Towards optimisation of photocurrent from fullerene excitons in organic solar cells

Stoichko D. Dimitrov, Zhenggang Huang, Florent Deledalle, Christian B. Nielsen, Bob C. Schroeder, Raja Shahid Ashraf, Safa Shoaee, Iain McCulloch, James R. Durrant*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Photocurrent from fullerene excitons in polymer-fullerene solar cells is optimised by employing a series of low bandgap diketopyrrolopyrrole-containing polymers with differing molecular weights. The low LUMO level of this donor polymer prevents efficient charge generation from polymer excitons, allowing us to focus on charge and photocurrent generation specifically from fullerene excitons. We employ femtosecond transient absorption spectroscopy and transmission electron microscopy to show a correlation between fullerene domain size and the kinetics of polaron generation from fullerene excitons, and relate these observations to device efficiency. Charge generation from fullerene excitons is shown to occur on the 0.5 ns timescale, limited by the kinetics of diffusion of fullerene excitons to domain interfaces with donor polymers. For devices employing the highest molecular weight donor polymer, ∼7 mA cm -2 of photocurrent is observed from fullerene excitons, leading to an overall device efficiency of 5.2%.

Original languageEnglish (US)
Pages (from-to)1037-1043
Number of pages7
JournalEnergy and Environmental Science
Volume7
Issue number3
DOIs
StatePublished - Mar 2014

ASJC Scopus subject areas

  • Environmental Chemistry
  • Renewable Energy, Sustainability and the Environment
  • Nuclear Energy and Engineering
  • Pollution

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