Supercharging cell-level potential-induced degradation (PID) testing using a salt-enriched hybrid polymer layer

Abstract

Potential-induced degradation of the shunting type (PID-s) is a well-known problem for photovoltaic modules. However, standard PID testing at the cell or module level takes 96 h due to the time it takes for the Na ions to diffuse from the glass to the solar cell through the ethylene-vinyl acetate (EVA) encapsulant. This is too slow to monitor production quality in the fast-paced solar cell industry. Moreover, it results in the encapsulation of solar cells, significantly restricting characterization options after PID testing. In this work, we replace the EVA in the PID testing setup with a salt-enriched hybrid polymer, which provides the solar cell with direct access to sodium (Na) ions while at the same time avoiding encapsulation during the testing process. Solar cells that underwent PID-s testing with the salt-enriched hybrid polymer showed a maximum degradation after only 12 min, over two orders of magnitude faster than standard PID-s testing using EVA, which took 4,300 min (∼72 h) to reach maximum degradation. Hence, PID-s testing using the salt-enriched hybrid is significantly faster than conventional techniques and avoids encapsulation, thus allowing for more detailed post-PID cell analysis. This new test shows that some solar cells can recover from PID-s, which was corroborated by extending the standard test to 300 h. This important novel insight shines a new light on the PID-s mechanism and the impact of this failure mode in field operation.