Influence of photovoltaic welding strip on module

There are two forms of photovoltaic welding strip applied to photovoltaic modules: interconnection strip or bus bar and PV bus bar. In a typical silicon solar cell, both are needed. The interconnection strip is directly welded on the silicon crystal to connect the solar cells in the solar panel with each other. The interconnection strip carries the current generated by the solar cell to the PV bus. PV bus bar is a hot-dip tinned copper conductor installed around the periphery of solar panel. The PV bus connects the interconnection strip to the junction box. Thin film solar panels generally require busbars.

Photovoltaic welding strip is the key component of solar panel and an important factor to increase the efficiency of solar panel. The high efficiency of solar panels can only be achieved with high-quality photovoltaic welding strips properly installed in solar panels. High quality photovoltaic welding strip can also increase the production efficiency of solar panels and reduce the scrap rate. The quality of photovoltaic strip and its welding to solar cells are important factors for the efficiency and durability of solar panels.

1. At present, the welding strips in the market are mainly divided into silver containing and silver free welding strips. In addition to being expensive, the silver containing welding strip has its own advantages:

1) Increase the metallurgical bonding between solder and the metal to be welded. After welding, the mechanical strength and conductivity will be high.

2) After adding silver, the melting point of ternary alloy is lower than that of binary alloy, and its weldability and fluidity are increased.

3) The resistivity will decrease and the temperature resistance will increase.

2. The resistance of the welding strip is mainly determined by the size of the welding strip itself and the material of the copper substrate. The composition of the surface tin coating will not significantly affect the resistance of the welding strip. Increasing the width or thickness of the welding strip can reduce the resistance of the welding strip. This improvement plays the same role in both traditional welding methods and new low-temperature connection methods such as conductive silver glue or conductive tape connection. However, the welding strip wider than the width of the front electrode will block the incident light and cause current loss. We recommend using thicker welding strips without affecting the fragmentation rate.

3. The solar cell covered by the welding strip cannot absorb sunlight. Some welding strip companies have launched reflective welding strips. The front of the welding strip is silver plated and calendered with a longitudinal groove structure. This structure can reflect the light incident on the welding strip to the inner surface of the glass layer of the module at a relevant angle, and project it back to the battery surface after total reflection on the glass air interface. The captured light can make the module generate additional power, which can theoretically increase the efficiency of the module by about 2%.

4. Key quality parameters of photovoltaic welding strip

The performance index of photovoltaic welding strip is important in itself. The type and purity of copper determine the conductivity of the material and the softness of the welding strip. The composition of the flux, the thickness of the covering layer and the covering composition affect the quality of the solder joint, thus affecting the durability of the solar panel.

The high extensibility of photovoltaic welding strip is very important to prevent solder joint failure between bus bar and interconnection welding strip. This failure may occur due to the extension / tension caused by temperature oscillation during the operation of solar panel. During the service life of the solar panel, the continuous and sometimes fierce temperature oscillation makes the solder joint withstand the test during the service life of the solar panel (average 25 years).

Therefore, the influence of welding strip on component power generation is not only the design material of welding strip itself, but also the selection of welding strip, lamination process and quality control of welding strip production. It is necessary to understand the solder strip from all aspects, although the industry may pay more attention to packaging materials and battery chips.