The shading area of the photovoltaic welding strip is reduced by reducing the width of the main grid line and the PV welding strip, and the total amount of light received by the solar cell is increased. However, the contact resistance of the whole PV assembly is too large, which increases the electrical loss of the photovoltaic module.
According to IEC61215 standard, the light emitted by solar simulator is vertically incident on the surface of photovoltaic welding strip through glass and EVA. The change of surface structure of photovoltaic welding strip will change the reflection path of light on the surface of photovoltaic welding strip, affecting the size of α 1 in Fig. 1.
The quality of welding strip will directly affect the current collection efficiency of photovoltaic module, so it has a great impact on the power of photovoltaic module. The so-called photovoltaic welding strip is to coat binary or ternary low-melting alloy on the surface of copper strip with given specification.
The thickness of silicon wafer is 160 μm, the thickness of PV copper strip is 0.1 mm, the thickness of Sn alloy coating is 15 μm and 25 μm respectively. The physical properties of materials used in solar cell welding are shown in Table 6.
Connection of Cells in Photovoltaic Modules. As shown in Fig. 5, the solar cells in the modules with different surface structures of welding strips have no cracks, and there is no open welding, false welding and desoldering, which indicates that it can be used for the subsequent research.
The ununiform temperature field, mismatched thermal expansion coefficient and local plastic deformation during welding are the root causes of residual welding stress. The influence of welding process on the yield of solar cells has been discussed above.