Mapping the electronic structure of polypyrrole with image-based electrochemical scanning tunnelling spectroscopy

Roger Goncalves, Robert S. Paiva, Andrés M. R. Ramírez, Jonathan Mwanda, Ernesto C. Pereira, Angel Cuesta Ciscar* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Conducting polymers are semiconductors whose applications cover a wide range of devices. Their versatility is due, in addition to other factors, to properties that can be easily modulated according to the intended application. It is therefore important to study and map the electronic structure of these materials for a better correlation between structure and properties. Electrochemical scanning tunnelling spectroscopy (EC-STS) can be a powerful tool to characterize the electronic structure of the semiconductor interface. In this work we have used image-based EC-STS (IB-EC-STS) to describe quantitatively the band structure of an electrochemically deposited polypyrrole film. IB-EC-STS located the band edge of the polymer’s valence band (VB) at 0.95 V vs. RHE (-5.33 eV in the absolute potential scale) and the intragap polaron states formed when the polymer is doped, at 0.46 V vs. RHE (-4.84 eV). The IB-EC-STS data were cross checked with electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis of the interfacial capacitance. The DOS spectrum obtained from EIS data is consistent with the STS-deduced location of the VB and the polarons.
Original languageEnglish
JournalElectrochemical Science Advances
Publication statusAccepted/In press - 25 Mar 2021

Keywords

  • polypyrrole
  • electronic structure
  • electrochemical scanning tunnelling microscopy
  • impedance spectroscopy

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