KR102342518B1 - Conductive paste composition for electrode of solar cell and solar cell comprising electrode manufactured using the same - Google Patents

Abstract

The present invention is a conductive paste for a solar cell electrode, a paste including a metal powder, a glass frit, and an organic vehicle, wherein the glass frit includes lead (Pb) and tellurium (Te), and an oxide of antimony (Sb) Further comprising, based on the total weight of the conductive paste, the glass frit contains 21 mole % to 29 mole % of PbO, 34 mole % to 38 mole % of _{TeO 2 , and antimony (Sb)} ) A conductive paste for a solar cell electrode, characterized in that the oxide content is contained in an amount of 2 mole % to 5 mole %. have.

Description

Conductive paste composition for a solar cell electrode and a solar cell comprising an electrode manufactured using the same

The present invention relates to a conductive paste composition for a solar cell electrode and a solar cell including an electrode manufactured using the same.

A solar cell is a semiconductor device that converts solar energy into electrical energy, and generally has a p-n junction type and has the same basic structure as a diode. 1 shows the structure of a general solar cell device, the solar cell device is generally constructed 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 mu m, an antireflection film 30 and a front electrode 100 are formed thereon. Further, a rear electrode 50 is formed on the rear surface side of the p-type silicon semiconductor substrate.

The front electrode 100 is formed by applying a conductive paste containing silver as a main component, glass frit, an organic vehicle, and an additive on the anti-reflection film 30 . After firing to form an electrode, the rear electrode 50 is coated with an aluminum paste composition consisting of aluminum powder, glass frit, organic vehicle and additives by screen printing, etc. It is formed by firing. During this firing, aluminum diffuses into the p-type silicon semiconductor substrate, thereby forming an Al-Si alloy layer between the back electrode and the p-type silicon semiconductor substrate, and at the same time forming a p+ layer (40) as an impurity layer by diffusion of aluminum atoms. ) is formed. By the presence of such a p + layer, a BSF (Back Surface Field) effect of preventing recombination of electrons and improving the collection efficiency of generated carriers is obtained. A rear silver electrode 60 may be further positioned under the rear aluminum electrode 50 .

The process of forming a metal electrode on both sides of a silicon wafer is a process of printing a paste containing metal powder and glass frit using a screen printing method, and then forming the electrode through a drying and firing process. Currently, it is most widely used in the crystalline solar cell mass production line, and the characteristics of the solar cell are achieved through a high-temperature sintering process. In particular, the front electrode undergoes burnout of organic materials such as organic vehicles, and melting, expansion, and contraction of inorganic materials such as conductive particles and glass frit during high-temperature sintering at 750°C or higher, forming contact resistance and short circuit due to securing light receiving area. A current Isc is formed.

On the other hand, in the front electrode during firing, the anti-reflection film is eroded through the oxidation-reduction reaction of the glass frit powder, and conductive metal crystal grains are precipitated in the form of conductive powder crystals in the glass frit powder precipitated at the interface of the substrate, and the precipitated metal crystal grains are bulk It is known that it not only serves as a bridge between the front electrode and the silicon substrate, but also exhibits a tunneling effect or direct adhesion with the bulk electrode depending on the thickness of the glass frit powder.

Conventionally, in order to improve the contact resistance between the electrode and the high sheet resistance (100 Ω/sq or more) wafer, a method of including a _{Pb-Te-based (PbO, TeO 2 ) component in the glass frit was used.} Even in the case of high sheet resistance (100 Ω/sq or more), there is a problem in that the open-circuit voltage (VOC) is reduced in the cell, and soldering is disadvantageous.
<Prior art literature>
<Patent Literature>
Korea Patent Publication No. 2019-0051398 (published on May 15, 2019)

The present invention is to solve the above problems, based on a Pe-Te-based glass frit, and adding antimony (Sb) oxide as an excitation fining agent to maintain a low series resistance (Series Resistance, Rs) while maintaining an open voltage (Open- An object of the present invention is to provide a conductive paste composition for an active solar cell that can improve electrical properties in which circuit volts, VOC) increase and physical properties in which soldering is improved.

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.

As a means for solving the above problems,

In one embodiment, the present invention is a paste comprising a metal powder, a glass frit and an organic vehicle, wherein the glass frit comprises lead (Pb) and tellurium (Te), and the glass frit is an oxide of antimony (Sb). It provides a conductive paste for a solar cell electrode, characterized in that it further comprises.

