Four new DTS-BTD copolymers (P1-P4) differing by the concentration of electron-donating and -withdrawing substituents along the backbone have been synthesized and characterized by 2D-WAXS and in bottom-contact FETs. While all copolymers can self-assemble into lamellar superstructures, only P2 and P4 show a propensity to R-stack. P4 exhibits a hole mobility as high as 0.02 cm(2) V-1 s(-1) in excellent agreement with the close pi-stacking and lamellar distances found by structural analysis (0.36 and 1.84 nm, respectively) and absorbs homogenously across the entire visible spectrum as solar cell applications require.