High‐Performance Organic Solar Cells Enabled by 3D Globally Aromatic Carboranyl Solid Additive

Abstract A key factor in optimizing organic solar cells (OSCs) is the precise control of blend film morphology to enhance exciton dissociation and charge transport. Solid additives play a vital role in this process, with 3D polyhedral or spherical molecules being ideal candidates due to their delocalized π‐orbitals and omnidirectional charge transport. However, the application of classical fullerene derivatives as spherical additives is limited by their synthetic complicacy and poor solubility. Herein, the potential of 3D globally aromatic carboranyl cages as solid additives, specifically 1‐amino‐ o ‐carborane (CB‐NH 2 ) and 1‐carboxy‐ o ‐carborane (CB‐COOH), is explored to fine‐tune the film morphology and improve the performance of OSCs. These spherical molecules provide an extensive surface for hydrogen bonding interactions, which serve as the driving force for manipulating the vertical phase separation and active layer crystallinity. Remarkably, CB‐NH 2 ‐processed devices with well‐tuned morphology yield a remarkable power conversion efficiency of 19.48%, highlighting the effectiveness of 3D carboranyl additives on improving OSC performance. This work challenges the reliance on fullerene derivatives as spherical additives and offers new insights into the mechanisms by which 3D globally aromatic additives can achieve high performance in OSCs, emphasizing the significance of molecular engineering in the development of next‐generation solar cell technology.