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Study on the effect of fluorine substitution on the photovoltaic properties of dithieno[3,2-b:2',3'-d]pyrrole-benzo[c][1,2,5]thiadiazole conjugate small molecule donor materials

Abstract

Two new small molecule donors namely ICT4 and ICT6 with D1-A-D2-A-D1 architecture having 2,4-bis(2-ethylhexyl)-4H-dithieno[3,2-b:2',3'-d]pyrrole (EHDTP, D1) and ethylhexyl)oxy)benzo[1,2-b:4,5-b']dithiophene (OBDT, D2) as terminal and central donor and 4,8-bis((2- benzo[c][1,2,5]thiadiazole (BT for ICT4) and 5,6-difluorobenzo[c][1,2,5]thiadiazole (F2BT for ICT6) as acceptor (A) moieties are synthesized and their optical, electronic and photovoltaic properties are investigated. Both ICT4 and ICT6 are have considerable solubility in various solvents and possess efficient light absorption ability [ (x 105 mol-1 cm-1) is 0.99 and 1.06, respectively for ICT4 and ICT6) and appropriate frontier molecular orbital energy offsets with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). Bulk heterojunction solar cells (BHJSCs) are fabricated using ICT4/ICT6 and PC71BM as donor and acceptors, respectively and BHJSCs with the two step annealed (thermal followed by solvent vapor annealing) active layers of ICT4 and ICT6 shows overall power conversion efficiency (PCE) of 5.46 % and 7.91 %, respectively. Superior photovoltaic performance of ICT6 based BHJSCs is due to the favourable morphology with nanoscale interpenetrating network in the ICT6:PC71BM active layer induced by the fluorine atoms on BT acceptor, which significantly enhances the dissociation of excitons, charge transport, charge collection efficiency and suppresses bimolecular recombination in the BHJ. Observed higher PCE of 7.91 % portray ICT6 as one of the best BT based donor material for small molecular BHJSCs.

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Publication details

The article was received on 26 Apr 2017, accepted on 07 Jul 2017 and first published on 10 Jul 2017


Article type: Paper
DOI: 10.1039/C7CP02729J
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Study on the effect of fluorine substitution on the photovoltaic properties of dithieno[3,2-b:2',3'-d]pyrrole-benzo[c][1,2,5]thiadiazole conjugate small molecule donor materials

    M. R. B, N. R. Chereddy, B. Shanigaram, B. Kotamarthi, S. Biswas, G. D. Sharma and J. R. Vaidya, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP02729J

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