KR102007861B1 - The manufacturing method of silver paste using the silver powder - Google Patents

Abstract

The present invention relates to a silver powder for a solar cell electrode, wherein the coating film formed of a paste containing the silver powder has a brightness index (L *) of 80 or more, measured using a spectrophotometer, and a method of manufacturing the same. The present invention relates to a power generation efficiency of a solar cell including a front electrode manufactured using a conductive paste including the silver powder by controlling the chromaticity of the silver powder prepared by adjusting the amount of phosphorus compound added in the process of preparing the silver powder. Provides the effect of elevating.

Description

Silver powder for solar cell electrodes and conductive paste containing the same {The manufacturing method of silver paste using the silver powder}

The present invention relates to a silver powder used for the electrode of the solar cell and a conductive paste containing the same.

A solar cell is a semiconductor device that converts solar energy into electrical energy and generally has a p-n junction. The basic structure is the same as that of a diode. 1 is a structure of a general solar cell device, and the solar cell device is generally configured using a p-type silicon semiconductor substrate 10 having a thickness of 180 to 250 μm. On the light-receiving surface side of the silicon semiconductor substrate, an n-type impurity layer 20 having a thickness of 0.3 to 0.6 µm, an antireflection film 30 and a front electrode 100 are formed thereon. In addition, the back electrode 50 is formed on the back side of the p-type silicon semiconductor substrate. The front electrode 100 is coated with a conductive paste containing silver-containing conductive particles, glass frit, organic vehicle, and the like on the antireflection film 30 and then fired to form an electrode. It is formed by applying an aluminum paste composition composed of aluminum powder, glass frit, and an organic vehicle by screen printing or the like, drying and firing at a temperature of 660 ° C. (melting point of aluminum) or more. During the firing, aluminum diffuses into the p-type silicon semiconductor substrate, whereby an Al-Si alloy layer is formed between the back electrode and the p-type silicon semiconductor substrate, and the p + layer 40 is formed as an impurity layer by diffusion of aluminum atoms. ) Is formed. The presence of such a p + layer results in a back surface field (BSF) effect that prevents electron recombination and improves the collection efficiency of product carriers. The rear silver electrode 60 may be further positioned below the rear aluminum electrode 50.

In order to enhance the power generation characteristics of the solar cell, the characteristics of the electrode are important. For example, the power generation efficiency is increased by lowering the resistance value of the electrode. In order to achieve this object, the formation of the electrode and the development of the material capable of minimizing the electrical resistance loss have been made.

The characteristics of the conductive paste including the silver powder for solar cell electrodes, in particular for the front electrode, greatly affect the power generation characteristics of the solar cell, and provide a thixotropic paste such as Korea Patent Publication No. 2013-0090276. Various studies have been made to improve printing characteristics to have an aspect ratio, or to improve the power generation characteristics of solar cells by uniformly contacting electrodes with a silicon substrate by adjusting materials and softening points of glass frits, such as Korean Patent Publication No. 2013-0104614. Although it continues, the relationship between the color of silver powder and the efficiency characteristic of a solar cell is not examined in depth.

1. Korean Patent Publication No. 2013-0090276 (2013.08.13) 2. Korean Patent Publication No. 2013-0104614 (2013.09.25)

The present invention provides a silver powder and a conductive paste that contribute to the improvement of power generation efficiency of a solar cell. More specifically, an object of the present invention is to improve the conversion efficiency of a solar cell by manufacturing a silver powder by adjusting chromaticity, and forming a front electrode using a conductive paste including the same.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention provides a reaction solution preparation step (S21) and a first reaction for preparing a second reaction solution including a first reaction solution including a silver ion, ammonia (NH ₃ ), nitric acid (HNO ₃ ), and a phosphorus compound and a reducing agent. A silver salt reduction step (S2) including a precipitation step (S22) of obtaining a silver powder by reacting the liquid and the second reaction solution; a silver powder manufacturing method for a solar cell electrode including a silver powder having a controlled chromaticity To provide.

In addition, by adjusting the amount of the phosphorus compound in the reaction solution production step (S21) is characterized in that the chromaticity of the prepared silver powder.

In addition, the phosphorus compound is characterized in that it comprises any one or more selected from the group consisting of sodium pyrophosphate (Sodium Pyrophosphate), and sodium phosphate (sodium phosphate).

