Synthesis and characterization of fluorine atom substituted new BDT-based polymers for use in organic solar cells
•A 3,4-difluoroalkylthienyl-substituted BDT-based donor–acceptor polymer (PBDTFT-ttTPD) was synthesized.•The fluorinated alkylthienyl substituents in the BDT unit yielded lower HOMO level compared to that in the corresponding nonfluorinated BDT.•A PBDTFT-ttTPD device exhibited a Voc of 0.79V, which...
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Published in | Synthetic metals Vol. 210; pp. 273 - 281 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
01.12.2015
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Subjects | |
Online Access | Get full text |
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Summary: | •A 3,4-difluoroalkylthienyl-substituted BDT-based donor–acceptor polymer (PBDTFT-ttTPD) was synthesized.•The fluorinated alkylthienyl substituents in the BDT unit yielded lower HOMO level compared to that in the corresponding nonfluorinated BDT.•A PBDTFT-ttTPD device exhibited a Voc of 0.79V, which is 0.08V larger than the value obtained from a PBDTT-ttTPD device.
A series of benzo[1,2-b:4,5-b′]dithiophene (BDT)-based donor–acceptor conjugated polymers were synthesized using a Stille cross-coupling reaction. The new fluorinated polymer (PBDTFT-ttTPD) contained 3,4-difluoroalkylthienyl benzo[1,2-b:4,5-b′]dithiophene (BDTFT) donor units and thienothienylthieno[3,4-c]pyrrole-4,6-dione (ttTPD) as acceptor units. A nonfluorinated alkylthienyl-substituted BDT-based polymer (PBDTT-ttTPD) was synthesized and its optoelectronic and photovoltaic properties were compared with those of PBDTFT-ttTPD. The number-averaged molecular weights (Mn) of PBDTT-ttTPD and PBDTFT-ttTPD were found to be 22,500 and 24,100g/mol, with dispersities of 2.3 and 2.0, respectively. The band gap energies of PBDTT-ttTPD and PBDTFT-ttTPD were 1.87eV and 1.89eV, respectively. The HOMO levels of PBDTT-ttTPD and PBDTFT-ttTPD were −5.68eV and −5.78eV, respectively. These results indicated that the inclusion of 3,4-difluorothienyl-BDT units in the polymers provided a very effective approach to lowering the HOMO and LUMO energy levels. The field-effect mobilities of PBDTT-ttTPD and PBDTFT-ttTPD were determined to be 9.2×10−4cm2V−1s−1 and 2.7×10−4cm2V−1s−1, respectively. A polymer solar cell device prepared using PBDTFT-ttTPD as the active layer was found to exhibit a power conversion efficiency (PCE) of 3.27% with an open circuit voltage of 0.79V under AM 1.5G (100mW/cm2) conditions. |
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ISSN: | 0379-6779 1879-3290 |
DOI: | 10.1016/j.synthmet.2015.10.013 |