Compositional Gradients and Electron Flux in Ion-Blocked Multivalent Redox Polymers and Polymer Bilayers:  A Theoretical Consideration

Pichot, François; Bloom, Corey J.; Rider, and Lonn S.; Elliott, C. Michael

doi:10.1021/jp981141e

Cited by 11 publications

(8 citation statements)

References 22 publications

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“…With this statement we would like to distinguish our work from other work that has been published in the field of solid-state mixed-valent systems. 23,[29][30][31][32] In the former articles it is generally assumed that there is local charge neutrality in the bulk of a mixed-valent solidstate device.…”

Section: Discussionmentioning

confidence: 99%

“…22 For the steady state operation of Ru͑II͒ devices, a model has been proposed, which assumes a field free bulk where the charge transport occurs through diffusion. 23 Very recently, the transient current and light response of Ru͑II͒ devices with Ga:In cathodes were modeled. 24 This work follows an electrochemical approach in which the electric field is assumed to drop mainly at the electrode interfaces.…”

Section: Introductionmentioning

confidence: 99%

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Operational mechanism of light-emitting devices based on Ru(II) complexes: Evidence for electrochemical junction formation

Rudmann

Shimada

Rubner

2003

Journal of Applied Physics

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In this work, the operational mechanism of single-layer light-emitting electrochemical cells (LECs) based on the small molecule tris(2,2’ bipyridyl) ruthenium(II) [Ru(II)] was investigated using capacitance and resistance measurements. The current–voltage and capacitance–voltage characteristics of such devices suggest that an electrochemical junction is formed during operation with a high electric field across the junction. A similar mechanism has been proposed for polymer LECs. In the case of Ru(II) devices, electrically conducting regions adjacent to the electrodes are the result of mixed-valent states that form due to oxidation and reduction of the complex. The junction thickness is a function of the type of counterions used and the operating voltage. Thinner junctions were observed for devices with high ionic conductivity and at higher operating voltages. Transient capacitance and resistance measurements show that the junction formation is faster in devices with higher ion mobility and during higher operating voltages. In addition, the capacitance and resistance exhibit a relaxation time after the device is turned off. This relaxation shows that the electrochemical junction stays present in a device for some time (several seconds to minutes) once a device is turned off. The electrochemical junction disappears as the counterions relax back. Furthermore, a theoretical model is presented, which shows that due to the concentration gradient of mixed-valent states during operation, an electric field has to be present in the device. The model also shows that there can be no local charge neutrality in the bulk of the device during operation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Operational mechanism of light-emitting devices based on Ru(II) complexes: Evidence for electrochemical junction formation

Rudmann

Shimada

Rubner

2003

Journal of Applied Physics

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“…al. 47 Upon application of a bias, the negative counterions drift toward the anode (ITO), resulting in a current that decays with time. As these ions accumulate at the anode, they lower the barrier for hole injection.…”

Section: Resultsmentioning

confidence: 99%

“…The device characteristics of OLEDs based on transition metal complexes have been the subject of past publications 10,18-22 and appear to be consistent with the predictions of models developed by deMello et al and Pichot et. al . Upon application of a bias, the negative counterions drift toward the anode (ITO), resulting in a current that decays with time.…”

Section: Resultsmentioning

confidence: 99%

Electroluminescence in Ruthenium(II) Dendrimers

Barron¹,

Bernhard²,

Houston³

et al. 2003

J. Phys. Chem. A

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We have investigated the electroluminescent properties of polyamidoamine dendrimers containing pendant [Ru(bpy) 3 ] +2 chromophores. Devices were made using indium tin oxide (ITO) and gold electrodes, and they were compared to devices made from [Ru(bpy) 3 ]+2 films. The turn-on time, steady-state current, and electroluminescence efficiency were analyzed in order to provide information about the ionic and electronic carrier mobilities and the degree of self-quenching of luminescence in these materials.

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“…In earlier work, we demonstrated this method as a three-electrode technique to separately form the n- and p-type regions of a p–n junction . The method relies on the use of a polyelectrolyte-based supporting electrolyte to control the ions available to support redox processes in solid films. , Herein, we demonstrate the use of PMEC to fabricate polyacetylene-based junctions with systematically varying n-type dopant density and to control the fraction of ionic functional groups that become internally compensated. The resulting p–n junctions are characterized using current–voltage, capacitance–voltage, and spectral response measurements, and these results are compared to ideal p–n junction models.…”

Section: Introductionmentioning

confidence: 99%

Polyacetylene p–n Junctions with Varying Dopant Density by Polyelectrolyte-Mediated Electrochemistry

Robinson

Lonergan

2013

J. Phys. Chem. C

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Polyelectrolyte-mediated electrochemistry is demonstrated as a three-electrode technique to fabricate polyacetylene-based p–n junctions where the dopant density of the n-type layer is systematically varied. The approach utilizes a bilayer structure consisting of anionically and cationically functionalized polyacetylenes and a polyelectrolyte-based supporting electrolyte to control the ions available to support electrochemistry in the selective formation of n- and p-doped regions. Through control over the cationic functional group density and electrode potential, the dopant density of the n-type region is varied from 1019 to 1020 cm–3. Due in part to low carrier mobility and the presence of ionic functional groups, the properties of the junctions are distinct from classic inorganic p–n junctions in that they exhibit neither the voltage-dependent capacitance of a semiconductor depletion layer nor the classic Shockley, diffusion-based current–voltage behavior. Variation of the ionic functional group and dopant density enables the current–voltage curves to be tuned from symmetric to asymmetric with rectification ratios up to 1600 at 1.8 V and with equilibrium exchange current densities varying from 1 × 10–10 to 1 × 10–4 A cm–2. Under illumination, open-circuit voltages near 0.5 V are observed despite the absence of any substantial offset in frontier orbital positions of the constituent materials, as is the common motif in organic photovoltaics.

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Compositional Gradients and Electron Flux in Ion-Blocked Multivalent Redox Polymers and Polymer Bilayers: A Theoretical Consideration

Cited by 11 publications

References 22 publications

Operational mechanism of light-emitting devices based on Ru(II) complexes: Evidence for electrochemical junction formation

Operational mechanism of light-emitting devices based on Ru(II) complexes: Evidence for electrochemical junction formation

Electroluminescence in Ruthenium(II) Dendrimers

Polyacetylene p–n Junctions with Varying Dopant Density by Polyelectrolyte-Mediated Electrochemistry

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