Bilayer–ternary polymer solar cells fabricated using spontaneous spreading on water

Fallon J.M. Colberts, Martijn M. Wienk, Ruurd Heuvel, Weiwei Li, Vincent M. Le Corre, L. Jan Anton Koster, René A.J. Janssen

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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.

Original languageEnglish
Article number1802197
Number of pages12
JournalAdvanced Energy Materials
Issue number32
Publication statusPublished - 15 Nov 2018


  • bilayer–ternary solar cells
  • polymer solar cells
  • sequential deposition
  • spontaneous spreading
  • bilayer-ternary solar cells


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