In addition, the phosphorus compound is characterized in that it comprises 0.01 to 0.1 parts by weight based on 100 parts by weight of the silver nitrate (AgNO ₃ ).

In addition, the silver ion is a silver salt solution containing silver nitrate (AgNO ₃ ) is included in the first reaction solution, the first reaction solution is based on 100 parts by weight of the silver nitrate (AgNO ₃ ), 100 to 150 ammonia By weight, 40 to 120 parts by weight of the nitric acid (HNO ₃ ), the second reaction liquid is characterized in that it comprises 10 to 20 parts by weight of the reducing agent with respect to 100 parts by weight of the silver nitrate (AgNO ₃ ). .

In addition, the reducing agent is characterized in that at least one member selected from the group consisting of ascorbic acid, alkanolamine, hydroquinone, hydrazine and formalin.

In addition, the precipitation step (S22) is characterized in that the step of reacting by dropwise addition or batch addition of the second reaction solution in the state of stirring the first reaction solution.

In addition, the surface treatment step (S4) to hydrophobize the surface of the silver powder by adding a surface treatment agent containing stearic acid ethanol to the silver powder obtained after the silver salt reduction step (S2);

In addition, the present invention is a silver powder having an average particle size of 1.30 to 1.51 μm, the brightness index (L *) measured by using a spectrophotometer for a coating film formed of a paste containing the silver powder, characterized in that 80 or more It provides a silver powder for solar cell electrodes.

In another aspect, the present invention is a metal powder containing the silver powder for the solar cell electrode; Glass frit; It provides a conductive paste for a solar cell electrode comprising; and an organic vehicle.

 In another aspect, the present invention provides a solar cell comprising an electrode formed by using the conductive paste for the solar cell electrode.

The silver powder prepared by adding the phosphorus compound according to the present invention has a brightness index (L *) of 80 or more, and the conductive paste containing the silver powder having the chromaticity controlled may be used for the production of solar cell electrodes, particularly front electrodes. In addition, it has an excellent conversion efficiency and resistance characteristics to provide the effect of improving the solar cell power generation efficiency.

In addition, the contrast with the silicon wafer used as the P-type silicon semiconductor substrate provides an easy effect in evaluating the printing characteristics of the electrode.

1 is a schematic cross-sectional view of a general solar cell device.

Prior to describing the present invention in detail below, it is understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is limited only by the scope of the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise indicated.

Throughout this specification and claims, unless otherwise indicated, the termcomprise, constitutes, and configure means to include the referenced article, step, or group of articles, and step, and any other article It is not intended to exclude a stage or group of things or groups of stages.

On the other hand, various embodiments of the present invention can be combined with any other embodiment unless clearly indicated to the contrary. Any feature indicated as particularly preferred or advantageous may be combined with any other feature and features indicated as preferred or advantageous. Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention and the effects thereof.

Silver powder according to an embodiment of the present invention comprises a front electrode prepared by using a conductive paste containing the silver powder by adjusting the chromaticity of the silver powder prepared by adjusting the amount of the phosphorus compound in the manufacturing process It provides the effect of increasing the power generation efficiency of solar cells.

 When the brightness index (L *) of the silver powder manufactured is 80 or more, it has been found to have an effect of increasing the power generation efficiency of the solar cell, and also due to the difference in contrast with the silicon wafer used as a P-type silicon semiconductor substrate. It provides an easy effect in evaluating the printing characteristics of the electrode.

 When the brightness index (L *) of the silver powder to be produced is less than 80, the distinction from the silicon wafer is not clear, so it is disadvantageous in evaluating printing characteristics. In addition, the low color of the silver powder means that the crystallinity of the silver powder is low or the degree of unevenness of the surface is high, which has a bad effect on the power generation efficiency of the solar cell, causing the efficiency to be lowered.

Method for producing a silver powder according to an embodiment of the present invention is a silver salt manufacturing step (S1); Silver salt reduction step (S2); Purification step such as filtration and washing (S3); And a surface treatment step (S4). The production method of silver powder according to the present invention necessarily includes a silver salt reduction step (S2), other steps can be omitted.

Silver salt preparation step (S1) according to an embodiment of the present invention to prepare a silver salt solution containing silver ions (Ag +) by acid treatment of silver (Ag +) in the form of ingots, ribs, granules As a step, the silver powder may be prepared by directly preparing a silver salt solution through this step, but a later step may be performed using a commercially available silver nitrate (AgNO ₃ ), a silver salt complex, or a silver intermediate solution. .

