CN105355710B - A kind of solar cell machining process - Google Patents

Abstract

The invention discloses a solar cell sheet processing technology capable of reducing production cost and waste discharge in the production process. The process includes silicon wafer inspection, surface texturing, diffusion junction, phosphorus silicon glass removal, wet etching, anti-reflection coating, screen printing, rapid sintering, and the use of various waste liquids generated during the production of solar cells It is used to recycle and dispose of unqualified solar cells produced in the production process, which not only avoids a large amount of waste liquid discharge and environmental pollution caused by the destruction of unqualified solar cells, but also recycles silicon wafers, silver-coated copper powder, and aluminum paste. It can be directly supplied to the production line of solar cells, which not only achieves the reuse of waste liquid, but also reduces the generation of waste, and makes more use of environmentally friendly production, which can greatly reduce the amount of raw materials used in the processing of solar cells, thereby reducing solar energy. Production cost of cells. It is suitable for popularization and application in the field of solar cells.

Description

A kind of solar cell processing technology

technical field

The invention relates to the field of solar cells, in particular to a process for processing solar cells.

Background technique

With the rapid development of society and economy, the demand for energy is increasing day by day, the depletion of fossil energy and the pollution to the ecological environment are seriously threatening the sustainable development of society and economy. Therefore, there is an urgent need to replace it with renewable energy. As an inexhaustible and inexhaustible green renewable energy source, solar energy has received widespread attention worldwide.

The principle of solar cells is mainly based on the semiconductor material silicon, and impurities are doped into the silicon crystal by means of a diffusion process: when impurities such as boron and phosphorus are doped, there will be a hole in the silicon crystal to form an n-type semiconductor; , after doping phosphorus atoms, there will be an electron in the silicon crystal to form a p-type semiconductor, and the p-type semiconductor and n-type semiconductor will combine to form a pn junction. When sunlight irradiates the silicon crystal, the n-type semiconductor in the pn junction Holes move to the p-type region, while electrons in the p-type region move to the n-type region, thereby forming a current from the n-type region to the p-type region, forming a potential difference in the pn junction, which forms a solar cell.

The processing technology of solar cells is divided into silicon wafer detection - surface texturing - diffusion junction - dephosphorous silicon glass - wet etching - anti-reflection coating - screen printing - rapid sintering, etc. The details are as follows:

1. Wafer detection

Silicon wafers are the carrier of solar cells. The quality of silicon wafers directly determines the conversion efficiency of solar cells. Therefore, it is necessary to inspect incoming silicon wafers. This process is mainly used for on-line measurement of some technical parameters of silicon wafers, these parameters mainly include silicon wafer surface roughness, minority carrier lifetime, resistivity, P/N type and micro cracks, etc. This group of equipment is divided into automatic loading and unloading, silicon wafer transmission, system integration and four detection modules. Among them, the photovoltaic silicon wafer detector detects the surface roughness of the silicon wafer, and at the same time detects the appearance parameters such as the size and diagonal of the silicon wafer; the micro crack detection module is used to detect the internal micro cracks of the silicon wafer; there are two other Detection modules, one of the online testing modules mainly tests the bulk resistivity and type of silicon wafers, and the other module is used to detect the minority carrier lifetime of silicon wafers. Before the detection of minority carrier lifetime and resistivity, it is necessary to detect the diagonal lines and micro cracks of silicon wafers, and automatically remove damaged silicon wafers. The silicon wafer inspection equipment can automatically load and unload wafers, and can put unqualified products in a fixed position, thereby improving the detection accuracy and efficiency.

2. Surface cashmere

The preparation of the monocrystalline silicon texture is to use the anisotropic etching of silicon to form millions of tetrahedral pyramids, that is, pyramid structures, on the silicon surface per square centimeter. Due to the multiple reflection and refraction of the incident light on the surface, the absorption of light is increased, and the short-circuit current and conversion efficiency of the battery are improved. The anisotropic etching solution of silicon usually uses hot alkaline solution to prepare textured silicon, and after etching the textured surface, general chemical cleaning is carried out. Surface-prepared silicon wafers should not be stored in water for a long time to prevent contamination, and should be diffused and formed as soon as possible.

