Dispersive Charge Transfer State Electroluminescence in Organic Solar Cells

Raju Lampande, Adrian Pizano, Manting Gui, Robert Cawthorn, Barry P. Rand, Noel C. Giebink

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The notion of quasi-equilibrium is central to most solar cells; however, it has been questioned in organic photovoltaics (OPVs) owing to strong energetic disorder that frustrates efficient relaxation of electrons and holes within their respective density of states (DOS). Here, modulation electroluminescence (EL) spectroscopy is applied to OPVs and it is found that the frequency response of charge transfer (CT) state EL on the high energy side of the spectrum differs from that of the low energy side. This observation confirms that static disorder contributes substantially to the linewidth of the steady-state EL spectrum and is unambiguous proof that the distribution of CT states formed by electrical injection in the dark is not in quasi-equilibrium. These results emphasize the need for caution when analyzing OPV cells on the basis of reciprocity models that assume quasi-equilibrium holds, and highlight a new method to study this unusual aspect of OPV operation.

Original languageEnglish (US)
Article number2300394
JournalAdvanced Energy Materials
Volume13
Issue number24
DOIs
StatePublished - Jun 23 2023

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science

Keywords

  • density of states
  • disorder
  • non-equilibrium
  • organic photovoltaics
  • relaxation

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