Silver salt reduction step according to an embodiment of the present invention (S2) is a step of depositing silver particles by reducing the silver ions by adding a phosphorus compound, a reducing agent and ammonia to the silver salt solution, silver ions, ammonia , Preparing a first reaction solution containing nitric acid and a phosphorus compound and a second reaction solution including a reducing agent (S21) and a precipitation step of reacting the first reaction solution and the second reaction solution to obtain a silver powder. (S22).

In the reaction solution preparation step (S21) according to the embodiment of the present invention, ammonia, nitric acid, and phosphorus compounds are added to the silver salt solution containing silver ions, stirred, and dissolved to prepare a first reaction solution.

The silver ion is not limited as long as it is a material included in the form of a silver cation. For example, it may be silver nitrate (AgNO ₃ ), a silver salt complex or a silver intermediate. Preferably, silver nitrate (AgNO ₃ ) is used. Hereinafter, the use of silver nitrate (AgNO ₃ ) containing silver ions will be described as an example.

Ammonia (NH ₃ ) may be used in the form of an aqueous solution, and in the case of using a 25% aqueous ammonia solution, 100 to 150 parts by weight is added based on 100 parts by weight of silver nitrate (AgNO ₃ ). When the aqueous ammonia solution is added below 100 parts by weight, the reaction pH is low, so that all of the silver ions are not reduced, or there is a problem in forming a uniform particle distribution. There is a problem that is too high. Preferably, the aqueous solution of 25% ammonia is added in an amount of 120 to 140 parts by weight based on 100 parts by weight of silver nitrate (AgNO ₃ ). The ammonia includes its derivatives.

Nitric acid (HNO ₃ ) may be used in the form of an aqueous solution, and when using a 60% aqueous nitric acid solution, 40 to 120 parts by weight is added based on 100 parts by weight of silver nitrate (AgNO ₃ ). When nitric acid (HNO ₃ ) is added below 40 parts by weight, it is difficult to control the size of the silver powder, and when nitric acid (HNO ₃ ) is added in excess of 120 parts by weight, the organic matter content increases significantly. have. Preferably, an aqueous solution of 60% nitric acid is added in an amount of 80 to 100 parts by weight based on 100 parts by weight of silver nitrate (AgNO ₃ ). The nitric acid includes its derivatives.

Phosphorus compound is used to include any one or more selected from the group consisting of pyrophosphate and phosphate, preferably sodium pyrophosphate, sodium phosphate, more preferably Sodium pyrophosphate is recommended to use. The phosphorus compound may be added in an amount of 0.01 to 0.1 parts by weight based on 100 parts by weight of silver nitrate (AgNO ₃ ) to adjust the chromaticity of the silver powder finally prepared. Silver powder having a brightness index (L *) of 80 or more can be prepared by adding a phosphorus compound in an amount within the above range. When the phosphorus compound is added in less than 0.01 parts by weight, there is a problem that the chromaticity control effect is significantly reduced, and when the phosphorus compound is added in excess of 0.1 parts by weight, there is a problem in that the fine powder is increased to increase the particle size.

The first reaction solution containing silver ions, ammonia, nitric acid and phosphorus compounds may be prepared in an aqueous solution state by adding silver ions, aqueous ammonia solution, aqueous nitric acid solution and phosphorus compound to a solvent such as water, stirring and dissolving the same. It may be prepared in the form.

Reaction liquid preparation step (S21) according to an embodiment of the present invention also prepares a second reaction liquid containing a reducing agent.

The reducing agent may be at least one selected from the group consisting of ascorbic acid, alkanolamine, hydroquinone, hydrazine and formalin, and among these, hydroquinone may be preferably selected. The amount of the reducing agent is preferably included in an amount of 10 to 20 parts by weight based on 100 parts by weight of silver nitrate (AgNO ₃ ) included in the first reaction solution. When using less than 10 parts by weight, all of the silver ions may not be reduced, when using more than 20 parts by weight there is a problem that the organic content increases. Preferably, the second reaction solution is prepared using 14 to 16 parts by weight of a reducing agent based on 100 parts by weight of silver nitrate.

The second reaction solution containing a reducing agent may be prepared in an aqueous solution state by adding a reducing agent to a solvent such as water and stirring the solution.

