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

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

Research output: Contribution to journalArticlepeer-review

4 Scopus Citations

Abstract

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 languageAmerican English
Pages (from-to)5633-5640
Number of pages8
JournalJournal of Physical Chemistry Letters
Volume14
Issue number24
DOIs
StatePublished - 2023

NREL Publication Number

  • NREL/JA-5900-86070

Keywords

  • conjugated polymers
  • n-doping
  • on-site Coulomb interaction
  • photoelectron spectroscopy
  • polarons

Fingerprint

Dive into the research topics of 'Spectral Signatures of a Negative Polaron in a Doped Polymer Semiconductor: Energy Levels and Hubbard U Interactions'. Together they form a unique fingerprint.

Cite this