Field-representative evaluation of PID-polarization in TOPCon PV modules by accelerated stress testing

Abstract

Potential-induced degradation-polarization (PID-p) can reduce module power, but how to project the extent to which PID-p may occur in field conditions considering the factors of system voltage, condensed moisture, temperature, and illumination has not been clarified. Using tunnel oxide passivated contact (TOPCon) modules, this work demonstrates a method to test full-size crystalline silicon PV modules for PID-p to provide field-representative results. In initial screening tests with positive or negative 1000 V electrical bias applied at 60°C for 96 h using Al foil electrodes on the glass surfaces, the module type exhibited reversible PID-p only on the front face when the cell circuit was in negative voltage potential. No PID was detected on the rear after testing in either polarity. We then evaluated the PID-p sensitivity on the front side under different UV irradiances while maintaining the glass surface wet to estimate real-world susceptibility to PID-p. The magnitude of the observed behavior was fit using a previously developed charge transfer and depletion by light model. Whereas power loss with −1000 V applied to the cell circuit at 60°C for 96 h in the dark was about 30%, testing the module front under 0.051 W·m⁻² nm⁻¹ at 340 nm UVA irradiation using fluorescent tubes, the mean degradation was only 3%. When the modules were tested in the dark for PID-p with in situ dark current–voltage (I-V) characterization, the thermal activation energy for degradation was 0.71 eV; for recovery in the dark, it was 0.58 eV. Whereas recovery from the degraded state at 60°C in the dark without voltage bias was 5% absolute in 38 h, rapid recovery of about 5% absolute was observed with 1000 W·s/m² exposure at 25°C using a flash tester.