This chapter introduces monocrystalline silicon and polycrystalline silicon photovoltaic modules
1.1 Monocrystalline silicon photovoltaic modules
Monocrystalline silicon photovoltaic modules are processed by monocrystalline silicon solar cells through packaging technology. The early crystalline silicon photovoltaic modules mainly used wafer-shaped monocrystalline silicon solar cells. At that time, the representative manufacturer was Siemens, and in China, Ningbo Solar (Sundi), Yunnan Semiconductor Factory (TianDa) and other companies produced it. Figure 1-1 shows the monocrystalline silicon wafer cell module produced by Sundi. With the improvement of single crystal furnace technology, the diameter of single crystal pull rods can be made larger and larger, so that the diameter and area of single crystal silicon wafers can be increased. The monocrystalline solar cells made by cutting the monocrystalline silicon round rods generally have rounded corners, which are also called chamfers. The diameter of the chamfered corners is getting smaller and smaller with the advancement of technology, so that the single crystal cells can be continuously improved. The utilization rate of crystalline silicon rods improves the efficiency of cells and modules. The polycrystalline silicon battery has no chamfers and is completely square, which is the easiest feature for single crystal silicon and polycrystalline silicon batteries to identify. In the early days of monocrystalline silicon cells, due to the limitation of the diameter of monocrystalline silicon rods, the processed cell size was generally 100mm100mm or 125mm125mm. With the development of technology, the general monocrystalline silicon cell size is now 156mm156mm, and the assembled component products usually use 6 strings of 10 cells = 60 cells in series and 6 strings of 12 cells = 72 cells in series are two types of battery layout.
Figure 1-1 Sundi company monocrystalline silicon wafer battery module
1.2 Polycrystalline silicon photovoltaic modules
Polycrystalline silicon photovoltaic modules are mainly composed of polycrystalline silicon solar cells. The industrialization of polycrystalline silicon solar cells is an important technological advancement in the photovoltaic industry, and it is also a key breakthrough in realizing the low-cost development of crystalline silicon photovoltaic modules. The successful application of polycrystalline silicon wafers in solar cell production is mainly attributed to advances in material science, namely, the directional solidification crystal growth technology of polycrystalline silicon ingots and the passivation technology of hydrogen-containing silicon nitride thin film materials in the battery process. Polycrystalline silicon wafers are cut from polycrystalline silicon ingots. Polycrystalline silicon ingots are generally produced by directional solidification casting, with low energy consumption and simple process. Since the production cost of polycrystalline silicon wafers is much lower than that of monocrystalline silicon wafers, polycrystalline silicon photovoltaic modules have gradually become mainstream products on the market. Polysilicon technology developed rapidly around 2008. Polysilicon cells can be directly made into a size of 156mm156mm. Usually, 6 strings of 10 cells = 60 cells in series and 6 strings of 12 cells = 72 cells in series are used in two types of cell layout. Figure 1-2 shows a single crystal silicon and polycrystalline silicon photovoltaic module with 60 cells connected in series.
Figure 1-2 Single crystal silicon and polycrystalline silicon photovoltaic modules connected in series with 60 cells
Polycrystalline silicon solar cells have crystal defects such as grain boundaries, Li crystals, and stacking faults, and their efficiency is about 1% to 2% lower than that of monocrystalline silicon. However, because the polycrystalline silicon wafers are almost perfectly square, the laying density of cells in polycrystalline silicon modules is relatively low high. With the improvement of monocrystalline silicon wafer production technology, the chamfers of monocrystalline silicon wafers are getting smaller and smaller, and the laying density gap between the two modules has been reduced to a certain extent. The efficiency of the final finished module mainly depends on the efficiency of solar cells, module size and Packaging process, etc.