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The solar energy industry continues to push the boundaries of efficiency and reliability. However, as innovative PV cell and module technologies emerge, new challenges arise in terms of durability and performance. A new report from the International Energy Agency’s Photovoltaic Power Systems Programme (IEA-PVPS) Task 13 provides a comprehensive analysis of the degradation and failure mechanisms in current PV technologies. A new IEA-PVPS Task 13 report, entitled “ Degradation and Failure Modes in New Photovoltaic Cell and Module Technologies”, provides a comprehensive analysis of degradation and failure mechanisms in current photovoltaic technologies. Degradation and failure modes have changed with recent innovations While new technologies pose new challenges, they also lead to positive trends. The changes in degradation and failure modes driven by current innovations are described below. Cell cracking – Studies show that the impact of cell cracking has been greatly reduced by the application of multi-wire technology. Cracks used to form large dead zones easily, whereas the multi-wire cell design mitigates the likelihood and thus reduces the risk of power loss and hot spot. LID/LeTID – Light-induced (and high temperature) degradation (LID/LeTID) has been solved by changing boron to gallium as a dopant for Si-wafers, and some other optimization measures also help. In addition, standard test procedures are available to check the impact of LID/LeTID on long-term performance, even for recent innovations. PID – Potential-induced degradation (PID) is caused by high system voltage and can be influenced by light, in particular UV irradiation. PID tests for modules with passivated emitter and total back scattering (PERT) cells have shown that additional light during a PID test can effectively prevent degradation. In one case it has been shown that a UV irradiance equivalent to the UV content in the AM1.5 standard spectrum at 1000 Wm² can reduce the PID effect for a module with TOPCon cells to below 3%. In contrast, in this case no UV irradiation during the PID test leads to a degradation of 28%. For PV modules with SHJ cells a new potential PID degradation mechanism is identified. However, no PID-affected modules corresponding to this mode have yet been found in the field. To assess the impact of irradiation in real installations, the upcoming PID standard IEC TS 62804-1 (2025) offers a combined potential and light test procedure. UVID – In some solar PV modules with TOPCon and SHJ cells, UV-induced degradation (UVID) occurs following accelerated aging testing. It is not yet clear whether the degradation can be reversed by outdoor exposure and how the test can be transferred from the laboratory to the field. It should be noted that UVID is a solvable problem, as some modules are UV stable in accelerated testing. Reflection or absorption of UV radiation before it reaches the c-Si/passivation interfaces (e.g. by the encapsulation material) can mitigate UVID. Encapsulation degradation and failure – Current standardised tests of PV modules (e.g. IEC 61215 series) often fail to reveal relevant degradation pathways as they focus on the electrical performance of PV modules but not on the stability of polymeric materials. Therefore, many PV modules are found in the field with damaged lamination material. Stresses combined with, for example, temperature changes, humidity and UV radiation can reveal these polymer-related degradation pathways. Since encapsulation material degradation cannot be reversed and often leads to safety issues, these additional tests are recommended for new encapsulation materials. Glass breakage – Thin glass (thickness = 2 mm) used in new glass/glass modules sometimes results in unpredictably high rates of glass breakage. In documented cases, 5% to 10% of module rear glass panes broke within the first two years after installation. Mechanical load testing according to IEC 61215 cannot detect this weak point as it would require parallel testing on dozens of modules instead of just one to assess the failure rate. Poor contacts in junction boxes – Electrical contacts in junction boxes are not soldered properly more often due to the new module layout having shorter cross-connection strips, resulting in increased bypass diode (BPD) disconnection. Faults in the junction box can cause fires and power loss in entire module strings. However, disconnected BPDs are difficult to detect in already installed PV systems. The report recommends that 100% of BPDs be checked for operation during production. A PV system installation should be 100% checked if there are signs of this type of failure occurring in selected modules. MHP-based photovoltaic technology – This report also includes a concise summary on the reliability of metal halide perovskite (MHP)-based photovoltaic modules according to the current scientific literature. There are many known degradation pathways for which remedies exist at conceptual or laboratory level. For example, protective encapsulation against UV radiation, moisture and oxygen basically helps to stabilize perovskite solar cells. However, among others, two prominent challenges are temperature and ion migration stability. Limited temperature stability and high ion mobility lead to unresolved degradation pathways under normal operating conditions such as shading and high system voltage. There are new degradation modes in tandem solar cells with MHP. For example, the reverse voltage states that occur in the top and bottom cells under shading conditions depend on the irradiation spectrum and cannot yet be reproduced by standard qualification tests. New tests addressing these shading conditions are important to evaluate new degradation pathways that do not occur in single-junction PV modules. Conclusion This report is aimed at a broader audience, including cell and module manufacturers as well as PV system owners. It provides detailed explanations of degradation modes, their impact on module/system performance, identification and testing methods, and possible mitigation strategies. Updated PV Failure Fact Sheets (PVFS) based on the report can also be downloaded from the IEA PVPS website. |
