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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-dichlorothieno3,2-bthiophene (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.
Cao et al. (Mon,) studied this question.