One-type-fits-all-systems: Strategies for preventing potential-induced degradation in crystalline silicon solar photovoltaic modules

In this work, we investigate the relationship between potential-induced degradation (PID) and the bill of material used in module manufacturing. We manufacture samples with different combination of materials, using two types of solar cells (conventional vs PID-free c-Si cells), two types of ethylene-vinyl acetate (EVA) films with low/high resistivity, and two types of backsheets with, respectively, low/high breathability properties, and subject the mini-modules to extended PID testing. Our results clearly indicate that, when using a breathable polymeric backsheet, to have a "PID-free" module the combination of PID-free cells and high-resistive EVA encapsulants is recommendable. The use of a conventional c-Si cell in combination with a high-resistive EVA encapsulant is still more effective than the use of PID-free cells in combination with low-quality EVA. Further, our results initially show that the breathability properties of the backsheet have apparently no influence on PID degradation. A second set of experiments using sandwich structures with increased resistance properties to water ingress (ie, glass and backsheets with barrier layers as rear covers and an edge sealant), however, indicates that preventing or reducing the diffusion of moisture in the encapsulant layer plays a role in further mitigating the impact of PID. This finding is supported by simulations of moisture ingress in the sandwich structures. Finally, we show that the use of a glass rear cover-compared with a polymeric backsheet-does not contribute in worsening the PID effect. On the contrary, by reducing moisture ingress in the front encapsulant layer, it delays the occurrence of PID.