TWI647195B - Paste composition, solar cell electrode and solar cell for preparing solar cell electrodes - Google Patents

Abstract

The invention discloses a paste composition, a solar cell electrode and a solar cell for preparing solar cell electrodes. Wherein, the paste composition comprises a conductive powder, an organic vehicle and a glass powder, wherein the glass powder comprises 0.1 to 20 wt% of PbO, 30 to 60 wt% of Bi ₂ O ₃ , 1.0 to 15 wt% of TeO ₂ and 8 ~30 wt% of WO ₃ and the mass ratio of TeO ₂ to WO ₃ is from 0.5:1 to 1.75:1. The solar cell electrodes prepared using the paste composition of the present invention, and the solder have excellent bond strength and minimize series resistance (Rs), thereby providing high conversion efficiency.

Description

 Paste composition, solar cell electrode and solar cell for preparing solar cell electrodes  

The present invention relates to the field of solar cell manufacturing technology, and in particular to a paste composition, a solar cell electrode and a solar cell for preparing solar cell electrodes.

Solar cells use the photovoltaic effect to convert the photons of sunlight into electricity through the p-n junction. In a solar cell, a front electrode and a rear electrode are respectively formed on upper and lower surfaces of a semiconductor wafer or substrate having a p-n junction. Then, the photoelectric effect of the p-n junction is induced by sunlight entering the semiconductor wafer, and electrons generated by the photoelectric effect of the p-n junction supply current to the outside through the electrode. The composition for the electrode is placed on the wafer, patterned and baked to form an electrode of the solar cell.

Increasing the efficiency of the solar cell by continuously reducing the thickness of the emitter may instead result in shunting, which will degrade the performance of the solar cell. In addition, solar cells have gradually increased in area to increase efficiency. However, in this case, there may be a problem of deterioration in efficiency due to an increase in contact resistance of the solar cell.

The solar cells are connected to each other by a bonding tape to constitute a solar cell element. At present, the solar cell electrode manufactured by a typical lead-containing glass powder has insufficient adhesion to the ribbon, and the low adhesion between the electrode and the ribbon causes high series resistance and deterioration of conversion efficiency.

The present invention aims to provide a paste composition, a solar cell electrode and a solar cell for preparing a solar cell electrode, so as to solve the problem of insufficient adhesion between the electrode of the solar cell and the ribbon in the prior art, and the low between the electrode and the ribbon. Adhesion can cause high technical problems of series resistance and deterioration of conversion efficiency.

In order to achieve the above object, according to an aspect of the invention, a paste composition for preparing a solar cell electrode is provided. The paste composition comprises a conductive powder, an organic vehicle and a glass powder, wherein the glass powder comprises 0.1 to 20 wt% of PbO, 30 to 60 wt% of Bi ₂ O ₃ , 1.0 to 15 wt% of TeO ₂ and 8 to 30 wt%. % WO ₃ and the mass ratio of TeO ₂ to WO ₃ is 0.5:1 to 1.75:1.

Further, the glass frit further includes an oxide selected from the group consisting of Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, SrO, BaO, P ₂ O ₅ , ZnO, SiO ₂ , B ₂ O _{3 .} One or more of the group consisting of TiO ₂ and NiO.

Further, the amount of the oxide added to the glass powder is 1 to 25 wt%.

Further, the glass powder has an average particle diameter D50 of 0.1 to 10 μm.

Further, the paste composition contains 60 to 95% by weight of conductive powder, 1.0 to 20% by weight of an organic vehicle, 0.1 to 5% by weight of a glass powder, and the balance of additives.

Further, the additive is one or more selected from the group consisting of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, a UV stabilizer, an antioxidant, and a coupling agent.

Further, the conductive powder is silver powder.

Further, the average particle diameter D50 of the silver powder is 0.1 to 10 μm.

According to another aspect of the invention, a solar cell electrode is provided. The solar cell is prepared from the paste composition of any of the above.

According to still another aspect of the present invention, a solar cell including an electrode is provided. The electrode is the above-described solar cell electrode prepared from the paste composition of the present invention.

The solar cell electrodes prepared using the paste composition of the present invention, and the solder have excellent bond strength and minimize series resistance (Rs), thereby providing high conversion efficiency.

100‧‧‧ wafer or substrate

102‧‧‧n layer

101‧‧‧p layer

210‧‧‧Back electrode

230‧‧‧ front electrode

The accompanying drawings, which are incorporated in the claims of the claims In the drawings: FIG. 1 shows a schematic view of a solar cell fabricated using a paste composition in accordance with an embodiment of the present invention.

It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the drawings in conjunction with the embodiments.

