HJT Module Inspection: The Core Safeguard for the Implementation of High-Efficiency Photovoltaic Tec

　　Heterojunction (HJT) modules, with their technical advantages such as high open-circuit voltage, low temperature coefficient, bifaciality, and compatibility with ultra-thin silicon wafers, are becoming the core direction for the high-efficiency transformation of the photovoltaic industry. However, their intrinsic characteristics—like the amorphous silicon/crystalline silicon heterostructure and the use of ultra-thin substrates—impose far more stringent requirements on production quality control compared to traditional modules. Inspection, serving as the quality gate throughout the entire module lifecycle, is not only a core method for verifying product performance but also a critical support for ensuring the long-term revenue of PV power plants. The technical depth and coverage breadth of inspection directly determine the successful realization of HJT's technological advantages.

　　The inspection system for HJT modules must precisely match their structural characteristics, establishing a comprehensive evaluation framework covering electrical performance, defect diagnosis, and reliability.

　　Electrical Performance Testing: The Core Foundation

　　Electrical performance testing is fundamental, focusing on accurately capturing the module's power generation capability and environmental adaptability. Unlike conventional modules, HJT modules are highly sensitive to spectral response. Current-Voltage (IV) characteristic testing must employ a Class AAA solar simulator compliant with the AM1.5G standard, ensuring accuracy through strict spectral matching calibration. Testing must focus on key parameters like open-circuit voltage (Voc), short-circuit current (Isc), and fill factor (FF), with particular emphasis on low-irradiance performance and temperature coefficient measurement. The former relates to power generation efficiency under cloudy conditions, while the latter directly impacts power stability in high-temperature environments. Industry standards typically require the maximum power temperature coefficient to be no lower than -0.30%/°C. For bifacial HJT modules, a dual-side illumination test method is necessary to accurately quantify the bifacial gain ratio and avoid performance miscalculation from single-side testing.

　　Visual and Internal Defect Inspection: A Key Barrier Against Early Failure

　　The ultra-thin silicon wafers (some already below 110μm) and fine electrode structure of HJT modules offer very low tolerance for manufacturing process variations. Visual inspection must strictly identify defects like paste leakage, broken fingers, and print misalignment according to standards such as T/CPIA 0055.2-2024. For instance, the allowable broken distance for front-side fine grid fingers should not exceed 0.5mm, with no more than 4 breaks per cell. Internal defect diagnosis relies on the synergistic application of Electroluminescence (EL) and Photoluminescence (PL) imaging: EL inspection, conducted in a dark environment, can detect micro-cracks, poor soldering, etc., while PL inspection, using laser excitation imaging, can accurately identify passivation layer defects and abnormal interface recombination at the heterojunction, providing direct evidence for process optimization. Applying these non-destructive testing technologies can increase the pre-shipment defect detection rate to over 99%, curbing potential power degradation at the source.

　　Reliability Testing: The Core Method for Verifying Long-Term Service Life

　　Reliability testing is essential for verifying the long-term service capability of HJT modules and requires specialized test protocols designed for their material properties. Environmental adaptability tests should cover damp heat, salt mist, UV aging, and other typical conditions. Specifically, the 1000-hour damp heat test at 85°C/85% relative humidity effectively evaluates the hydrolysis stability of the amorphous silicon film and encapsulant materials. For modules deployed in specific environments, targeted testing is needed: modules for desert areas require enhanced sand dust abrasion and high-temperature resistance tests, while those for coastal regions need to validate anti-corrosion performance through a 96-hour neutral salt spray test. Mechanical load testing must fully consider the brittleness of thin wafers, applying positive and negative loads of 5400Pa using a step-loading method to simulate extreme wind and snow pressure, alongside hail impact tests using 25mm diameter ice balls to verify impact resistance. Furthermore, Potential Induced Degradation (PID) testing is indispensable. By applying a negative bias voltage under high temperature and humidity, it ensures the module's power degradation rate is controlled within 5%, guaranteeing performance stability over a 25-year service life.

　　The Evolution of Inspection Technology

　　As HJT technology scales up, inspection technology is evolving towards greater precision and intelligence. To meet the demands of large-format module testing, inspection equipment has achieved simultaneous improvements in test area coverage and precision; IV curve testers now feature microsecond-level sampling speeds, accurately capturing transient power characteristics. The deep integration of AI technology is revolutionizing inspection modes. Through algorithm training, automatic classification and root cause analysis of defects like micro-cracks and broken fingers are achieved, with recognition accuracy exceeding 99%. This is combined with Manufacturing Execution Systems (MES) to build a full-process quality traceability system from wafer to module. In the future, with the development of perovskite/HJT tandem cells, inspection technology will further break through bottlenecks in assessing the spectral response range and interface characteristics, providing crucial support for the industrialization of next-generation high-efficiency modules.

　　In conclusion, inspection of HJT modules is not merely a technical means of quality control but the core guarantee for realizing their high-efficiency value. From the precise quantification of electrical performance to the comprehensive validation of reliability, from defect screening at production to quality traceability throughout the entire lifecycle, the continuous advancement and standardization of inspection technology will propel the large-scale application of HJT modules in PV power plants, injecting stable and efficient green power into the global energy transition.