@article{8342,
  author = {F. J. M. Colberts and M. M. Wienk and R. Heuvel and W. W. Li and V. M. le Corre and L. J. A. Koster and R. A. J. Janssen},
  title = {Bilayer-Ternary Polymer Solar Cells Fabricated Using Spontaneous Spreading on Water},
  abstract = {A new method is presented to fabricate bilayer organic solar cells via sequential deposition of bulk‐heterojunction layers obtained using spontaneous spreading of polymer–fullerene blends on a water surface. Using two layers of a small bandgap diketopyrrolopyrrole polymer–fullerene blend, a small improvement in power conversion efficiency (PCE) from 4.9% to 5.1% is obtained compared to spin‐coated devices of similar thickness. Next, bilayer–ternary cells are fabricated by first spin coating a wide bandgap thiophene polymer–fullerene blend, followed by depositing a small bandgap diketopyrrolopyrrole polymer–fullerene layer by transfer from a water surface. These novel bilayer–ternary devices feature a PCE of 5.9%, higher than that of the individual layers. Remarkable, external quantum efficiencies (EQEs) over 100% are measured for the wide bandgap layer under near‐infrared bias light illumination. Drift‐diffusion calculations confirm that near‐infrared bias illumination can result in a significant increase in EQE as a result of a change in the internal electric field in the device, but cannot yet account for the magnitude of the effect. The experimental results indicate that the high EQEs over 100% under bias illumination are related to a barrier for electron transport over the interface between the two blends.},
  year = {2018},
  journal = {Advanced Energy Materials},
  volume = {8},
  pages = {1802197},
  month = {11/2018},
  doi = {10.1002/aenm.201802197},
  language = {eng},
}