ABSTRACTConjugated polymers are highly desirable for the photovoltaic applications. We report the synthesis, characterization, optoelectronic properties, and solar cell application of two polymers, namely, poly[(9,9‐didodecylfluorene‐2,7‐diyl)‐alt‐(2,2′:5′,2″‐terthiophene‐5,5″‐diyl)] (P1) and poly[(1,4‐bis(dodecyloxy)benzene‐2,5‐diyl)‐alt‐(2,2′:5′,2″‐terthiophene‐5,5″‐diyl)] (P2). The polymers were synthesized via Stille cross‐coupling reaction, and were characterized by the gel permeation chromatography, nuclear magnetic resonance, Fourier transform infrared, UV–vis, thermogravimetric analysis, and cyclic voltammetry analyses. The two copolymers are processable due to their good solubility in organic solvents (tetrahydrofuran, CHCl3, toluene, chlorobenzene, and o‐dichlorobenzene). The optical band gaps (UV–vis, film, and Egopt) of the P1 and P2 are 2.04 and 2.00 eV, respectively. The density functional theory output structures showed that S…O space interaction is likely responsible for the higher planarity of P2. The polymers showed low HOMO energy levels (P1: −5.33 eV, P2: −5.05 eV). The EHOMO for P1 is close to the EHOMO (−5.4 eV) of an ideal polymer, which is an important, rare, and main origin of the observed higher Voc (801–808 mV). The onset decomposition temperatures (Td) for the P1 and P2 are 418°C and 365°C, respectively. The polymer solar cell based on the P1: C60 (1: 1) and P2: C60 (1: 1) blend showed a power conversion efficiency (PCE) of 0.94 and 0.71%, respectively. The composite polymer : PC60BM = 1 : 2 increased PCE of the P1 (1.65%) and P2 (1.09%) under AM 1.5 illumination (100 mW/cm2). The study provided important examples to design donor–donor (D–D) polymers for the photovoltaic applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42147.