New Anthracene-Containing Phenylene- or Thienylene- Vinylene Copolymers: Synthesis, Characterization, Photophysics, and Photovoltaics Panagiotis D. Vellis, 1 John A. Mikroyannidis, 1 Diego Bagnis, 2 Luca Valentini, 2 Jose ` M. Kenny 2 1 Chemical Technology Laboratory, Department of Chemistry, University of Patras, GR-26500 Patras, Greece 2 Civil and Enviromental Engineering Department, NIPLAB-INSTM, University of Perugia, 05100 Terni, Italy Received 14 October 2008; accepted 23 December 2008 DOI 10.1002/app.29967 Published online 2 April 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Four new conjugated alternating vinylene- copolymers, PAP6, PAT, PA, and TAT, incorporating an- thracene rings along the backbone were synthesized by Heck coupling. They were very soluble in common organic sol- vents and absorbed at the range of 300–500 nm with optical band gaps of 2.38–2.47 eV. They behaved in solution as green emitters, with maximum photoluminescence at 455– 518 nm. Finally, these soluble copolymers were used as donor material to realize bulk heterojunction solar cell with (6,6)-C 61 -butyric acid methyl ester as the acceptor. More effi- cient photovoltaic cells were obtained from the copolymer that carried hexyloxy than dodecyloxy side groups. V V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1173–1181, 2009 Key words: synthesis; photophysics; phenylenevinylene; thienylenevinylene; anthracene; photovoltaic cells INTRODUCTION Over the last few decades, photovoltaic (PV) cells based on organic semiconducting materials have been actively investigated for low-cost alternatives to conventional inorganic PV cells. Conjugated poly- mers, especially, have tremendous potential for future PV cells because they can be easily processed and tailored to all needs due to the infinite variabili- ty of organic materials. Organic soluble narrow band gap polymers are particularly desirable for photovoltaics due to their spectral absorption, which matches the solar terres- trial radiation. 1–4 They are also needed for deep red and near-infrared (IR) emitting devices, 1 for applica- tions using n- and p-type conductors, 5 especially due to their potentially multicolored states. 6,7 The donor– acceptor approach (D–A) is one of the most effective ways of building a narrow band gap polymer. The high-lying HOMO of a donor fragment combined with the low-lying LUMO of an acceptor gives rise to a –(D–A) x – repeat unit structure with an unusu- ally small HOMO-LUMO separation and narrow band gap. 8–10 The presence of a double bond of a defined con- figuration (1) reduces the overall aromatic character of the planar structures and hence increases the p- electron localization, and (2) restricts the rotational freedom inherent to thiophenes, 11,12 which increases the energy-band gap. 13 The introduction of a vinyl- ene unit into polymeric structures is a well-known method for forming coplanar molecules with an extended p-conjugated length, which should help to maximize the organization of the molecules in thin films. 14–16 Anthracene is an organic semiconductor, 17–20 extensively investigated over many decades, and it consists of three linear phenyl rings in its crystal structure. The electronic conduction of anthracene is due to free electrons and holes present in the crystal. The activation energy of anthracene reported in the literature ranges from 0.9 to 1.6 eV based on the type of the sample and the technique involved. 21–28 Conductivity in anthracene is by two mechanisms, namely, by hopping (production of charge carriers) and/or by tunneling (mobility of charge carriers). Mixing two polymers typically leads to phase sep- aration and creation of microstructured D–A junc- tions. Additionally, with the use of D–A polymers of different band gaps, the device can be made sensi- tive over a wide spectral range. A g P value of 1% and incident-photon-to-current conversion efficiency of 6% at low light intensities have been reported for a bulk-heterojunction system formed from two dif- ferent conjugated polymers: poly[2-methoxy-5-(2-eth- ylhexyloxy)-1,4-phenylene vinylene] as the donor, in composite with cyano (CN) poly-dialkoxy-p-phenyle- nevinylene (PPV) as the acceptor. 29 Initially, solar cells made with blends of PPV derivatives have Journal of Applied Polymer Science, Vol. 113, 1173–1181 (2009) V V C 2009 Wiley Periodicals, Inc. Correspondence to: J. A. Mikroyannidis (mikroyan@ chemistry.upatras.gr) and L. Valentini (mic@unipg.it).