Using 9,10-bis(dodecyloxy)phenanthrene as electron-donating unit and 4,7-dithienyl-5,6-bis(dodecyloxy)benzothiadiazole, 4,7-dithienyl-5,6-bis(octyloxy)benzoxadiazole, 5,8-dithienyl-2,3-bis(para-octyloxyphenyl)quinoxaline, and 5,8-dithienyl-2,3-bis(meta-octyloxyphenyl)quinoxaline as electron-accepting unit, four D-A copolymers PPA-DTBT, PPA-DTBX, PPA-p-DTQ, and PPA-m-DTQ, respectively, were successfully synthesized as new polymeric donors for photovoltaic cells. All the alternating copolymers can show two absorption bands, both in solutions and thin films. The optical bandgaps of the polymers are quite close, which are between 1.93 and 2.00 eV. The HOMO and LUMO levels of the polymers are also comparable of -5.52 +/- 0.03 eV and -3.57 +/- 0.03 eV, respectively. Thus, using the dialkoxyphenanthrene as the D unit could afford D-A copolymers with deep-lying HOMO levels, which would be an important factor to achieve high open-circuit voltages (V-oc) in bulk-heterojunction solar cells. With the copolymers as the donor and PC71BM as the acceptor, the resulting solar cells could display good V-oc between 0.86 and 0.88 V. Among the four copolymers, PPA-DTBT containing the dialkoxybenzothiadiazole unit showed the best power conversion efficiency of 3.03% because of its relatively higher hole mobility and better phase separation. The results suggest that dialkoxyphenanthrene is a valuable electron-donating unit in the constructions of D-A copolymers for efficient solar cells with high V-oc. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4966-4974