3. Diffusion knot

Solar cells need a large-area PN junction to convert light energy into electrical energy, and the diffusion furnace is a special equipment for manufacturing PN junctions of solar cells. The tubular diffusion furnace is mainly composed of four parts: the upper and lower parts of the quartz boat, the exhaust gas chamber, the furnace body part and the gas cabinet part. Diffusion generally uses a liquid source of phosphorus oxychloride as a diffusion source. Put the P-type silicon chip in the quartz container of the tubular diffusion furnace, use nitrogen gas to bring phosphorus oxychloride into the quartz container at a high temperature of 850-900 degrees Celsius, and react with the silicon chip to obtain phosphorus atom. After a certain period of time, phosphorus atoms enter the surface layer of the silicon wafer from all sides, and permeate and diffuse into the silicon wafer through the gaps between the silicon atoms, forming the interface between the N-type semiconductor and the P-type semiconductor, that is, the PN junction. The PN junction produced by this process has good uniformity, the non-uniformity of sheet resistance is less than 10%, and the minority carrier lifetime can be greater than 10ms. Manufacture of PN junction is the most basic and critical process in solar cell production. Because it is the formation of the PN junction that the electrons and holes no longer return to the original place after flowing, thus forming a current, and the current is drawn out with a wire, which is direct current.

4. Phospho-silicate glass

This process is used in the production and manufacturing process of solar cells. The silicon wafer is soaked in an acidic solution by chemical etching to cause a chemical reaction to form a soluble complex to remove the surface of the silicon wafer after diffusion and junction. A layer of phosphosilicate glass is formed.

5. Wet etching

Because in the diffusion process, even if the back-to-back diffusion is adopted, phosphorus will inevitably be diffused on all surfaces of the silicon wafer including the edges. The photogenerated electrons collected on the front side of the PN junction will flow to the back side of the PN junction along the area diffused with phosphorus along the edge, causing a short circuit. Therefore, the doped silicon around the solar cell must be etched to remove the PN junction at the edge of the cell. This process is usually accomplished using wet etching techniques.

6. Anti-reflection coating

The reflectivity of the polished silicon surface is 35%. In order to reduce the surface reflection and improve the conversion efficiency of the cell, a layer of silicon nitride anti-reflection film needs to be deposited. In industrial production, PECVD equipment is often used to prepare anti-reflection coatings. PECVD stands for plasma enhanced chemical vapor deposition. Its technical principle is to use low-temperature plasma as an energy source. The sample is placed on the cathode of glow discharge under low pressure, and the sample is heated to a predetermined temperature by glow discharge, and then an appropriate amount of reaction gas SiH4 and NH3 is introduced. After a series of chemical reactions and plasma reactions, a solid film, that is, a silicon nitride film, is formed on the surface of the sample. Generally, the film thickness deposited by this plasma-enhanced chemical vapor deposition process is about 70nm. A film of this thickness has optical functionality. Using the principle of thin film interference, the reflection of light can be greatly reduced, the short-circuit current and output of the battery will be greatly increased, and the efficiency will also be considerably improved.

7. Screen printing

After the process of texturing, diffusion and PECVD, the solar cell has been made into a PN junction, which can generate current under light. In order to export the generated current, it is necessary to make positive and negative electrodes on the surface of the cell. There are many processes for manufacturing electrodes, and screen printing is currently the most common production process for making solar cell electrodes. Screen printing is to print predetermined graphics on the substrate by embossing. The equipment consists of three parts: silver and aluminum paste printing on the back of the battery, aluminum paste printing on the back of the battery and silver paste printing on the front of the battery. Its working principle is: use part of the mesh of the screen pattern to penetrate the slurry, apply a certain pressure on the slurry part of the screen with a scraper, and move towards the other end of the screen at the same time. The ink is squeezed from the mesh of the graphics part to the substrate by the scraper during the movement. Due to the viscosity of the slurry, the imprint is fixed within a certain range, and the squeegee is always in linear contact with the screen printing plate and the substrate during printing, and the contact line moves with the movement of the squeegee, thus completing the printing process.

Eight, rapid sintering

The silicon wafer after screen printing cannot be used directly. It needs to be sintered quickly in a sintering furnace to burn off the organic resin binder, leaving almost pure silver electrodes tightly bonded to the silicon wafer due to the effect of glass. When the silver electrode and crystalline silicon reach the eutectic temperature, the crystalline silicon atoms are blended into the molten silver electrode material in a certain proportion, thereby forming an ohmic contact between the upper and lower electrodes, and improving the open circuit voltage and fill factor of the cell. The key parameters make it have resistance characteristics to improve the conversion efficiency of the cell.