In addition, other means not mentioned will be clearly understood by those skilled in the art from the following description.

In the present invention, excellent contact resistance properties are maintained by adding antimony (Sb) oxide to the Pb-Te-based glass frit of the front conductive paste for solar cell electrodes, and the firing damage to the wafer of the front electrode occurring in the solar cell firing process is reduced. By reducing it, the Voc characteristic can be improved. In addition, it is possible to improve the soldering characteristics, which is a disadvantage of the conventional Pb-Te-based glass frit.

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

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

Throughout this specification and claims, unless stated otherwise, the term comprise, comprises, comprising is meant to include the stated object, step or group of objects, and steps, and any other object. It is not used in the sense of excluding a step or a group of objects or groups of steps.

On the other hand, various embodiments of the present invention may be combined with any other embodiments 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, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

The paste according to an embodiment of the present invention is a paste suitable for use in forming a solar cell electrode. Antimony (Sb) oxide is added to a Pb-Te-based glass frit to maintain excellent contact resistance properties, and is generated in the solar cell firing process. Provided is a conductive paste composition for a solar cell electrode that can improve Voc characteristics and improve soldering characteristics by reducing the firing damage to the wafer of the front electrode. More specifically, the conductive paste composition may include a metal powder, a glass frit, a metal oxide, an organic vehicle, and the like. In addition, various additives may be included.

As the metal powder, silver powder, copper powder, nickel powder, aluminum powder, etc. may be used. For the front electrode, silver powder is mainly used, and for the rear electrode, aluminum powder is mainly used. As the metal powder, one of the above-mentioned powders may be used alone, an alloy of the above-mentioned metal may be used, or at least two of the above-mentioned powders may be used as a mixed powder.

The content of the metal powder is preferably 40 to 95% by weight based on the total weight of the conductive paste composition in consideration of the thickness of the electrode formed during printing and the wire resistance of the electrode. If it is less than 40% by weight, the specific resistance of the formed electrode may be high, and if it is more than 95% by weight, there is a problem in that the content of other components is not sufficient, so that the metal powder is not uniformly dispersed. More preferably, it is included in an amount of 80 to 90% by weight.

When the conductive paste contains silver powder for forming the front electrode of a solar cell, the silver powder is preferably a pure silver powder. In addition, a silver-coated composite powder having at least a surface of a silver layer, or an alloy containing silver as a main component (alloy) and the like can be used. In addition, other metal powders may be mixed and used. For example, aluminum, gold, palladium, copper, nickel, etc. are mentioned.

The average particle diameter (D50) of the metal powder may be 0.1 to 10 μm, and 0.5 to 5 μm is preferable in consideration of ease of pasting and density during firing, and the shape is at least one of spherical, needle, plate, and amorphous. may be more than one species. The metal powder may be used by mixing two or more types of powders having different average particle diameters, particle size distributions, shapes, and the like.

The glass frit is melted during high-temperature sintering to induce densification of the metal powder and cause an interfacial reaction with the anti-reflection film to etch the anti-reflection film to fix the conductive metal to the substrate, which is an oxidation-reduction reaction of some elements is reduced and produced as a by-product.

In general, the glass frits each contain at least _two of PbO, TeO 2 , Bi ₂ O ₃ , SiO _{2 ,} B ₂ O ₃ , Al ₂ O ₃ , ZnO, WO ₃ , Sb ₂ O _{3 ,} alkali metal oxides and alkaline earth metal oxides. More than one species may be included. In addition, a metal oxide may be further included, and the metal oxide may further include at least one selected from among NiO, CuO, MgO, CaO, RuO, and MoO.

The glass frit according to the present invention contains antimony (Sb) oxide and is a Pb-Te-based glass frit that is excellent in lowering contact resistance, and provides a composition of a glass frit that can improve contact resistance (wettability) and spreadability do. That is, during high-temperature sintering for electrode formation, the anti-reflection film is etched to excellently adhere the conductive metal to the substrate, thereby lowering the contact resistance, while reducing the spread of the electrode to form an electrode having a high aspect ratio (ratio of line width to line width). It provides a composition of a glass frit that can be used. In particular, it is possible to minimize the plastic damage of the n-layer at a high temperature, and it is possible to improve the adhesion and thus make the open-circuit voltage (Voc) excellent. In addition, it is possible to reduce the leaching phenomenon generated during ribbon soldering of the electrode, so that the soldering characteristics are improved.

