Polycrystalline silicon wafer texturing auxiliary and application method thereof

Abstract

The invention provides a polycrystalline silicon wafer texturing auxiliary and an application method thereof. The auxiliary comprises a silver inducer, an oxidizing agent, a buffering agent, a dispersing agent and deionized water. The auxiliary is added to a traditional isotropic texturing liquid composed of mixed liquor of hydrofluoric acid and nitric acid, then a polycrystalline silicon wafer is immersed in the texturing liquid, and isotropic corrosion and anisotropic corrosion occur on the surface of the silicon wafer, thereby obtaining a silicon surface with coexisting isoropic corrosion pits whose reflectivity is lower than 10% and anisotropic inverted pyramid morphology. The function of the buffering agent is to maintain the stability of a PH value of the texturing liquid; the oxidizing agent can suppress anisotropic corrosion of the silver inducer, thereby avoiding formation of too deep holes; and the dispersing agent can avoid the ''raindrop'' defect, and also wraps nano-silver particles attached to the surface of the silicon wafer, thereby substantially reducing cleaning difficulty of the silicon wafer after texturing. The polycrystalline silicon wafer texturing auxiliary provided by the invention overcomes some deficiencies of existing polycrystalline silicon texturing methods, and is particularly suitable for texturing of a polycrystalline silicon wafer cut by diamond wires.

Description

technical field [0001] The invention relates to the technical field of solar cells, in particular to a polycrystalline silicon wafer texturing auxiliary agent and an application method thereof. Background technique [0002] Due to the existence of grains with multiple orientations on polycrystalline silicon wafers, isotropic acid etching is generally used to prepare the textured surface to reduce the surface reflectivity, but there are three problems in this method: 1) The surface reflectivity of the silicon wafer after texture is high, and the reflection The corrosion rate is generally above 20%, which severely restricts the photoelectric conversion efficiency of polycrystalline silicon solar cells; 2) The reaction solution needs to be cooled to below 10°C during the texturing process. Since the corrosion reaction is a violent exothermic reaction, the energy consumption of this method is very large ; 3) This texturing method is only suitable for polysilicon wafers obtaine...

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Problems solved by technology

[0002] Due to the existence of grains with multiple orientations on polycrystalline silicon wafers, isotropic acid etching is generally used to prepare the textured surface to reduce the surface reflectivity, but there are three problems in this method: 1) The surface reflectivity of the silicon wafer after texture is high, and the reflection The corrosion rate is generally above 20%, which severely restricts the photoelectric conversion efficiency of polycrystalline silicon solar cells; 2) The reaction solution needs to be cooled to below 10°C during the texturing process. Since the corrosion reaction is a violent exothermic reaction, the energy consumption of this method is very large ; 3) This texturing method is only suitable for polysilicon wafers obtained by mortar cutting, and diamond wire cutting is a more economical and environmentally friendly method, which is bound to replace the traditional mortar cutting method. There are few and shallow cutting defects on the surface of polysilicon wafers, and the traditional acid etching method cannot obtain a surface with qualified reflectivity. It is for this reason that diamond wire-cut polysilicon wafers have not been widely used in cell manufacturers

[0003] Patent CN101800264A mentions the method of preparing polysilicon textured surface by dry plasma etching. Although a lower surface reflectivity can be obtained, the surface of the silicon wafer is easily damaged by plasma bombardment, and subsequent treatment is required. Otherwise, the surface of the silicon wafer will be seriously compounded and cannot Obtain high-efficiency solar cells. In addition, the equipment investment of this method is large, and the utilization rate of the reaction gas raw materials is low due to vacuuming. The main gas raw materials are fluoride or sulfide, which are highly toxic gases.

[0004] Patents CN103456804A and CN102051618A mention the use of metal-induced corrosion to prepare textured surfaces. This method utilizes the catalytic action of metal ions to prepare nanowire structures or nanohole structures with low reflectivity on the surface of silicon wafers. This method exists as follows Problems: 1) This method is an anisotropic etching method, and it is very sensitive to the surface conditions of silicon wafers, so it is difficult to adapt to polycrystalline silicon wafers cut by diamond wire; "Raindrop" traces are left on the surface, which affects the appearance uniformity of the silicon wafer surface; 3) Due to factors such as pH value, the experimental repeatability of this method is not good; 4) The characteristic size of the prepared textured structure is often only a few Nanometer or dozens of nanometers, the surface area is huge, and effective surface passivation cannot be implemented in the follow-up, resulting in very serious surface recombination, which makes the photoelectric conversion efficiency of the prepared solar cell low

Since the chemical components in the texturing liquid are volatile at room temperature, these components will volatilize faster at high temperatures, making it difficult to control the composition ratio of the texturing liquid

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