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Issue 11, 2016
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Enhancement of charge transport properties of small molecule semiconductors by controlling fluorine substitution and effects on photovoltaic properties of organic solar cells and perovskite solar cells

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Abstract

We prepared a series of small molecules based on 7,7′-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2,6-diyl)bis(4-(5′-hexyl-[2,2′-bithiophene]-5-yl)benzo[c][1,2,5]thiadiazole) with different fluorine substitution patterns (0F–4F). Depending on symmetricity and numbers of fluorine atoms incorporated in the benzo[c][1,2,5]thiadiazole unit, they show very different optical and morphological properties in a film. 2F and 4F, which featured symmetric and even-numbered fluorine substitution patterns, display improved molecular packing structures and higher crystalline properties in a film compared with 1F and 3F and thus, 2F achieved the highest OTFT mobility, which is followed by 4F. In the bulk heterojunction solar cell fabricated with PC71BM, 2F achieves the highest photovoltaic performance with an 8.14% efficiency and 0F shows the lowest efficiency of 1.28%. Moreover, the planar-type perovskite solar cell (PSC) prepared with 2F as a dopant-free hole transport material shows a high power conversion efficiency of 14.5% due to its high charge transporting properties, which were significantly improved compared with the corresponding PSC device obtained from 0F (8.5%). From the studies, it is demonstrated that low variation in the local dipole moment and the narrow distribution of 2F conformers make intermolecular interactions favorable, which may effectively drive crystal formations in the solid state and thus, higher charge transport properties compared with 1F and 3F.

Graphical abstract: Enhancement of charge transport properties of small molecule semiconductors by controlling fluorine substitution and effects on photovoltaic properties of organic solar cells and perovskite solar cells

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Publication details

The article was received on 03 Jun 2016, accepted on 06 Jul 2016 and first published on 27 Jul 2016


Article type: Edge Article
DOI: 10.1039/C6SC02448C
Chem. Sci., 2016,7, 6649-6661
  • Open access: Creative Commons BY-NC license
    All publication charges for this article have been paid for by the Royal Society of Chemistry

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    Enhancement of charge transport properties of small molecule semiconductors by controlling fluorine substitution and effects on photovoltaic properties of organic solar cells and perovskite solar cells

    J. H. Yun, S. Park, J. H. Heo, H. Lee, S. Yoon, J. Kang, S. H. Im, H. Kim, W. Lee, B. Kim, M. J. Ko, D. S. Chung and H. J. Son, Chem. Sci., 2016, 7, 6649
    DOI: 10.1039/C6SC02448C

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