The syntheses, properties, and optoelectronic device characteristics of four new 3,6-carbazole-based donor/acceptor conjugated copolymers are reported. Such copolymers are used to explore the effects of acceptor strength and backbone coplanarity on the electronic and optoelectronic properties. The optical bandgaps of the studied copolymers are PCzQ (2.29 eV) > PCzDTQ (1.91 eV) > PCzTP (1.75 eV) > PCzDTTP (1.49 eV), which are much smaller than the parent poly(3,6-carbazole). The power conversion efficiency of the photovoltaic cells fabricated from blends of copolymer/PC61BM or PC71BM reached 1.01 and 1.73% by varying the film thickness or blend ratio. The experimental results suggest the potential application of 3,6-carbazole acceptor conjugated copolymers in optoelectronic devices.