- A 3-Fluoro-4-hexylthiophene-Based Wide Bandgap Donor Polymer for 10.9% Efficiency Eco-Friendly Nonfullerene Organic Solar Cells
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Nonfullerene organic solar cells (NFOSCs) are attracting increasing academic and industrial interest due to their potential uses for flexible and lightweight products using low-cost roll-to-roll technology. In this work, two wide bandgap (WBG) polymers, namely P(fTh-BDT)-C6 and P(fTh-2DBDT)-C6, are designed and synthesized using benzodithiophene (BDT) derivatives. Good oxidation stability and high solubility are achieved by simultaneously introducing fluorine and alkyl chains to a single thiophene (Th) unit. Solid P(fTh-2DBDT)-C6 films present WBG optical absorption, suitable frontier orbital levels, and strong π–π stacking effects. In addition, P(fTh-2DBDT)-C6 exhibits good solubility in both halogenated and nonhalogenated solvents, suggesting its suitability as donor polymer for NFOSCs. The P(fTh-2DBDT)-C6:3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthienyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC-Th) based device processed using chlorobenzene/1,8-diiodooctane (CB/DIO) exhibits a remarkably high power conversion efficiency (PCE) of 11.1%. Moreover, P(fTh-2DBDT)-C6:ITIC-Th reaches a high PCE of 10.9% when processed using eco-friendly solvents, such as o-xylene/diphenyl ether (DPE). The cell processed using CB/DIO maintains 100% efficiency after 1272 h, while that processed using o-xylene/DPE presents a 101% increase in efficiency after 768 h and excellent long-term stability. The results of this study demonstrate that simultaneous fluorination and alkylation are effective methods for designing donor polymers appropriate for high-performance NFOSCs.
- Yu, Jeong Eun,Jeon, Sung Jae,Choi, Jun Young,Han, Yong Woon,Ko, Eui Jin,Moon, Doo Kyung
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- 3-Fluoro-4-hexylthiophene as a building block for tuning the electronic properties of conjugated polythiophenes
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3-Fluoro-4-hexylthiophene has been prepared by a synthetic route involving perbromination of 3-hexylthiophene followed by protection of the 2- and 5-positions of thiophene by trimethylsilyl groups and bromine/fluorine exchange. As expected, 3-hexyl-4-fluorothiophene oxidizes at a higher potential than 3-hexylthiophene; however, all attempts to electropolymerize this new thiophenic monomer have remained unsuccessful. Three terthienyls containing 3-hexylthiophene, 3-fluoro-4-hexylthiophene, and 3-bromo-4-hexylthiophene as the median group have been synthesized and used as substrates for electropolymerization. The electronic properties of the starting terthienyls and the resulting polymers have been analyzed by cyclic voltammetry and UV-vis spectroscopy, and the effects of substitution of the median thiophene ring are discussed.
- Gohier, Frédéric,Frère, Pierre,Roncali, Jean
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- Influence of backbone fluorination in regioregular poly(3-alkyl-4-fluoro)thiophenes
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We report two strategies toward the synthesis of 3-alkyl-4-fluorothiophenes containing straight (hexyl and octyl) and branched (2-ethylhexyl) alkyl groups. We demonstrate that treatment of the dibrominated monomer with 1 equiv of alkyl Grignard reagent leads to the formation of a single regioisomer as a result of the pronounced directing effect of the fluorine group. Polymerization of the resulting species affords highly regioregular poly(3-alkyl-4-fluoro)thiophenes. Comparison of their properties to those of the analogous non-fluorinated polymers shows that backbone fluorination leads to an increase in the polymer ionization potential without a significant change in optical band gap. Fluorination also results in an enhanced tendency to aggregate in solution, which is ascribed to a more co-planar backbone on the basis of Raman and DFT calculations. Average charge carrier mobilities in field-effect transistors are found to increase by up to a factor of 5 for the fluorinated polymers.
- Fei, Zhuping,Boufflet, Pierre,Wood, Sebastian,Wade, Jessica,Moriarty, John,Gann, Eliot,Ratcliff, Erin L.,Mcneill, Christopher R.,Sirringhaus, Henning,Kim, Ji-Seon,Heeney, Martin
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p. 6866 - 6879
(2015/06/16)
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