Rapid Solar PV Module Evolution Puts Reliability In Spotlight

Driven by pressure to cut costs as solar module prices stay very low, the solar PV industry is adopting new technologies faster than ever, seeking to both cut costs and increase efficiency. However, with this speed, testing labs are noticing some quality issues, raising the question of whether solar module reliability is being compromised. 

Modules are meant to last for decades; hence, every design choice matters. Therefore, it is of extreme importance that balancing innovation with long-term reliability is crucial for trust in the industry.

“Exciting to see the levels of innovation in the solar PV industry, but the fear is that reliability should not become the trade-off for this rapid speed of innovation,” said Head of Technology at TaiyangNews, Shravan Chunduri, while laying the background for the TaiyangNews Virtual Conference on Reliable PV Module Design 2025 on November 6, 2025. The event gathered experts to discuss how to achieve reliable module design and mass manufacturing despite rapid changes and cost pressures. 

TÜV Rheinland Warns of Rising Failures 

Johannes Stang, Head of the Solar Lab at TÜV Rheinland and the conference keynote speaker, echoed this thought and stressed that the performance and lifespan of a solar module depend heavily on its quality. Even minor defects can affect reliability, reduce returns, and weaken consumer confidence. 

Over the past year, TÜV Rheinland has observed higher failure rates in new projects. Stang said nearly every qualification or test project revealed issues, many of which were detected during early measurements. Environmental stress was a major factor, often affecting mechanical stability and electrical performance due to design or material decisions. 

Common failures include moisture-related issues, delamination, and degradation, such as PID and UID. Stang highlighted that choosing suitable materials and maintaining strong process control can prevent many of these problems. Delamination and cell cracking, in particular, can be reduced with proper material selection and careful manufacturing. 

According to Stang, module design and material compatibility are critical factors in ensuring long-term durability of solar modules. Manufacturers must carry out thorough quality checks, maintain traceable material and process data, and ensure trained personnel handle production. 

He added that both in-line and end-of-line testing are essential. Quality must be monitored at every stage – from the glass to the electrical connections. Complying with international standards, too, plays a key role in ensuring modules remain reliable, durable, and efficient throughout their lifetime of 25 years or more. 

Ultimately, Stang reflected that quality is not only about compliance but about building trust in solar energy as a long-term solution. 

LONGi Highlights HPBC 2.0 Reliability and Performance Advantages 

Dr. Heng Sun, Senior Manager of LONGi Central R&D Institute, provided an in-depth look at how the company’s core cell technology platform, the HPBC 2.0 back contact (BC) cell, is redefining the performance benchmark for PV modules. Sun said, the Hi-MO 9 series, as one of the HPBC 2.0-integrated flagship products, achieved a triple leap in ultra-high conversion efficiency, annual energy yield, and full lifetime reliability by orchestrating simultaneous innovations across the entire value chain – from strengthened silicon wafers and cell passivation, carrier collections to module design. These enhancements are validated through rigorous accelerated aging tests that cover optical, thermal, and mechanical stress regimes, ensuring that every watt delivered in the field is backed by robust structural integrity and safety margins. For example, whereas local shading typically causes an entire substring to be bypassed in TOPCon, it occurs only at the cell level in HPBC 2.0. In a half-cell shaded scenario, HIMO 9 incurs nearly 70% (66.8 %) less power loss than TOPCon, according to LONGi. 

Additionally, Sun shared that under identical shading conditions, the peak hot-spot temperature of BC-based Hi-MO 9 modules is 66°C to 77°C lower than that of traditional counterparts, significantly below TOPCon levels. These unique features enhanced long-term reliability and substantial power generation for solar farms, he added. 

Whether deployed in coastal high-humidity regions, desert environments with extreme diurnal temperature fluctuations, or sites subject to shading and elevated ambient temperatures, each variant of the scenario-oriented PV module is meticulously engineered to sustain peak operational performance and mitigate degradation mechanisms, claimed Sun.  

Specifically, the modules integrate advanced encapsulation materials with low water vapor transmission rates, anti-reflective coatings resistant to thermal cycling, and unique bypass feature for shaded conditions. He added that these design interventions effectively suppress moisture-induced corrosion, thermal stress cracking, and hotspot effects, thereby extending the service life of the modules and maximizing the return on investment for photovoltaic system deployments. 

