SPLTRAK Abstract Submission
Evaluation of PV Module Packaging Strategies of Monofacial and Bifacial PERC Using Degradation Pathway Network Modeling
Sameera Nalin Venkat1, Jiqi Liu1, Jakob Wegmueller1, Kunal Rath1, Xuanji Yu1, Xinjun Li2, Jean-Nicolas Jaubert3, Jennifer L. Braid4, Roger H. French1, Laura S. Bruckman1
1SDLE Research Center, Department of Materials Science and Engineering, Case Western Reserve University (CWRU), Cleveland, OH, United States
/2Cybrid Technologies Inc., Suzhou, Jiangsu, China
/3System Technology & Reliability Testing, Canadian Solar Inc. (CSI), Suzhou, Jiangsu, China
/4Sandia National Laboratories, Albuquerque, NM, United States

In order to improve photovoltaic (PV) module lifetime and reduce the levelized cost of electricity for widespread applications, it is of utmost importance to understand the degradation behavior of modules. Several modeling techniques are being actively explored by researchers to gain insights into the degradation mechanisms that cause power loss. However, it is often assumed that degradation modes are independent of each other, which does not explain the complex nature of degradation. 

In this study, we have utilized network structural equation modeling (netSEM) to identify dominant degradation pathways that lead to power loss in 4-cell PV minimodules with the help of stressor, mechanistic variables and response. Using the two principles of netSEM, we were able to explore pairwise relationships between variables as well as multivariate regression to gain insights into degradation behavior. 

We have compared two sets of minimodules that differ on the basis of passivated emitter and rear cell (PERC) (monofacial/bifacial) and rear encapsulation (UV-cutoff/opaque). The minimodules with specific encapsulation (EVA/POE) and module architectures (GB/DG) were fabricated at CWRU and exposed to modified damp heat (mDH: 80℃ and 85% relative humidity) and mDH+full spectrum light (FSL: 420 Wm-2 irradiance) for a total of 2520 hours. Including baseline measurements, every 504 hours, I-V and Suns-Voc measurements were collected for degradation modeling.

We observe that GB minimodules with bifacial PERC and opaque rear encapsulation undergo the highest power loss of 10-17% at the end of exposure. On the other hand, GB minimodules with monofacial PERC and UV-cutoff rear encapsulation were seen to have an  average power loss of 3-6%. Using netSEM modeling and marginal effect results, the power loss is most likely caused by corrosion, which acts as one of the dominant degradation modes.