According to the different types of solar cells, the production processes of different solar cells will also be different. An important step in determining the performance of cell is the cleaning and texturing of the solar cells. The quality of the production process of monocrystalline silicon solar cells can determine whether they have high use value in the application process. Millennial Solar's 3D Confocal Microscope can easily inspect the textured surface of solar cells and use the data it generates to inspect the cleaning, texturing and screen printing processes of monocrystalline silicon solar cells. In this issue of Millennial Solar, we will introduce you to the cleaning and texturing of monocrystalline silicon solar cells!

How monocrystalline silicon solar cells work

Monocrystalline silicon solar cells are a common type of solar cell, and their working principle is to use the photoelectric effect to convert solar energy into electrical energy. When sunlight strikes a solar cell, the photons are absorbed by the semiconductor material, exciting electrons and holes. Electrons and holes are separated in the p-n junction. The electrons move to the n-type semiconductor and the holes move to the p-type semiconductor, forming a potential difference. This potential difference is the voltage of the solar cell. If electrodes are drawn out on both sides of the cell and a load is connected, "photo-induced current" will pass through the load.

Textured monocrystalline silicon solar cells

The preparation of monocrystalline silicon textured surface is the use of anisotropic etching of silicon to form millions of tetrahedral cones, also called pyramid structures, per square centimeter of silicon surface. Due to the multiple reflections and refractions of incident light on the surface, the absorption of light is increased, and the short-circuit current and conversion efficiency of the cell are improved. Anisotropic corrosion solutions for silicon usually use hot alkaline solutions. Available alkali include sodium hydroxide, potassium hydroxide, lithium hydroxide and ethylenediamine.

Most of them use cheap dilute sodium hydroxide solution with a concentration of about 1% to prepare textured silicon, and the corrosion temperature is 70-85°C. In order to obtain a uniform textured surface, alcohols such as ethanol and isopropyl alcohol should be added to the solution as chelating agents to accelerate the corrosion of silicon. Before preparing the textured surface, the silicon wafer needs to undergo preliminary surface etching. Use alkaline or acidic etching solution to remove about 20~25μm. After etching the textured surface, perform general chemical cleaning. Silicon wafers that have been surface-prepared should not be stored in water for a long time to prevent contamination, and must be diffused and sintered as soon as possible.

3D Confocal Microscope

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Millennial Solar 3D Confocal Microscope is an optical instrument specially used in the photovoltaic industry to inspect the quality of grid lines on the surface of photovoltaic cells. Based on the principle of optical technology, combined with precision Z-direction scanning module, 3D modeling algorithm, etc., the device surface is non-contactly scanned and a 3D image of the surface is established. The height and width of the grid lines on the photovoltaic cells and the texture on the surface are measured through the system software. The number of pyramids is quantitatively tested to provide feedback on the quality of photovoltaic cell cleaning, texturing and screen printing processes.

The production of high-efficiency monocrystalline silicon solar cells is often based on high-quality monocrystalline silicon materials and mature processing techniques. In order to ensure the ultra-high photoelectric conversion rate of monocrystalline silicon solar cells, its process flow needs to be strictly controlled. 3D Confocal Microscope can accurately control the production process of monocrystalline silicon solar cells, allowing manufacturers to produce high-quality solar cells faster and more efficiently! Millennial Solar will put quality and service first,  strive to make great progress in the future development!