More specifically, for excellent contact resistance in the conventional Pb-Te-based glass frit, lead oxide (PbO) and tellurium oxide (TeO) are included in an amount of 30 mol% or more and 35 mol% or more, respectively, so that the glass transition temperature is lowered to a low temperature In order to solve this problem, the contact resistance can be excellently improved because it is melted in In the present invention, PbO and Te ₂ O are used in a specific content, and antimony (Sb) oxide is included in a specific content to improve contact resistance, increase open-circuit voltage (Voc), and simultaneously open soldering characteristics. to provide.

More specifically, the components and content of the glass frit according to the present invention include 21 to 29 mol% of PbO, 34 to 38 mol% of _{TeO 2} , and 2 to 5 mol% of _{Sb 2} O _{3 on an oxide basis, and the remainder} The content may include any one or more of Bi2O3, SiO2, B2O3, Al2O3, ZnO, and WO3 as other oxides. It can lower the series resistance (Rs) in the high sheet resistance cell and provide a synergistic effect of open voltage (Voc) and soldering.

Preferably, in the high sheet resistance (100 ~ 110 Ω / sq) PERC cell, PbO is 21 ~ 29 mol%, TeO ₂ is 34 ~ 38 mol%, Sb ₂ O ₃ contains 2 ~ 5 mol%, (Sb ₂ O ₃ Molar ratio / PbO molar ratio) x 100 value is 10 to 25%, (Sb ₂ O ₃ Molar ratio / TeO ₂ molar ratio) x 100 It is preferable that the value is 5 to 15%.

In addition, preferably, in the high sheet resistance (120 ~ 130 Ω / sq) PERC cell, PbO is 21 ~ 29 mol%, TeO ₂ is 34 ~ 38 mol%, Sb ₂ O ₃ contains 2 ~ 5 mol%, (Sb ₂ O ₃ Molar ratio / PbO molar ratio) x 100 value is 5 to 15%, (Sb ₂ O ₃ Molar ratio / TeO ₂ molar ratio) x 100 It is preferable that the value is 5 to 15%.

If the content of PbO and TeO ₂ is too high, it is not environmentally friendly, and there is a problem that the line width of the electrode becomes large during firing due to the viscosity when melting is too low. Therefore, PbO and TeO ₂ are preferably included within the above range in the glass frit.

In addition, when the Sb ₂ O ₃ content is formed in the electrode within the above content range, the glass frit may be uniformly distributed in the electrode. As a result, it has excellent etching ability during firing, does not cause a shunt problem due to excessive etching, and does not interfere with the reaction with the anti-reflection film, thereby lowering the contact resistance and increasing the open circuit voltage (Voc) to increase the conversion efficiency of the solar cell can increase In addition, even when an excessive amount of glass frit is included, soldering (sordering) characteristics are strengthened, thereby improving adhesion characteristics.

The glass frit according to the present invention solves the contact resistance problem by adjusting the content ratio of Pb and Te, which has a great influence on improving the contact resistance, and additionally contains antimony (Sb) oxide in a specific content to provide a high sheet resistance (100 Ω/sq) Above) It can be supported by the Examples and Experimental Examples to be described later that it is possible to solve the problem that the voltage before opening (Voc) is reduced in the cell and the soldering (sordering) characteristic is disadvantageous.

In particular, by including the antimony (Sb) oxide in a specific content, the reactivity during sintering is improved, and damage to the n-layer can be minimized, particularly at high temperatures, and adhesion can be improved and the open circuit voltage (Voc) can be improved.

The glass transition temperature (Tg) of the glass frit according to the composition is 200 to 300 ℃. The glass frit according to the present invention has a low glass transition temperature of 300° C. or less, so that the melting uniformity can be increased, and the cell characteristic uniformity can be improved. In addition, excellent contact characteristics can be secured even during rapid firing, and it can be optimized for high sheet resistance (100 ~ 130Ω/sq) solar cells. In addition, it is possible to prevent an increase in electrode line width by combining the organic content of each component, to improve contact resistance at a high surface resistance (100 to 130 Ω/sq), and to improve short-circuit current characteristics.

On the other hand, 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 a mixture of various types of particles having different average particle diameters may be used. Preferably, at least one glass frit having an average particle diameter of 1 μm or more and 5 μm or less is used, and more preferably, a glass frit having an average particle diameter of 1 μm or more and 3 μm or less is used. Through this, the reactivity during firing can be improved, and an increase in the line width of the electrode can be reduced.

