We　report　on　the　synthesis　and　characterization　of　a　series　of　donor-acceptor　copolymers　(PF1,　PF2,　PF3　or　PF4)　based　on　a　dinaphtho-s-indacene　(DNI)　donor　unit　and　four　different　acceptor　units.　The　molecular　weights　of　the　copolymers　were　determined　by　using　gel　permeation　chromatography,　and　their　electrochemical　properties　were　investigated　by　cyclic　voltammetry.　All　four　copolymers　showed　deep-lying　highest　occupied　molecular　orbital　energy　levels.　Inverted　bulk　heterojunction　solar　cells　were　fabricated　by　using　the　synthesized　copolymers　as　the　electron　donor　material　and　6,6-phenyl-C71-butyric　acid　methyl　ester　(PC71BM)　as　the　electron　acceptor　material.　Inverted　solar　cells　based　on　PF1:PC71BM　(1:4,　w/w)　exhibited　a　power　conversion　efficiency　(PCE)　of　3.07%,　a　high　open-circuit　voltage　(V　oc)　of　0.99　V,　a　short-circuit　current　density　(Jsc)　of　7.85　mA/cm2,　and　a　fill　factor　of　39.5%　under　the　AM1.5G　illumination.　With　the　same　fabrication　method,　the　inverted　devices　based　on　PF2,　PF3　and　PF4　showed　PCEs　of　2.62,　1.18　and　1.32%,　and　Voc　values　of　0.97,　0.91　and　0.80　V,　respectively.　©　2014　Elsevier　Ltd.　All　rights　reserved.