Encapsulation Choices for TOPCon Modules 

Bo Jin, Overseas Sales Manager at HANGZHOU FIRST, presented the company’s high-quality encapsulation solutions for the PV world’s current mainstream technology, high-efficiency TOPCon solar PV modules. As the main failure modes of TOPCon modules are DH-induced corrosion, PID, and UVID, Jin stressed that pastes have a ‘decisive’ impact on the corrosion resistance of TOPCon cells. 

For glass-glass TOPCon modules, he highlighted 2 front-side premium materials – POE and EPE – while a more economical option uses anti-acid S406P EVA on both sides. The cost difference between EPE and POE is steadily shrinking. 

For glass-backsheet modules, the premium configuration pairs FIRST TF4N POE on the front with low-acid EVA and a standard backsheet on the rear. To tackle UVID problems in TOPCon cells, Bo Jin recommended adding either a UV cut-off film or a UV conversion film. 

Overall, he emphasized that POE remains a safe, reliable encapsulation option regardless of cell type. 

Reliable Back-Contact Design 

GCL’s Technical Support Director for Europe, Rojen Malachi, outlined the company’s vertically integrated production setup – 30 GW of module capacity, 16 GW of n-type cells, 35 GW of wafers, and 480,000 tons of FBR silicon – which he said allows tight control over product quality and reliability. 

He detailed GCL’s work to reduce early-life degradation, noting that some competitors have shown up to 5% loss under UV60 exposure, whereas GCL’s enhanced passivation stack and process controls keep UV-induced degradation to around 1.2%, with stable recovery, as reflected in clearer EL images compared to conventional cells. 

He also addressed rising concerns about rear side glass failures. GCL uses rear-side glass with mesh coating and a light-redirecting film to improve tempering, which reduces stress points and the risk of spontaneous fractures – an increasing issue as glass becomes thinner. 

Malachi presented the new GPC 2.0 back-contact module, designed for higher real-world yield. Explaining its salient features, Malachi shared that its optimized GPC architecture delays bypass diode activation until roughly 20% shading, compared with about 10% in standard modules. Reverse-current operating control limits hotspot formation, while linear busbars distribute stress evenly to reduce micro-crack initiation and propagation. Together, these features strengthen shade tolerance, thermal safety, and mechanical stability. 

GCL’s TOPCon 2.0 and 3.0 modules improve reliability by using smaller 3-cut or 4-cut cells instead of full cells. The smaller-cell architecture enhances thermal stability, mechanical durability, and long-term field performance, added Malachi.  

He additionally noted that GCL has begun commercial-scale tandem perovskite production, with the first modules recently rolling off the line in China and global availability planned. 

Key Reliability Insights from Fraunhofer ISE 

Ingrid Haedrich, Head of Group Degradation Analysis and Modelling PV Modules at Fraunhofer ISE, highlighted several reliability findings from field observations and laboratory studies. 

She explained that PV modules experience what she termed a ‘dark storage’ effect: when stored in the dark, their power output temporarily drops. In one test, modules were taken off-site and stored in darkness from 11:30 a.m. to 4:00 p.m., resulting in a 0.6% power loss. This effect is especially relevant for nighttime drone inspections, where EL images can show dark cells that may not indicate permanent degradation. 

Haedrich also discussed emerging reliability concerns with TOPCon technology, including UVID effects and a rising number of glass-breakage cases in the field. Even certified modules have reported failures. She noted correlations between reduced surface pre-stress, lower mechanical strength, and characteristic large round break patterns. Simulations at Fraunhofer ISE further show that laminate sagging between frames can cause crack lines that follow stress patterns in the rear glass. 

To mitigate these issues, she outlined potential approaches, including AI-based visual inspection, microscopic scanning of glass edges, and transillumination with polarized light to assess stress uniformity. Manufacturers continue to debate whether to strengthen modules, modify installation environments, or pursue both strategies. Haedrich concluded by underscoring the open question: Will these measures be enough to prevent future failures? 

