TWI741283B - Composition for electrodes of solar cell and solar cell - Google Patents

Abstract

A composition for electrodes of a solar cell including an aluminum oxide layer, an electrode formed of the same, and a solar cell including the same, are disclosed. The composition includes: a conductive powder; a glass frit; and an organic vehicle. The glass frit includes lead, bismuth, tungsten, and an alkali metal, wherein tungsten is present in an amount of 0.1 wt% to 7 wt% in the glass frit in terms of oxide content, the alkali metal is present in an amount of 5 wt% to 8 wt% in the glass frit in terms of oxide content, and a weight ratio of the alkali metal to tungsten is 0.8 or more in terms of oxide content.

Description

Composition for solar battery electrode and solar battery

The present invention relates to a composition for a solar cell electrode including an aluminum oxide layer as a passivation layer, an electrode formed from the composition, and a solar cell including the electrode. More specifically, the present invention relates to a composition for a solar cell electrode, an electrode formed from the composition, and a solar cell including the electrode, wherein the composition includes a specific glass frit to form an aluminum oxide The electrodes in the layered solar cell reduce the series resistance while improving the conversion efficiency of the solar cell.

[Cross references to related applications]

This application claims the rights and interests of Korean Patent Application No. 10-2018-0090985 filed with the Korean Intellectual Property Office on August 3, 2018. The entire disclosure of the Korean patent application is incorporated into this case by reference. for reference.

The way solar cells generate electricity is to use the photovoltaic effect of the PN junction to convert sunlight photons into electricity. In solar cells, on the upper and lower surfaces of semiconductor wafers or substrates with PN junctions The front electrode and the back electrode are respectively formed on the surface. Then, the photovoltaic effect of the PN junction is induced by sunlight entering the semiconductor wafer, and the electrons generated by the photovoltaic effect of the PN junction provide current to the outside through the electrode. The electrode of the solar cell is formed on the wafer by applying, patterning and baking the composition for the electrode of the solar cell.

The typical composition of solar cell electrodes has limitations in reducing series resistance and improving the conversion efficiency of solar cells. In recent years, a technology of forming an aluminum oxide layer on the front surface of a solar cell has been developed to improve the processability and conversion efficiency of the solar cell.

The background art of the present invention is disclosed in Japanese Unexamined Patent Publication No. 2015-144162.

The object of the present invention is to provide a composition for a solar cell electrode that can reduce series resistance when forming an electrode in a solar cell including an aluminum oxide layer, while improving the conversion efficiency of the solar cell.

According to one aspect of the present invention, a composition for a solar cell electrode including an aluminum oxide layer includes: conductive powder, glass frit, and an organic carrier; the glass frit includes lead, bismuth, tungsten, and alkali metals, wherein the oxide In terms of content, tungsten is present in the glass frit in an amount of 0.1% to 7% by weight, and in terms of oxide content, the alkali metal is present in the glass frit in an amount of 5% to 8% by weight, And based on the oxide content, the weight ratio of the alkali metal to tungsten is 0.8 or greater.

In some examples, based on the oxide content, lead may be present in the glass frit in an amount of 1% to 30% by weight, and based on the oxide content, there may be 1% to 25% by weight in the glass frit. The amount of bismuth in weight %.

In some examples, the alkali metal may be lithium.

In some examples, the glass frit may further include at least one metal or metal oxide selected from the group consisting of boron (B), magnesium (Mg), tellurium (Te), phosphorus (P), gallium (Ga), cerium (Ce), iron (Fe), silicon (Si), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti), tin (Sn), indium (In), vanadium (V), barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn), aluminum (Al), zinc (Zn) and their oxides.

In some examples, based on the oxide content, 30% to 80% by weight of the at least one metal or metal oxide may be present in the glass frit.

In some examples, based on the oxide content, the glass frit may further include 10% to 60% by weight of tellurium, 0% to 30% by weight or less than 30% by weight of zinc, and 0% to 10% by weight. Or less than 10% by weight of molybdenum.