The sintering furnace is divided into three stages: pre-sintering, sintering, and cooling. The purpose of the pre-sintering stage is to decompose and burn the polymer binder in the slurry, and the temperature rises slowly at this stage; in the sintering stage, various physical and chemical reactions are completed in the sintered body to form a resistive film structure, so that it truly has resistive characteristics At this stage, the temperature reaches a peak value; in the cooling stage, the glass is cooled, hardened and solidified, so that the resistive film structure is fixedly adhered to the substrate.

The processing technology of the above-mentioned solar cells has the following problems in actual use: a large amount of alkaline waste liquid will be produced in the process of preparing suede silicon with hot alkaline solution, and a large amount of acid will be produced in the process of removing phosphorus silicon glass. Waste liquid, a large amount of hydrofluoric acid waste liquid and nitric acid waste liquid will be produced in the wet etching process. At present, most of these waste liquids are treated by acid-base neutralization and then discharged directly, resulting in the damage of solar cells. The production cost is higher, which not only causes waste of raw materials, but also pollutes the environment and is not environmentally friendly.

In addition, the life cycle of solar cells is generally 25 years. When the conversion efficiency drops to a certain level, the solar cells fail and become unqualified solar cells, which need to be scrapped and updated. In general, solar energy is regarded as An energy source with minimal waste generation, no waste that is harmful to the environment will be generated during the use of the components, but the solid waste generated after the solar cells are scrapped cannot be ignored. After 2020, the solid waste of solar cells in my country will increase significantly, and the cumulative amount of waste will also gradually increase. The treatment, disposal and recycling of solar cells will become an important environmental protection issue. At the same time, a large number of unqualified solar cells will be produced due to various reasons in the production process of solar cells. Most of them adopt the method of centralized destruction. The main materials contained in solar cells are silicon, silver, aluminum, etc. Silicon, silver, and aluminum are all raw materials needed in the production process of solar cells. If unqualified solar cells are directly Destruction will not only cause a huge waste of raw materials, but at the same time, the battery residue after destruction will also pollute the environment, which is not environmentally friendly.

Contents of the invention

The technical problem to be solved by the present invention is to provide a solar cell chip processing technology that can reduce production cost and waste discharge in the production process.

The technical solution adopted by the present invention to solve the technical problems is: the solar cell processing technology comprises the following steps:

A. Detect silicon wafers that need to be processed and remove unqualified silicon wafers;

B. Put the tested qualified silicon wafers into the alkaline solution for surface texture treatment, and collect the residual alkaline waste liquid after the texture treatment;

C. Put the textured silicon wafer into the diffusion equipment for diffusion and junction processing;

D. Put the silicon wafers processed by diffusion into an acidic solution for dephosphorous silicon glass treatment, and collect the residual acidic waste liquid after the dephosphorous silicon glass treatment;

E. Carry out wet etching treatment on the silicon wafers obtained after diffusion bonding; first use hydrofluoric acid to rinse each surface of the silicon wafers obtained after diffusion bonding and rinse the residual hydrofluoric acid waste liquid Collect it, after cleaning the dephosphorous silicon glass solar cells obtained in the step D; then put the silicon wafer into a nitric acid solution for etching and collect the residual nitric acid waste liquid after etching, and then use an alkaline solution to Clean the etched silicon wafer and collect the residual alkaline solution after cleaning, and finally clean the silicon wafer with pure water and dry it;

F, using PECVD equipment to prepare a silicon nitride reflective layer on the surface of the silicon wafer that has been wet-etched;

G. Print positive and negative electrodes on the upper and lower surfaces of the silicon wafer coated with the anti-reflection film by screen printing;

H. Putting the screen-printed silicon wafer into a sintering device to obtain a solar cell after sintering treatment;

I. Put the unqualified solar cells into the collected alkaline waste liquid to remove part of the aluminum layer of the aluminum back field of the solar cells, and then put the unqualified solar cells soaked in the alkaline waste liquid into the collected The remaining aluminum layer of the solar cells is removed from the acidic waste liquid to obtain aluminum-free solar cells and aluminum-containing waste liquid. The aluminum-containing waste liquid is chemically converted into alumina and then used to prepare electronic aluminum paste. The electronic aluminum paste is used for The slurry for screen printing in step G; after cleaning the aluminum-removing solar cells, immerse in the collected nitric acid waste liquid to leach the silver on the surface of the aluminum-removing solar cells to obtain the silver-removing solar cells and the silver-containing acid solution put into the collected hydrofluoric acid waste liquid to remove the silver solar cells to remove the silicon nitride reflective layer on the surface of the silver solar cells, and obtain pure silicon chips after cleaning the silicon nitride solar cells. Silicon wafers are processed into qualified solar cells after steps A to H; copper powder is added to silver-containing acid solution to make silver-coated copper powder for preparing electronic paste, which is used for screen in step G Printed paste.

