Electrochemical Mechanisms of Leakage-Current in Photovoltaic Modules

Michael Kempe, Peter Hacke, Joshua Morse, Jichao Li, Yu-Chen Shen, Katherine Han

Research output: Contribution to journalArticlepeer-review

3 Scopus Citations

Abstract

This paper analyzes the mechanisms and pathways for leakage current flow observed in Si photovoltaic modules subjected to high temperature and humidity and a large voltage bias with respect to ground. The current inside of the frame is in the form of electron motion, but in the glass and polymer, it is in at least a large part attributable to the movement of ions. When the mode of current flow changes from electronic to ionic conduction, electrochemical reactions will take place at the interface. This can include reactions that produce volatile chemical species like H2, COx, and O2, along with ionic species such as OH and H3O+. Here, we see evidence of the importance of different charge carriers with different diffusion rates and the influence of electrochemical processes involved. The application of negative voltage to the cell circuit affects the resistivity of glass producing surfaces with poor conductivity but with some increases in the electrochemical potential producing complicated interactions that are important when the voltage is changed. In the polymer, there is the development of a space charge region and a chemical gradient providing two oppositional forces to current flow, which when released create a complicated discharge process. Here, we give a basic understanding of the charge/discharge of PV cells highlighting how the specific mechanisms are important in understanding some of the degradation processes in PV modules. We find that there is evidence of multiple significant charge carrier species with different diffusion time scales. The glass/polymer interface forms a depleted region of higher resistance after prolonged exposure to current. Charge also builds up at the polymer to cell antireflective coating interface and mostly flows to the gridlines to experience electrochemical reactions. These complexities result in non-linear behavior where the apparent resistivities of the different layers change during charge/discharging processes, making the modeling of the current flow extremely difficult.

Original languageAmerican English
Pages (from-to)700-715
Number of pages16
JournalProgress in Photovoltaics: Research and Applications
Volume31
Issue number7
DOIs
StatePublished - 2023

Bibliographical note

Publisher Copyright:
© 2023 Alliance for Sustainable Energy, LLC and The Authors. Progress in Photovoltaics: Research and Applications published by Progress in Photovoltaics: Research and Applications.

NREL Publication Number

  • NREL/JA-5K00-83216

Keywords

  • capacitance
  • corrosion
  • delamination
  • leakage current
  • module
  • photovoltaic
  • potential induced degradation (PID)

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