Tailoring the Buried Interface by Dipolar Halogen-Substituted Arylamine for Efficient and Stable Perovskite Solar Cells

Improving the quality of the buried interface is decisive for achieving stable and high-efficiency perovskite solar cells. Herein, we report the interface engineering by using dipolar 2,4-difluoro-3,5-dichloroaniline (DDE) as the adhesive between titanium dioxide (TiO₂) and MAPbI₃. By manipulation of the anchoring groups of DDE, this molecule not only passivated defects of TiO₂ but also optimized the energy level alignment. Furthermore, the perovskite film on the modified TiO₂ surface showed improved crystallinity, released residual stress, and reduced trap states. Therefore, these benefits directly contribute to achieving a power conversion efficiency of up to 22.10%. The unencapsulated device retained 90% of initial power conversion efficiencies (PCE) after continuous light illumination for 1000 h and 93% of initial PCE after exposure to air with a relative humidity of 30-40% for over 3000 h. Moreover, the performance of PSCs based on FA_0.15MA_0.85PbI₃ has also increased from 20.48 to 23.51%. Our results demonstrate the effectiveness and universality of dipolar halogen-substituted arylamine (DDE) for enhancing PSC performance.