Further, the specific method of adding copper powder to the silver-containing acid solution to make silver-coated copper powder is as follows: adding copper powder to the silver-containing acid solution to obtain a solid-liquid mixture, the silver-containing acid solution and copper powder The weight ratio is 1.5-3, and the solid-liquid mixture is pumped into the grinding equipment and circulated for 20-50 minutes to obtain silver-coated copper powder.

Further, the weight ratio of the silver-containing acid solution to the copper powder is 2.

Further, the particle size of the copper powder is 2-3 microns.

Further, the time for the solid-liquid mixture to be sucked into the grinding equipment for circulation and grinding is 30 minutes.

Further, the temperature of the silver-containing acid solution is 20°C.

Further, the concentration of the alkaline waste liquid collected in the step B is 5%.

Further, the concentration of the acid waste liquid collected in the step D is 5%.

Further, the concentration of the hydrofluoric acid waste liquid collected in the step E is 0.5%.

Further, the concentration of the nitric acid waste liquid collected in the step E is 1.5%.

The beneficial effects of the present invention are: the solar cell processing technology collects a large amount of alkaline waste liquid, acid waste liquid, hydrofluoric acid waste liquid, and nitric acid waste liquid generated in the processing process, so as to eliminate scrap failure and waste generated in the production process. Put the unqualified solar cells into the collected alkaline waste liquid to remove part of the aluminum layer of the aluminum back field of the solar cells, and then put the unqualified solar cells soaked in the alkaline waste liquid into the collected acidic waste liquid Remove the remaining aluminum layer of the solar cells in the process to obtain aluminum-free solar cells and aluminum-containing waste liquid. The aluminum-containing waste liquid is chemically converted into alumina and then used to prepare electronic aluminum paste. The electronic aluminum paste is used for screen printing The slurry of the aluminum-removing solar cell is cleaned, soaked in the collected nitric acid waste liquid, and the silver on the surface of the aluminum-removing solar cell is leached to obtain a silver-removing solar cell and silver-containing acid solution; the silver-removing solar cell is Put the sheet into the collected hydrofluoric acid waste liquid to remove the silicon nitride reflective layer on the surface of the silver-removed solar cell sheet, and obtain a pure silicon sheet after cleaning the silicon-nitride solar cell sheet, and the silicon sheet can be reused The raw material for processing solar cells, adding copper powder to the silver-containing acid solution to make silver-coated copper powder is used to prepare electronic paste, which is used for screen printing paste. This process utilizes the production process of solar cells The various waste liquids generated in the process are used to recycle and treat the scrapped and failed solar cells produced during the production process, which not only avoids a large amount of waste liquid discharge and environmental pollution caused by the destruction of unqualified solar cells, but also recycles Silver-coated copper powder and aluminum paste can be directly supplied to the solar cell production line, which not only achieves the reuse of waste liquid, but also reduces the generation of waste, and makes more use of environmentally friendly production, which can greatly reduce the waste of raw materials in the process of solar cell processing. usage, thereby reducing the production cost of solar cells.

detailed description

The solar cell processing technology includes the following steps:

A. Detect silicon wafers that need to be processed and remove unqualified silicon wafers;

B. Put the tested qualified silicon wafers into the alkaline solution for surface texture treatment, and collect the residual alkaline waste liquid after the texture treatment;

C. Put the textured silicon wafer into the diffusion equipment for diffusion and junction processing;

D. Put the silicon wafers processed by diffusion into an acidic solution for dephosphorous silicon glass treatment, and collect the residual acidic waste liquid after the dephosphorous silicon glass treatment;