The content of the glass frit is preferably 1 to 15% by weight based on the total weight of the conductive paste composition. If it is less than 1% by weight, there is a risk of incomplete firing and high electrical resistivity. There is a possibility that the component is too large to increase the electrical resistivity. Preferably, it is included in an amount of 1 to 10% by weight, more preferably 1 to 5% by weight.

The organic vehicle is not limited, but may include an organic binder and a solvent. Sometimes the solvent can be omitted. The organic vehicle is not limited, but may be 3 to 25 wt%, preferably 5 to 15 wt%, based on the total weight of the conductive paste composition.

The organic vehicle is required to maintain a uniformly mixed state of metal powder and glass frit. For example, when a conductive paste is applied to a substrate by screen printing, the conductive paste is homogenized, resulting in blurring of the print pattern. and properties for suppressing flow and improving discharge properties and plate separation properties of the conductive paste from the screen plate are required.

The organic binder included in the organic vehicle is not limited, but examples of the cellulose ester-based compound include cellulose acetate and cellulose acetate butyrate, and the cellulose ether compound includes ethyl cellulose, methyl cellulose, hydroxypropyl cellulose, and hydroxyethyl Examples include cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose, and examples of acrylic compounds include polyacrylamide, poly methacrylate, polymethyl methacrylate, polyethyl methacrylate, and the like. , polyvinyl butyral, polyvinyl acetate and polyvinyl alcohol may be exemplified as the vinyl type. At least one organic binder may be selected and used.

As a solvent used for dilution of the composition, alpha-terpineol, texanol, dioctyl phthalate, dibutyl phthalate, cyclohexane, hexane, toluene, benzyl alcohol, dioxane, diethylene glycol, ethylene glycol monobutyl ether, ethylene It is preferable to use at least one selected from the group consisting of glycol monobutyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and the like.

As an additive, the use of a dispersant, a thickener, a thixotropic agent, a leveling agent, etc. may be selected, and the dispersant may include BYK-110, 111, 108, 180, and the like, and the thickener may include BYK-410. 411. 420, and the like, and the thixotropic agent may include BYK-203, 204, 205, and the leveling agent may include, but are not limited to, BYK-308, 378, 3440, and the like.

The present invention also provides a method for forming an electrode of a solar cell, characterized in that the conductive paste is applied on a substrate, dried and fired, and a solar cell electrode manufactured by the method. In the method for forming the solar cell electrode of the present invention, except for using the conductive paste including the coated glass frit as described above, the methods commonly used for manufacturing the solar cell may be used for the substrate, printing, drying and firing. of course there is For example, the substrate may be a silicon wafer.

When an electrode is formed by using the conductive paste according to the present invention, wetting characteristics and spreadability are improved, thereby increasing the light receiving area of the solar cell and improving the contact resistance, so that the open circuit voltage (Voc) in the high sheet resistance (100 Ω/sq or more) cell ) to improve the power generation efficiency of the solar cell. In addition, it is possible to reduce the leaching phenomenon that occurs during ribbon soldering of the electrode.

In addition, the conductive paste according to the present invention has a structure such as a crystalline solar cell (P-type, N-type), a Passivated Emitter Solar Cell (PESC), a Passivated Emitter and Rear Cell (PERC), and a Passivated Emitter Real Locally Diffused (PERL). It can be applied to all changed printing processes such as double printing and dual printing.

One. Experimental example One ( high surface resistance (100~ 110 Ω / sq ) PERC cell characteristics measurement)

(One) Example and comparative example

A glass frit mixed with the composition (eg, mole%) as shown in Table 1 was prepared, and the binder, dispersant, leveling agent, glass frit, etc. in Table 2 were added to the mixing container in the same amount as shown in Table 2 below. After dispersing using a sambon mill, silver powder was mixed and dispersed using a sambon mill. Thereafter, degassing was performed under reduced pressure to prepare a conductive paste.

division glass frit A glass frit B glass frit C glass frit D glass frit E Glass frit F glass frit G glass frit H Glass frit I Glass Frit J glass frit
ingredient content
(mole%) PbO (A) 22.81 21.47 21.79 21.80 22.00 22.05 22.12 22.20 22.30 22.40 TeO ₂ (B) 37.88 35.66 36.16 36.21 36.54 36.61 36.74 36.87 37.03 37.20 Sb ₂ O ₃ (C) 0 5.87 4.47 4.42 3.54 3.35 3.03 2.68 2.26 1.80 other metals
oxide 39.31 37.00 37.58 37.57 37.92 37.99 38.11 38.25 38.41 38.60 C/A 0 27.34 20.51 20.28 16.09 15.19 13.70 12.07 10.13 8.04 C/B 0 16.46 12.35 12.21 9.69 9.15 8.25 7.27 6.10 4.84

