Spectral Signatures of a Negative Polaron in a Doped Polymer Semiconductor: Energy Levels and Hubbard U Interactions

Dominique Lungwitz, Syed Joy, Ahmed E. Mansour, Andreas Opitz, Chamikara Karunasena, Hong Li, Naitik A. Panjwani, Karttikay Moudgil, Kan Tang, Jan Behrends, Stephen Barlow, Seth R. Marder, Jean Luc Brédas, Kenneth Graham, Norbert Koch, Antoine Kahn

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The modern picture of negative charge carriers on conjugated polymers invokes the formation of a singly occupied (spin-up/spin-down) level within the polymer gap and a corresponding unoccupied level above the polymer conduction band edge. The energy splitting between these sublevels is related to on-site Coulomb interactions between electrons, commonly termed Hubbard U. However, spectral evidence for both sublevels and experimental access to the U value is still missing. Here, we provide evidence by n-doping the polymer P(NDI2OD-T2) with [RhCp*Cp]2, [N-DMBI]2, and cesium. Changes in the electronic structure after doping are studied with ultraviolet photoelectron and low-energy inverse photoemission spectroscopies (UPS, LEIPES). UPS data show an additional density of states (DOS) in the former empty polymer gap while LEIPES data show an additional DOS above the conduction band edge. These DOS are assigned to the singly occupied and unoccupied sublevels, allowing determination of a U value of ∼1 eV.

Original languageEnglish
Pages (from-to)5633-5640
Number of pages8
JournalJournal of Physical Chemistry Letters
Issue number24
StatePublished - Jun 22 2023

Bibliographical note

Publisher Copyright:
© 2023 American Chemical Society.

ASJC Scopus subject areas

  • General Materials Science
  • Physical and Theoretical Chemistry


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