E. Carry out wet etching treatment on the silicon wafers obtained after diffusion bonding; first use hydrofluoric acid to rinse each surface of the silicon wafers obtained after diffusion bonding and rinse the residual hydrofluoric acid waste liquid Collect it, after cleaning the dephosphorous silicon glass solar cells obtained in the step D; then put the silicon wafer into a nitric acid solution for etching and collect the residual nitric acid waste liquid after etching, and then use an alkaline solution to Clean the etched silicon wafer and collect the residual alkaline solution after cleaning, and finally clean the silicon wafer with pure water and dry it;

F, using PECVD equipment to prepare a silicon nitride reflective layer on the surface of the silicon wafer that has been wet-etched;

G. Print positive and negative electrodes on the upper and lower surfaces of the silicon wafer coated with the anti-reflection film by screen printing;

H. Putting the screen-printed silicon wafer into a sintering device to obtain a solar cell after sintering treatment;

I. Put the unqualified solar cells into the collected alkaline waste liquid to remove part of the aluminum layer of the aluminum back field of the solar cells, and then put the unqualified solar cells soaked in the alkaline waste liquid into the collected The remaining aluminum layer of the solar cells is removed from the acidic waste liquid to obtain aluminum-free solar cells and aluminum-containing waste liquid. The aluminum-containing waste liquid is chemically converted into alumina and then used to prepare electronic aluminum paste. The electronic aluminum paste is used for The slurry for screen printing in step G; after cleaning the aluminum-removing solar cells, immerse in the collected nitric acid waste liquid to leach the silver on the surface of the aluminum-removing solar cells to obtain the silver-removing solar cells and the silver-containing acid solution put into the collected hydrofluoric acid waste liquid to remove the silver solar cells to remove the silicon nitride reflective layer on the surface of the silver solar cells, and obtain pure silicon chips after cleaning the silicon nitride solar cells. Silicon wafers are processed into qualified solar cells after steps A to H; copper powder is added to silver-containing acid solution to make silver-coated copper powder for preparing electronic paste, which is used for screen in step G Printed paste.

The solar cell processing technology collects a large amount of alkaline waste liquid, acid waste liquid, hydrofluoric acid waste liquid, and nitric acid waste liquid generated during the processing process, and puts the scrapped and invalid solar cells produced during the production process into the collected alkaline waste liquid to remove part of the aluminum layer of the aluminum back field of the solar cells, and then put the unqualified solar cells soaked in the alkaline waste liquid into the collected acidic waste liquid to remove the remaining parts of the solar cells The aluminum layer is obtained from aluminum-removed solar cells and aluminum-containing waste liquid, which is chemically converted into alumina and then used to prepare electronic aluminum paste, which is used for screen printing paste; aluminum-removed solar energy After the cells are cleaned, they are soaked in the collected nitric acid waste solution to leach the silver on the surface of the de-aluminum solar cells to obtain the de-silvered solar cells and the silver-containing acid solution; put the de-silvered solar cells into the collected hydrogen Remove the silicon nitride reflective layer on the surface of the desilvered solar cell sheet in the hydrofluoric acid waste liquid to obtain a pure silicon chip after cleaning the silicon nitride solar cell sheet, and the silicon chip can be reused as a processing raw material for the solar cell sheet. Copper powder is added to the silver-containing acid solution to make silver-coated copper powder for the preparation of electronic paste, which is used for screen printing paste. This process utilizes various waste liquids generated during the production of solar cells It is used to recycle and dispose of unqualified solar cells produced in the production process, which not only avoids a large amount of waste liquid discharge and environmental pollution caused by the destruction of unqualified solar cells, but also recycles silicon wafers, silver-coated copper powder, and aluminum paste. It can be directly supplied to the production line of solar cells, which not only achieves the reuse of waste liquid, but also reduces the generation of waste, and makes more use of environmentally friendly production, which can greatly reduce the amount of raw materials used in the processing of solar cells, thereby reducing solar energy. Production cost of cells.