Precipitation step (S22) according to an embodiment of the present invention is a step of obtaining a silver powder by reacting the first reaction solution and the second reaction solution, stirring the first reaction solution prepared by the reaction solution preparation step (S21) The second reaction liquid can be slowly added dropwise or added in a batch to react. Preferably, after the batch addition, the mixture is further stirred for 5 to 10 minutes to grow the particles in the mixed solution in a short time, so that the reduction reaction is ended in a batch to prevent aggregation between the particles and to improve dispersibility.

On the other hand, in the embodiment of the present invention does not exclude the addition of the dispersant to react in order to improve the dispersibility of the silver particles and prevent aggregation. Examples of dispersants include fatty acids, fatty acid salts, surfactants, organometallics, chelate formers and protective colloids.

However, when the dispersant is added, the remaining organic matter content may be increased, so it is desirable to control the particle size, the remaining organic matter content, and the crystallite diameter of the silver powder without adding the dispersant.

Purification step (S3) according to an embodiment of the present invention is a silver salt reduction step (S2) after completing the silver particle precipitation reaction to remove and wash the silver powder dispersed in an aqueous solution or slurry using filtration and the like Step S31 is included. More specifically, after the silver particles in the silver powder dispersion are precipitated, the supernatant of the dispersion is discarded and filtered using a centrifuge, and the filter medium is washed with pure water. The washing process must be done by completely removing the wash water from which the powder has been washed. It is also possible to optionally add the aforementioned dispersants to the reaction complete solution prior to filtration to prevent aggregation of the silver powder.

In addition, the purification step (S3) according to an embodiment of the present invention may further comprise a drying and disintegration step (S34) after washing.

Surface treatment step (S4) according to an embodiment of the present invention is a step of hydrophobizing the hydrophilic surface of the silver powder, it may be made selectively. More specifically, the surface treatment agent containing a stearic acid ethanol solution can be added to the silver powder obtained after filtration, and hydrophobicity can be provided to a silver powder. After that, silver powder can be obtained through filtration, washing, drying and pulverization. When surface treatment of silver powder, the powder should be well dispersed, and the surface treatment is sufficient. If the water content is low, the dispersion efficiency is poor, so it is better to surface-treat a certain amount with water content.

Silver powder prepared according to the silver powder manufacturing method according to an embodiment of the present invention has an average particle size of 1.30 to 1.51 ㎛, and has a chromaticity characteristic with a brightness index (L *) of 80 or more.

The present invention also provides a conductive paste comprising silver powder prepared according to one embodiment of the present invention. More specifically, the conductive paste according to the present invention comprises a metal powder, a glass frit and an organic vehicle.

As the metal powder, silver powder having a chromaticity characteristic having an average particle size of 1.30 to 1.51 µm and a chromaticity index (L) of 80 or more is used. Preferably, silver powder prepared according to one embodiment of the present invention is used.

The content of the metal powder is preferably 85 to 95% by weight based on the total weight of the conductive paste composition in consideration of the electrode thickness formed during printing and the line resistance of the electrode.

There is no restriction | limiting in particular in the composition, particle diameter, and shape of the said glass frit. Lead-free glass frits can be used as well as leaded glass frits. Preferably, as a component and content of the glass frit, PbO is 5 to 29 mol%, TeO ₂ is 20 to 34 mol%, Bi ₂ O ₃ is 3 to 20 mol%, SiO _{2 is} 20 mol% or less, 10 mol% or less of B ₂ O ₃ , alkali metals (Li, Na, K, etc.) and alkaline earth metals (Ca, Mg, etc.) may contain 10 to 20 mol%. By combining the organic content of the above components, it is possible to prevent the increase of the electrode line width, to improve the contact resistance at the sheet resistance, and to improve the short-circuit current characteristics.

The average particle diameter of the glass frit is not limited, but may have a particle diameter within the range of 0.5 to 10 μm, and may be used by mixing multi-sheet particles having different average particle diameters. Preferably, at least 1 type of glass frit uses that whose average particle diameter (D50) is 2 micrometers or more and 10 micrometers or less. This makes it possible to improve reactivity during firing, to minimize damage of n layers, especially at high temperatures, to improve adhesion, and to improve open voltage (Voc). In addition, it is possible to reduce the increase in the line width of the electrode during firing.