According to an exemplary embodiment of the present invention, a paste composition for preparing a solar cell electrode is provided. The paste composition comprises a conductive powder, an organic vehicle and a glass powder, wherein the glass powder comprises 0.1 to 20 wt% of PbO, 30 to 60 wt% of Bi2O3, 1.0 to 15 wt% of TeO2, and 8 to 30 wt% of WO3. And the mass ratio of TeO2 to WO3 is 0.5:1~1.75:1. Preferably, the conductive powder is silver powder.

The solar cell electrodes prepared using the paste composition of the present invention, and the solder have excellent bond strength and minimize series resistance (Rs), thereby providing high conversion efficiency.

According to an exemplary embodiment of the present invention, the glass frit further includes an oxide selected from the group consisting of Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, P2O5, ZnO, SiO2, B2O3, TiO2, NiO. One or more of them. The amount of the oxide added to the glass powder is 1 to 25 wt%, that is, 1 to 25 wt% of the total weight of the glass powder.

According to an exemplary embodiment of the present invention, the paste composition comprises 60 to 95% by weight of conductive powder, 1.0 to 20% by weight of an organic vehicle, 0.1 to 5% by weight of a glass powder, and the balance of additives. Wherein the additive is one or more selected from the group consisting of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, a UV stabilizer, an antioxidant, and a coupling agent.

According to an exemplary embodiment of the present invention, a solar cell electrode is provided. The solar cell is prepared from the paste composition of any of the above.

According to an exemplary embodiment of the present invention, a solar cell including an electrode is provided. The electrode is the above-described solar cell electrode prepared from the paste composition of the present invention.

According to an exemplary embodiment of the present invention, the solar cell electrode component comprises silver powder, lead oxide-yttria-yttria-tungsten oxide-based glass powder, and an organic vehicle. Now, the composition of the solar cell electrode of the present invention will be described in more detail.

(A) Silver powder

According to an exemplary embodiment of the present invention, a paste composition for preparing a solar cell electrode contains silver powder as a conductive powder. The fineness of the silver powder can be on the order of nanometers or micrometers. For example, the silver powder may have a fineness of several tens to several hundreds of nanometers, or several to several tens of micrometers. Alternatively, the silver powder may be a mixture of two or more silver powders having different particle sizes.

The silver powder may have a spherical shape, a flake or an amorphous shape.

The silver powder preferably has an average particle diameter (D50) of from about 0.1 μm to about 10 μm, more preferably an average particle diameter (D50) of from about 0.5 μm to about 5 μm. The average particle diameter can be measured using an apparatus such as Mastersize 2000 (Malvern Co., Ltd.) after the conductive powder is dispersed by ultrasonic wave in isopropyl alcohol (IPA) at 25 ° C for 3 minutes. Within this average particle size range, the composition can provide low contact resistance and low line resistance.

The silver powder may be present in an amount from about 60% to about 95% by weight, based on the total weight of the composition. Within this range, the conductive powder can prevent deterioration of conversion efficiency due to an increase in electrical resistance. More preferably, the electrically conductive powder is present in an amount of from about 70% by weight to about 95% by weight.

(B) Lead oxide-yttria-yttria-tungsten oxide-based glass powder

The glass powder is used to enhance the adhesion between the conductive powder and the wafer or the substrate, and the contact resistance is reduced by forming the silver crystal grains in the emitter region by etching the anti-reflection layer and melting the silver powder during the sintering of the conductive paste. . In addition, the glass frit softens and lowers the sintering temperature during the sintering process.

When the area of the solar cell is increased in order to increase the efficiency of the solar cell, there may be a problem that the contact resistance of the solar cell increases. Therefore, it is necessary to minimize the series resistance (Rs) and the effect on the p-n junction. In addition, as the suitable sintering temperatures for various wafers having different surface resistances vary over a wide range, the glass frit needs to ensure sufficient thermal stability to withstand a larger sintering temperature window.

The solar cells are connected to each other by a bonding tape to constitute a solar cell element. In this case, the low adhesive strength between the solar cell electrode and the ribbon may cause the battery to detach or lower the reliability. In the present invention, in order to ensure that the solar cell has desired electrical and physical properties such as adhesive strength, a lead oxide-yttria-yttria-tungsten oxide-based glass powder (PbO-Bi ₂ O ₃ -TeO ₂ -WO is used) ₃ ) Based glass powder.

In the present invention, the lead oxide-yttria-yttria-tungsten oxide-based glass powder may comprise from about 0.1% by weight to about 20% by weight of lead oxide, from about 30% by weight to about 60% by weight of cerium oxide, and about 1.0% by weight to About 20% by weight of cerium oxide, about 5% by weight to about 25% by weight of tungsten oxide, and the mass ratio of TeO ₂ to WO3 is from 0.5:1 to 1.75:1. Within this range, the glass powder can ensure excellent bond strength and excellent conversion efficiency.

