Modeling subcell degradation rates in perovskite-silicon tandem solar modules

<p class="p1"><span class="s1">Researchers in the Netherlands developed a model to identify tolerable degradation rates of the top cell in perovskite-silicon tandem modules. Simulations showed that an increase in tandem module efficiency from 28.0% to 32.9% could raise the tolerable degradation rate by approximately 50%.</span></p><p>To be able to identify the tolerable degradation rate of perovskite subcells in monolithic two-terminal tandem modules, researchers at <a href="https://www.pv-magazine.com/2025/04/23/tu-delft-researchers-build-23-4-efficient-heterojunction-solar-cell-with-localized-front-contacts/" rel="noopener" target="_blank">Delft University of Technology (TU Delft)</a> in the Netherlands developed a dual model. It predicts lifetime energy yield and degradation rates under a variety of environmental conditions.</p>
<p>“In this study, the novelty is that we combine a physical approach with a scenario-based approach in order to determine the tolerable degradation rate,” first author of the research, Youri Blom, told <strong>pv magazine</strong>, noting that the fully simulation-based approach relied on measurement data from several literature sources.</p>
<p>Similar studies in the past have relied on either a physical approach for conventional crystalline silicon modules or a fully scenario-based approach for perovskite-based modules.</p>
<p>“To see how the tolerable degradation rate of the perovskite cell depends on the climate, we combine these two approaches to have i) climate-dependent information for the silicon bottom cell, and ii) a scenario approach for the perovskite top cell,” explained Blom, noting that modelling is required for perovskite devices because there is insufficient outdoor data available to calibrate and design physical equations.</p>
<p>After identifying the tolerable degradation rates for the perovskite cell, ensuring that the perovskite-silicon module continues to outperform the crystalline silicon module, various degradation scenarios were analyzed. The degradation mechanisms included in the model were discoloration, moisture-induced degradation (MID), thermal cycling-induced degradation (TC), and light-induced degradation (LID), as these mechanisms are most severe or occurring most frequently, according to the paper.</p>
<p>Limitations of the previously validated PVMD Toolbox used for building the model did not permit to consider hotspot and potential induced degradation (PID), the researchers noted.</p>
<p>The environmental stress factor-dependent degradation was investigated four locations, each with a distinct climate: Delft, Lagos, Lisbon and Shanghai. The cell modelled was a 144 half-cut perovskite-silicon tandem device with a G12 wafer size connected in a butterfly topology with three bypass diodes. The cell stack was based on a 32.5% efficient two terminal design from the literature.</p>
<p>The results showed that in Delft, &#8220;where there is a high module lifetime, the perovskite top cell needs to be very stable as a degradation rate of only 1.9% can be tolerated,&#8221; but in Lagos, where the &#8220;module lifetime is short, a larger perovskite degradation rate of 7.6% can be tolerated,&#8221; according to the paper.</p>
<p>The team noted that the type of degradation, either current or voltage loss, in the subcell influences the overall power loss differently. For example, a 10% current loss in the perovskite subcell results in an 8.7% power loss, while a 10% voltage loss leads to a 6.2% power loss. &#8220;This shows that the degradation in both the perovskite and silicon subcell is relevant, and a single degradation rate is not sufficient,&#8221; it said.</p>
<p><a class="anchor anchor-primary" href="https://www.sciencedirect.com/science/article/pii/S0927024826000103?via%3Dihub#figA.1" name="bfigA.1"></a>Further results demonstrated that increasing module efficiency from 28.0% to 32.9% raised the tolerable degradation rate by approximately 50%.</p>
<p>As part of the research, the group developed a simplified model to reduce computationally intensive simulations, an Arrhenius-based model. Module efficiency and ambient temperature are used to “effectively and accurately” predict results for chosen locations with a root mean square error of 0.34% per year.</p>
<p>In addition, an efficient empirical model was created to calculate the degradation rate for other locations and cell efficiencies. “It can be used by other researchers or manufactures,” said Blom</p>
<p>The model may also be applied to environmental impact studies of perovskite-silicon modules. “By using life cycle analysis (LCA) results from literature, the comparison between crystalline silicon and perovskite/silicon can be extended to environmental footprint as well,” said Blom.</p>
<p>Currently, the research group is working on topics related to the circularity of PV modules, such as analyzing PV sustainability including PV-related critical raw material demand, designing PV modules for circularity as shown in <a href="https://www.pv-magazine.com/2026/01/26/tu-delft-unveils-liquid-solar-module-encapsulation-tech/" rel="noopener" target="_blank">its recently reported work on liquid PV module encapsulation,</a> and investigating module aging, which includes this study, according to Blom.</p>
<p>The work is detailed in “<a href="https://doi.org/10.1016/j.solmat.2026.114169" rel="noopener" target="_blank">Combining physical- and scenario-based modeling to identify tolerable degradation rates of perovskite in monolithic two-terminal perovskite/silicon tandem modules</a>,” published in <em>Solar Energy Materials and Solar Cells</em>.</p>