Screen printing technology in solar cell manufacturing
A solar cell is a device that converts solar energy into electrical energy using the photovoltaic effect. It is the basis and core of solar power generation. At present, there are two main challenges in the production of photovoltaic cells. Firstly, how to increase the conversion efficiency of solar cells to increase the amount of electricity generated per square meter of panel components. Secondly, how to enhance the manufacturing power of solar cells through existing technology before increasing investment costs. The screen printing technology for the production of the back field and positive electrode of solar cell wafers is becoming more and more mature and popular in the production of photovoltaic cells.
Solar cell screen printing
The position of screen printing in the manufacturing process of photovoltaic cells.
The process of manufacturing crystalline silicon photovoltaic cells involves printing back electrodes, aluminum back fields, and front electrodes. The quality of electrode printing largely determines the performance of the solar cell. Therefore, it is a major link in the process of photovoltaic cell manufacturing. Using screen printing technology, a highly chemically active metal paste is printed on the silicon wafer, and the metal paste is cured by drying and then quickly fired at high temperature. Under the action of the chemically active metal paste, an alloy layer is formed between the metal and the silicon crystal, resulting in good contact and aluminum back fields.
Screen printing technology
Screen printing is a method of printing pre-designed graphics onto a substrate by using pressure. The equipment is composed of three parts: printing of silver and aluminum paste on the back of the battery, aluminum paste on the back of the battery, and silver paste on the front of the battery. The working principle is that the screen graphic's mesh holes allow the paste material to pass through, and a certain amount of pressure is applied to the paste portion on the screen with a scraper while moving towards the other end of the screen. The paste material is squeezed out of the graphic part's mesh holes onto the substrate during movement. The print is fixed in a certain range due to the viscosity of the paste material. The doctor blade is always linearly in contact with the screen and substrate during printing, and the contact line moves with the scraper, completing the printing process and obtaining the printed graphics. Screen printing technology is a way to compress the mixture of conductive paste containing metal into mesh holes, creating new circuits and electrodes on the crystalline silicon wafer and deriving photovoltaic cells from photoelectrons. The metal-containing slurry is pressed onto the crystalline silicon wafer with an already formed P-N junction. The silver and aluminum paste is separately pressed into a back electrode in which the slurry contains the impurities and generates a P+ layer. The aluminum backfield reduces the amount of carrier composite material, converging particles with positive charges to increase voltage. Printing silver paste has a great advantage in collecting particles with positive and negative charges and making it easier to generate electrodes. The back electrode is an electrode of a photovoltaic cell plate printed with silver and aluminum paste (or silver paste) on the backside of the battery sheet (i.e., on an untreated surface). The fact that aluminum is a P-type impurity reflects the function of the backfield. The slurry required for actual manufacturing is mainly aluminum paste. The demand of the back electrode printing for slurry includes: being the actual positive electrode of the photovoltaic cell, requiring good welding skills, and so on. There is a column of fine grid lines and the main electrode with an average spacing on the surface and front of the photovoltaic cell, and there is a reduced anti-reflection film. The positive electrode of the photovoltaic cell is actually the negative pole in physics, and the grid lines play a role in collecting current. The ultimate goal of the photovoltaic cell is to have a high, thin positive electrode. The main power grid not only has the function of collecting current but also has good welding properties. The most important material required for the front electrode in actual production is silver paste.
Quality Control of Wire Mesh
In the actual manufacturing process, in order to ensure the quality and stability of battery silicon plate printing, it is necessary to test the quality of battery silicon plate printing and check the integrity of screen printing. The following aspects are generally considered: whether the print pattern of the back electrode is complete, whether the lines are smooth, whether there is no leakage of slurry, no deviation, no edge collapse. Whether the print pattern of the back field is complete, whether there is no pulp leakage, deviation, edge collapse, loss, silicon leakage, falling off, aluminum loops, aluminum beads, aluminum thorns and other phenomena. Whether the pattern of the positive electrode is complete, whether there are bias, broken edges, open lines, false prints, fine grid line thickening, and loss of the main electrode. Test the print quality of each process.