3D Pseudo-Para Solid Additive for Morphology Regulation in Binary Organic Solar Cells for Achieving 19.57% Efficiency

Abstract Precisely controlling active layer morphology using solid additives is a key approach to achieving efficient organic solar cells (OSCs). However, most existing solid additives are confined to planar molecular structures, whereas three-dimensional (3D) solid additives remain largely unexplored, and their structure–morphology relationships still remain unclear. Herein, we design and develop a novel 3D pseudo-para solid additive, 4,12-dithiophene[2.2]paracyclophane (DPCF), to systematically investigate the influence of the pseudo-para configuration on aggregation behavior, molecular packing, and device performance. Detailed mechanistic studies reveal that DPCF engages in electrostatic non-covalent interactions with the Y6 acceptor, effectively promoting dense molecular packing and ordered orientation while simultaneously reducing the π–π stacking distance and enhancing the crystal coherence length. In addition, DPCF can optimize the phase separation scale of the active layer, facilitating exciton dissociation and charge transfer. Consequently, the PM6:Y6 binary device achieves a power conversion efficiency (PCE) of 18.11%, representing one of the highest values for the corresponding device architecture. Notably, DPCF-treated PM6:L8-BO and PM6:BTP-eC9 devices deliver high PCEs of 18.63 and 19.57%, respectively. This work not only demonstrates the unique advantages of the pseudo-para configuration in solid additive design but also provides new insights for the development of high-efficiency three-dimensional solid additives.