Synthesis, Photophysical, and Device Properties of Novel Dendrimers Based on a Fluorene-Hexabenzocoronene (FHBC) Core Wallace W. H. Wong,* ,† David J. Jones, † Chao Yan, † Scott E. Watkins, ‡ Simon King, § Saif A. Haque, § Xiaoming Wen, † Kenneth P. Ghiggino, † and Andrew B. Holmes † School of Chemistry, Bio21 Institute, UniVersity of Melbourne, Vic. 3010, Australia, CSIRO Molecular and Health Technologies, Ian Wark Laboratory, Clayton South, Vic. 3169, Australia, and Department of Chemistry, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom wwhwong@unimelb.edu.au Received December 18, 2008 ABSTRACT The synthesis of easily functionalized and highly soluble fluorene-containing hexabenzocoronenes (FHBC) has been achieved in high yield at a gram scale. Conjugated triarylamine oligomers were coupled to the FHBC cores via Buchwald-Hartwig coupling, and the photophysical properties of resulting dendritic materials were examined by ultrafast laser spectroscopic techniques. Efficient quenching of the triarylamine oligomer fluorescence was observed paving the way for the inclusion of these materials in bulk heterojunction solar cells. In preliminary studies, solar cell devices with external quantum efficiencies above 5% have been fabricated. Hexabenzocoronene (HBC) is a planar aromatic molecule consisting of 13 fused six-membered rings (Figure 1). 1 It belongs to the family of polycyclic aromatic hydrocarbons consisting of flat disklike cores. HBC and its derivatives have been shown to self-assemble into columnar structures giving rise to ordered morphology in films. 2,3 This property is potentially very useful in bulk heterojunction solar cells where the active layer consists of an electron and a hole transport material usually blended together in a random fashion. The self-assembly of materials into ordered struc- tures in a bulk heterojunction could increase the efficiency of the photovoltaic device by facilitating charge separation † University of Melbourne. ‡ CSIRO. § Imperial College London. (1) Wu, J.; Pisula, W.; Mu¨llen, K. Chem. ReV. 2007, 107, 718. Herwig, P. T.; Kayser, C. W.; Mu¨llen, K.; Spiess, H. W. AdV. Mater. 1996, 8, 510. (2) (a) Destrade, C.; Nyugen, T. H.; Gasparoux, H.; Malthete, J.; Levelut, A. M. Mol. Cryst. Liq. Cryst. 1981, 71, 111. (b) Carfanga, C.; Roviello, A.; Sirigu, A. Mol. Cryst. Liq. Cryst. 1995, 122, 151. (c) Raja, K. S.; Ramakrishnan, S.; Raghunathan, V. A. Chem. Mater. 1997, 9, 1630. (d) Zamir, S.; Singer, D.; Spielberg, N.; Wachtel, E. J.; Zimmermann, H.; Poupko, R.; Luz, Z. Mol. Cryst. Liq. Cryst. 1996, 21, 39. (3) (a) Ito, S.; Wehmeier, M.; Diedrich Brand, C.; Ku¨bel, C.; Epsch, R.; Rabe, J. P.; Mu¨llen, K. Chem.-Eur. J. 2000, 6, 4327. (b) Kastler, M.; Pisula, W.; Wasserfallen, D.; Pakula, T.; Mu¨llen, K. J. Am. Chem. Soc. 2005, 127, 4286. ORGANIC LETTERS 2009 Vol. 11, No. 4 975-978 10.1021/ol8029164 CCC: $40.75  2009 American Chemical Society Published on Web 01/22/2009