TVT-Based New Building Block with Enhanced π-Electron Delocalization for Efficient Non-Fused Photovoltaic Acceptor

To address the high-cost issue that impedes the large-scale fabrication and industrialization of organic solar cells (OSCs), it is crucial to design low-cost photovoltaic materials with simplified synthesis procedures. In this study, a novel fully non-fused acceptor, ATVT-BO, featuring a triisopropylbenzene-substituted (E)-1,2-di(thiophen-2-yl)ethene (TVT) unit as the central core is designed and synthesized. A control acceptor, A4T-BO, with the same alkyl chains but a bithiophene central core, is also synthesized for comparison. Theoretical calculations and practical measurements reveal that compared to A4T-BO, the insertion of an ethylene bond in ATVT-BO enhances the molecular planarity and reduces the aromaticity, leading to enhanced π-electron delocalization and thus improved electron mobility and a red-shifted optical absorption spectrum. The 3D molecular packing mode of ATVT-BO, characterized by tight intermolecular interactions, also promotes efficient charge transport in OSCs. Consequently, when paired with the low-cost polymer PTVT-T, featuring an ester-substituted TVT structure, as the photoactive layer, the PTVT-T:ATVT-BO-based device achieves a remarkable power conversion efficiency of 14.8%, distinctly higher than that of PTVT-T:A4T-BO-based cell. The result highlights the significant potential of TVT units in creating both low-cost polymer donors and fully non-fused acceptors, which opens up new possibilities for designing low-cost photoactive materials in OSCs.