Correlation between the Open-Circuit Voltage and Charge Transfer State Energy in Organic Photovoltaic Cells

Yunlong Zou, Russell J. Holmes

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

In order to further improve the performance of organic photovoltaic cells (OPVs), it is essential to better understand the factors that limit the open-circuit voltage (VOC). Previous work has sought to correlate the value of VOC in donor-acceptor (D-A) OPVs to the interface energy level offset (EDA). In this work, measurements of electroluminescence are used to extract the charge transfer (CT) state energy for multiple small molecule D-A pairings. The CT state as measured from electroluminescence is found to show better correlation to the maximum VOC than EDA. The difference between EDA and the CT state energy is attributed to the Coulombic binding energy of the CT state. This correlation is demonstrated explicitly by inserting an insulating spacer layer between the donor and acceptor materials, reducing the binding energy of the CT state and increasing the measured VOC. These results demonstrate a direct correlation between maximum VOC and CT state energy. (Figure Presented).

Original languageEnglish (US)
Pages (from-to)18306-18311
Number of pages6
JournalACS Applied Materials and Interfaces
Volume7
Issue number33
DOIs
StatePublished - Aug 26 2015

Keywords

  • charge transfer state
  • electroluminescence
  • heterojunction
  • open-circuit voltage
  • organic photovoltaic cells

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