Diffusion process for crystalline silicon solar cell

Abstract

The invention discloses a diffusion process for a crystalline silicon solar cell, and aims to shorten process time for a single tube and effectively improve diffusion uniformity and repeatability. The diffusion process is based on the conventional process, a small nitrogen flow and a dry oxygen flow are increased according to a certain proportion in source introduction, and diffusion time is shortened at the same time. By the process, the diffusion uniformity can be remarkably enhanced, the depth and surface concentration of a PN junction are well controlled, and the photoelectric conversion efficiency of the crystalline silicon solar cell is improved. The diffusion process is easily edited only by modifying conventional process parameters, convenient to operate, and applicable to industrial production, and can be applied to a large-scale solar power production line; and a production progress can be accelerated.

Description

technical field [0001] The invention belongs to the field of manufacturing crystalline silicon solar cells, in particular to a diffusion process for crystalline silicon solar cells. Background technique [0002] In the solar cell manufacturing process, diffusion is the core process and is used to form the PN junction. There are generally three methods for phosphorus diffusion, one is phosphorus oxychloride (POCl 3 ) liquid source diffusion, the second is chain diffusion after spraying phosphoric acid aqueous solution, and the third is chain diffusion after screen printing phosphorus slurry, and what the present invention adopted is the first method. [0003] POCl 3 It is an impurity source that is widely used in phosphorus diffusion at present, and it decomposes at high temperature to generate phosphorus pentachloride (PCl 5 ) and phosphorus pentoxide (P 2 o 5 ), the reaction formula is as follows: [0004] 5POCl 5 =3 PCl 3 +P 2 o 5 [0005] 2P 2 o 5 +5Si=5SiO ...

AI Technical Summary

Problems solved by technology

Generally, phosphorus oxychloride (POCl 3 ) has the following disadvantages in the diffusion of liquid sources: (1) the uniformity of the single piece is poor; (2) the repeatability is poor, and there is a deviation in the square resistance between the pieces; (3) the single-tube process takes a long time

[0007] The components of small nitrogen and large nitrogen are both nitrogen, but the flow rate is different. The large nitrogen is used as a protective gas throughout every step of the process, and it is continuously fed from the beginning to the end. The small nitrogen can only pass through the two steps of pre-diffusion and diffusion. into, used to carry phosphorus oxychloride (POCl 3 ) liquid source for diffusion, dry oxygen is introduced in the steps of oxidation, pre-diffusion and diffusion, and belongs to the gas participating in the reaction. The inlet pipe is sprayed into the furnace body. As shown in Table 6, the pre-expansion step is 600s, and the diffusion step is 1400s. When the source is connected, the small nitrogen flow rate is 2000ml / m, and the maximum nitrogen flow rate is 35000ml / m. The oxygen content is 2500ml / m. Obviously, the existing single-tube process takes a long time. In order to avoid these shortcomings, the diffusion process must be improved to optimize the diffusion effect

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