Hail-Resistant Module Design 

Alejandro Coll Garcia, Product Manager for Southern Europe at Chinese DMEGC Solar, elaborated on the company’s focus on reliability and installation-friendly design. DMEGC, a leading Chinese manufacturer of magnetic materials and active in solar for many years, is now operating nearly 24 GW of cell and 21 GW of module manufacturing capacity. It also runs its own module testing laboratory, where it evaluates products under different environmental conditions. 

Its double-glass TOPCon modules offer strong protection against humidity. The company also develops module variants tailored to different applications, such as lightweight versions for rooftops in France or models designed for overhead mounting in Germany. For the latter, Coll Garcia claims that DMEGC is the only Tier-1 Chinese manufacturer with certification from the Deutsches Institut für Bautechnik (DIBt), or the German Institute for Building Technology, required for construction-sector installations. 

For the French market, DMEGC has specially designed a lightweight module that enables 80% of surfaces currently unused to be used for PV systems. Weighing 15 kg, 7.5 kg/m², these are 39% lighter than a standard module and offer high hail resistance. 

To address frequent hail damage in the field, Coll Garcia said that DMEGC uses a reinforced design with 3.2 mm front glass and 2.0 mm rear glass, improving impact resistance and overall mechanical strength. These products are mostly focused on the Central EU and Nordic nations. 

Reliability-Driven Cell Design 

Xinrui An, R&D Manager at Jietai Solar (JTPV) of the Drinda Group, presented the cell maker’s efforts, with its 44 GW annual production capacity, to ensure module reliability. He shared that JTPV strengthens module reliability by addressing both UV-induced degradation and damp-heat stress through targeted cell design and material improvements. 

To limit UVID, for instance, the company has developed a front passivation scheme that reduces hydrogen sensitivity and UV absorption, improving UV60 from over 2% to around 1% with only a minor efficiency impact. For damp heat, JTPV adjusts Ag paste composition, firing recipes, and coating durability to minimize reactions with acetic acid, achieving excellent DH1000 results – about 3.5% power loss for single glass modules and 1.5% for double glass modules, ‘far below’ the industry average.  

JTPV also improves reliability through its new cut-line technology, which removes emitter material along laser-cut edges to reduce damage and recombination. Calling it a more versatile alternative to half-cut edge passivation (HEP), An said this treatment minimizes laser-induced damage and edge recombination by locally etching and passivating the emitter area with AlOx/SiNx.  

The standard cut lines are about 300 μm wide, but can be customized to accommodate larger cutting tolerances as per client requirements, he added.  

Panel Debates the Need for Expanded Testing 

The conference wrapped up with a panel discussion moderated by TaiyangNews’ Shravan Chunduri. Panelists Ingrid Haedrich of Fraunhofer ISE, Rojen Malachi of GCL, and Xinrui An of JTPV debated whether the current reliability standards adequately address emerging cell and module technologies. The panel agreed that while cell-level testing is well covered, module-level evaluations need to evolve, especially for glass quality, glare, and tint effects. 

Fraunhofer ISE’s Ingrid Haedrich emphasized that accelerated stress testing remains essential and must be tailored to specific material combinations. She also noted the need for low-impact glass quality tests to strengthen IEC protocols. 

GCL’s Rojen Malachi highlighted the company’s close collaboration with labs and TÜV, adding that glare and tint testing should be included in standards for all module types to reduce confusion. 

JTPV’s Xinrui An stated that most existing protocols still cover key reliability risks but warned that UV exposure and damp heat remain significant challenges for today’s high-efficiency modules. 

Complete presentations and panel discussion recordings of this conference are available on the TaiyangNews YouTube Channel.  

TaiyangNews will close the year 2025 with its annual flagship event, the 4-day High Efficiency Solar Technologies 2025 Virtual Conference in December. Each day will be dedicated to a high-efficiency cell technology: Back Contact on December 3, TOPCon 1 on December 4, followed by TOPCon 2 on December 9, and HJT on December 10. Along with leading industry names in attendance, the conference will take an in-depth look at the cell technology trends shaping the future of solar manufacturing. Registrations are open here.