Bottom‐Up Defect Modification Through Oily‐Allicin Modified Buried Interface Achieving Highly Efficient and Stable Perovskite Solar Cells

Abstract The buried interface properties of the perovskite solar cells (PSCs) play a crucial role in the power conversion efficiency (PCE) and operational stability. The metal‐oxide/perovskite heterogeneous interfaces are highly defective and cause serious ion migration. However, the buried and unexposed bottom interface and simultaneous stabilization of grain boundaries receive less attention and effective solutions. To tackle this problem, a solid–liquid strategy is employed by introducing oily‐additive allicin at the buried interface to passivate the shallow (V_I and Vo) and deep traps (V_Pb and Pb_I). Interestingly, oily status allicin fills the pinholes at the heterointerface and wraps the perovskite grains, suppressing the ion migration during the photoaging process. As a result, an outstanding PCE of 25.07% is achieved with a remarkable fill factor (FF) of 84.03%. The modified devices can maintain 94.51% of the original PCE after light soaking under 1‐sun illumination for 1000 h. This work demonstrates a buried interface modification method that employs an eco‐friendly additive, which helps promote the development of PSCs with high performance and stability.