Two local built-in potentials of H2S processed CZTSSe by complex impedance spectroscopy

Sanghyun Lee, Kent J. Price, Dae Hwan Kim

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


We have fabricated CZTSSe solar cells with H2S sulfo-selenization processes and investigated the electronic structure at the PN hetero- and back contact junctions by impedance spectroscopy. By decoupling each junction's impedance spectroscopic responses, we systematically characterized the built-in potential of two local junction interfaces. A developed equivalent circuit model has been optimized for decoupling each junction's property at different frequency bands. Modeling and numerical simulations were conducted with the in-house MATLAB modeling suites connected to external simulators of Sentaurus TCAD and LEVM/LEVMW software to estimate the impact of each junction component to impedance spectra. The optimized model is comprised of a parallel circuit combination with resistance and capacitor-like elements (constant phase elements), connected to one inductive element. The conversion efficiency of CZTSSe devices is 6.2% with bandgap energy 1.13 eV based on external quantum efficiency measurements. From the equivalent circuit model, the built-in potential of the hetero-junction is characterized as 956 meV, which is ~3% smaller than an ideal case from TCAD, 987 meV. Conversely, the built-in potential of the back contact junction is 476 meV. The apparent built-in potential is estimated as 480 meV from the Mott-Schottky equation.

Original languageEnglish
Pages (from-to)11-18
Number of pages8
JournalSolar Energy
StatePublished - Sep 1 2021

Bibliographical note

Publisher Copyright:
© 2021


  • Back contact junction
  • Built-in potential
  • CZTSSe
  • Hetero-junction
  • Interface
  • Spectroscopy

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science


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