On the reliability of acquiring molecular junction parameters by Lorentzian fitting of I / V curves

Fitting the I / V curves of molecular junctions by simple analytical models is often done to extract relevant molecular parameters such as energy level alignment or interfacial electronic coupling to build up useful property-relationships. However, such models can suffer from severe limitations and...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2020-01, Vol.22 (46), p.26702-26706
Main Authors: Delmas, Vincent, Diez-Cabanes, Valentin, van Dyck, Colin, Scheer, Elke, Costuas, Karine, Cornil, Jérôme
Format: Article
Language:English
Subjects:
Chemical Sciences
Coupling (molecular)
Curve fitting
Energy levels
Mathematical models
Parameters
Resistance
Seebeck effect
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Summary:Fitting the I / V curves of molecular junctions by simple analytical models is often done to extract relevant molecular parameters such as energy level alignment or interfacial electronic coupling to build up useful property-relationships. However, such models can suffer from severe limitations and hence provide unreliable molecular parameters. This is illustrated here by extracting key molecular parameters by fitting computed voltage-dependent transmission spectra and by comparing them to the values obtained by fitting the calculated I / V curves with a typical Lorentzian model used in the literature. Doing so, we observe a large discrepancy between the two sets of values which warns us about the risks of using simple fitting expressions. Interestingly, we demonstrate that the quality of the fit can be improved by imposing the low bias conductance and Seebeck coefficient of the junction to be recovered in the fitting procedure.
ISSN:1463-9076
1463-9084
DOI:10.1039/d0cp05372d