Two donor polymers containing thiophene (T) and thienothiophene (TT) as the electron rich, and diketopyrrolopyrrole (DPP) as the electron poor, moieties were synthesized and utilized in organic photovoltaic (OPV) devices. We appended n-decyl side chains onto the thiophenes directly adjacent to the di-hexyldecyl substituted DPP center core to ensure solubility of the resulting polymers. We observed the impact of active layer morphologies, as determined by grazing-incidence wide angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM), on solar cell characteristics. Compared to devices fabricated with the thiophene-containing polymer P(T-DPP), devices with poly(thienothiophene-alt-diketopyrrolopyrrole), P(TT-DPP), exhibited higher average power conversion efficiency (PCE) of 3.0% and short circuit current (J(sc)) of 10.4 mA/cm(2). This higher performance is attributed to an improved charge transport and extraction as a result of a greater degree of intermixing in P(TT-DPP) and fullerene thin film. (C) 2016 Elsevier Ltd. All rights reserved.