Evaluation of the PID-s susceptibility of modules encapsulated in materials of varying resistivity

A common mechanism of potential-induced degradation is by shunting (PID-s) in PV modules, usually associated with the transport of sodium ions (Na+) through the encapsulant and penetrating the front junction of solar cells under voltage stress. Encapsulants with high volume resistivity have been suggested as a potentially cost-effective solution to this degradation mechanism. In this work, we examine three polyolefin elastomer (POE) encapsulants with volume resistivity varying over two orders of magnitude (ranging from 9 × 10 ¹³ to 1 × 10 ¹⁶ Ω·cm) that show equivalent and complete resistance to PID at the damp heat stress test level of 85°C and 85% relative humidity and -1000 V system voltage stress. Performance is compared with a PID-susceptible ethylene vinyl acetate (EVA) encapsulant with resistivity 1 × 10 ¹³ Ω·cm. The independence of PID susceptibility with respect to the resistivity of the polyolefin is attributed to the impermeability of POEs to Na ⁺ ions. Specific ions (i.e. Na ⁺ ), rather than charge-carrying species in general, are responsible for this degradation mechanism.