On Methodologies for Assessment of Long-Term Potential-Induced Degradation of Double-Glass Tunnel Oxide Passivated Contact Photovoltaic Modules

Polarization-type potential-induced degradation (PID-p) has become a risk for tunnel oxide passivated contact (TOPCon) solar cell modules. For the sake of intimating the long-term PID-p degradation of the modules under outdoor illumination, this study investigates the impact of different types and timing of illumination on the PID-p on the double-sided EVA encapsulated TOPCon modules: 1) multiple cycles of a PID test in the dark followed by a 2 kWh UV recovery; 2) PID tests under 170 W/m² UV illumination; and 3) PID tests under 800 W/m² simulated steady-state solar illumination. We find that all three testing methods lead to less power degradation than that in the dark after 96 h so that TOPCon photovoltaic modules will not suffer from severe PID-p risk in short term when running outdoors. After 672 h, the module subjected to PID tests under 800 W/m² simulated steady-state solar illumination shows the lowest degradation of −3.18%. This method more closely resembles the long-term outdoor operating conditions, where the module generating voltage under illumination forms a ground potential. Moreover, excessive UV irradiation in the testing method may exacerbate the UV-induced degradation issue and accelerate the aging of the encapsulant.