In the above embodiment, the specific method of adding copper powder to the silver-containing acid solution to make silver-coated copper powder can be obtained by using the existing chemical method to prepare silver powder and then wrapping it on the surface of copper powder, but this chemical preparation method The prepared silver-coated copper powder has low silver content, low density of the silver coating layer, poor electrical conductivity, high production cost and low efficiency. The present invention provides a new preparation method of silver-coated copper powder: adding copper powder to silver-containing acid solution to obtain a solid-liquid mixture, the weight ratio of the silver-containing acid solution to copper powder is 1.5-3, and the solid The liquid mixture is pumped into the grinding equipment and circularly ground for 20 to 50 minutes to obtain silver-coated copper powder. This method only needs to add copper powder into the silver-containing acid solution according to a certain weight ratio, and then pump it into the grinding equipment for 20-50 minutes of circular grinding. The solid-liquid mixture of copper powder and silver-containing acid solution is grinding A chemical reaction occurs during the process, and part of the copper powder undergoes a substitution reaction with the silver-containing acid solution to replace the silver ions to form silver powder. The resulting silver powder is deposited on the surface of the copper powder particles. Since the solid-liquid mixture is also subjected to grinding equipment during the grinding process Grinding force, more silver powder is deposited on the surface of the copper powder under the grinding force, and the silver layer formed on the surface of the copper powder particles under the grinding force will be denser and better in coating, and the silver-coated copper powder The conductivity is also greatly improved. It has been verified by experiments that the silver content in the silver-coated copper powder obtained by the above method can reach more than 55%, which greatly improves the overall performance of the silver-coated copper powder, thereby reducing the consumption of silver-coated copper powder and reducing the consumption of silver-coated copper powder. Production costs are improved, and product benefits are improved.

In order to ensure that all the silver ions can be substituted and enough silver powder is deposited on the surface of the copper powder particles, the weight ratio of the silver-containing acid solution to the copper powder is 2.

In order to maximize the silver content in the silver-coated copper powder, the particle size of the copper powder is 2-3 microns, so that the copper powder particles have a large enough relative surface area to deposit more silver powder.

In order to make the replacement reaction more complete and allow more silver powder to be deposited on the surface of the copper powder particles, the time for the solid-liquid mixture to be pumped into the grinding equipment for circular grinding is preferably 30 minutes. Further, the temperature of the silver-containing acid solution is 20°C.

In order to further reduce the production cost of solar cells while ensuring the texturing effect, the alkaline solution used in the step B is preferably sodium hydroxide solution. Because sodium hydroxide solution is cheap and easy to obtain, it can greatly reduce its production cost. In order to ensure the effect of removing aluminum, the concentration of the sodium hydroxide waste liquid collected in the step B is 3-7%. Further, in order to ensure the effect of removing aluminum and reduce the cost as much as possible, the concentration of the sodium hydroxide waste liquid collected in the step B is 5%.

In order to ensure the effect of dephosphorous silicon glass treatment and further reduce the production cost of solar cells, the acidic solution used in the step D is hydrochloric acid, which is highly corrosive and can ensure the effect of dephosphorous silicon glass treatment. At the same time, The price of hydrochloric acid is relatively cheap, which can greatly reduce its production cost. In order to ensure the aluminum removal effect and reduce the cost as much as possible, the concentration of the hydrochloric acid waste liquid collected in the step D is 3-7%. Further, in order to ensure the effect of removing aluminum and reduce the cost as much as possible, the concentration of the hydrochloric acid waste liquid collected in the step D is 5%.

In order to ensure the desilvering effect, the concentration of the nitric acid waste liquid collected in the step E is 1-2%. In order to dissolve and remove all the silver on the surface of the solar cells and reduce the cost as much as possible, the concentration of the nitric acid waste liquid collected in the step E is preferably 1.5%.

In order to ensure the silicon nitride removal effect, the concentration of the hydrofluoric acid waste liquid collected in the step E is 0.2-0.8%. In order to completely remove the silicon nitride film on the surface of the solar cells and reduce the cost as much as possible, the concentration of the hydrofluoric acid waste liquid collected in the step E is 0.5%.

Example

Treat 100kg of solar cells with 100L of collected 5% sodium hydroxide waste solution, react until neutral, remove part of the aluminum layer, and then soak the solar cells in 300L of collected 5% hydrochloric acid waste solution until the aluminum layer is completely removed; then put the collected 100L nitric acid waste solution with a concentration of 1.5% into the aluminum-removed solar cells to completely dissolve the silver to obtain a silver-containing acid solution; put the silver-removed solar cells into a concentration of 20L Silicon nitride is removed in 0.5% hydrofluoric acid waste liquid to obtain 80kg of pure silicon chips with a recovery rate of about 90%; finally, the aluminum in the aluminum-containing solution is converted into alumina to obtain about 20kg of alumina with a recovery rate of about to 93%, the temperature of the silver-containing acid solution is controlled at 20°C, and flake copper powder with a particle size of 2-3 microns is added to form a solid-liquid mixture after mixing. The quality of the added flake copper powder is Half of the mass, the solid-liquid mixture formed after mixing is pumped into a sand mill for high-speed circular grinding for 30 minutes to obtain silver-colored silver-coated copper powder with a silver content of about 55%, D50=1-2 microns, and a conductivity of 1.5×10-5Ω cm.

