Advanced Materials

Energy Level Alignment and Sub-Bandgap Charge Generation in Polymer:Fullerene Bulk Heterojunction Solar Cells

Authors

  • Sai-Wing Tsang,

    1. Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32611, USA
    Current affiliation:
    1. These authors contributed equally to this paper.
    Search for more papers by this author
  • Song Chen,

    1. Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32611, USA
    Current affiliation:
    1. These authors contributed equally to this paper.
    Search for more papers by this author
  • Franky So

    Corresponding author
    1. Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32611, USA
    • Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32611, USA.
    Search for more papers by this author

Abstract

Using charge modulated electroabsorption spectroscopy (CMEAS), for the first time, the energy level alignment of a polymer:fullerene bulk heterojunction photovoltaic cell is directly measured. The charge-transfer excitons generated by the sub-bandgap optical pumping are coupled with the modulating electric field and introduce subtle changes in optical absorption in the sub-bandgap region. This minimum required energy for sub-bandgap charge genreation is defined as the effective bandgap.

original image

Ancillary