Functionalized isothianaphthene monomers that promote quinoidal character in donor-acceptor copolymers for organic photovoltaics

Abstract
A series of low band gap isothianaphthene-based (ITN) polymers with various electron-withdrawing substituents and intrinsic quinoidal character were synthesized, characterized, and tested in organic photovoltaic (OPV) devices. The three investigated ITN cores contained either ester, imide, or nitrile functionalities and were each synthesized in only four linear steps. The relative electron-withdrawing strength of the three substituents on the ITN moiety was evaluated and correlated to the optical and electronic properties of ITN-based copolymers. The ester- and imide-containing p-type polymers reached device efficiencies as high as 3% in bulk heterojunction blends with phenyl C 61-butyric acid methyl ester (PC 61BM), while the significantly electron-deficient nitrile-functionalized polymer behaved as an n-type material with an efficiency of 0.3% in bilayer devices with poly(3-(4-n-octyl)phenylthiophene) (POPT). © 2012 American Chemical Society.

Citation
Douglas, J. D., Griffini, G., Holcombe, T. W., Young, E. P., Lee, O. P., Chen, M. S., & Fréchet, J. M. J. (2012). Functionalized Isothianaphthene Monomers That Promote Quinoidal Character in Donor–Acceptor Copolymers for Organic Photovoltaics. Macromolecules, 45(10), 4069–4074. doi:10.1021/ma300589k

Acknowledgements
This work was supported in part by the Director, Office of Science, Office of Basic Energy Sciences, Material Sciences and Engineering Division, of the U.S. Department of Energy under Contract DE-AC02-05CH11231 and the Frechet "Various Donors" gift fund for the support of research in new materials. G.G. thanks Fondazione Banca del Monte di Lombardia, T.W.H. thanks the National Science Foundation, and M.S.C. thanks the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry for fellowships. The authors also thank Professors Robert Bergman and Peter Vollhardt for helpful discussions.

Publisher
American Chemical Society (ACS)

Journal
Macromolecules

DOI
10.1021/ma300589k

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