Reassessing the use of one-electron energetics in the design and characterization of organic photovoltaics

Brett M. Savoie, Nicholas E. Jackson, Tobin J Marks, Mark A Ratner

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

We present results showing that common approximations employed in the design and characterization of organic photovoltaic (OPV) materials can lead to significant errors in widely adopted design rules. First, we assess the validity of the common practice of using HOMO and LUMO energies in place of formal redox potentials to characterize organic semiconductors. We trace the formal justification for this practice and survey its limits in a way that should be useful for those entering the field. We find that while the HOMO and LUMO energies represent useful descriptive approximations, they are too quantitatively inaccurate for predictive material design. Second, we show that the excitonic nature of common organic semiconductors makes it paramount to distinguish between the optical and electronic bandgaps for materials design. Our analysis shows that the usefulness of the "LUMO-LUMO Offset" as a design parameter for exciton dissociation is directly tied to the accuracy of the one-electron approximation. In particular, our results suggest that the use of the "LUMO-LUMO Offset" as a measure of the driving force for exciton dissociation leads to a systematic overestimation that should be cautiously avoided.

Original languageEnglish
Pages (from-to)4538-4547
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume15
Issue number13
DOIs
Publication statusPublished - Apr 7 2013

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Electrons
Semiconducting organic compounds
organic semiconductors
electrons
approximation
excitons
dissociation
Energy gap
energy
electronics
LDS 751
Oxidation-Reduction

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Physics and Astronomy(all)

Cite this

Reassessing the use of one-electron energetics in the design and characterization of organic photovoltaics. / Savoie, Brett M.; Jackson, Nicholas E.; Marks, Tobin J; Ratner, Mark A.

In: Physical Chemistry Chemical Physics, Vol. 15, No. 13, 07.04.2013, p. 4538-4547.

Research output: Contribution to journalArticle

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AB - We present results showing that common approximations employed in the design and characterization of organic photovoltaic (OPV) materials can lead to significant errors in widely adopted design rules. First, we assess the validity of the common practice of using HOMO and LUMO energies in place of formal redox potentials to characterize organic semiconductors. We trace the formal justification for this practice and survey its limits in a way that should be useful for those entering the field. We find that while the HOMO and LUMO energies represent useful descriptive approximations, they are too quantitatively inaccurate for predictive material design. Second, we show that the excitonic nature of common organic semiconductors makes it paramount to distinguish between the optical and electronic bandgaps for materials design. Our analysis shows that the usefulness of the "LUMO-LUMO Offset" as a design parameter for exciton dissociation is directly tied to the accuracy of the one-electron approximation. In particular, our results suggest that the use of the "LUMO-LUMO Offset" as a measure of the driving force for exciton dissociation leads to a systematic overestimation that should be cautiously avoided.

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