Three-dimensional bowl-shaped solid additive achieves 20.52% efficiency organic solar cells with enhanced thermal stability via curvature-mediated morphology regulation

Abstract

High-performance organic solar cells (OSCs) demand precise control over the active layer morphology, as it greatly influences exciton dissociation and charge transport. Solid additives offer a powerful strategy for improved molecular stacking and fine-tuned film morphology. However, most existing additives rely on planar molecular structures, while three-dimensional (3D) fullerene derivatives often suffer from tedious synthesis and poor solubility. Here, we introduced two polycyclic aromatic solid additives, 3D bowl-shaped corannulene and planar coronene with simple structures, into the benchmark PM6:L8-BO system to explore the impact of molecular curvature of additives on OSC performance. The unique curvature of corannulene generates a strong dipole moment, enhancing molecular packing and fostering favorable intermolecular interactions. This, in turn, optimizes nanoscale phase separation, mitigates energy losses, and facilitates efficient charge transfer. As a result, OSCs processed with corannulene achieved an impressive power conversion efficiency of 20.52% and exceptional thermal stability, with an experimentally determined T₈₅ lifetime of 2007 h, dramatically surpassing the 52-h lifetime of as-cast devices. These results demonstrate the potential of curved molecular additives in optimizing blend morphology and improving crystallinity, offering new avenues for the development of high-performance and long-lifetime OSCs.