We studied three different benzothiadiazole-triphenylamine (BTD-TPA) derivatives as donor materials for bulk-heterojunction organic photovoltaics (OPVs), and investigated the resulting OPV performance. We found that the increased concentration of (6,6)-phenyl C61 butyric acid methyl ester (PCBM) as acceptor material and the decreased thickness of active layers led to high-performance OPVs with sufficient percolated pathways for the photogenerated mobile carriers to the respective electrodes. The highest performance was observed for OPVs based on BTD-Th-TPA:PCBM (1:2, w/w) with thickness of 76 nm, yielding a power-conversion efficiency of 1.0% under 100 mW/cm² of AM 1.5 illumination and incident photon conversion efficiency of 32% at a wavelength of 540 nm.