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Photoelectrochemical and Electrochemical Characterization of Sub-Micro-Gram Amounts of Organic Semiconductors Using Scanning Droplet Cell Microscopy.

Kollender JP, Gasiorowski J, Sariciftci NS, Mardare AI, Hassel AW - J Phys Chem C Nanomater Interfaces (2014)

Bottom Line: The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte.A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell.The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemical Technology of Inorganic Materials, Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, and Christian Doppler Laboratory for Combinatorial Oxide Chemistry at the Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz , Altenberger Str. 69, 4040 Linz, Austria.

ABSTRACT
A model organic semiconductor (MDMO-PPV) was used for testing a modified version of a photoelectrochemical scanning droplet cell microscope (PE-SDCM) adapted for use with nonaqueous electrolytes and containing an optical fiber for localized illumination. The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte. A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell. The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy. Additionally, the photoelectrochemical properties were investigated under illumination conditions, and the photocurrents found were at least 3 orders of magnitude higher than the dark (background) current, revealing the usefulness of this compact microcell for photovoltaic characterizations.

No MeSH data available.


Related in: MedlinePlus

Impedance spectra measured on MDMO-PPVat different applied potentials.
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fig7: Impedance spectra measured on MDMO-PPVat different applied potentials.

Mentions: In an attempt to study the electrical properties of the MDMO-PPV/electrolytesystem, electrochemical impedance spectroscopy was performed usingthe PE-SDCM. Usually, conjugated polymers in their undoped form haveinsulating properties. Upon doping, their electrical properties canchange drastically. Generally, at low doping levels they are consideredas semiconductors. With increasing the doping level, their electricalresistance further decreases and they can show metal-like behavior.During the EIS study shown here, the frequency dependent changes ofthe impedance are monitored as a function of the applied DC bias (offset).Before each EIS experiment, a potentiostatic pretreatment was performedfor 70 s in order to equilibrate the electrochemical processes.The used equilibration time of 70 s was chosen in agreement to theprevious potentiostatic experiments, which showed a current densitystabilization after this time interval (see Figure 5). All impedance spectra were recorded at a single addressedspot using sequentially increasing biases up to 1.4 V. After eachspectrum, the bias was increased by 0.2 V and the frequency dependenceof the impedance was determined again. In Figure 7, the corresponding Bode plots are shown in part (a) togetherwith the associated phase shifts in part (b). As can be noticed, forbiases below 0.6 V, there is no change in the shape and value of theimpedance. In this bias range, the high frequency impedance suggestsan electrolyte resistance of approximately 105 Ω.Similarly, the impedance value observable at the lowest frequencyindicates a working electrode resistance in the order of 108 Ω. Starting with the applied bias of 0.6 V, a deviation ofboth the impedance and phase shift at low frequencies appears. Thisdecrease is related to the oxidation of MDMO-PPV, resulting in anexpected insulator-to-metal transition.11 This decrease is continuing up to a bias of 1 V, where the workingelectrode impedance decreases by almost 2 orders of magnitude. Inthe same time, the phase shift changes substantially, finally reachinga value under −25°, observable at the middle of the investigatedfrequency range. At even higher applied potentials, an unexpectedincrease in the impedance can be observed. This effect can be relatedto dissolution of the oxidized MDMO-PPV layer, resulting in a changein the working electrode geometry.


Photoelectrochemical and Electrochemical Characterization of Sub-Micro-Gram Amounts of Organic Semiconductors Using Scanning Droplet Cell Microscopy.

Kollender JP, Gasiorowski J, Sariciftci NS, Mardare AI, Hassel AW - J Phys Chem C Nanomater Interfaces (2014)

Impedance spectra measured on MDMO-PPVat different applied potentials.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4120669&req=5

fig7: Impedance spectra measured on MDMO-PPVat different applied potentials.
Mentions: In an attempt to study the electrical properties of the MDMO-PPV/electrolytesystem, electrochemical impedance spectroscopy was performed usingthe PE-SDCM. Usually, conjugated polymers in their undoped form haveinsulating properties. Upon doping, their electrical properties canchange drastically. Generally, at low doping levels they are consideredas semiconductors. With increasing the doping level, their electricalresistance further decreases and they can show metal-like behavior.During the EIS study shown here, the frequency dependent changes ofthe impedance are monitored as a function of the applied DC bias (offset).Before each EIS experiment, a potentiostatic pretreatment was performedfor 70 s in order to equilibrate the electrochemical processes.The used equilibration time of 70 s was chosen in agreement to theprevious potentiostatic experiments, which showed a current densitystabilization after this time interval (see Figure 5). All impedance spectra were recorded at a single addressedspot using sequentially increasing biases up to 1.4 V. After eachspectrum, the bias was increased by 0.2 V and the frequency dependenceof the impedance was determined again. In Figure 7, the corresponding Bode plots are shown in part (a) togetherwith the associated phase shifts in part (b). As can be noticed, forbiases below 0.6 V, there is no change in the shape and value of theimpedance. In this bias range, the high frequency impedance suggestsan electrolyte resistance of approximately 105 Ω.Similarly, the impedance value observable at the lowest frequencyindicates a working electrode resistance in the order of 108 Ω. Starting with the applied bias of 0.6 V, a deviation ofboth the impedance and phase shift at low frequencies appears. Thisdecrease is related to the oxidation of MDMO-PPV, resulting in anexpected insulator-to-metal transition.11 This decrease is continuing up to a bias of 1 V, where the workingelectrode impedance decreases by almost 2 orders of magnitude. Inthe same time, the phase shift changes substantially, finally reachinga value under −25°, observable at the middle of the investigatedfrequency range. At even higher applied potentials, an unexpectedincrease in the impedance can be observed. This effect can be relatedto dissolution of the oxidized MDMO-PPV layer, resulting in a changein the working electrode geometry.

Bottom Line: The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte.A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell.The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemical Technology of Inorganic Materials, Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, and Christian Doppler Laboratory for Combinatorial Oxide Chemistry at the Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz , Altenberger Str. 69, 4040 Linz, Austria.

ABSTRACT
A model organic semiconductor (MDMO-PPV) was used for testing a modified version of a photoelectrochemical scanning droplet cell microscope (PE-SDCM) adapted for use with nonaqueous electrolytes and containing an optical fiber for localized illumination. The most attractive features of the PE-SDCM are represented by the possibility of addressing small areas on the investigated substrate and the need of small amounts of electrolyte. A very small amount (ng) of the material under study is sufficient for a complete electrochemical and photoelectrochemical characterization due to the scanning capability of the cell. The electrochemical behavior of the polymer was studied in detail using potentiostatic and potentiodynamic investigations as well as electrochemical impedance spectroscopy. Additionally, the photoelectrochemical properties were investigated under illumination conditions, and the photocurrents found were at least 3 orders of magnitude higher than the dark (background) current, revealing the usefulness of this compact microcell for photovoltaic characterizations.

No MeSH data available.


Related in: MedlinePlus