Cross‐Linkable Cathode Interlayer for Inverted Organic Solar Cells with Enhanced Efficiency and Stability

Abstract Interlayer materials play a critical role in fabricating high‐performance organic solar cells (OSCs). Herein, a cross‐linked and n ‐doped cathode interlayer (CIL), namely, c ‐NDI:N, for highly efficient and stable organic solar cells is developed. This study demonstrates that the combination of high‐temperature cross‐linking along with n ‐doping endows the c ‐NDI:N@200 °C film with excellent robustness, high conductivity, and good film morphology. The inverted OSC using c ‐NDI:N@200 °C as CIL exhibits the highest power conversion efficiency of 17.5%, and most notably, appears in a negligible decline in device performance as the film thickness of CIL increases to ≈100 nm. Furthermore, c ‐NDI:N can serve as a protecting layer to shield the device against water ingress. Interestingly, c ‐NDI:N device can be used under water for photoelectrochemical water‐splitting, highlighting the great application of c ‐NDI:N CIL in inverted OSCs.