AbstractTwo donor–acceptor (D–A) type conjugated copolymers, P1 and P2, are designed and synthesized. A classical benzothiadiazole acceptor is used to replace a thiophene unit in the polymer chain of P1 to obtain P2 terpolymer. Compared with P1, P2 exhibits broader absorption spectra, higher absorption coefficient, deeper lowest unoccupied molecular orbital level, and a relatively lower band gap. As a result, the P2‐based solar cell exhibits a high power conversion efficiency (PCE) of 6.60%, with a short‐circuit current (J _sc) of 12.43 mA cm⁻², and a fill factor (FF) of 73.1%, which are higher than those of the P1‐based device with a PCE of 4.70%, a J _sc of 9.43 mA cm⁻², and an FF of 61.6%.