The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F‐Se and DIBP3F‐S, which bridged two segments of Y6‐derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O‐shaped conformations other than S‐ or U‐shaped counter‐ones. Notably, this O‐shaped conformation is likely governed by a distinctive “conformational lock” mechanism, arising from the intensified intramolecular π–π interactions among their two terminal groups within the dimers. PSCs based on DIBP3F‐Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F‐S‐based cells (16.11 %) and ranking among the highest efficiencies for OA‐based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high‐performance PSCs.
Joining of imidazole, pyrimidine, and oxazole to other conjugated core units was explored in pursuit of yielding monomers to synthesize organic semiconducting polymers. Regioregular oxazoleflanked thiophene, benzothiadiazole, naphthalene diimide (NDI), and thienopyrroledione (TPD) were successfully isolated via stannylation of oxazole and the Stille coupling of brominated core units (overall yields ranging from ca. 40 to 60%). From subsequent direct arylation polymerization, NDI/oxazole/TPD-containing regioisomeric polymers were obtained with optical and electrochemical orbital energetics in the semiconducting regime.
Self-polycondensation of 3-iodocarbazole derivatives in the presence of CuI catalysts produces the corresponding 3,9-carbazole-based polymers. Unsubstituted poly(3,9-carbazole) P2 has a limited solubility, whereas poly(3,9-carbazole) P1 with a tert-butyl group at the 6-position of the carbazole is soluble in common organic solvents. These polymers are regarded as an extended form of polyaniline. However, contrary to polyaniline, they are thermally and chemically stable owing to the highly twisted structure between adjacent repeat units. In addition, P1 is highly stable when applying potentials of up to 1.50 V. Due to the high stability toward oxidation, the cast films of these polymers display well-defined visible fluorescence in their neutral states. When the films are exposed to nitro-aromatic vapors (modeled by nitro-explosives), energy transfer induced fluorescent quenching occurs. Upon exposure of the quenched films to air, the fluorescence is restored. Overall, the substituted P1 film exhibits better sensing abilities than the unsubstituted P2 film due to the bulky tert-butyl groups.
The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F‐Se and DIBP3F‐S, which bridged two segments of Y6‐derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O‐shaped conformations other than S‐ or U‐shaped counter‐ones. Notably, this O‐shaped conformation is likely governed by a distinctive “conformational lock” mechanism, arising from the intensified intramolecular π–π interactions among their two terminal groups within the dimers. PSCs based on DIBP3F‐Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F‐S‐based cells (16.11 %) and ranking among the highest efficiencies for OA‐based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high‐performance PSCs.
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