Abstract
Solid additives have garnered significant attention due to their numerous advantages over liquid additives. This study explores the potential of the green-fluorescent conjugated polymer denoted Atums Green as a solid additive in green-solvent-based PBDB-TF-T1:BTP-4F-12 solar cells. Even tiny amounts of Atums Green doping significantly improve the device performance. For the reference solar cell without any additive, we find that device degradation is not caused by chemical redox reactions but by changes in crystallinity and microstructure evolution during aging in air under illumination. Operando GIWAXS and GISAXS are used to investigate the structure evolution. We discover a four-stage degradation process for the reference cell. In general, the lattice spacing and crystallite coherence length decrease, while the domain sizes increase, which causes the loss of shirt-circuit current J(SC) and fill factor FF. Furthermore, a decomposition component is detected in GIWAXS and GISAXS, corresponding to the loss of the open-circuit voltage V(OC). Atums Green doping effectively suppresses the evolution of crystallinity and domain sizes as well as the continuous decomposition, thereby enhancing the device stability under illumination in air. This finding reveals the kinetic degradation process of organic solar cells, establishes a correlation between the morphological properties and device performance, and further demonstrates the promising potential of Atums Green doping in organic solar cells.