Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors

Journal Article · Mon Oct 06 00:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4898068· OSTI ID:22350854

Gmucová, K. ^[1]; Schauer, F. ^[2]

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1. Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia)
2. Faculty of Education, Trnava University in Trnava, 918 43 Trnava (Slovakia)

We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bond defect states induced by ultraviolet treatment above the highest occupied molecular orbital in a prototypical σ-conjugated polymer, poly[methyl(phenyl)silylene]. The results agree well with those of our previous DOS reconstruction by post-transient space-charge-limited-current spectroscopy, which was, however, limited to a narrow energy range. In addition, good agreement of the DOS values measured on two common π-conjugated organic polymer semiconductors, polyphenylene vinylene and poly(3-hexylthiophene), with the rather rare previously published data demonstrate the accuracy of the proposed method.

• OSTI ID: 22350854
• Journal Information: Applied Physics Letters, Vol. 105, Issue 14; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACCURACY
CRYSTAL DEFECTS
CURRENTS
DENSITY
ELECTRIC POTENTIAL
ELECTROCHEMISTRY
ELECTROLYTES
ELECTRONIC STRUCTURE
IMPEDANCE
INTERFACES
MOLECULAR ORBITAL METHOD
ORGANIC POLYMERS
ORGANIC SEMICONDUCTORS
REDOX REACTIONS
SPACE CHARGE
SPECTROSCOPY
TRANSIENTS
ULTRAVIOLET RADIATION