期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 134, 期 40, 页码 16597-16606出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja3050713
关键词
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资金
- National Science Foundation [NSF-DMR 0856060]
- Office of Basic Energy Sciences of the U.S. Department of Energy [DE-DC0001009]
- Air Force Office of Scientific Research [FA9550-11-1-0063]
- MRSEC Program of the National Science Foundation [DMR05-20415]
- ConvEne IGERT Program [NSF-DGE 0801627]
- National Science Foundation (GRFP)
- Center for Scientific Computing at the CNSI
- MRL: NSF MRSEC [DMR-1121053]
- NSF [CNS-0960316]
- Direct For Computer & Info Scie & Enginr [960316] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien [0840521] Funding Source: National Science Foundation
- Division Of Chemistry [0840521] Funding Source: National Science Foundation
- Division Of Computer and Network Systems [960316] Funding Source: National Science Foundation
We examine the correlations of the dipole moment and conformational stability to the self-assembly and solar cell performance within a series of isomorphic, solution-processable molecules. These charge-transfer chromophores are described by a D-1-A-D-A-D-1 structure comprising electron-rich 2-hexylbithiophene and 3,3'-di-2-ethylhexylsilylene-2,2'-bithiophene moieties as the donor units D-1 and D, respectively. The building blocks 2,1,3-benzothiadiazole (BT) and [1,2,5]thiadiazolo[3,4-c]pyridine (PT) were used as the electron-deficient acceptor units A. Using a combination of UV-visible spectroscopy, field-effect transistors, solar cell devices, grazing incident wide-angle X-ray scattering, and transmission electron microscopy, three PT-containing compounds (1-3) with varying regiochemistry and symmetry, together with the BT-based compound 5,5'-bis{(4-(7-hexylthiophen-2-yl)thiophen-2-yl)-[1,2,5]thiadiazolobenzene}-3,3'-di-2-ethylhexylsilylene-2,2'-bithiophene (4), are compared and contrasted in solution, in thin films, and as blends with the electron acceptor [6,6]-phenyl-C-70-butyric acid methyl ester. The molecules with symmetric orientations of the PT acceptor, 1 and 2, yield highly ordered blended thin films. The best films, processed with the solvent additive 1,8-diiodooctane, show donor crystallite length scales on the order or 15-35 nm and photovoltaic power conversion efficiencies (PCEs) of 7.0 and 5.6%, respectively. Compound 3, with an unsymmetrical orientation of PT heterocycles, shows subtle differences in the crystallization behavior and a best PCE of 3.2%. In contrast, blends of the BT-containing donor 4 are highly disordered and give PCEs below 0.2%. We speculate that the differences in self-assembly arise from the strong influence of the BT acceptor and its orientation on the net dipole moment and geometric description of the chromophore.
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