(Other metal oxides in Table 1 may be composed of any one or more of Bi2O3, SiO2, B2O3, Al2O3, ZnO, and WO3)

division
(Ingredient content: g) Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 EC 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 EFKA-4330 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 BYK180 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 Texanol 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Butyl cellosolve 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Thixatrol ST 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Dimethyl adipate 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 silver powder 89.5 89.5 89.5 89.5 89.5 89.5 89.5 89.5 89.5 89.5 Glass frit (A to J) 2 2 2 2 2 2 2 2 2 2

(In Table 2, Comparative Example 1 has glass frit A as the configuration, and Examples 1 to 9 have glass frits B to J as the configuration)

(2) Measurement of solar cell characteristics

The conductive pastes prepared according to Examples 1 to 9 and Comparative Example 1 were pattern-printed on the front surface of the wafer by a 40 μm mesh screen printing technique, and using a belt-type drying furnace at 200 to 350 ° C. for 20 to 30 seconds. dried. After that, Al paste was printed on the back side of the wafer and dried in the same way. A solar cell was manufactured by firing the cell formed by the above process at a temperature between 500 and 900° C. for 20 to 30 seconds using a belt-type firing furnace.

The prepared cell is a solar cell efficiency measuring device (Halm, cetisPV-Celltest 3), conversion efficiency (Eff), short-circuit current (Isc), open-circuit voltage (Voc), curve factor (FF) and series resistance ( Rs) was measured and shown in Table 3 below.

In addition, after manufacturing the solar cells, after bonding the ribbon of SnPbAg composition to the electrode, hold one end of the bonded part using a tensile strength meter and pull it 180 degrees until the front electrode and the ribbon are peeled off. (N) was measured. The measured adhesion (Sordering) is shown in Table 3.

division Isc(A) Voc (V) Eff (%) FF (%) Rs (Ω) Adhesion (N) Comparative Example 1 9.643 0.6657 21.24 80.79 0.00018 1.5 Example 1 8.611 0.6682 21.18 80.54 0.00033 1.5 Example 2 9.637 0.6685 21.32 80.82 0.00029 1.5 Example 3 9.654 0.6668 21.30 80.82 0.00017 2.5 Example 4 9.663 0.6662 21.35 80.98 0.00015 3 Example 5 9.645 0.6664 21.40 81.31 0.00017 3 Example 6 9.665 0.6662 21.37 81.03 0.00017 3 Example 7 9.610 0.6674 21.31 81.16 0.00021 3 Example 8 9.658 0.6682 21.42 81.06 0.00022 2.5 Example 9 9.634 0.6652 21.17 80.66 0.00021 1.5

As shown in Table 3, as a result of measuring the high sheet resistance (100 ~ 110 Ω/sq) PERC cell characteristics, the glass frit _{contains only metal oxides PbO and TeO 2} (Comparative Example 1), additionally metal oxide Sb ₂ O ₃ , it can be seen that the conversion efficiency and adhesion of the solar cell are increased. However, even in this case, looking at the cases of Example 1 and Comparative Example 1, when Sb ₂ O ₃ 5 mole% or more, C/A 25% or more, and C/B 15% or more, the open circuit voltage (VOC) increased, but the series It can be seen that the resistance (Rs) also increases and the adhesive force does not change. In addition, looking at the case of Example 9 and Comparative Example 1, when Sb ₂ O ₃ 2 mole% or less, C/A 10% or less, and C/B 5% or less, the open circuit voltage (VOC) is reduced and the series resistance (Rs) It can be seen that this increased, and the adhesive force did not change. Therefore, preferably, when Sb ₂ O ₃ is 2 to 5 mole%, C/A is in the range of 10 to 25%, and C/B is in the range of 5 to 15% (Examples 2 to 8), low series It can be seen that all of the resistance (Rs), high open circuit voltage (VOC) and adhesion characteristics are satisfied.