According to an exemplary embodiment of the present invention, the lead oxide-yttria-yttria-tungsten oxide-based glass powder may further include at least one oxide selected from the group consisting of lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), Potassium oxide (K ₂ O), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), phosphorus oxide (P ₂ O ₅ ), zinc oxide (ZnO), cerium oxide (SiO ₂ ), boron oxide (B ₂ O ₃ ), titanium oxide (TiO ₂ ), nickel oxide (NiO).

The glass frit may be prepared by any typical method from lead oxide-yttria-yttria-tungsten oxide plus at least one of the above oxides. For example, the oxide is mixed with lead oxide-yttria-yttria-tungsten oxide in a certain ratio. Mixing can be carried out using a ball mill or a planetary mill. The combined composition is melted at a temperature of from about 900 ° C to about 1300 ° C and then quenched to about 25 ° C. The obtained material is pulverized using a disc grinder, a planetary mill or the like to provide a glass frit.

The glass powder may have an average particle diameter D50 of from about 0.1 μm to about 10 μm and an amount of from about 0.1% by weight to about 5% by weight based on the total amount of the composition. The glass powder may have a spherical or amorphous shape.

(C) organic carrier

The organic carrier imparts the appropriate viscosity and rheological properties required for the conductive paste printing process by mechanical mixing with the inorganic components in the solar cell electrodes.

The organic vehicle may be any typical organic vehicle used for the solar cell electrode composition, and may include a binder resin, a solvent, and the like.

The binder resin may be selected from an acrylate resin or a cellulose resin. Ethyl cellulose is usually used as the binder resin. Further, the binder resin may be selected from the group consisting of ethyl hydroxyethyl cellulose, nitrocellulose, a blend of ethyl cellulose and phenolic resin, alkyd resin, phenol, acrylate, xylene, polybutene, poly Ester, urea, melamine, vinyl acetate resin, wood rosin, polymethacrylate of alcohol, and the like.

The solvent may be selected, for example, from hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl carbitol (diethylene glycol monobutyl ether), dibutyl carbitol (diethylene glycol) Butyl ether), butyl carbitol acetate (monobutyl ether acetate), propylene glycol monomethyl ether, hexanediol, terpineol, methyl ethyl ketone, benzyl alcohol, γ-butyrolactone, Ethyl lactate and combinations thereof.

The organic vehicle may be present in an amount from about 1% to about 20% by weight, based on the total weight of the composition. Within this range, the organic vehicle can provide sufficient adhesive strength and excellent printability to the composition.

(D) Additives

The composition may further include typical additives as needed to enhance flow properties, processability and stability. The additive may include, but is not limited to, a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, a UV stabilizer, an antioxidant, a coupling agent, and the like. These additives may be used singly or as a mixture thereof. These additives may be present in an amount of from about 0.1% to about 5% by weight of the composition, although the amount may be varied as desired.

According to an exemplary embodiment of the invention, a solar cell fabricated using a paste composition is used. As shown in FIG. 1, the back electrode 210 and the front electrode 230 may be formed by printing a battery electrode composition on a wafer or substrate 100 including a p-layer 101 and an n-layer 102 serving as an emitter, and sintering. For example, a preliminary process for preparing a back electrode is carried out by printing a composition on the back side of a wafer and drying the printed composition at about 200 ° C to about 400 ° C for about 10 seconds to 60 seconds. Further, a preliminary process for preparing the front electrode can be performed by printing a paste on the front surface of the wafer and drying the printed composition. Then, the front electrode and the back electrode may be formed by sintering the wafer at about 400 ° C to about 950 ° C, preferably about 850 ° C to about 950 ° C for about 30 seconds to 50 seconds.

Next, the present invention will be described in more detail by reference to examples. However, it should be noted that the examples are provided for illustrative purposes only and are not to be construed as limiting the invention in any way.

For the sake of clarity, a detailed description that is clear to those skilled in the art is omitted.

Examples and comparative examples

The oxides were mixed according to the composition shown in Table 1, and melted and sintered at 900 ° C to 1400 ° C to prepare lead oxide-yttria-yttria-tungsten oxide-based glass having an average particle diameter (D50) of 2.0 μm. Powder.

As an organic binder, 1.0% by weight of ethyl cellulose was sufficiently dissolved in 9.0% by weight of butyl carbitol at 60 ° C, and 86% by weight of spherical silver powder having an average particle diameter of 1.5 μm was added, 1.5. % by weight of the prepared lead oxide-yttria-yttria-tungsten oxide-zinc oxide glass powder and 0.5% by weight of the thixotropic agent Thixatrol ST into a binder solution, followed by grinding in a three-roll mill to prepare Solar cell electrode composition.

