Robust Bipolar Light Emission and Charge Transport in Symmetric Molecular Junctions

Molecular junctions consisting of a Ru­(bpy)3 oligomer between conducting carbon contacts exhibit an exponential dependence of junction current on molecular layer thickness (d) similar to that observed for other aromatic devices when d < 4 nm. However, when d > 4 nm, a change in transport mech...

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Published inJournal of the American Chemical Society Vol. 139; no. 22; pp. 7436 - 7439
Main Authors Tefashe, Ushula M, Nguyen, Quyen Van, Lafolet, Frederic, Lacroix, Jean-Christophe, McCreery, Richard L
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 07.06.2017
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Summary:Molecular junctions consisting of a Ru­(bpy)3 oligomer between conducting carbon contacts exhibit an exponential dependence of junction current on molecular layer thickness (d) similar to that observed for other aromatic devices when d < 4 nm. However, when d > 4 nm, a change in transport mechanism occurs which coincides with light emission in the range of 600–900 nm. Unlike light emission from electrochemical cells or solid-state films containing Ru­(bpy)3, emission is bipolar, occurs in vacuum, has rapid rise time (<5 ms), and persists for >10 h. Light emission directly indicates simultaneous hole and electron injection and transport, possibly resonant due to the high electric field present (>3 MV/cm). Transport differs fundamentally from previous tunneling and hopping mechanisms and is a clear “molecular signature” relating molecular structure to electronic behavior.
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ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.7b02563