The content of the glass frit is preferably 1 to 5% by weight based on the total weight of the conductive paste composition. If the content of the glass frit is less than 1% by weight, incomplete firing may occur to increase the electrical resistivity. There are too many components, and there exists a possibility that an electrical resistivity may also become high.

The organic vehicle is not limited, but an organic binder and a solvent may be included. Sometimes the solvent can be omitted. The organic vehicle is not limited but is preferably 1 to 10% by weight based on the total weight of the conductive paste composition.

The organic vehicle is required to maintain a uniformly mixed state of the metal powder and the glass frit. For example, when the conductive paste is applied to the substrate by screen printing, the conductive paste is made homogeneous and the print pattern is blurred. And properties for suppressing flow and improving the dischargeability and plate separation property of the conductive paste from the screen plate.

The organic binder included in the organic vehicle is not limited, but examples of the cellulose ester-based compound include cellulose acetate, cellulose acetate butylate, and the like, and cellulose ether compounds include ethyl cellulose, methyl cellulose, hydroxy flophyll cellulose, and hydroxy ethyl. Cellulose, hydroxy propyl methyl cellulose, hydroxy ethyl methyl cellulose, and the like. Examples of the acryl-based compound include poly acrylamide, poly methacrylate, poly methyl methacrylate, and poly ethyl methacrylate. Examples of the vinyl type include polyvinyl butyral, polyvinyl acetate, and polyvinyl alcohol. At least one organic binder may be selected and used.

Solvents used for dilution of the composition include alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol mono butyl ether, ethylene At least one compound selected from the group consisting of glycol mono butyl ether acetate, diethylene glycol mono butyl ether, diethylene glycol mono butyl ether acetate and the like is preferably used.

The conductive paste composition according to the present invention may further include additives commonly known as necessary, for example, a dispersant, a plasticizer, a viscosity modifier, a surfactant, an oxidant, a metal oxide, a metal organic compound, and the like.

The present invention also provides a method for forming an electrode of a solar cell and a solar cell electrode produced by the method, wherein the conductive paste is coated on a substrate, dried and baked. Except for using the conductive paste containing the silver powder of the above characteristics in the method of forming a solar cell electrode of the present invention, the substrate, printing, drying and firing can be used as the method commonly used in the manufacture of solar cells as well to be. For example, the substrate may be a silicon wafer.

Examples and Comparative Examples

(1) Example 1

128 g of pure nitric acid, 157 g of ammonia (concentration of 25%), 126 g of nitric acid (concentration of 60%), and 0.024 g of sodium pyrophosphate were added and stirred to dissolve the first aqueous solution. Meanwhile, 20 g of hydroquinone was added to 1000 g of room temperature pure water, followed by stirring to dissolve the second aqueous solution. Subsequently, the 1st aqueous solution was made to stir, the 2nd aqueous solution was added collectively to this 1st aqueous solution, and further stirred for 5 minutes after completion | finish of addition, and the particle was grown in the mixed liquid. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(2) Example 2

128 g of pure nitric acid, 157 g of ammonia (concentration of 25%), 126 g of nitric acid (concentration of 60%), and 0.032 g of sodium pyrophosphate were added thereto, stirred, and dissolved to prepare a first aqueous solution. Meanwhile, 20 g of hydroquinone was added to 1000 g of room temperature pure water, followed by stirring to dissolve the second aqueous solution. Subsequently, the 1st aqueous solution was made to stir, the 2nd aqueous solution was added collectively to this 1st aqueous solution, and further stirred for 5 minutes after completion | finish of addition, and the particle was grown in the mixed liquid. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(3) Example 3

128 g of pure nitric acid, 157 g of ammonia (concentration of 25%), 126 g of nitric acid (concentration of 60%), and 0.04 g of sodium pyrophosphate were added thereto, stirred, and dissolved to prepare a first aqueous solution. Meanwhile, 20 g of hydroquinone was added to 1000 g of room temperature pure water, followed by stirring to dissolve the second aqueous solution. Subsequently, the 1st aqueous solution was made to stir, the 2nd aqueous solution was added collectively to this 1st aqueous solution, and further stirred for 5 minutes after completion | finish of addition, and the particle was grown in the mixed liquid. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(4) Comparative Example 1

