Study
Lightweight photovoltaic modules are increasingly important for expanding solar deployment into new applications such as vehicle integrated systems and low load bearing structures. Silicon heterojunction technology is a leading high efficiency platform due to its superior conversion efficiency, bifacial design and low temperature processing, with record cell efficiencies now exceeding 27%. However, when conventional glass is replaced with polymer based front sheets, the resulting reduction in UV shielding introduces significant reliability concerns under field conditions.
A study titled ‘Mitigation of UV-Induced Degradation in Lightweight SHJ Solar Modules via a UV-Downshifting Encapsulation Strategy’, investigates UV induced degradation in lightweight silicon heterojunction solar modules using three encapsulation strategies, namely UV blocking, UV transmitting and UV downshifting materials. Following accelerated indoor UV exposure of 120 kWh per square metre, equivalent to around 30 months of outdoor operation in Jülich, Germany, the modules showed relative efficiency losses of 2.17% for UV blocking encapsulation, 9.25% for UV transmitting encapsulation and 6.15% for UV downshifting encapsulation.
Performance losses were primarily driven by reductions in open circuit voltage and fill factor, with detailed analysis showing that pseudo fill factor degradation was the dominant contributor. This points to deterioration in surface passivation within the solar cell structure under UV exposure. In addition, increasing series resistance related losses were observed, linked mainly to degradation of interconnection foils rather than direct UV effects, suggesting a secondary role of environmental stressors such as moisture and oxygen ingress.
While UV downshifting encapsulation helped reduce UV related damage by converting high energy photons into longer wavelengths, its effectiveness declined over time. The utilisation efficiency of the downshifting layer dropped from around 34% to 21% after UV exposure, likely due to photooxidation processes within the polymer matrix. This reduction limits long term protection in lightweight module configurations.
Schematic of the lightweight SHJ single-cell solar module with dual-layer front encapsulant. Authors provided
To address these limitations, a dual layer encapsulation concept combining UV blocking and UV downshifting materials was developed. This architecture enables both protection from harmful UV radiation and improved spectral utilisation of incoming light. Modules using this combined approach retained more than 98% of their initial performance after UV exposure and delivered 8.92% relative higher efficiency compared to UV transmitting configurations, demonstrating a clear performance advantage.
Overall, the findings show that UV induced degradation in lightweight silicon heterojunction modules is strongly influenced by encapsulation design, with passivation loss at the cell level and polymer stability at the module level both playing critical roles. The dual layer strategy offers a practical pathway to improve durability while maintaining high energy yield, supporting broader deployment of lightweight photovoltaic systems in constrained structural applications. Further work is required to optimise downshifting stability and extend spectral conversion deeper into the visible range for long term field performance gains.
Link to the full paper HERE
Author: Bryan Groenendaal
May 20, 2026
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