CN106653953B - It is a kind of to thermally decompose the method for preparing silicon dioxide passivation layer - Google Patents

Abstract

The invention belongs to the field of new energy, and in particular relates to a method for preparing a silicon dioxide passivation layer by pyrolysis. The viscous glue liquid mixed with metasilicic acid, shellac, and thinner is evenly brushed on the surface of the diffused silicon wafer and dried, and then the silicon wafer is placed in a high-temperature inert gas environment for a period of time. That is, the passivation of the silicon wafer surface is completed. In the process of thermal decomposition of shellac itself, the degree of compatibility between the silicon dioxide obtained by the decomposition of metasilicate and the silicon wafer substrate is promoted, the generated silicon dioxide is prevented from falling off, and the binding force and stability of the passivation layer are improved.

Description

A kind of thermal decomposition prepares the method for silicon dioxide passivation layer

technical field

The invention belongs to the field of new energy, and in particular relates to a method for preparing a silicon dioxide passivation layer by pyrolysis.

Background technique

A solar cell is a semiconductor device that can convert the sun's light energy into heat energy. Since it does not need water, oil, fuel and other resources when working, it only needs light to generate electricity, so it is called contemporary clean and pollution-free renewable energy. resources, and the installation and maintenance are simple, long service life, unattended, and more and more widely used in various fields.

Due to the existence of a large number of surface defects in polycrystalline silicon solar cells, the performance of the cells is affected. In order to obtain higher photoelectric conversion efficiency, it is necessary to perform a silicon dioxide passivation process on the surface of the cells. Current research shows that silicon dioxide and aluminum oxide are the best rear passivation materials, but traditional silicon dioxide needs to be formed by high-temperature thermal oxidation of silicon wafers, which requires high energy consumption and requires at least a heating temperature of 650°C, which is harmful to silicon wafers. The thermal damage itself is relatively large, and the growth and deposition equipment of alumina is also very expensive.

Contents of the invention

In order to solve the problems mentioned in the above background technology part, the present invention provides a new method for preparing silicon dioxide passivation layer by thermal decomposition:

(1) Prepare the glue of the passivation precursor

Mix metasilicic acid (H ₂ SiO ₃ ), shellac, and diluent and stir thoroughly to obtain viscous glue.

Among them, the mass ratio of metasilicate (H ₂ SiO ₃ ), shellac, and diluent is 1:5-10:4-6, and the diluent is ethanol;

(2) Apply the viscous glue obtained in step (1) evenly on the surface of the diffused silicon wafer and dry it, then place the silicon wafer in an inert gas environment at 300-400°C for 15-25 minutes , natural cooling, that is, to complete the passivation of the silicon wafer surface,

Wherein, the drying temperature is 80° C., and the inert gas is nitrogen.

In the high temperature process, the present invention decomposes metasilicate to generate silicon dioxide to passivate the silicon wafer, and there is also the intervention of shellac. Shellac is used as a tackifier in the early coating process. It will be completely decomposed by heat, so that there is no impurity on the surface of the passivated silicon wafer; more importantly, shellac also promotes the bonding between the silicon dioxide obtained by the decomposition of metasilicate and the silicon wafer substrate during the process of its own thermal decomposition. The degree of compatibility prevents the generated silicon dioxide from falling off, and improves the bonding force and stability of the passivation layer.

Detailed ways

blank control

Silicon wafer without any passivation treatment.

Example 1

Using the scheme of this application, carry out passivation treatment on silicon wafers with the same material and specifications as those in the above-mentioned blank control, and the specific operations are as follows:

(1) Mix metasilicic acid (H ₂ SiO ₃ ), shellac, and ethanol in a mass ratio of 1:8:4, and then fully stir to obtain a viscous glue;

(2) Apply the viscous glue obtained in step (1) evenly on the surface of the diffused silicon chip and fully dry it at 80°C, then place the silicon chip in a nitrogen atmosphere at 350°C for 22 minutes, Natural cooling is to complete the passivation of the silicon wafer surface.

Comparative Example 1

Only do not add shellac in step (1), and control the consumption of the metasilicic acid that brushes on the silicon wafer surface in the step (2) with embodiment 1, all the other operations are also all with embodiment 1.

