Impedance Spectroscopic Indication for Solid State Electrochemical Reaction in (CH3NH3)PbI3 Films

Arava Zohar, Nir Kedem, Igal Levine, Dorin Zohar, Ayelet Vilan, David Ehre, Gary Hodes, David Cahen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

89 Scopus citations

Abstract

Halide perovskite-based solar cells still have limited reproducibility, stability, and incomplete understanding of how they work. We track electronic processes in [CH3NH3]PbI3(Cl) ("perovskite") films in vacuo, and in N2, air, and O2, using impedance spectroscopy (IS), contact potential difference, and surface photovoltage measurements, providing direct evidence for perovskite sensitivity to the ambient environment. Two major characteristics of the perovskite IS response change with ambient environment, viz. -1- appearance of negative capacitance in vacuo or post-vacuo N2 exposure, indicating for the first time an electrochemical process in the perovskite, and -2- orders of magnitude decrease in the film resistance upon transferring the film from O2-rich ambient atmosphere to vacuum. The same change in ambient conditions also results in a 0.5 V decrease in the material work function. We suggest that facile adsorption of oxygen onto the film dedopes it from n-type toward intrinsic. These effects influence any material characterization, i.e., results may be ambient-dependent due to changes in the material's electrical properties and electrochemical reactivity, which can also affect material stability.

Original languageEnglish
Pages (from-to)191-197
Number of pages7
JournalJournal of Physical Chemistry Letters
Volume7
Issue number1
DOIs
StatePublished - 7 Jan 2016
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015 American Chemical Society.

Keywords

  • contact potential difference
  • halide perovskite solar cells
  • impedance spectroscopy
  • surface photovoltage

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