Two p-type polymers, PONDPP and PTADPP were synthesized by Suzuki coupling reaction to investigate the effect of alkoxy aromatic donor units in diketopyrrolopyrrole (DPP)-based copolymers on OTFTs and OPVs. PONDPP containing dialkoxynaphthalene exhibits excellent field-effect performances, with a hole mobility of 0.324 cm(2)/V while PTADPP containing dialkoxyanthracene exhibits mobility of 4.5 x 10(-3) cm(2)/V at 200 degrees C annealing. Bulk heterojunction type polymer solar cells based on these polymers as the electron donor materials, with PC71BM as the acceptor, showed maximum power conversion efficiency (PCE) of 0.9% for PONDPP and 1.1% for PTADPP under AM 1.5 illumination. From photophysical and structural studies, we found that naphthalene unit was introduced to the DPP unit to enhance more the molecular ordering compared to anthracene unit. (C) 2014 Elsevier B.V. All rights reserved.