128 g of silver nitrate, 157 g of ammonia (concentration 25%), and 126 g of nitric acid (concentration 60%) were added to 660 g of pure water at room temperature, followed by stirring to dissolve to prepare a first aqueous solution. Meanwhile, 20 g of hydroquinone was added to 1000 g of room temperature pure water, followed by stirring to dissolve the second aqueous solution. Subsequently, the 1st aqueous solution was made to stir, the 2nd aqueous solution was added collectively to this 1st aqueous solution, and further stirred for 5 minutes after completion | finish of addition, and the particle was grown in the mixed liquid. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

First aqueous solution Second aqueous solution Water (g) lunar caustic
Solution (g) ammonia
Aqueous solution (g) Nitric acid (g) Pyrophosphate
Sodium (% / AgNO ₃ ) Water (g) Reducing agent (g) Example 1 660 128 157 126 0.019% 1000 20 Example 2 660 128 157 126 0.025% 1000 20 Example 3 660 128 157 126 0.031% 1000 20 Comparative Example 1 660 128 157 126 0.00% 1000 20

As shown in Table 1, the phosphorus compound may adjust the chromaticity of the silver powder prepared by being added within the range of 0.01 to 0.10 weight based on the weight of the silver nitrate solution in the first reaction solution composition.

(5) surface treatment of silver powder

In order to impart hydrophobicity to the silver powder prepared according to the above Examples and Comparative Examples was subjected to the surface treatment. The silver powder was added to pure water, which is four times the weight of the silver powder, and the homomixer (for K & S company, Lab) was stirred at 3000 RPM for 20 minutes to disperse the dried powder. Then, stearic acid ethanol solution (stearic acid content 8.89% by weight) was added 2.4% by weight of silver powder and stirred for 20 minutes. After that, stirring was stopped, the mixture was filtered using a centrifuge, the filter medium was washed with pure water, and dried to obtain a surface-treated silver powder. This silver powder was ground in a food mixer and crushed in a jet-mill.

(6) conductive paste

The electroconductive paste was obtained by mixing 89.5 weight% of silver powder after the said surface treatment, 1.92 weight% of glass frits, 5.20 weight% of an organic vehicle, and 3.38 weight% of additives with the magnetoelectric vacuum stirring defoaming apparatus, and using a three bone roll.

(7) solar cell

The obtained conductive paste was pattern printed on the front surface of the wafer by a 50 μm mesh screen printing technique, and dried at 200 to 350 ° C. for 20 to 30 seconds using a belt type drying furnace. After printing the Al paste on the back of the wafer and dried in the same way. The cell formed by the above process was calcined for 20 seconds to 30 seconds between 500 to 900 ° C. using a belt type kiln to manufacture solar cells.

Experimental Example

(1) SEM size (μm) and crystallite diameter measurement

The silver powders prepared according to the above Examples and Comparative Examples were measured using a scanning electron microscope manufactured by JEOL, and then averaged by measuring the diameter size of each of the 100 powders, and then measuring the SEM size (μm). Table 2 shows.

Powder X-ray diffraction was performed on the silver powders prepared according to the above Examples and Comparative Examples using an X-ray diffractometer X'pert manufactured by PANalytical. It is shown in Table 2 by measuring the crystallite diameter (Å) using.

SEM size
(Μm) Crystallite size (Å) Example 1 1.51 362 Example 2 1.30 356 Example 3 1.38 364 Comparative Example 1 1.71 309

As shown in Table 2, the silver powder prepared according to one embodiment of the present invention is in the range of 1.30 to 1.51 μm, and the crystallite diameter is in the range of 350 to 370 mm 3.

(2) chromaticity analysis

10 g of a binder mixed with 7.7% by weight of ETHOCELTM Std200 Ethylcellulose (The Dow Chemical Company) and 92.3% by weight of Buthyl cabitol acetate and 90 g of silver powder prepared according to Examples and Comparative Examples were used as a magneto-electric vacuum stirring degassing apparatus. After mixing, a conductive paste was obtained using a three-bone roll.

The conductive paste thus obtained was printed on an alumina substrate so as to have a coating film of width 15 mm x length 15 mm or more and dried at 80 ° C. The lightness index (L *) of this coating film was measured with the spectrophotometer (konika minolta, CM-600d).

