Bias-Polarity-Dependent Direct and Inverted Marcus Charge Transport Affecting Rectification in a Redox-Active Molecular Junction

Yingmei Han, Cameron Nickle, Maria Serena Maglione, Senthil Kumar Karuppannan, Javier Casado-Montenegro, Dong Chen Qi, Xiaoping Chen, Anton Tadich, Bruce Cowie, Marta Mas-Torrent, Concepció Rovira, Jérôme Cornil, Jaume Veciana, Enrique del Barco, Christian A. Nijhuis*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

4 Citations (Scopus)
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Abstract

This paper describes the transition from the normal to inverted Marcus region in solid-state tunnel junctions consisting of self-assembled monolayers of benzotetrathiafulvalene (BTTF), and how this transition determines the performance of a molecular diode. Temperature-dependent normalized differential conductance analyses indicate the participation of the HOMO (highest occupied molecular orbital) at large negative bias, which follows typical thermally activated hopping behavior associated with the normal Marcus regime. In contrast, hopping involving the HOMO dominates the mechanism of charge transport at positive bias, yet it is nearly activationless indicating the junction operates in the inverted Marcus region. Thus, within the same junction it is possible to switch between Marcus and inverted Marcus regimes by changing the bias polarity. Consequently, the current only decreases with decreasing temperature at negative bias when hopping is “frozen out,” but not at positive bias resulting in a 30-fold increase in the molecular rectification efficiency. These results indicate that the charge transport in the inverted Marcus region is readily accessible in junctions with redox molecules in the weak coupling regime and control over different hopping regimes can be used to improve junction performance.

Original languageEnglish
Article number2100055
JournalAdvanced science
Volume8
Issue number14
DOIs
Publication statusPublished - 21 Jul 2021

Keywords

  • charge transport
  • inverted Marcus region
  • molecular diodes
  • molecular tunnel junctions
  • self-assembly
  • UT-Gold-D

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