Comparative Example 2

Compared with Example 1, only the placement time of the silicon wafer under 350°C nitrogen atmosphere in step (2) is prolonged, and the rest of the operations and material selection are the same as in Example 1:

(1) Mix metasilicic acid (H ₂ SiO ₃ ), shellac, and ethanol in a mass ratio of 1:8:4, and then fully stir to obtain a viscous glue;

(2) Apply the viscous glue obtained in step (1) evenly on the surface of the diffused silicon chip and fully dry it at 80°C, then place the silicon chip in a nitrogen atmosphere at 350°C for 30 minutes, Natural cooling is to complete the passivation of the silicon wafer surface.

Example 2

Using the scheme of this application, carry out passivation treatment on silicon wafers of the same material and specifications as in the blank control, the specific operations are:

(1) Mix metasilicic acid (H ₂ SiO ₃ ), shellac, and ethanol in a mass ratio of 1:6:6 and stir thoroughly to obtain a viscous glue;

(2) Apply the viscous glue obtained in step (1) evenly on the surface of the diffused silicon chip and fully dry it at 80°C, then place the silicon chip in a nitrogen atmosphere at 320°C for 24 minutes, Natural cooling is to complete the passivation of the silicon wafer surface.

Based on the above-mentioned blank control, Example 1, Comparative Example 1 and Example 2, the silicon wafers whose surfaces were passivated by silicon dioxide were assembled into solar cells using the same existing assembly process, and a unified detection method was adopted. Detection:

Compared with the blank control, the filling factor of embodiment 1 has increased by 12.6%, and the increase of photoelectric performance has fully illustrated: shellac has decomposed and volatilized in the passivation process, because if shellac is used as a kind of binding material all the time If the passivation layer and the substrate are connected, an interlayer will inevitably be formed to cause the separation of elemental silicon and silicon dioxide, and the passivation can only be effective after the surface of the silicon substrate is realized. The photoelectric mechanism of the silicon wafer has no influence;

Compared with blank control, comparative example 1 only increases the filling factor by 3.1%. This is because in the absence of thermal decomposition of shellac, the binding force itself between the silicon dioxide and the matrix generated after the end is just very weak. It is easy to fall off in the medium and thus cannot passivate the surface of the substrate;

Compared with blank control, comparative example 2 has increased fill factor by 12.6%, which is consistent with the effect of example 1, and this has further illustrated: in the high temperature treatment time (22 minutes) of example 1, brushing on the silicon chip surface The metasilicic acid and shellac have been completely decomposed, so the continuous application of high temperature under anaerobic conditions has no effect on the chemical composition of the silicon wafer surface, thus no longer affecting the photoelectric performance;

Compared with the blank control in Example 2, the fill factor increased by 11.3%.

Claims (5)

1. a method for preparing silicon dioxide passivation layer by pyrolysis, is characterized in that: described preparation method is, (1) Fully stir after metasilicate, shellac, diluent are mixed, obtain viscous glue; (2) Apply the viscous glue obtained in step (1) evenly on the surface of the diffused silicon chip and dry it, then place the silicon chip in a high-temperature inert gas environment for a period of time, and cool it naturally. In the high-temperature inert gas environment, the temperature is 300-400°C, The time for placing the silicon wafer in the high-temperature inert gas environment is 15-25 minutes. 2. The method for preparing a silicon dioxide passivation layer by pyrolysis as claimed in claim 1, characterized in that: in step (1), the mass ratio of metasilicate, shellac, and diluent is 1:5 to 10: 4~6. 3. The method for preparing silicon dioxide passivation layer by pyrolysis as claimed in claim 1, characterized in that: the diluent described in step (1) is ethanol. 4. The method for preparing a silicon dioxide passivation layer by pyrolysis according to claim 1, characterized in that: in step (2), the drying temperature is 80°C. 5. The method for preparing a silicon dioxide passivation layer by pyrolysis as claimed in claim 1, characterized in that: in the high-temperature inert gas environment described in step (2), the temperature is 300 to 400° C., and the inert gas is nitrogen.