Therefore, _{when using a glass frit having a configuration that Sb 2} O ₃ is 2 to 5 mole%, C/A is in the range of 10 to 25%, and C/B is in the range of 5 to 15%, high sheet resistance (100 to 110) Ω/sq), it can be seen that the contact resistance condition is satisfied, the adhesion is increased, and the conversion efficiency of the solar cell is excellent.

2. Experimental example 2 ( high surface resistance (120~ 130 Ω / sq ) PERC cell characteristics measurement)

(One) Example and comparative example

A glass frit mixed with the composition (eg, mole %) as shown in Table 4 was prepared, and the binder, dispersant, leveling agent, glass frit, etc. in Table 4 were added in the same amount as shown in Table 4 in the mixing container. After dispersing using a sambon mill, silver powder was mixed and dispersed using a sambon mill. Thereafter, degassing was performed under reduced pressure to prepare a conductive paste.

division Glass frit K Glass frit L glass frit M Glass frit N Glass Frit O Glass frit P Glass frit Q Glass frit R Glass frit S glass frit T glass frit
ingredient content
(mole%) PbO (A) 29.61 27.90 28.31 28.32 28.58 28.64 28.73 28.83 28.95 29.09 TeO ₂ (B) 36.81 34.67 35.18 35.20 35.52 35.59 35.71 35.83 35.99 36.15 Sb ₂ O ₃ (C) 0 5.79 4.41 4.36 3.49 3.30 2.98 2.64 2.23 1.78 other metals
oxide 33.58 31.64 32.1 32.12 32.41 32.47 32.58 32.70 32.83 32.98 C/A 0 20.75 15.58 15.40 12.21 11.52 10.37 9.16 7.70 6.12 C/B 0 16.70 12.54 12.39 9.83 9.27 8.35 7.37 6.20 4.92

(Other metal oxides in Table 4 may be composed of at least one of Bi2O3, SiO2, B2O3, Al2O3, ZnO, and WO3)

division
(Ingredient content: g) Comparative Example 2 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 EC 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 EFKA-4330 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 BYK180 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 Texanol 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Butyl cellosolve 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Thixatrol ST 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Dimethyl adipate 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 silver powder 89.5 89.5 89.5 89.5 89.5 89.5 89.5 89.5 89.5 89.5 Glass frit (K to T) 2 2 2 2 2 2 2 2 2 2

(In Table 5, Comparative Example 2 has a glass frit K as a configuration, and Examples 10 to 18 have a glass frit K to T as a configuration)

(2) Measurement of solar cell characteristics

The conductive pastes prepared according to Examples 10 to 18 and Comparative Example 2 were pattern-printed on the entire surface of the wafer by a screen printing technique of 40 μm mesh, and using a belt-type drying furnace at 200 to 350° C. for 20 to 30 seconds. dried. After that, Al paste was printed on the back side of the wafer and dried in the same way. A solar cell was manufactured by firing the cell formed by the above process at a temperature between 500 and 900° C. for 20 to 30 seconds using a belt-type firing furnace.

The prepared cell is a solar cell efficiency measuring device (Halm, cetisPV-Celltest 3), conversion efficiency (Eff), short-circuit current (Isc), open-circuit voltage (Voc), curve factor (FF) and series resistance ( Rs) was measured and shown in Table 5 below.

In addition, after manufacturing the solar cells, after bonding the ribbon of SnPbAg composition to the electrode, hold one end of the bonded part using a tensile strength meter and pull it 180 degrees until the front electrode and the ribbon are peeled off. (N) was measured. The measured adhesion (Sordering) is shown in Table 6.

division Isc(A) Voc (V) Eff (%) FF (%) Rs (Ω) Adhesion (N) Comparative Example 2 9.728 0.6665 21.48 80.91 0.00023 One Example 10 9.718 0.6644 21.23 80.31 0.00040 One Example 11 9.722 0.6693 21.49 80.65 0.00039 One Example 12 9.727 0.6707 21.65 81.04 0.00030 2 Example 13 9.716 0.6715 21.66 81.09 0.00032 2.5 Example 14 9.35 0.6707 21.68 81.11 0.00022 2.5 Example 15 9.734 0.6699 21.61 80.92 0.00025 2.5 Example 16 9.719 0.6691 21.62 81.20 0.00022 2.5 Example 17 9.716 0.6710 21.63 81.01 0.00021 1.5 Example 18 9.709 0.6666 21.53 81.23 0.00018 One

