In this paper, we report the design, synthesis and semiconducting behavior of two conjugated D-A polymers P-BPDTT and P-BPDBT which entail BPD, a Pechmann dye framework, as electron accepting moieties, and thieno[3,2-b]thiophene and 2,2'-bithiophene as electron donating moieties. Their HOMO/LUMO energies and bandgaps were estimated based on the respective cyclic voltammgrams and absorption spectra of thin films. P-BPDTT possesses lower LUMO level and narrower bandgap than P-BPDBT. On the basis of the characterization of the field-effect transistors, a thin film of P-BPDTT exhibits ambipolar semiconducting properties with hole and electron mobilities reaching 1.24 cm(2) V-1 s(-1) and 0.82 cm(2) V-1 s(-1), respectively, after thermal annealing. In comparison, thin film of P-BPDBT only shows p-type semiconducting behavior with hole mobility up to 1.37 cm(2) V-1 s(-1). AFM and XRD studies were presented to understand the interchain arrangements on the substrates and the variation of carrier mobilities.