In some examples, the composition may include: 60% to 95% by weight of the conductive powder; 0.1% to 20% by weight of the glass frit; and the balance of the organic carrier.

In some examples, the composition may further include at least one additive selected from the group consisting of a dispersant, a thixotropic agent, a plasticizer, a viscosity stabilizer, a defoamer, a pigment, an ultraviolet stabilizer, an antioxidant, and a coupling agent .

According to another aspect of the present invention, there is provided a An electrode formed by the composition of the electrode of a solar battery.

According to another aspect of the present invention, a solar cell includes: a wafer, an aluminum oxide layer formed on at least one surface of the wafer, and an electrode adjacent to the aluminum oxide layer, wherein the electrode is used according to the present invention. It is formed from the composition of the solar cell electrode.

The present invention provides a composition for a solar cell electrode, which can reduce series resistance when forming an electrode in a solar cell including an aluminum oxide layer, and at the same time improve the conversion efficiency of the solar cell.

10: Front electrode

20: chip

30: Silicon oxide layer

32: silicon nitride layer

34: Alumina layer

40: back electrode

Fig. 1 is a schematic cross-sectional view of a solar cell according to an example of the present invention.

X且

Y”。 In this application, the term "X to Y" indicates "X or greater than X to Y or less than Y" or "

X and

Y".

One aspect of the present invention relates to a composition for a solar cell electrode. The composition is used to form an electrode of a solar cell including an aluminum oxide layer and includes conductive powder, glass frit, and an organic carrier; the glass frit includes lead , Bismuth, tungsten, and alkali metals, wherein, based on the oxide content, there is tungsten in the glass frit in an amount of 0.1% to 7% by weight by weight, and based on the oxide content, it is present in the glass frit The alkali metal in an amount of 5 wt% to 8 wt%, and according to the oxide content In total, the weight ratio of the alkali metal to tungsten is 0.8 or greater. Within these ranges, the composition can reduce series resistance when forming an electrode in a solar cell including an aluminum oxide layer, while improving the conversion efficiency of the solar cell.

In this specification, "alumina" may be Al ₂ O ₃ , but it is not limited to this.

The composition for a solar cell electrode according to the present invention can be used to form a front electrode or a back electrode of a solar cell including an aluminum oxide layer as an electrode adjacent to the aluminum oxide layer, but is not limited to this.

Now, each component of the composition for solar cell electrodes according to the present invention will be explained in more detail.

[Conductive powder]

The conductive powder may include silver (Ag) powder. Silver powder may have nano-level fineness or micron-level fineness. For example, the silver powder may have an average particle diameter of tens of nanometers to hundreds of nanometers or an average particle diameter of several micrometers to tens of micrometers. Alternatively, the silver powder may be a mixture of two or more silver powders having different particle sizes.

In another example, the following materials can be used instead of silver (Ag) powder as the conductive powder: gold (Au) powder, palladium (Pd) powder, platinum (Pt) powder, copper (Cu) powder, chromium ( Cr) powder, cobalt (Co) powder, aluminum (Al) powder, tin (Sn) powder, lead (Pb) powder, zinc (Zn) powder, iron (Fe) powder, iridium (Ir) powder, osmium (Os) Powder, rhodium (Rh) powder, tungsten (W) powder, molybdenum (Mo) powder and nickel (Ni) powder.

The aforementioned metal powders can be used alone or in the form of a mixture or an alloy. Preferably, silver powder is used as the conductive powder.

The conductive powder can have various particle shapes, such as spherical, flake-shaped, or without Fixed shape, there is no restriction on this.

The conductive powder may have an average particle diameter (D50) of 0.1 μm to 10 μm, specifically 0.5 μm to 5 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. . Within this range, the composition can reduce series resistance and contact resistance. Here, after dispersing the conductive powder in isopropyl alcohol (IPA) at 25°C for 3 minutes through ultrasonic action, a particle size analyzer (model 1064LD, CILAS Co., Ltd. )) to measure the average particle size (D50).

