EVO5N 625W Bifacial N-type TOPCon 156 Cells Solar Module

1. Texturing

The texturing section (a total of 6 lines) includes in turn

pre-cleaning

Pure water washing before velvet

Texturing*3

Pure water washing after velvet

after cleaning

After washing, wash with pure water

pickling

Pure water washing after pickling

slow pulling pre-dehydration

drying*5 etc.

2. Boron diffusion

The purpose of the diffusion process is to form a PN junction on the silicon wafer to realize the conversion of light energy into electrical energy. The PN junction manufacturing equipment is a diffusion furnace. The project uses gaseous boron trichloride to diffuse the silicon wafer in the diffusion furnace. Boron atoms diffuse into the silicon wafer and form a layer of borosilicate glass on the surface of the silicon wafer. The main reaction equation is:

4BCl3+3O2→2B2O3+6Cl2↑

2B2O3+3Si→3SiO2+4B

3. SE laser redoping

The laser doping technology is to do heavy doping on the contact part of the metal grid line (electrode) and the silicon wafer, while keeping the light doping (low concentration doping) outside the electrode. Pre-diffusion is carried out on the surface of the silicon wafer by thermal diffusion to form light doping; at the same time, the surface BSG (borosilicate glass) is used as a local laser heavy doping source. Through the local thermal effect of the laser, the atoms in the BSG rapidly diffuse into the silicon wafer for the second time to form a local heavy doping region.

4. Post-oxidation

Where the surface of the silicon wafer is treated by laser SE, the oxide layer on the boron diffusion surface (light incident surface) is destroyed by the spot energy of the laser. During alkali polishing and etching, an oxide layer is required as a mask layer to protect the phosphorus diffusion surface (light incident surface) of the silicon wafer. Therefore, it is necessary to repair the oxide layer on the surface scanned by laser SE.

5. POPAID deposition in-situ doping

The POPAID process is a key process for integrating the plate coating prepared by the tunnel oxide layer and the doped silicon layer.

6. Annealing

Place the silicon wafer in a reaction tube made of quartz glass, and the reaction tube is heated by a resistance wire heating furnace to a certain temperature (the commonly used temperature is 900-1200°C, and it can be lowered to below 600°C under special conditions). When oxygen passes through the reaction tube, a chemical reaction occurs on the surface of the silicon wafer:

Si (solid state) + O2 (gas state) → SiO2 (solid state)

7. BOE cleaning

Pickling tank*2

washed

After pickling (HCL/HF/DI)

washed

slow lifting

drying*6

8. Front coating

The basic principle is to use high-frequency photo-discharge to generate plasma to affect the film deposition process, promote the decomposition, combination, excitation, and ionization of gas molecules, and promote the generation of reactive groups.

The main chemical reactions that occur during PECVD deposition of silicon oxynitride films are:

SiH4+NH3+N2O→xSi2O2N4+N2↑+yH2↑

9. Backside coating

The main chemical reactions that occur during PECVD deposition of silicon oxynitride films are:

SiH4+NH3+N2O→xSi2O2N4+N2↑+yH2↑

10. Metallization

1) printing

During the printing process, the slurry is above the screen, and the scraper is pressed against the screen with a certain pressure, so that the screen deforms and contacts the surface of the silicon wafer. The slurry touches the surface of the silicon wafer through extrusion; the surface of the silicon wafer has a strong adsorption force, which snatches the slurry out of the mesh. At this time, the scraper is in operation, and the previously deformed stencil will make the slurry fall smoothly on the surface of the silicon wafer under the action of good restoring force. Among them, the silver paste is a paste printing paste made of ultrafine high-purity silver and aluminum powder as the main metal, and a certain amount of organic binder and resin as auxiliary agents.

2) Sintering

Sintering is to sinter the main fine grid paste printed on the silicon wafer into a cell at high temperature so that the electrodes are embedded in the surface, forming a firm mechanical contact and a good electrical connection, and finally forming an ohmic contact between the electrode and the silicon wafer itself.

3) Electroinjection

After the cells are sintered, the method of direct electric injection of carriers (reverse injection of direct current) is used to change the charge state of the hydrogen in the silicon body, so that the attenuated boron-oxygen complex can be well passivated and transformed into a stable regenerative ecology, and finally achieve the purpose of anti-light decay.

11. Test packaging

After the solar cell is manufactured, the electrical performance parameters of the solar cell will be tested with testing instruments (such as measuring its I-V curve and light conversion rate and other electrical parameters). After the test is completed, the battery will be automatically divided into multiple levels according to certain standards.