Cost pressure is driving toward systemic failures in PV modules, making early detection more important
According to TÜV Rheinland, material compatibility, manufacturing discipline, and process control form the 3 core pillars of PV module quality
Qualification and surveillance testing show rising failure rates, especially for insulation, moisture ingress, UV degradation, and rear-side issues
As the global PV industry continues to drive down costs, module manufacturers are operating under unprecedented price pressure. While this has accelerated deployment, it has also raised concerns about the module’s long-term reliability, safety, and bankability. New cell architectures, material substitutions, and faster production ramp-ups are placing additional stress on module designs that are expected to perform reliably for 25 years. The quality assurance, failure analysis, and robust testing frameworks are becoming increasingly critical for both manufacturers and project developers to manage long-term risk.
Johannes Stange, Laboratory Manager and Head of Solar Services at TÜV Rheinland, presented the keynote address at the TaiyangNews Reliable PV Module Design Conference. His talk, titled Status of Quality and Failure Modes in a Market Characterized by Very High Cost Pressure, elaborated on PV module quality and emerging failure modes in a market shaped by intense cost pressure.
Stange’s presentation covered the quality aspects in PV modules, common failure modes, and testing and certification approaches. According to Stange, module quality directly determines its performance, lifetime, and safety. Even small defects in materials or manufacturing can result in power loss, safety hazards, or premature failure. Poor-quality modules degrade faster and undermine customer confidence. Under intense cost pressure, quality risks are becoming systemic, making early detection and quality assurance essential for long service lifetimes.
From TÜV Rheinland’s perspective, module quality is built on 3 pillars: material quality, manufacturing quality, and qualification testing. These pillars encompass material selection, production processes, process control, workforce competence, and testing and certification. The pillars include materials, manufacturing processes, process control, workforce skills, and testing. Stange noted that PV modules use different materials and designs, including glass-glass and glass-foil, framed, and frameless formats. He added that without carefully selected and compatible materials, long-term reliability cannot be ensured.
While progress has been made in component standardization, such as international standards for polymeric backsheets and electrical components, TÜV Rheinland emphasizes that material compatibility and long-term stability under combined stresses are increasingly important, particularly for modern n-type and bifacial module designs.
Stange highlighted manufacturing as another decisive factor, specifically the role of structured quality management systems, such as ISO 9001, in supporting process control and improvement. Supplier audits, material inspections, approved supplier lists, and supplier qualifications were described as essential tools for maintaining quality. He added that local sourcing of equipment and services can reduce downtime and improve maintenance responsiveness.
Process control, however, remains a frequent weakness observed during factory inspections. Inline and offline testing during stringing and soldering are critical for early defect detection and for avoiding costly scrap or rework after lamination. Stange emphasized full traceability, which enables faster root-cause analysis and continuous improvement based on field feedback. Another important factor is skilled personnel, particularly in soldering and stringing, where workmanship directly affects long-term reliability.
Stange explained that while type approval testing mainly targets early-life failures and does not represent full lifetime validation, it still provides a baseline for safety and quality. He highlighted the importance of qualification testing under real production conditions, working closely with manufacturers.
The keynote then described failure modes as an increasing concern. TÜV Rheinland has observed a rising number of test failures and observations in recent projects, with insulation and wet leakage current failures frequently detected during initial measurements. These issues raise serious concerns about electrical safety. Visual defects, failures in environmental stress tests, mechanical load failures, and problems affecting electrical coordination have also become more common, with some modules no longer meeting Class II safety requirements.
Stange clarified that this trend does not imply that all modules on the market are of poor quality. Rather, it reflects the growing impact of design decisions and material substitutions made under cost pressure. Common failure modes include cell cracks, moisture ingress, delamination, UV-induced polymer discoloration, and degradation mechanisms such as PID, LID, LETID, and UV-induced degradation (UVID). He said that these risks must be addressed through appropriate material selection and robust process control, especially as new cell technologies are introduced.
He cited recent laboratory examples, including delamination and moisture ingress, cell breakage under mechanical load, inadequate designs for tracker applications with asymmetric loading, UV-induced cracking of type labels, lamination bubbles near module edges affecting electrical safety, BIPV-specific lamination issues, hotspot damage, and UVID in n-type bifacial technologies such as HJT and TOPCon. In one case, UV exposure of 60 kWh/m² resulted in power losses of around 4%, with little additional degradation at higher doses, indicating that significant losses can occur early under field-relevant UV exposure.
In conclusion, Stange noted that TÜV Rheinland has developed internal specifications to address these risks and detect failure modes as early as possible. He emphasized that a broad range of standards and testing solutions already exists to support manufacturers across the PV value chain and to address risks observed both in laboratory testing and real-world deployments.
The full presentation is available on the TaiyangNews YouTube channel here.
