Cathode interface engineering for high-efficiency organic solar cells: Ultrathin antimony oxide nanobelt-doped zinc...

As a widely used electron transport layer (ETL) in inverted organic solar cells (OSCs), zinc oxide (ZnO) often suffers from such limitation as low carrier transport capability, energy level mismatch with the active layer, and abundant surface defects, which collectively restrict the OSC efficiency. Cathode interface engineering-targeted modification of interface between the cathode electrode and active layer-has emerged as a crucial strategy to address these challenges. In this contribution, we demonstrate that incorporating ultrathin antimony oxide (Sb₂O₃) nanobelts (NBs) into ZnO effectively reduces its work function, minimizes the interfacial energy barrier and improves electron extraction. Furthermore, Sb₂O₃ NBs function as nucleation templates to facilitate the growth of denser and smoother ZnO films, which improves charge transport, suppresses charge recombination losses, and enhances favorable phase separation in the active layer. Consequently, the PM6:Y6-based OSCs with Sb₂O₃ NBs-doped ZnO (ZnO:Sb₂O₃ NBs) as an ETL achieve a power conversion efficiency (PCE) of 17.16 % while maintaining an excellent ambient stability (retaining over 92.3 % of their initial PCE after 288 h of storage under a relative humidity below 10 %). This current work establishes ZnO:Sb₂O₃ NBs as a highly effective ETL modification strategy, providing valuable insights for developing high-performance and flexible ETLs in next-generation OSCs.