a stronger interaction between -SO₃^- and the uncoordinated Pb²⁺ than –NH₂ of NASNa, which is concordance with our density functional theory (DFT) calculations. This surface coordination increases the crystallinity of the perovskite films, thus resulting in a lower rate of carrier recombination and promoting efficient carrier extraction and transport. The device achieves a champion device efficiency of 24.01% (0.082 cm²) and the efficiency of corresponding minimodule reaches 20.11% (3 × 0.523 cm²). Furthermore, an unencapsulated optimized device maintains 93.92% of its initial power conversion efficiency after stored in a dry box for 1440 h and exhibits excellent thermal stability at 85 °C. This work presents an effective method to improve the quality of the pivotal SnO₂/perovskite interface further advancing the future development of high-performance PSCs and modules.