The electrode composition prepared as above was deposited by screen printing on a front surface of a single crystal slab in a predetermined pattern, followed by drying in an infrared drying oven. Then, the composition for preparing the back aluminum electrode was printed on the back surface of the wafer and dried in the same manner. The cell sheet processed by the above procedure was fired in a belt firing furnace at 910 ° C for 40 seconds. The solar energy efficiency tester (CT-801) was used to measure the conversion efficiency (%) of the battery, the series resistance Rs (mΩ), the open circuit voltage (Voc), and the like. Then, the electrode of the battery is welded to the ribbon with a solder using a soldering iron at 300 ° C to 400 ° C. Then, the adhesive strength (N/mm) of the battery electrode and the ribbon was measured using a tester at a peel angle of 180 and a tensile rate of 50 mm/min. The measured conversion efficiencies and tensile tests are shown in Table 1.

Examples 1-8 and Comparative Examples 1-9

Examples 1 to 8 and Comparative Examples 1 to 9 were prepared using the composition of the glass frit as shown in Table 1, and the compositions for solar cell electrodes were prepared in the same manner, and physical properties were evaluated. It is to be noted that the examples and comparative examples in Table 1 are intended to highlight the features of one or more of the inventions, and are not intended to limit the scope of the invention, nor to illustrate that the comparative examples are outside the scope of the invention. Further, the inventive subject matter is not limited to the specific details described in the examples and the comparative examples.

As shown in Table 1, the solar cell electrodes produced from the glass frit compositions prepared in Examples 1 to 8 had high adhesion strength to the solder ribbon and excellent conversion efficiency as compared with Comparative Examples 1 to 9. . Comparative Examples 1-9 show either lower cell efficiencies or lower pull forces, or both.

Comparative Example 1 indicates that the glass composition does not contain PbO, or Comparative Example 2 indicates that the glass composition contains a higher PbO content, and the efficiency and tensile force of the produced solar electrode are lower than those of the invention. Similarly, Comparative Examples 3 and 4 indicate that the glass powder has a lower or higher Bi2O3 content, and the resulting solar cell is less efficient. Comparative Examples 5 and 6 show that the content of WO3 is out of the scope of the present invention, and the resulting solar cell may have lower efficiency or lower tensile force or both. Comparative Examples 7, 8 and 9 indicate that the ratio of higher or lower TeO2 to WO3 content is outside the scope of the present invention, and the resulting solar cell may have lower efficiency or lower tensile force or both. low.

The invention examples show that the glass frit component is 0.1 wt% to 20 wt% of lead oxide, 30 wt% to 60 wt% of cerium oxide, 1.0 wt% to 20 wt% of cerium oxide, 5 wt% to 25 wt% of tungsten oxide, TeO2 and WO3. The ratio of the content is in the range of 0.5:1 to 1.75:1, and the solar cell produced has higher performance.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims (10)

A paste composition for preparing a solar cell electrode, comprising: a conductive powder, an organic vehicle, and a glass powder, wherein the glass frit comprises 0.1 to 20 wt% of PbO, and 30 to 60 wt% of Bi ₂ O ₃ , 1.0 to 15 wt% of TeO ₂ and 8 to 30 wt% of WO ₃ , and the mass ratio of TeO ₂ to WO ₃ is 0.5:1 to 1.75:1. The paste composition according to claim 1, wherein the glass frit further comprises an oxide selected from the group consisting of Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, and SrO. One or more of the group consisting of BaO, P ₂ O ₅ , ZnO, SiO ₂ , B ₂ O ₃ , TiO ₂ , and NiO.  The paste composition according to claim 2, wherein the oxide is added to the glass powder in an amount of from 1 to 25% by weight.    The paste composition according to claim 1, wherein the glass frit has an average particle diameter D50 of 0.1 to 10 μm.    The paste composition according to claim 1, wherein the paste composition comprises 60 to 95% by weight of the conductive powder, 1.0 to 20% by weight of the organic vehicle, and 0.1 to 5% by weight of the Glass powder, and the balance of additives.    The paste composition according to claim 5, wherein the additive is selected from the group consisting of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, an antifoaming agent, a pigment, a UV stabilizer, an antioxidant, and One or more of the group consisting of coupling agents.    The paste composition according to claim 1, wherein the conductive powder is silver powder.    The paste composition according to claim 7, wherein the silver powder has an average particle diameter D50 of 0.1 to 10 μm.    A solar cell electrode prepared by the paste composition according to any one of claims 1 to 8.    A solar cell comprising an electrode, characterized in that the electrode is a solar cell electrode as claimed in claim 9.