Exploiting Bis‐Sulfonimide Featuring Multiple <i>d–p</i> π Bonds to Construct Interlayers for Organic Solar Cells

Herein, bis-sulfonimide (BSI), characterized by multiple d-pπ bonds rather than typical p-pπ bonds, is unprecedently utilized as a general and extendable building block to develop a series of multifunctional cathode interlayer materials (CIMs) for organic solar cells (OSCs). An illustrative CIM, BSIz-TT-PDI, demonstrates favorable alcohol processability, superior work function tunability, appropriate energy levels, strong self-doping effect, and decent crystallinity. These attributes contribute to its high conductivity exceeding 5×10^-3 S/cm, as well as precise optimization of the interfacial connection between the active layer and metal cathode. Therefore, BSIz-TT-PDI-based OSCs delivers an outstanding efficiency of 18.08 % using PM6:Y6 active layer while retaining 84 % of its initial performance after tracking at the maximum power point under continuous illumination for 1100 hours. Additionally, the devices maintain over 94 % of the optimal performance across a film thickness range of BSIz-TT-PDI from 5 to 90 nm. Moreover, BSIz-TT-PDI exhibits high compatibility with various active layers, enabling a record efficiency of 19.80 % with the PM6:BTP-eC9:L8-BO active layer. This work not only introduces a new library of water/alcohol-soluble n-type semiconductors containing BSI, while also pioneers the creation of thickness-insensitive CIMs for stable and efficient OSCs by integrating electron-withdrawing components with d-pπ bonds.