@article{SchubertYinCastellanietal.2009,
  author    = {Schubert, Marcel and Yin, Chunhong and Castellani, Mauro and Bange, Sebastian and Tam, Teck Lip and Sellinger, Alan and Hoerhold, Hans-Heinrich and Kietzke, Thomas and Neher, Dieter},
  title     = {Heterojunction topology versus fill factor correlations in novel hybrid small-molecular/polymeric solar cells},
  issn      = {0021-9606},
  doi       = {10.1063/1.3077007},
  year      = {2009},
  abstract  = {The authors present organic photovoltaic (OPV) devices comprising a small molecule electron acceptor based on 2- vinyl-4,5-dicyanoimidazole (Vinazene (TM)) and a soluble poly(p-phenylenevinylene) derivative as the electron donor. A strong dependence of the fill factor (FF) and the external quantum efficiency [incident photons converted to electrons (IPCE)] on the heterojunction topology is observed. As-prepared blends provided relatively low FF and IPCE values of 26\% and 4.5\%, respectively, which are attributed to significant recombination of geminate pairs and free carriers in a highly intermixed blend morphology. Going to an all-solution processed bilayer device, the FF and IPCE dramatically increased to 43\% and 27\%, respectively. The FF increases further to 57\% in devices comprising thermally deposited Vinazene layers where there is virtually no interpenetration at the donor/acceptor interface. This very high FF is comparable to values reported for OPV using fullerenes as the electron acceptor. Furthermore, the rather low electron affinity of Vinazene compound near 3.5 eV enabled a technologically important open circuit voltage (V-oc) of 1.0 V.},
  language  = {en}
}
@article{InalCastellaniSellingeretal.2009,
  author    = {Inal, Sahika and Castellani, Mauro and Sellinger, Alan and Neher, Dieter},
  title     = {Relationship of photophysical properties and the device performance of novel hybrid small-molecular/polymeric solar cells},
  issn      = {1022-1336},
  doi       = {10.1002/marc.200900221},
  year      = {2009},
  abstract  = {We investigate solar cells comprised of a vinazene derivative (HV-BT) as the electron acceptor and the well- known polymer poly(3-hexylthiophene) as the electron donor. In the as-prepared blend, most of the excited state species, including the excimers on HV-BT, are quenched at the heterojunction. Although the photophysical properties of the blends change upon annealing, the blend solar cells largely remain uninfluenced by such treatments. A significant improvement is, however, observed when inducing phase separation at a longer length scale, for example, in solution-processed bilayer devices. Hereby, both the fill factor (FF) and the open circuit voltage are considerably increased, pointing to the importance of the heterojunction topology and the layer composition at the charge extracting contacts. An optimized device exhibits a power conversion efficiency of close to 1\%.},
  language  = {en}
}