Evidence of Polarization‐Type Potential‐Induced Degradation (PID‐p) in the Field and Investigation of the Recovery Mechanism on Bifacial p ‐PERC Modules

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Abstract
This study investigates the polarization‐type potential‐induced degradation (PID‐p) of bifacial glass/glass ‐type passivated emitter rear contact ( ‐PERC) modules in the field and their recovery behavior. Modules were installed with three mounting configurations providing different albedo conditions. System voltage ( 600, 1500, and +1500 V) was applied to the cell circuits, with respect to the grounded module frames. No degradation was observed for positively biased modules, but PID‐p was identified on the rear side when cells are negatively biased, with maximum power dropping during the first days and stabilizing at values up to 8% loss. Electroluminescence images revealed a variation of the cells' PID‐p susceptibility within a module. Three parameters were shown to impact the degradation rate: rear albedo light, voltage, and wetness conditions. Degraded modules were recovered either by (1) a positive bias (+1500 V), (2) outdoor illumination with the front side facing sun, (3) outdoor illumination with the rear side facing sun, or (4) dark storage. A recovery pattern was identified with – parameters decreasing to a local minimum before increasing to full recovery. The proposed mechanism is based on the band bending at the rear ‐type Si/AlO interface, going from inversion to depletion and accumulation states. Full recovery was achieved in 2–7 h for the modules recovered with the rear side facing sun, four to eight nights for the modules positively biased at night, and 10–20 days for the modules with the front side facing sun. Dark storage showed slower recovery rates as – parameters were not improving even after 1 month. The recovery rates were correlated with the net Coulombs transferred during the preceding PID stress: When more Coulombs are transferred during the degradation, the extent of degradation is greater, leading to slower recovery rates.
Funding Information
  • Office of Energy Efficiency and Renewable Energy (DE‐EE0009345)
  • National Laboratory of the Rockies (DE‐AC36‐08GO28308)

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