The conductive powder may be present in an amount of 60% to 95% by weight based on the total weight of the composition for the solar cell electrode. Within this range, the composition can improve the conversion efficiency of the solar cell and is easy to prepare in the form of a paste. Preferably, based on the total weight of the composition for the solar cell electrode, there is 70% to 90% by weight, for example 60% by weight, 61% by weight, 62% by weight, 63% by weight, 64% by weight, 65% by weight , 66% by weight, 67% by weight, 68% by weight, 69% by weight, 70% by weight, 71% by weight, 72% by weight, 73% by weight, 74% by weight, 75% by weight, 76% by weight, 77% by weight, 78 Weight%, 79% by weight, 80% by weight, 81% by weight, 82% by weight, 83% by weight, 84% by weight, 85% by weight, 86% by weight, 87% by weight, 88% by weight, 89% by weight, 90% by weight , 91% by weight, 92% by weight, 93% by weight, 94% by weight or 95% by weight of conductive powder.

[Frit glass]

The glass frit acts on the baking process stage of the composition of the solar cell electrode, etches the anti-reflective layer and melts the conductive powder to form in the emitter area Crystal grains of conductive powder. In addition, the glass frit improves the adhesion between the conductive powder and the chip, and is softened during the baking process to lower the baking temperature.

The glass frit includes lead, bismuth, tungsten, and alkali metals, wherein, based on the oxide content, there is an amount of 0.1% to 7% by weight in the glass frit. Based on the oxide content, the glass The alkali metal is present in the material in an amount of 5 wt% to 8 wt%, and the weight ratio of the alkali metal to tungsten is 0.8 or more than 0.8 based on the oxide content. When the content of tungsten and the alkali metal and the weight ratio of the alkali metal to tungsten are within the aforementioned ranges, the electrode formed from the composition can provide a reduction when used in a solar cell including an aluminum oxide layer. The series resistance to improve the conversion efficiency of solar cells.

According to the oxide content, there may be 1% to 30% by weight, specifically 5% to 30% by weight, such as 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight %, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight or Lead in an amount of 30% by weight. Within this range, the composition can be baked at a low temperature.

According to the oxide content, there may be 1 wt% to 25 wt%, specifically 5 wt% to 20 wt%, for example 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, Bismuth in an amount of 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, or 25% by weight. Within this range, the electrode formed of the composition can have improved adhesion to the ribbon.

Based on the oxide content, there may be 0.1% to 7% by weight, specifically 1% to 6% by weight, such as 0.1% by weight, 0.5% by weight, 1% by weight, 2% by weight, Tungsten in an amount of 3 wt%, 4 wt%, 5 wt%, 6 wt%, or 7 wt%. Within this range, the weight ratio of the alkali metal to tungsten mentioned above can be easily satisfied, and the electrode formed of the composition can still provide a reduced series connection even when it is adjacent to the aluminum oxide layer. Resistance, thereby improving solar cell efficiency.

The alkali metal may include at least one of lithium (Li), sodium (Na), and potassium (K). Preferably, lithium is used as the alkali metal to facilitate the preparation of glass frit. Based on the oxide content, there may be 5 wt% to 8 wt%, specifically 5 wt% to 7 wt%, such as 5 wt%, 6 wt%, 7 wt% or 8 wt% in the glass frit. The amount of alkali metals. Within this range, the weight ratio of the alkali metal to tungsten mentioned above can be easily satisfied, and the electrode formed of the composition can still provide a reduced series connection even when it is adjacent to the aluminum oxide layer. Resistance, thereby improving solar cell efficiency.

In the glass frit, based on the oxide content, the weight ratio of the alkali metal to tungsten may be 0.8 or more than 0.8. Within this range, even when adjacent to the alumina layer, the electrode formed of the composition can still provide a reduced series resistance, thereby improving the Solar cell efficiency. Preferably, the weight ratio of the alkali metal to tungsten is 0.8 to 7, more preferably 0.8 to 5, such as 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 , 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4 , 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9 Or 7.

