1-Dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide Interface Design  for Stable and Effective...

Power conversion efficiency (PCE) is limited by the high density of defects and poor energy level alignment of the SnO₂/perovskite (PVK) buried interface in perovskite solar cells (PSCs). Herein, a synergistic molecular interface engineering strategy is designed by using an ionic liquid, 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide salt (DMIMTFSI) to modify this critical interface. The strong electron-withdrawing TFSI^- anion induces a downward shift of the conduction band of SnO₂, thereby optimizing energy level alignment and facilitating electron extraction. Meanwhile, the DMIM⁺ cation passivates interfacial defects through robust chemical interactions with Pb²⁺ and I^- ions. Furthermore, the long alkyl chain of DMIMTFSI templates the formation of an ordered porous PbI₂ morphology, which improves the crystallinity of the overlying PVK film. The DMIMTFSI modification reduces the trap-state density by 31.86%, prolongs the carrier lifetime by 39.42%, and increases the built-in potential from 0.95 to 1.02 V. Therefore, the DMIMTFSI-modified device achieves a PCE of 24.14%, significantly outperforming the pristine device of 22.34%. The unencapsulated modified device retained 87% of its initial PCE after being stored for 1000 h under ambient conditions, demonstrating excellent environmental stability. This work provides a viable multifunctional interface engineering pathway toward high-performance and stable PSCs.