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Title: The dynamic behavior of thin-film ionic transition metal complex-based light-emitting electrochemical cells

Light-emitting electrochemical cells (LECs) have received increasing attention during recent years due to their simple architecture, based on solely air-stabile materials, and ease of manufacture in ambient atmosphere, using solution-based technologies. The LEC's active layer offers semiconducting, luminescent as well as ionic functionality resulting in device physical processes fundamentally different as compared with organic light-emitting diodes. During operation, electrical double layers (EDLs) form at the electrode interfaces as a consequence of ion accumulation and electrochemical doping sets in leading to the in situ development of a light-emitting p-i-n junction. In this paper, we comment on the use of impedance spectroscopy in combination with complex nonlinear squares fitting to derive key information about the latter events in thin-film ionic transition metal complex-based light-emitting electrochemical cells based on the model compound bis-2-phenylpyridine 6-phenyl-2,2´-bipyridine iridium(III) hexafluoridophosphate ([Ir(ppy)₂(pbpy)][PF₆]). At operating voltages below the bandgap potential of the ionic complex used, we obtain the dielectric constant of the active layer, the conductivity of mobile ions, the transference numbers of electrons and ions, and the thickness of the EDLs, whereas the transient thickness of the p-i-n junction is determined at voltages above the bandgap potential. Most importantly, we find that charge transport is dominated by themore » ions when carrier injection from the electrodes is prohibited, that ion movement is limited by the presence of transverse internal interfaces and that the width of the intrinsic region constitutes almost 60% of the total active layer thickness in steady state at a low operating voltage.« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [1]
  1. Department of Materials Science VI: Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91058 Erlangen (Germany)
  2. (Germany)
  3. Siemens AG, Corporate Technology, CT RTC MAT IEC-DE, 91058 Erlangen (Germany)
Publication Date:
OSTI Identifier:
22305969
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 10; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CARRIERS; ELECTRIC CONTACTS; ELECTRIC POTENTIAL; ELECTROCHEMICAL CELLS; ELECTROCHEMISTRY; IMPEDANCE; INJECTION; INTERFACES; LIGHT EMITTING DIODES; LUMINESCENCE; OPERATION; PERMITTIVITY; SEMICONDUCTOR JUNCTIONS; SPECTROSCOPY; STEADY-STATE CONDITIONS; THICKNESS; THIN FILMS; TRANSIENTS; VISIBLE RADIATION