Photovoltaic cell nondestructive laser scribing technology

The technological innovation based on the cutting of photovoltaic cells has derived a wide range of new photovoltaic module products, such as half-cell modules, 210-cell three-cell modules, shingled modules, plate interconnect modules, seamlessly welded multi-bus grid modules, etc., laser Splitting has become an indispensable process for the iterative upgrade of component products.

Conventional laser scribing technology in the market is mainly based on laser ablation and mechanical splitting technology: first, a laser is used to process a cutting path through the surface of the battery on the back of the battery, and then a mechanical method is used to split the battery slices along the cutting path. Although the introduction of multi-knife laser cutting technology reduces the damage of conventional laser scribing machines to the cells to basically meet the requirements of enterprises, with the ultra-small cell spacing (zero spacing or even negative spacing), large-size silicon wafers and ultra-low temperature batteries With the birth of process routes, conventional laser scribing processes cannot meet the requirements of ultra-high processing quality. With years of technical accumulation, Han's Photovoltaic Equipment has launched a revolutionary non-destructive laser scribing technology, and strives to promote it as the mainstream market. This technical solution completely solves the inevitable cell damage problem of conventional laser scribing machines.

The core principle of the non-destructive laser scribing technology is the laser thermal stress control fracture technology: the laser is used to quickly heat the material locally, followed by the supporting cooling technology to produce an uneven temperature field, which will generate temperature on the material surface Gradient, thereby inducing the generation of thermal stress; where the laser spot is in a state of compressive stress, and the laser spot is in a state of tensile stress before and after the laser spot. Because the compressive stiffness of brittle materials is much greater than the tensile strength, when the tensile stress reaches the breaking strength of the material, The material will fracture, and the fracture will steadily expand with the moving track of the laser and subsequent cooling. The premise is that an ultra-small notch is processed on the edge of the cell, and the fracture expansion will start from the notch.

The main differences and advantages of non-destructive laser scribing technology and conventional laser scribing technology are as follows:

Section morphology

The cutting track formed by conventional laser scribing on the surface of the battery: the width is 30μm, the depth is 60-90μm, and the lateral heat-affected zone on the surface will expand to about 80μm. The cross-sectional morphology is shown in Figure 3. About 50% of the cross-sections are thermally damaged. ; The cut-off surface of the non-destructive laser scribed silicon wafer is clean and there is no damage point. The main reason is that there is no laser high temperature ablation process in the non-destructive scribe process.

Processing dust

The conventional laser scribing process requires the removal of silicon material in the cutting channel, which generates a large amount of silicon dust, which requires a specially designed dust removal device, otherwise it is easy to cause fire; while the amount of dust generated by the non-destructive laser scribing process is very small and can be ignored;

Processing temperature

The temperature control range of the non-destructive laser scribing process is 150-250℃, which is a low temperature process;

Performance Testing

Three-point bending strength: Compared with the whole cell, the strength of the non-destructive laser scribing cell remains almost unchanged, while the strength of the conventional laser scribing cell is reduced by more than 10%, which further proves that the non-destructive laser scribing machine solves the battery The problem of chip damage, which is conducive to the control of the fragmentation rate and repair rate during the product processing, and at the same time can enhance the reliability of the product in the long-term outdoor application environment, thereby reducing the cost of the enterprise. The above advantages are conducive to the industry's large-size silicon wafers and The introduction of a new process of more than three scribing; in terms of electrical performance, compared with conventional laser scribing, the power of non-destructive laser scribing PERC components is slightly increased, mainly due to the reduction of thermal damage.

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