In addition to lead, bismuth, tungsten, and alkali metals, the glass frit may further include metals and/or metal oxides. For example, the glass frit may include at least one metal or metal oxide selected from the group consisting of boron (B), magnesium (Mg), tellurium (Te), phosphorus (P), gallium (Ga), Cerium (Ce), iron (Fe), silicon (Si), cesium (Cs), strontium (Sr), molybdenum (Mo), titanium (Ti), tin (Sn), indium (In), vanadium (V), Barium (Ba), nickel (Ni), copper (Cu), sodium (Na), potassium (K), arsenic (As), cobalt (Co), zirconium (Zr), manganese (Mn), aluminum (Al), Zinc (Zn) and its oxides.

Here, based on the oxide content, there may be 30% to 80% by weight, specifically 50% to 75% by weight, for example, 30% by weight, 31% by weight, 32% by weight, 33% by weight in the glass frit. Weight%, 34% by weight, 35% by weight, 36% by weight, 37% by weight, 38% by weight, 39% by weight, 40% by weight, 41% by weight, 42% by weight, 43% by weight, 44% by weight, 45% by weight , 46% by weight, 47% by weight, 48% by weight, 49% by weight, 50% by weight, 51% by weight, 52% by weight, 53% by weight, 54% by weight, 55% by weight, 56% by weight, 57% by weight, 58 Weight%, 59% by weight, 60% by weight, 61% by weight, 62% by weight, 63% by weight, 64% by weight, 65% by weight, 66% by weight, 67% by weight, 68% by weight, 69% by weight, 70% by weight, 71% by weight, 72% by weight, 73% by weight, 74% by weight, 75% by weight, 76% by weight, 77% by weight %, 78% by weight, 79% by weight, or 80% by weight of metal. Within this range, metals can improve solar cell efficiency without changing the effects of lead, bismuth, tungsten, and alkali metals.

In an example, based on the oxide content, there may be 10% to 60% by weight, specifically 20% to 60% by weight, for example, 10% by weight, 11% by weight, 12% by weight in the glass frit. , 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25 Weight%, 26% by weight, 27% by weight, 28% by weight, 29% by weight, 30% by weight, 31% by weight, 32% by weight, 33% by weight, 34% by weight, 35% by weight, 36% by weight, 37% by weight , 38% by weight, 39% by weight, 40% by weight, 41% by weight, 42% by weight, 43% by weight, 44% by weight, 45% by weight, 46% by weight, 47% by weight, 48% by weight, 49% by weight, 50 Tellurium in an amount of wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, or 60 wt%. Within this range, the glass frit can be easily prepared, while the electrode formed of the composition can exhibit improved properties in terms of electrical resistance.

In an example, based on the oxide content, there may be 0 wt% to 30 wt%, specifically 1 wt% to 30 wt%, more specifically 10 wt% to 20 wt%, in the glass frit, For example, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10 Weight%, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight , 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight or 30% by weight of zinc. Within this range, the electrode formed of the composition can exhibit improved properties in terms of resistance.

In an example, based on the oxide content, 0 wt% to 10 wt%, specifically 0.1 wt% to 5 wt%, such as 0 wt%, 0.1 wt%, 0.5 wt% may be present in the glass frit. , 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, or 10% by weight of molybdenum. Within this range, the etching of the anti-oxidation film can be easily controlled.

In an example, based on the oxide content, there may be 10% by weight or less than 10% by weight, specifically 0.1% to 10% by weight or 0.1% to 5% by weight, such as 0% by weight, in the glass frit. %, 0.1% by weight, 0.5% by weight, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, or 10% by weight Amount of magnesium. Within this range, the electrode formed from the composition can exhibit improved properties in terms of electrical resistance and adhesion to the strip.

