The Front and Rear Side Contributions to the Potential Induced Degradation of Bifacial Silicon Heterojunction Solar Modules

38th European Photovoltaic Solar Energy Conference and Exhibition; 573-577 Recent studies showed that silicon heterojunction (SHJ) solar cells may be prone to potential induced degradation (PID), when encapsulated with a low volume resistivity ethylene vinyl acetate (EVA). This, however, can be prevented when using high-volume resistivity encapsulants (e.g. ionomer or polyolefin elastomers (POE)), or an edge sealant in combination with EVA. Here, we perform PID tests in a climatic chamber (85°C/85% RH) on glass/glass onecell mini-modules, by using different combinations of encapsulants. We combine EVAand POE, interchanging their position between the front- and rear-sides (i.e. POE/EVA and EVA/POE), with the aim of studying the PID mechanism and analyzing the contribution from each side. The SHJ solar cells employed are bifacial rear-emitter cells. We demonstrate that for all combinations, the addition of a POE layer contributes to considerably slowing the degradation kinetics. Although not completely prevented, after 450 hours of PID exposure (corresponding to nearly 5 times the duration of the IEC prestandard), the deceleration of PID is mostly successful when the POE layer is placed at the rear-side of the module (i.e. EVA/POE encapsulation scheme). After 450 hours of PID test, the POE/POE and EVA/EVA samples degrade by 0.3% and 31%, respectively. If a POE is placed only on the front- or rear-side, the corresponding degradation is, respectively, of 21% and 8%.