A diffusion technique applied on silicon solar battery

Abstract

The invention relates to a diffusion process which is applied in a silicon solar cell, the diffusion steps can be mainly divided into two steps, which specifically include: (1) a first diffusion is carried out: a silicon wafer is placed in a diffusion furnace, big nitrogen, small nitrogen and oxygen are introduced simultaneously, the diffusion temperature is at 800 to 860 DEG C and the time is 15 to 30 minutes; (2) the temperature of the diffusion furnace is increased to 870 to 920 DEG C, the silicon wafer is stably placed for 10 to 30 minutes and then is distributed; (3) a second diffusion is carried out: the diffusion temperature is at 870 to 920 DEG C, the time is 1 to 10 minutes; (4) the diffusion process is finished, the temperature of the diffusion furnace is decreased and the silicon wafer is taken out. The invention can obtain more optimized doping curve in an emission region based on the method, thereby reducing the Auger recombination which is caused by high doping in the emission region and improving the short-circuit current of the cell by 0.5 to 1mA / cm<2>. A sheet resistance in the emission region and a contact resistance between the emission region and a grid line can not be increased by using the method; furthermore, all the diffusion steps are continuously carried out in a furnace tube, and the complexity of the technique is not increased.

Description

technical field [0001] The invention relates to a diffusion process, in particular to a diffusion process applied to silicon solar cells. Background technique [0002] Diffusion technology is the most important process of monocrystalline silicon and polycrystalline silicon solar cells. Its purpose is to form an emitter region with the conductivity type opposite to that of the substrate, thereby forming a PN junction. Usually monocrystalline silicon and polycrystalline silicon solar cells use P-type substrates, phosphorus oxychloride (POCl 3 ) liquid source diffusion, through a series of chemical reactions and phosphorus atom diffusion process to form a phosphorus-doped N-type emitter region. Generally, the diffusion temperature is set at 830-870°C, and the power-on time is 20-35 minutes; during the high temperature process, POCl 3 Nitrogen (generally called this part of nitrogen as small nitrogen) is carried into the quartz tube, and nitrogen (generally called this part of...

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Problems solved by technology

If the concentration of the emission area is low, that is, the sheet resistance is high, the resistance of the emission area must increase, which increases the resistance of the current moving to the electrode of the grid line in the emission area; and because the conduction between the electrode and the emission area depends on the tunneling effect, The contact resistance between the electrode and the emitter region is also related to the doping amount. The higher the doping, the smaller the contact resistance; if the doping is too low, the contact resistance will increase rapidly, and even ohmic contact cannot be formed.

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