In one example, the glass frit may be a Pb-Bi-W-alkali metal-Te-Mg-based glass frit including lead, bismuth, tungsten, alkali metals, tellurium, and magnesium. According to the oxide content, the Pb-Bi-W-alkali metal-Te-Mg glass frit may include 1% to 30% by weight of lead, 1% to 25% by weight of bismuth, and 0.1% to 7% by weight. Wt% tungsten, 5 wt% to 8 wt% alkali metal, 10 wt% to 60 wt% tellurium, and 0.1 wt% % To 10% by weight of magnesium. Within this range, the electrode formed of the composition can provide reduced series resistance when used in a solar cell including an aluminum oxide layer, thereby improving solar cell efficiency.

In another example, the glass frit may be a Pb-Bi-W-alkali metal-Te-Mg-Zn glass frit including lead, bismuth, tungsten, alkali metal, tellurium, magnesium, and zinc. In terms of oxide content, the Pb-Bi-W-alkali metal-Te-Mg-Zn glass frit may include 1% to 30% by weight of lead, 1% to 25% by weight of bismuth, and 0.1% by weight To 7 wt% tungsten, 5 wt% to 8 wt% alkali metal, 10 wt% to 60 wt% tellurium, 0.1 wt% to 10 wt% magnesium, and 1 wt% to 30 wt% zinc. Within this range, the electrode formed of the composition can provide reduced series resistance when used in a solar cell including an aluminum oxide layer, thereby improving solar cell efficiency.

In yet another example, the glass frit may be a Pb-Bi-W-alkali metal-Te-Mg-Mo-based glass frit including lead, bismuth, tungsten, alkali metal, tellurium, magnesium, and molybdenum. In terms of oxide content, the Pb-Bi-W-alkali metal-Te-Mg-Mo glass frit may include 1% to 30% by weight of lead, 1% to 25% by weight of bismuth, and 0.1% by weight To 7 wt% tungsten, 5 wt% to 8 wt% alkali metal, 10 wt% to 60 wt% tellurium, 0.1 wt% to 10 wt% magnesium, and 0.1 wt% to 5 wt% molybdenum. Within this range, the electrode formed of the composition can provide reduced series resistance when used in a solar cell including an aluminum oxide layer, thereby improving solar cell efficiency.

In yet another example, the glass frit may be a Pb-Bi-W-alkali metal-Te-Mg-Mo-Zn series glass frit including lead, bismuth, tungsten, alkali metal, tellurium, magnesium, molybdenum, and zinc. According to the oxide content, the Pb-Bi-W-alkali metal-Te-Mg-Mo-Zn series glass frit can be Including 1% to 30% by weight of lead, 1% to 25% by weight of bismuth, 0.1% to 7% by weight of tungsten, 5% to 8% by weight of alkali metal, 10% to 60% by weight of Tellurium, 0.1% to 10% by weight of magnesium, 0.1% to 5% by weight of molybdenum, and 1% to 30% by weight of zinc. Within this range, the electrode formed of the composition can provide reduced series resistance when used in a solar cell including an aluminum oxide layer, thereby improving solar cell efficiency.

The shape and size of the glass frit are not particularly limited. For example, the glass frit may have an average particle diameter (D50) of 0.1 μm to 10 μm. The particle shape of the glass frit can be spherical or non-fixed. Here, the glass frit powder can be dispersed in isopropyl alcohol (IPA) at 25°C and subjected to ultrasonic action for 3 minutes, and then a particle size analyzer (model 1064LD, CILAS Co., Ltd.)) to measure the average particle size (D50). Preferably, the glass frit has an average of 0.5 μm to 10 μm, more preferably 0.5 μm to 2.0 μm, such as 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. Particle size (D50).

The glass frit can be prepared by any suitable method known in the art using lead oxide, bismuth oxide, tungsten oxide, and alkali metal oxides and metals and/or metal oxides. For example, the glass frit can be prepared by using a ball mill or a planetary mill to mix lead oxide, bismuth oxide, tungsten oxide, alkali metal oxides, and metals and/or metal oxides at a temperature of about 800°C to The mixture is melted at 1300°C, and the molten mixture is quenched to 25°C, and then the obtained product is pulverized using a disc mill, a planetary mill, or the like.

