Electrochemical mechanisms of leakage‐current in photovoltaic modules

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 H 2 , CO x , and O 2 , along with ionic species such as OH À and H 3 O + . 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.

Potential-induced degradation: a challenge in the commercialization of perovskite solar cells

“…However, Na + ions and moisture ingress together will cause irreversible electrochemical degradation of the tin oxide (SnO 2 )-based TCO coating. 16,17,61,114,[119][120][121] Consequently, the adhesion between TCO and the substrate is disrupted. Na serves as a reactant and its accumulation intensifies the mechanical stress at the respective interface.…”

“…However, Na + ions and moisture ingress together will cause irreversible electrochemical degradation of the tin oxide (SnO 2 )-based TCO coating. 16,17,61,114,119–121…”

Potential‐Induced Electrochemical Corrosion in Crystalline Silicon Solar Cells

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Corrosion is one of the significant degradation modes for crystalline silicon photovoltaic (c-Si PV) modules. [1][2][3][4][5][6][7] The major factor causing corrosion degradation of c-Si PV modules is moisture and atmospheric gases, which can permeate into glass/ back-sheet modules and glass/glass modules through permeable back-sheet and the edge of modules, respectively. [8,9] Once water vapor and gases come into PV modules, ethylene-vinyl acetate (EVA) encapsulant will be decomposed to generate acetic acid.

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