Narrow bandgap and hyperbranched polymers (h-PTDPP) are synthesized by directly arylation polymerization (DAP) of 2-bromo-thiophene-flanked diketopyrrolopyrrole (Br-TDPP) as the monomer. Their optical properties as well as chemical structures are studied. The detailed optimization of DAP conditions from catalyst, temperature, solvent, ligand to additive not only leads to high molecular weight h-PTDPP, but also provides some insight to minimize structural defects in DAP when brominated TDPP is involved as a monomer. The increase in the degree of branching results in lower charge-carrier mobilities in organic field-effect transistors involving h-PTDPP-3 as the semiconducting channel. (C) 2017 Wiley Periodicals, Inc.