Claims (10)

1. A solar cell processing technology, characterized in that comprising the following steps: A. Detect silicon wafers that need to be processed and remove unqualified silicon wafers; B. Put the tested qualified silicon wafers into the alkaline solution for surface texture treatment, and collect the residual alkaline waste liquid after the texture treatment; C. Put the textured silicon wafer into the diffusion equipment for diffusion and junction processing; D. Put the silicon wafers processed by diffusion into an acidic solution for dephosphorous silicon glass treatment, and collect the residual acidic waste liquid after the dephosphorous silicon glass treatment; E. Carry out wet etching treatment on the silicon wafers obtained after diffusion bonding; first use hydrofluoric acid to rinse each surface of the silicon wafers obtained after diffusion bonding and rinse the residual hydrofluoric acid waste liquid Collect it, after cleaning the dephosphorous silicon glass solar cells obtained in the step D; then put the silicon wafer into a nitric acid solution for etching and collect the residual nitric acid waste liquid after etching, and then use an alkaline solution to Clean the etched silicon wafer and collect the residual alkaline solution after cleaning, and finally clean the silicon wafer with pure water and dry it; F, using PECVD equipment to prepare a silicon nitride reflective layer on the surface of the silicon wafer that has been wet-etched; G. Print positive and negative electrodes on the upper and lower surfaces of the silicon wafer coated with the anti-reflection film by screen printing; H. Putting the screen-printed silicon wafer into a sintering device to obtain a solar cell after sintering treatment; I. Put the unqualified solar cells into the collected alkaline waste liquid to remove part of the aluminum layer of the aluminum back field of the solar cells, and then put the unqualified solar cells soaked in the alkaline waste liquid into the collected The remaining aluminum layer of solar cells is removed from the acid waste liquid to obtain aluminum-free solar cells and aluminum-containing waste liquid. The aluminum-containing waste liquid is converted into alumina by chemical means; the aluminum-free solar cells are cleaned and soaked in the collected The silver on the surface of the aluminum-removed solar cells is leached in the nitric acid waste liquid to obtain the silver-removed solar cells and the silver-containing acid solution; the silver-removed solar cells are put into the collected hydrofluoric acid waste liquid to remove the silver-removed solar cells The silicon nitride reflective layer on the surface is obtained to remove the silicon nitride solar cells and obtain pure silicon chips after cleaning, and the silicon chips are processed into qualified solar cells after steps A to H; copper is added to the silver-containing acid solution The powder is made into silver-coated copper powder for preparing electronic paste, which is used for screen printing paste in step G. 2. The solar cell processing technology as claimed in claim 1, characterized in that: the specific method of adding copper powder to make silver-coated copper powder in the silver-containing acid solution is as follows: adding copper to the silver-containing acid solution powder to obtain a solid-liquid mixture, the weight ratio of the silver-containing acid liquid to copper powder is 1.5-3, and the solid-liquid mixture is pumped into a grinding device and circulated for 20-50 minutes to obtain silver-coated copper powder. 3 . The solar cell processing technology according to claim 2 , wherein the weight ratio of the silver-containing acid solution to the copper powder is 2. 4 . 4. The solar battery sheet processing technology according to claim 3, characterized in that: the particle size of the copper powder is 2-3 microns. 5 . The solar cell processing technology according to claim 4 , wherein the time for the solid-liquid mixture to be pumped into the grinding equipment for circular grinding is 30 minutes. 6 . 6. The solar cell processing technology according to claim 5, wherein the temperature of the silver-containing acid solution is 20°C. 7. The solar cell processing technology according to claim 1, characterized in that: the concentration of the alkaline waste liquid collected in the step B is 5%. 8. The solar cell processing technology according to claim 7, characterized in that: the concentration of the acidic waste liquid collected in the step D is 5%. 9. The solar cell processing technology according to claim 8, characterized in that: the concentration of the hydrofluoric acid waste liquid collected in the step E is 0.5%. 10 . The solar cell processing technology according to claim 9 , wherein the concentration of the nitric acid waste liquid collected in the step E is 1.5%. 11 .