Discerning the Impact of a Lithium Salt Additive in Thin-Film Light-Emitting Electrochemical Cells with Electrochemical Impedance Spectroscopy.
Light-emitting electrochemical cells (LEECs) from small molecules, such as iridium complexes, have great potential as low-cost emissive devices. In these devices, ions rearrange during operation to facilitate carrier injection, bringing about efficient operation from simple, single-layer devices. Prior work has shown that the luminance, efficiency, and responsiveness of iridium LEECs is greatly enhanced by the inclusion of small fractions of lithium salts, but much remains to be understood about the origin of this enhancement. Recent work with planar devices demonstrates that lithium additives in iridium LEECs enhance double-layer formation. However, the quantitative influence of lithium salts on the underlying physics of conventional thin-film, sandwich structure LEECs, which beneficially operate at low voltages and generate higher luminance, has yet to be clarified. Here, we use electrochemical impedance spectroscopy to discern the impact of the lithium salt concentration on double-layer formation within the device and draw correlations with performance metrics, such as current, luminance, and external quantum efficiency.
Department of Physics, The University of Texas at Dallas , 800 West Campbell Road, PHY 36, Richardson, Texas 75080-3021, United States.
Lyndon D
LD
Bastatas
Department of Physics, The University of Texas at Dallas , 800 West Campbell Road, PHY 36, Richardson, Texas 75080-3021, United States.
Kuo-Yao
KY
Lin
Department of Chemistry, The University of Texas at Austin , 105 East 24th Street, Austin, Texas 78712-0165, United States.
Matthew D
MD
Moore
Department of Chemistry, The University of Texas at Austin , 105 East 24th Street, Austin, Texas 78712-0165, United States.
Kristin J
KJ
Suhr
Department of Physics, The University of Texas at Dallas , 800 West Campbell Road, PHY 36, Richardson, Texas 75080-3021, United States.
Melanie H
MH
Bowler
Department of Physics, The University of Texas at Dallas , 800 West Campbell Road, PHY 36, Richardson, Texas 75080-3021, United States.
Yulong
Y
Shen
Department of Chemistry, The University of Texas at Austin , 105 East 24th Street, Austin, Texas 78712-0165, United States.
Bradley J
BJ
Holliday
Department of Physics, The University of Texas at Dallas , 800 West Campbell Road, PHY 36, Richardson, Texas 75080-3021, United States.
Jason D
JD
Slinker