Fraunhofer ISE shared valuable insight into TOPCon degradation, glass quality, and wattage label deviations
Dual-glass TOPCon module exhibited more than 1% power degradation compared to its PERC counterpart
TOPCon module shows a typical 'W' patterned degradation curve after a modified stress sequence adopted by the lab
The lab found dual-glass modules with 2 mm thick glass, featuring lowest surface pre-stress value, break earlier than its counterparts
The wattage label value deviation statistics data stands at - 1.3% as of 2023
Major global calibration and accreditation laboratories in the PV value chain gain valuable expertise through extensive calibration, testing, and accreditation processes for diverse clients worldwide. Insights derived from this test data offer valuable trends in calibration, quality, and product reliability, benefiting clients like module manufacturers.
Ingrid Haedrich, Head of Group at Fraunhofer ISE – a renowned German calibration, testing, and accreditation laboratory – shared valuable insights drawn from recent years of test data at the TaiyangNews Reliable PV Module Design Conference 2024. Her presentation, based on data from Fraunhofer ISE’s calibration lab (CalLab) and testing lab (TestLab), was divided into 3 major parts – TOPCon degradation, Glass, and Label value. More than 15-year-old Fraunhofer ISE’s calibration lab (CalLab), accredited according to DIN EN ISO/IEC 17025, has a leading measurement uncertainty down to 1.1% for Pmpp. The Fraunhofer ISE’s testing lab (TestLab), under the certification body VDE Testing and Certification Institute, is responsible for the characterization and testing of modules.
TOPCon Modules
In her presentation, Haedrich highlighted 2 prominent failure modes observed in TOPCon modules: corrosion or moisture ingress and UVID (ultraviolet-induced degradation).
Based on extensive stress testing of TOPCon modules from up to 14 manufacturers, Fraunhofer ISE identified several evolving degradation trends. After the DH2000 damp heat aging test, glass-glass TOPCon modules exhibited more than 1% power degradation, compared to less than 1% in dual-glass PERC counterparts. Following 1,000 hours of damp heat testing, the TOPCon modules experienced a decline in Isc values, with a significant drop in the fill factor (FF) after the full 2,000-hour test. Meanwhile, glass-backsheet TOPCon modules showed higher power degradation, reaching up to 6%, though a few modules demonstrated notable resilience.
Addressing UVID degradation in TOPCon modules, Fraunhofer ISE implemented a modified stress test sequence comprising pre-aging, DH200, UV60, HF (1), UV60, and HF (2). During this sequence, a distinct 'W' pattern of power degradation emerged. The degradation caused by UV irradiation was partially reversed after each humidity freeze (HF) test. Haedrich noted that the W pattern varied across manufacturers, emphasizing the need for further investigations under outdoor field conditions to better understand this phenomenon.
Glass
In response to numerous inquiries about glass breakage issues observed after a few months in the field, Fraunhofer ISE conducted a series of tests to validate and investigate the root causes of these failures. Key tests included the SCALP test, which assesses the pre-stress of glass surfaces, and a mechanical load test to evaluate structural stability.
The SCALP test revealed that the glasses generally met high-quality standards in terms of manufacturer-defined surface pre-stress values. However, in the mechanical stability test, dual-glass modules with 2 mm thick glass on both sides – featuring the lowest surface stress values – failed earlier than their counterparts. Dual-glass modules with 1.6 mm glass and monofacial modules with 3.2 mm glass demonstrated superior durability. Additionally, Fraunhofer ISE introduced a mechanical load test with an inhomogeneous load profile to replicate real-world breakage patterns observed in the field.
Wattage Label Value
Fraunhofer ISE's Calibration Lab provided valuable insights into discrepancies between manufacturers' wattage label values and the actual measurements recorded during in-house testing. After filtering through extensive historical data, the lab analyzed 954 measurements. The findings showed that measured values were, on average, up to 2% lower than the module label values since 2016. Encouragingly, this deviation has improved, narrowing to approximately 1.3% by 2023.