The synthesis, characterization, and photovoltaic properties of a series of four conjugated polymers containing 2-aryl-2H-benzotriazoles and "bis(thiopheno)dialkylfluorenes" is described. The polymers were obtained via Suzuki-polycondensation and comprise alternating electron rich and electron poor building blocks. The impact of systematic structural changes on the electronic and morphological properties and device efficiencies were studied. Application of these polymers as light-harvesting and electron-donating materials in organic solar cells using PCBM derivatives as electron accepting materials resulted in power conversion efficiencies up to 1.8%. Both the properties of the pristine polymers and the device performance show that the impact of the substitution farther-off the backbone is negligible while substitution directly on the backbone has a major impact. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 5001-5011, 2011