What is the difference between monocrystalline and polycrystalline silicon for solar panels? Which one is more expensive?

Monocrystalline silicon solar panels are more expensive. The differences between the two are as follows:

1. Different manufacturing processes

To process monocrystalline solar cells, the silicon wafer must first be doped and diffused. Generally, the dopants are trace amounts of boron, phosphorus, antimony, etc. The diffusion is carried out in a high-temperature diffusion furnace made of quartz tubes. In this way, a P/N junction is formed on the silicon wafer. Then, the screen printing method is used to print the prepared silver paste on the silicon wafer to make a grid line. After sintering, the back electrode is made at the same time, and an anti-reflection source is coated on the surface with the grid line to prevent a large number of photons from being reflected by the smooth silicon wafer surface. At this point, the monomer of the monocrystalline silicon solar cell is made.

The process of processing polycrystalline solar cells is to select polycrystalline blocks or monocrystalline silicon head and tail materials with a resistivity of ~ ohm-cm, crush them, and use a 1:5 mixture of hydrofluoric acid and nitric acid for appropriate corrosion, then rinse with deionized water to neutralize, and dry them.

Use a quartz crucible to fill the polycrystalline silicon material, add an appropriate amount of borosilicate, put it into a casting furnace, and heat and melt it in a vacuum state. After melting, it should be kept warm for about 20 minutes, and then injected into the graphite mold. After slowly solidifying and cooling, a polycrystalline silicon ingot is obtained. This silicon ingot can be cast into a cube so that it can be sliced and processed into a square solar cell, which can improve the material utilization rate and facilitate assembly.

2. Different photoelectric conversion rates

The highest conversion efficiency of single-crystal silicon cells in the laboratory is 24.7%, and the conversion efficiency of ordinary commercial products is 10%-18%. The highest efficiency of polycrystalline silicon solar cells in the laboratory is 20.3%, and the general commercialization is generally 10%-16%. Although it seems that the conversion rate of single-crystal silicon is higher, the final efficiency of the finished solar panels made of single-crystal and polycrystalline cells is similar.

First, the lifespan and stability of single-crystal silicon solar cells are very good. Secondly, although the average conversion efficiency of single-crystal silicon solar cells is about 2% higher than that of polycrystalline silicon solar cells, because single-crystal silicon solar cells can only be made into quasi-squares (the four tops are arcs), when forming a solar cell module, there is a part of the area that cannot be filled, while polycrystalline silicon solar cells are square, and there is no such problem. Therefore, for solar panels, the efficiency is basically the same.

3. Different appearance

Color: The base color of the monocrystalline silicon surface is black or light blue, and the base color of the polycrystalline silicon surface is mostly blue or colorful.

Area: Compared with the monocrystalline panels of the same power, the area of the polycrystalline panels is slightly larger than that of the monocrystalline panels.

Solar panels: Due to the manufacturing process of monocrystalline silicon solar cells, the semi-finished silicon ingots are generally cylindrical. After slicing, the four corners of the single monocrystalline silicon cell are rounded. After splicing into solar panels, there will be obvious diamond-shaped gaps.

Polycrystalline silicon solar cells, generally, the semi-finished silicon ingots are cubic, and the single polycrystalline silicon cell is square after slicing. When spliced into solar panels, there is a higher filling rate, and the product is relatively more beautiful.

4. Different market trends and prices

Due to the different manufacturing processes of the two solar cell materials, the energy consumed in the manufacturing process of polycrystalline silicon solar cells is about 30% less than that of monocrystalline silicon solar cells.

In terms of production cost, polycrystalline silicon solar cells are cheaper than monocrystalline silicon solar cells, the material manufacturing is simpler, the power consumption is saved, and the total production cost is lower. Therefore, polycrystalline solar panels have been developed in large quantities today and are also the most widely used solar panels.

Therefore, the market price of monocrystalline solar panels is relatively high, but polycrystalline solar panels are more widely installed and used. However, since monocrystalline cells cannot cover the entire solar panel, and polycrystalline cells do not waste area, the power generation efficiency of the two is not much different.