@article{bibcite_8261,
  author = {R. Heuvel and J. J. van Franeker and R. A. J. Janssen},
  title = {Energy Level Tuning of Poly(phenylene-alt-dithienobenzothiadiazole)s for Low Photon Energy Loss Solar Cells},
  abstract = {Six poly(phenylene-alt-dithienobenzothiadiazole)-based polymers have been synthesized for application in polymer{\textendash}fullerene solar cells. Hydrogen, fluorine, or nitrile substitution on benzo-thiadiazole and alkoxy or ester substitution on the phenylene moiety are investigated to reduce the energy loss per converted photon. Power conversion efficiencies (PCEs) up to 6.6\% have been obtained. The best performance is found for the polymer{\textendash}fullerene combination with distinct phase separation and crystalline domains. This improves the maximum external quantum efficiency for charge formation and collection to 66\%. The resulting higher photocurrent compensates for the relatively large energy loss per photon (E loss = 0.97 eV) in achieving a high PCE. By contrast, the poly-mer that provides a reduced energy loss (E loss = 0.49 eV) gives a lower photocurrent and a reduced PCE of 1.8\% because the external quantum efficiency of 17\% is limited by a suboptimal morphology and a reduced driving force for charge transfer. (Figure presented.). {\textcopyright} 2017 The Authors. Published by WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim},
  year = {2017},
  journal = {Macromolecular Chemistry and Physics},
  volume = {218},
  pages = {1600502},
  doi = {10.1002/macp.201600502},
  language = {eng},
}