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A series of alternating donor–acceptor (D-A) conjugated copolymers PCO-PDI (P1), PCEH-PDI (P2),and PCD-PDI (P3) have been successfully designed and synthesized. Carbazole was used as the donor unit and perylene diimide was used as the acceptor unit. All the copolymers exhibited excellent solubility in common solvents. The decomposition temperatures of copolymers were around 365 °C (P1), 305 °C (P2), and 250 °C (P3) respectively in the air which was adequate for their applications in polymer solar cells (PSCs) and other optoelectronic devices. All the three copolymers showed broad absorption bands, giving optical band gaps of 1.63 e V (P1), 1.65 eV (P2) and 1.68 eV (P3) respectively which matched the value (1.5-1.7 eV) of the ideal polymers for PCE values exceeding 10%. In addition, the lowest occupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels of copolymers were -5.44 eV and -3.81 eV for P1, -5.47 eV and -3.82 eV for P2, -5.42 eV and -3.74 eV for P3 respectively. These great properties of copolymers could make them become alternative materials for PSCs applications.