Porphyrin‐Modified SnO₂ Electron Transport Layer for Efficient and Stable Inverted Organic Solar Cells

Abstract Compared with conventional devices, inverted organic solar cells (OSCs) generally exhibit superior stability, with the electron transport layer (ETL) and interface engineering playing key roles in enhancing both efficiency and stability. In this study, tetra‐phenyl porphyrin (TPP), a free base porphyrin, is utilized to modify commercially available tin oxide (SnO₂) nanoparticles, thus creating a high‐performance ETL for inverted OSCs. First‐principles calculations and characterizations reveal that TPP interacts effectively with the SnO₂ surface, reduces the work function, passivates the surface defects, and improves the conductivity of SnO₂. Compared to the power conversion efficiency (PCE, 15.37%) of the control PM6:Y6‐based devices, the hybrid ETL enables an improved PCE of 17.72%. Furthermore, the ternary device of PM6:L8‐BO:BTP‐eC9 achieves a PCE of 19.51% (Certificated efficiency: 19.13%, the record efficiency for inverted OSCs). This study presents a promising hybrid ETL strategy for developing highly efficient and stable organic solar cells.