Efficient Naphthalenediimide-Based Hole Semiconducting Polymer with Vinylene Linkers between Donor and Acceptor Units

We demonstrate a new method to reverse the polarity and charge transport behavior of naphthalenediimide (NDI)-based copolymers by inserting a vinylene linker between the donor and acceptor units. The vinylene linkers minimize the intrinsic steric congestion between the NDI and thiophene moieties to prompt backbone planarity. The polymers with vinylene linkers exhibit electron n-channel transport characteristics under vacuum, similar to the benchmark polymer, P(NDI2OD-T2). To our surprise, when the polymers are measured in air, the dominant carrier type switches from n- to p-type and yield hole mobilities up to 0.45 cm(2) s(-1) with hole to electron mobility ratio of three (mu(h)/mu(e), similar to 3), which indicates that the hole density in the active layer can be significantly increased by exposure to air. This increase is consistent with the intrinsic more delocalized nature of the highest occupied molecular orbital of the charged vinylene polymer, as estimated by density functional theory (DFT) calculations, which facilitates hole transport within the polymer chains. This is the first demonstration of an efficient NDI-based hole semiconducting polymer, which will enable new developments in all-polymer solar cells, complementary circuits, and dopable polymers for use in thermoelectrics.

Citation

Zhang L, Rose BD, Liu Y, Nahid MM, Gann E, et al. (2016) Efficient Naphthalenediimide-Based Hole Semiconducting Polymer with Vinylene Linkers between Donor and Acceptor Units. Chemistry of Materials 28: 8580–8590. Available: http://dx.doi.org/10.1021/acs.chemmater.6b03379.

Acknowledgements

L.Z., J. L., S.J.R., and A.L.B thank the Office of Naval Research (N0001471410053) and the National Science Foundation (DMR-1508627) for support of this work; Y.L. and T.P.R. acknowledge the support of the Office of Naval Research under contract N00014-15-1-2244; C.M. acknowledges funding from the Australian Research Council (FT10010075, DP130102616); B.D.R. and J.L.B. acknowledge the support from ONR-Global, Award N62909-15-1-2003, and from competitive research funding of King Abdullah University of Science and Technology. Parts of this research were undertaken on the soft X-ray and SAXS/WAXS beamlines of the Australian Synchrotron. L.Z. thanks the Fundamental Research Funds for the Central Universities (ZY1636).