Hidden cracks, hot spots, and PID effects are three important factors that affect the performance of crystalline silicon photovoltaic modules. Today, we will take you to understand the causes of hidden cracks in solar cells, how to identify and prevent them.

1、 Formation and classification of hidden cracks in photovoltaic modules
Hidden cracks are a common defect in crystalline silicon photovoltaic modules, commonly known as micro cracks that are not visible to the naked eye. Crystalline silicon components are prone to rupture due to their inherent crystal structure characteristics. In the production process of crystalline silicon components, many links may cause hidden cracks in the battery cells. The fundamental cause of hidden cracks:

External force: Battery cells are subjected to external forces during welding, lamination, framing, handling, testing, and other processes. Improper parameter settings, equipment malfunctions, or improper operation can cause hidden cracks.

High temperature: If the battery cells are not preheated at low temperatures and suddenly expand when exposed to high temperatures in a short period of time, it can cause hidden cracks, such as excessive welding temperature, unreasonable laminating temperature, and other parameter settings.

Raw materials: Defects in raw materials are also one of the main factors leading to hidden cracks.

According to the shape of hidden cracks in battery cells, they can be roughly divided into five types: tree like cracks, comprehensive cracks, oblique cracks, cracks parallel to the main grid line, cracks perpendicular to the grid line, and cracks that run through the entire battery cell.

2、 The impact of "hidden cracks" on component performance
The current generated by crystalline silicon solar cells is mainly collected and exported by the main and fine grid lines perpendicular to each other on the surface. Therefore, when hidden cracks (mostly parallel to the main gate line) cause the thin gate line to break, the current cannot be effectively delivered to the main gate line, resulting in partial or even complete failure of the battery cell, and may also cause fragments, hot spots, etc., while causing power attenuation of the component.

3、 Methods for identifying "hidden cracks"
EL (Electroluminescence) is an internal defect detection device for solar cells or components, which is a simple and effective method for detecting hidden cracks. By utilizing the principle of electroluminescence in crystalline silicon, high-resolution infrared cameras are used to capture near-infrared images of components, and defects in the components are obtained and determined. It has the advantages of high sensitivity, fast detection speed, and intuitive results. The following figure shows the detection results of EL, clearly displaying various defects and hidden cracks.

4、 Reasons for the formation of "hidden cracks"
There are many factors that can cause hidden cracks in components, and there are also many types of hidden cracks. However, not all hidden cracks will have an impact on battery cells, let alone "hidden" discoloration. As long as scientific prevention is taken, hidden cracks in components can be appropriately avoided. During the production process, it is necessary to avoid improper external force intervention on the battery cells and also pay attention to the range of temperature changes in the storage environment. During the welding process, the battery cells should be pre insulated (hand soldered) and the temperature of the soldering iron should meet the requirements. In the process of component production, transportation, installation, and maintenance, considering the easy cracking characteristics of crystalline silicon components, it is necessary to pay attention to and improve the operation process in various stages of installing power plants, and minimize the occurrence of hidden cracks in components.

5、 Key points for preventing hidden cracks in photovoltaic modules
During the production process and subsequent storage, transportation, and installation, avoid improper external forces on the battery cells, and also pay attention to the temperature range of the storage environment.

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