Silicon is a common material in solar energy because it is used to make solar panels. Two main types of silicon-based material used in solar panels are monocrystalline and polycrystalline silicon, both of which come from silicon wafers. This article will explain what monocrystalline silicon wafers are and the difference between them and polycrystalline silicon wafer.
1. What is monocrystalline silicon wafer?
A monocrystalline silicon wafer is made of a single crystal structure. This means that it is continuous and fracture free throughout the entire crystal structure. Because of its neat structure, it conducts electricity very well, which makes monocrystalline silicon wafers excellent for use in solar cells.
Characteristics of monocrystalline silicon wafers:
1. Crystalline structure: Monocrystalline silicon wafers are made from complete monocrystalline silicon crystals and have a very ordered lattice structure. This makes them excellent conductors of electricity and heat.
2. High purity: The process of making monocrystalline silicon wafers must be done to very strict standards, and the silicon material must be over 99.9999% pure. This high purity helps improve the performance and reliability of semiconductor devices.
3. Large size: Monocrystalline silicon wafers typically have large dimensions, with common diameters reaching several inches. This allows single crystal silicon wafers to be cut into multiple chips, improving production efficiency.
2. What is polycrystalline silicon wafer?
Polycrystalline silicon wafers are different from monocrystalline silicon wafers. They are made up of lots of different crystal structures that randomly form during the cooling process. This means that the surface of the wafer has different textures and colours, which creates a patterned look. They are also relatively cheap to make. However, because the crystal structure of polycrystalline silicon wafers is less neat than that of monocrystalline silicon wafers, they are slightly less efficient.
Characteristics of polycrystalline silicon wafers:
1. Crystalline structure: Polycrystalline silicon wafers are made up of many grains, with grain boundaries between them. These boundaries can make it hard for electrons to pass through, which affects the electrical properties of the wafer.
2. They are also less pure. Compared to silicon wafers made from a single crystal, polycrystalline silicon wafers have slightly lower purity. This is because when polycrystalline silicon is made, there may be impurities or defects inside the grains.
3. They are also relatively inexpensive. The process of making polycrystalline silicon wafers is simple and cheap. This makes them a good choice for certain applications where cost is important.
3. The difference between crystalline silicon wafers and polycrystalline silicon wafers
Monocrystalline silicon wafer and polycrystalline silicon wafer are two common silicon materials, but there are some differences in how they are structured and how well they work. The following text will explain the main differences between monocrystalline silicon wafers and polycrystalline silicon wafers:
1. Electrical properties: Single crystal silicon wafers have better electrical properties because they have a complete lattice structure and no grain boundaries. They conduct electricity better and have fewer impurities, making them suitable for manufacturing high-performance semiconductor devices.
2. Cost: The process of making monocrystalline silicon wafers is more complex and requires higher purity, which makes it more expensive. The preparation of polycrystalline silicon wafers is relatively simple and cost-effective.
3. Application areas: Monocrystalline silicon wafers are used to make high-performance semiconductor devices like integrated circuits and solar cells because they have better electrical properties. Polycrystalline silicon wafers are mainly used in fields where low performance is enough, for example in inverters and power modules.
4. Appearance: Monocrystalline silicon wafers usually have a uniform colour and texture, while polycrystalline silicon wafers have a granular or grain boundary texture.
It should be noted that monocrystalline silicon wafers and polycrystalline silicon wafers have different process requirements during the manufacturing process. Monocrystalline silicon wafers are made by growing a single crystal, which gives them a single grain. Polycrystalline silicon wafers are made by melting silicon and then quickly making it solid again. This is also one of the reasons for the differences in structure and performance between the two types.
Summarize
In practice, the right silicon material can be chosen based on the specific needs of the application. The right silicon material can be chosen based on what is needed for a particular application. The choice of monocrystalline or polycrystalline silicon is based on efficiency, cost and how it will be used. Monocrystalline silicon has a higher conversion efficiency due to its homogeneous crystal structure (about 15%-22%), which is suitable for scenarios where space is limited or where a high return is required over a long period (e.g. rooftop photovoltaics); polycrystalline silicon has a slightly lower efficiency (about 13%-18%), but the production cost is about 20% lower, which makes it more suitable for budget-sensitive or large-area ground-based power plants. If the project is in a region with high temperatures, monocrystalline silicon is better (temperature coefficient -0.3% to -0.5%/°C vs. -0.4% to -0.6%/°C for polycrystalline silicon). The current monocrystalline PERC technology is the most popular (more than 80% of the market by 2023), but polysilicon is still competitive for low-priced products. Focus on monocrystalline silicon to get the best efficiency and intensification, and use polysilicon to keep an eye on the initial cost.
