From <scp>1D</scp> to <scp>3D</scp> : A Systematic Study of Dibenzene Derivatives as Additives for Morphology and Performance Optimization in Organic Solar Cells ^†

Comprehensive Summary Introducing volatile solid additives into the active layer of organic solar cells (OSCs) is a widely used approach to improving power conversion efficiency (PCE). The molecular conformation of these additives plays a crucial role in determining the molecular packing behavior and phase separation of the active layer. In this study, we systematically explore the effects of three different dimensions‐dibenzene derivatives solid additives—one‐dimensional (1D) linear diphenylacetylene (DNE), two‐dimensional (2D) planar trans ‐stilbene (SNE), and three‐dimensional (3D) stereoscopic 1,2‐diphenylethane (DLE)—on device performance. Compared to the 3D additive DLE, both 1D DNE and 2D SNE show stronger interactions with the acceptor and promote its molecular packing. However, this induces an absorption red shift that significantly lowers open‐circuit voltage ( V OC ). In contrast, DLE retains a higher V OC (0.887 V) due to minimal spectral shift and mitigates the V OC ‐short‐circuit current density ( J SC ) trade‐off, thereby reaching a PCE of 19.62% in the PM6:L8‐BO system. Moreover, as a non‐halogenated additive processed with the green solvent toluene, DLE enables a high PCE of 19.33% in the PM6:BTP‐ec9 system, highlighting its promising potential for practical applications. Our findings establish a broadly applicable framework for understanding and harnessing conformation effects in solid additives to enhance OSC efficiency.