Summary of SE battery implementation methods

The so-called selective emitter (SE-selective emitter) crystalline silicon solar cell is heavily doped at the contact part between the metal grid line (electrode) and the silicon wafer, and lightly doped at the position between the electrodes. Such a structure can reduce the recombination of the diffusion layer, thereby improving the short-wave response of light, and at the same time reduce the contact resistance between the front metal electrode and silicon, so that the short-circuit current, open-circuit voltage and fill factor are all improved, thereby improving the conversion efficiency.

Advantages of this structural battery

1. Reduce series resistance and improve fill factor

2. Reduce carrier Auger recombination and improve surface passivation effect

3. Improve the short-wave spectrum response of light, increase short-circuit current and open-circuit voltage

1. Printing phosphorus pulp (Yunnan Normal University)

Features: Phosphorus slurry is easy to volatilize at high temperature and has poor selectivity. It can also achieve selective diffusion in one go.

2. Etching out the diffusion mask layer (Nanjing China Electronics)

Features: The barrier layer is made of silicon oxide or silicon nitride, and the etching slurry mainly uses the released hydrogen fluoride for etching. The film thickness of silicon oxide can also be controlled to form a semi-barrier film and diffuse at one time. The difficulties lie in the printing performance of the slurry, diffusion uniformity, and printing alignment.

3. Direct printing of mask layer (schmid, centrotherm)

Features: The mask must have good printing properties, good resistance to hydrofluoric acid, and be easy to remove. The process steps are simple. The difficulties are uniform diffusion and printing alignment. Schmid's SE battery turnkey project with etching method, Centrotherm's SE battery turnkey project with laser etching oxide film.

4. Wet Etching of Heavy Diffusion Layer/Plasma Etching of Heavy Diffusion Layer

Features: The wet method can use hydrofluoric acid and nitric acid system or strong alkali to corrode the exposed heavy diffusion layer into a shallow diffusion layer. Corrosion-resistant slurry is required. Dry plasma uses fluoride ions formed by fluorides such as carbon tetrafluoride or nitrogen fluoride to etch the exposed medium-doped part. The dry method can also use silver paste as a mask.

5. LDSE (New South Wales)

Features: Laser and electroplating are used, with many processes and complex technology. There are many options for electroplating. The conductivity of electroplated silver is about 10 times that of silver paste. Precious metals can be saved. Using nickel-copper-silver, or nickel-copper-tin structure can save precious metals. The cutout line can be made very dense and thin, or other optimized structures can be used.

6. Silicon ink technology (Innovalingt, OTB)

Features: Just adding one more printing machine can significantly improve efficiency. It is also easy to upgrade based on existing process equipment.