As indicated in Table 6, and the surface resistance (120 ~ 130 Ω / sq), when containing only a metal oxide PbO and TeO ₂ in the resulting glass frit is measured PERC cell characteristics further than (Comparative Example 2) Metal oxide Sb ₂ O ₃ , it can be seen that the conversion efficiency and adhesion of the solar cell are increased. However, even in this case, looking at the case of Example 10 and Comparative Example 2, when Sb ₂ O ₃ 5 mole% or more, C/A 15% or more, and C/B 15% or more, the open circuit voltage (VOC) decreases and the series resistance (Rs) was increased and it can be seen that the adhesive force did not change. In addition, looking at the case of Example 18 and Comparative Example 2, when Sb ₂ O ₃ 2 mole% or less and C/B 5% or less, the series resistance (Rs) decreased, but the open circuit voltage (VOC) synergistic effect was very weak. , it can be seen that the adhesive force does not change. Therefore, preferably, when Sb ₂ O ₃ is 2 to 5 mole%, C/A is in the range of 5 to 15%, and C/B is in the range of 5 to 15% (Examples 11 to 17), low series It can be seen that the resistance (Rs), high open circuit voltage (VOC), and all of the adhesion characteristics are satisfied.

Therefore, _{when using a glass frit having a configuration that Sb 2} O ₃ is 2 to 5 mole%, C/A is in the range of 5 to 15%, and C/B is in the range of 5 to 15%, high sheet resistance (120 to 130) Ω/sq), it can be seen that the contact resistance condition is satisfied, the adhesion is increased, and the conversion efficiency of the solar cell is excellent.

Features, structures, effects, etc. exemplified in each of the above-described embodiments may be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

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

Claims (12)

A paste comprising a metal powder, a glass frit and an organic vehicle, the paste comprising:
The glass frit includes lead (Pb) and tellurium (Te),
The glass frit further comprises an oxide of antimony (Sb),
Based on the total weight of the conductive paste, the content of the antimony (Sb) oxide comprises 2 mole% to 5 mole%,
The glass frit is characterized in that the Sb Oxide / Pb Oxide ratio calculated by Equation 1 is 5% to 25%,
The glass frit is a conductive paste for a solar cell electrode, characterized in that the Sb Oxide / Te oxide ratio calculated by Equation 2 is 5% to 15%.
[Equation 1]
Sb Oxide / Pb Oxide ratio (%) = (Sb ₂ O ₃ molar ratio / PbO molar ratio) X 100
[Equation 2]
Sb Oxide / Te Oxide ratio (%) = (Sb ₂ O ₃ molar ratio / TeO ₂ molar ratio) X 100
The method of claim 1,
Based on the total weight of the conductive paste, the glass frit has a PbO content of 21 mole % to 29 mole %.
The method of claim 1,
Based on the total weight of the conductive paste, the glass frit has a TeO ₂ content of 34 mole % to 38 mole % of the conductive paste for a solar cell electrode.
delete delete delete The method of claim 1,
The glass frit is a conductive paste for a solar cell electrode, characterized in that the Sb Oxide / Pb Oxide ratio calculated by Equation 1 is 10% to 25% under a sheet resistance condition of 100 ohm/sq to 110 ohm/sq.
The method of claim 1,
The glass frit is a conductive paste for a solar cell electrode, characterized in that the Sb Oxide / Pb Oxide ratio calculated by Equation 1 is 5% to 15% under the conditions of 110 ohm/sq to 130 ohm/sq sheet resistance.
The method of claim 1,
The glass frit is a conductive paste for a solar cell electrode, characterized in that the Sb Oxide / Te oxide ratio calculated by Equation 2 is 5% to 15% under a sheet resistance condition of 100 ohm/sq to 110 ohm/sq.
The method of claim 1,
The glass frit is a conductive paste for a solar cell electrode, characterized in that the Sb Oxide / Te oxide ratio calculated by Equation 2 is 5% to 15% under the conditions of 110 ohm/sq to 130 ohm/sq sheet resistance.
The method of claim 1,
Based on the total weight of the conductive paste, the content of the glass frit is a conductive paste for a solar cell electrode, characterized in that 1.0wt% to 3.0wt%.
In the solar cell having a front electrode on an upper portion of a substrate and a rear electrode on a lower portion of the substrate,
The front electrode is a solar cell, characterized in that it is manufactured by applying the conductive paste for a solar cell electrode according to any one of claims 1 to 3 and 7 to 10, followed by drying and firing.

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