A Broad-Spectrum Solid Additive to Further Boost High-Efficiency Organic Solar Cells via Morphology Regulation

Given the great potential for achieving record breaking organic solar cells (OSCs), newly explored solid additives that could optimize nanoscale morphology of active layers have rapidly gained widespread attention. Herein, a new volatile solid additive 2,5-dichlorothieno[3,2-b]thiophene (TT-Cl) is delicately explored, fully satisfying the design criteria of a planar conjugated skeleton with suitable molecular size, symmetrical geometry, and proper halogenation. When applied in the state-of-the-art OSCs with diverse active layers, the quite high crystallinity of TT-Cl and strong interactions with light-harvesting components lead to optimized molecular crystalline ordering, fibrillar networks, and vertical phase distributions, thus offering a significant performance enhancement. Consequently, PM6:Y6-based binary and ternary OSCs achieved PCEs of 18.20% and 18.95%, respectively. Moreover, PM6:CH23-based binary OSCs presented an outstanding PCE of 18.72%. Our work not only provides a broad-spectrum solid additive to optimize film morphologies powerfully but also manifests great potential for achieving a record-breaking PCE of OSCs.