Electrical Potential Investigation of Reversible Metastability and Irreversible Degradation of CdTe Solar Cells

Chun-Sheng Jiang, David Albin, Marco Nardone, K. Howard, A. Danielson, A. Munshi, T. Shimpi, Chuanxiao Xiao, Helio Moutinho, Mowafak Al-Jassim, Glenn Teeter, W. Sampath

Research output: Contribution to journalArticlepeer-review

7 Scopus Citations

Abstract

In this paper, we report on the stability of CdTe devices with a structure of TCO/MZO/CdSeTe/CdTe/back-contact. The device showed reversible transitions between the light-soak state (LSS) with the best device efficiency and the dark-soak state (DSS) with an inferior efficiency. However, it showed an irreversible degradation state (DgS) driven by long-hour light soaking at an elevated temperature. We have investigated transitions between these three states from the perspective of the electric field by nm-resolution potential imaging across the devices using Kelvin probe force microscopy (KPFM). The results exhibit different anomalous electric field profiles. At the LSS, the electric field exhibits a main peak inside the CdSeTe layer instead of the MZO/CdSeTe heterointerface, illustrating a buried homojunction (BHJ) of the device. At the DSS, a large electric field peak at the MZO/CdSeTe interface was measured, which probably resulted in the inferior fill factor at the DSS. At the DgS, the electric field peak at the MZO/CdSeTe interface increased further and a third electric field was measured at the back contact of the device. Device modeling using COMSOL software, in alignment with both the electric field and device current-voltage curves, elucidates that a low n-doped CdSeTe in the region near the MZO/CdSeTe interface caused the BHJ in the LSS and a loss of MZO doping and/or increase of the conduction band offset spike due to long-term stress caused the increased electric field near the MZO/CdSeTe interface at the DgS.

Original languageAmerican English
Article numberArticle No. 111610
Number of pages7
JournalSolar Energy Materials and Solar Cells
Volume238
DOIs
StatePublished - May 2022

Bibliographical note

Publisher Copyright:
© 2022 Elsevier B.V.

NREL Publication Number

  • NREL/JA-5K00-80794

Keywords

  • CdTe solar cell
  • Device modeling
  • Electric field
  • Kelvin probe force microscopy
  • Stability

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