4 years ago

Intermediate-Sized Conjugated Donor Molecules for Organic Solar Cells: Comparison of Benzodithiophene and Benzobisthiazole-Based Cores

Intermediate-Sized Conjugated Donor Molecules for Organic Solar Cells: Comparison of Benzodithiophene and Benzobisthiazole-Based Cores
Simon B. Blakey, Tatiana V. Timofeeva, Seth R. Marder, Guillermo C. Bazan, Stephen Barlow, Yadong Zhang, Junxiang Zhang, Maged Abdelsamie, Qinqin Shi, Aram Amassian, Timothy C. Parker, Siyuan Zhang, Evgheni V. Jucov
Two intermediate-sized donor molecules, BBTz-X and BDT-X, have been synthesized by the Stille coupling between 4-(4,4-bis(2-ethylhexyl)-6-(trimethylstannyl)-4H-silolo[3,2-b:4,5-b′]dithiophen-2-yl)-7-(5′-hexyl-[2,2′-bithiophen]-5-yl)-[1,2,5]thiadiazolo[3,4-c]pyridine and either 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-2,6-diiodobenzo[1,2-d:4,5-d′]bis(thiazole) or 2,6-dibromo-4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene, respectively. Both oxidation and reduction potentials for BBTz-X are anodically shifted relative to those for BDT-X, but the oxidation potential is more sensitive to the identity of the core; this is consistent with what is seen for DFT-calculated HOMO and LUMO energies and with a slightly blue-shifted absorption maximum for BBTz-X. Although DFT calculations, along with crystal structures of related compounds, suggest more planar molecular structures for BBTz-X than for BDT-X, film structures and the effects of various annealing processes on these films, as revealed by GIWAXS, are similar. The performance of BDT-X:PC61BM bulk-heterojunction solar cells is more sensitive to annealing conditions than that of BBTz-X:PC61BM cells, but under appropriate conditions, both yield power conversion efficiencies of >7%.

Publisher URL: http://dx.doi.org/10.1021/acs.chemmater.7b02665

DOI: 10.1021/acs.chemmater.7b02665

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