| 摘要: | 摘要： We report a detailed comparison of absorption spectroscopy, electrochemistry, DFT calculations, field-effect charge mobility, as well as organic photovoltaic characteristics between thiophene- and selenophene-bridged donor-acceptor low-band-gap copolymers. In these copolymers, a significant reduction of the band-gap energy was observed for selenophene-bridged copolymers by UV-visible absorption spectroscopy and cyclic voltammetry. Field-effect charge mobility studies reveal that the enhanced hole mobility of the selenophene-bridged copolymers hinges on the solubilising alkyl side chain of the copolymers. Both cyclic voltammetry experiments and theoretical calculations showed that the decreased band-gap energy is mainly due to the lowering of the LUMO energy level, and the raising of the HOMO energy level is just a secondary cause. These results are reflected in a significant increase of the short circuit current density ( J SC ) but a slight decrease of the open circuit voltage ( V OC ) of their bulk-heterojunction organic photovoltaics (BHJ OPVs), of which the electron donor materials are a selenophene-bridged donor-acceptor copolymer: poly{9-dodecyl-9H-carbazole- alt -5,6-bis(dodecyloxy)-4,7-di(selenophen-2-yl) benzo[ c ][1,2,5]-thiadiazole} ( pCzSe ) or poly{4,8-bis(2-ethylhexyloxy)benzo[1,2- b ;4,5- b ′]dithiophene- alt -5,6-bis(dodecyloxy)-4,7-di(selenophen-2-yl)benzo[ c ][1,2,5]-thiadiazole} ( pBDTSe ), or a thiophene-bridged donor-acceptor copolymer: poly{9-dodecyl-9 H -carbazole- alt -5,6-bis(dodecyloxy)-4,7-di(thiophen-2-yl)benzo[ c ][1,2,5]-thiadiazole} ( pCzS ) or poly{4,8-bis(2-ethylhexyloxy)benzo[1,2- b ;4,5- b ′]dithiophene- alt -5,6-bis(dodecyloxy)-4,7-di(thiophen-2-yl)benzo[ c ][1,2,5]-thiadiazole} ( pBDTS ); the electron acceptor material is [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Judging from our device data, the potential Se-Se interactions of the selenophene-bridged donor-acceptor copolymers, which is presumably beneficial for the fill factor (FF) of BHJ OPVs, is rather susceptible to the device fabrication conditions. Selenophene-bridged donor acceptor copolymers, which have lower LUMO energy levels, show enhanced efficiency for organic photovoltaics than their thiophene-bridged counterparts because of their absorption at longer wavelengths and stronger photocurrent at short wavelengths.
出版日期： 2012-09-25
資源來源： Alma/SFX Local Collection
識別號： ISSN: 0959-9428
識別號： EISSN: 1364-5501
識別號： DOI: 10.1039/c2jm33735e |
