Robust Bipolar Light Emission and Charge Transport in Symmetric Molecular Junctions
Author(s):
Ushula M. Tefashe, Quyen Van Nguyen, Frederic Lafole, Jean-Christophe Lacroix, Richard L. McCreery
Journal:
Journal of the American Chemical Society
Year:
2017
Volume:
139
Pages
7436–7439
DOI:
10.1021/jacs.7b02563
Abstract:
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 solidstate 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.