(3) Conversion efficiency analysis

Cell prepared according to the Examples and Comparative Examples using a solar cell efficiency measurement equipment (Halm, cetisPV-Celltest 3), the conversion efficiency, the short-circuit current, the open circuit voltage, the curve factor, the line resistance by observing the value of the comparative example Relative values based on 100 are shown in the table below.

Brightness Index (L *) Conversion efficiency (Eff) Short circuit current (Isc) Open Voltage (Voc) Curve Factor (FF) Wire resistance Example 1 83.79 101.38 100.48 100.55 100.35 92.45 Example 2 84.64 101.39 100.37 100.61 100.42 89.46 Example 3 85.27 101.21 100.60 100.72 099.90 94.63 Comparative Example 1 72.02 100.00 100.00 100.00 100.00 100.00

As shown in Table 3, in the case of a solar cell including an electrode made of a conductive paste containing a silver powder of the present invention having a brightness index (L *) of 80 or more, the line resistance is lower and the conversion efficiency is higher than that of the comparative example. It can be seen that the power generation efficiency of the battery is improved.

Features, structures, effects, and the like illustrated in the above-described embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, contents related to such combinations and modifications should be construed as being included in the scope of the present invention.

10: P-type silicon semiconductor substrate
20: N-type impurity layer
30: antireflection film
40: P + layer (BSF: back surface field)
50: back aluminum electrode
60: back silver electrode
100: front electrode

Claims (11)

A reaction solution preparation step of preparing a second reaction solution including a first reaction solution including a silver nitrate (AgNO ₃ ), ammonia (NH ₃ ), a nitric acid (HNO ₃ ), and a phosphorus compound and a reducing agent including silver ions (S21). ) And
Silver salt reduction step (S2) comprising a precipitation step (S22) of reacting the first reaction solution and the second reaction solution to obtain a silver powder; including,
The first reaction solution comprises 0.01 to 0.1 parts by weight of the phosphorus compound, 100 to 150 parts by weight of ammonia and 40 to 120 parts by weight of nitric acid (HNO ₃ ) based on 100 parts by weight of the silver nitrate (AgNO ₃ ). ,
The second reaction solution comprises 10 to 20 parts by weight of the reducing agent with respect to 100 parts by weight of the silver nitrate (AgNO ₃ ),
Silver powder manufacturing method for a solar cell electrode for producing a silver powder having a controlled chromaticity.
The method of claim 1,
The method for producing a silver powder for a solar cell electrode, characterized in that for controlling the chromaticity of the silver powder prepared by adjusting the amount of the phosphorus compound in the reaction solution production step (S21).
The method of claim 1,
The phosphorus compound is a sodium pyrophosphate (Sodium Pyrophosphate), and sodium phosphate (sodium phosphate) comprises any one or more selected from the group consisting of a silver powder for a solar cell electrode.
delete delete The method of claim 1,
The reducing agent is a silver powder for solar cell electrode, characterized in that at least one selected from the group consisting of ascorbic acid, alkanolamine, hydroquinone, hydrazine and formalin.
The method of claim 1,
The precipitation step (S22) is a method for producing a silver powder for a solar cell electrode, characterized in that for reacting by dropwise addition or batch addition of the second reaction solution in the state of stirring the first reaction solution.
The method of claim 1,
The surface treatment step (S4) to hydrophobize the surface of the silver powder by adding a surface treatment agent containing ethanol stearate to the silver powder obtained after the silver salt reduction step (S2); Dragon silver powder manufacturing method.
As a silver powder for forming a solar cell electrode prepared according to the method of claim 1 having an average particle size of 1.30 to 1.51 μm,
After mixing 10 g of the binder mixed with 7.7% by weight of ETHOCELTM Std200 Ethylcellulose (The Dow Chemical Company) and 92.3% by weight of Buthyl cabitol acetate and 90 g of the silver powder by using a magnetoelectric vacuum stirring defoaming apparatus, When the obtained electrically conductive paste was printed so that it might become a coating film 15 mm in width x 15 mm or more on alumina substrate, and it dried at 80 degreeC,
The silver powder for solar cell electrodes characterized by the above-mentioned brightness | luminance index (L *) measured by the spectrophotometer (konika minolta, CM-600d) 80 or more.
Metal powder comprising a silver powder for a solar cell electrode of claim 9;
Glass frit; And
Electroconductive paste for solar cell electrodes containing an organic vehicle.
A solar cell comprising an electrode formed using the conductive paste for solar cell electrodes of claim 10.

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