Based on the total weight of the composition for the solar cell electrode, there may be 0.1% to 20% by weight, specifically 0.5% to 10% by weight, 0.8% to 5% by weight, such as 0.1% by weight, 0.5% by weight %, 0.8% by weight, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, The glass frit is in an amount of 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, or 20% by weight. Within this range, the electrode formed from the composition can exhibit good properties in terms of series resistance, open circuit voltage, and short circuit current, thereby improving solar cell efficiency while having good electrical properties and improved adhesion.

[Organic Carrier]

The organic carrier is mechanically mixed with the inorganic components of the composition used for the solar cell electrode to give the composition suitable viscosity and rheological properties suitable for printing.

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

The binder resin may be selected from acrylate resin or cellulose resin. Ethyl cellulose is generally used as the binder resin. In addition, the binder resin may be ethyl hydroxyethyl cellulose, nitrocellulose, a blend of ethyl cellulose and phenol resin, or alkyd resin. ), phenol resin, acrylate ester resin, xylene resin, polybutene resin Polybutene resin, polyester resin, urea resin, melamine resin, vinyl acetate resin, wood rosin, or alcoholic polyurethane Polymethacrylate of alcohol and so on.

The solvent can be, for example, hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl carbitol (diethylene glycol monobutyl ether), dibutyl carbitol (diethylene glycol two Butyl ether), butyl carbitol acetate (diethylene glycol monobutyl ether acetate), propylene glycol monomethyl ether, hexylene glycol, terpineol, methyl ethyl ketone, benzyl alcohol, γ-butyl Lactone and ethyl lactate. These solvents can be used alone or in the form of a mixture of two or more of them.

The composition for the solar cell electrode may include the balance of the organic carrier. Preferably, based on the total weight of the composition for the solar cell electrode, there is 1% to 30% by weight, for example, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, and 6% by weight. , 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19 Weight%, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight or 30% by weight of organic Carrier. Within this range, the organic vehicle can provide sufficient adhesion strength and good printability to the composition.

[additive]

The composition for solar cell electrodes according to the present invention may further include any typical additives as needed to enhance fluidity, processability and stability. Place The additives may include dispersants, thixotropic agents, plasticizers, viscosity stabilizers, defoamers, pigments, ultraviolet stabilizers, antioxidants, and coupling agents. These additives can be used alone or in the form of a mixture. Based on the total weight of the composition for the solar cell electrode, there may be 0.1% to 5% by weight, such as 0.1% by weight, 0.5% by weight, 1% by weight, 2% by weight, 3% by weight, 4% by weight, or 5% by weight. The additive is in the amount of% by weight, but the content of the additive can be changed as needed.

[Solar cell electrode and solar cell including the solar cell electrode]

Other aspects of the present invention relate to an electrode formed of a composition for a solar cell electrode and a solar cell including the electrode.

The solar cell according to the present invention includes: a wafer, an aluminum oxide layer formed on at least one surface of the wafer, and an electrode adjacent to the aluminum oxide layer, wherein the electrode is used for the solar cell electrode according to the present invention. The composition is formed. For example, the solar cell according to the present invention may include a solar cell having a passivated emitter and rear cell (PERC) structure, but it is not limited thereto. The composition for a solar cell electrode according to the present invention can be used to form a front electrode or a back electrode, preferably a front electrode formed on the light receiving surface of a solar cell.

Fig. 1 is a schematic cross-sectional view of a solar cell according to an example of the present invention.

1, the solar cell according to this example may include a wafer 20, which includes a p-layer (or n-layer) and an n-layer (or p-layer) as emitters.

The upper surface of the wafer 20 corresponds to the front side of the solar cell. On chip 20 On the upper surface of the silicon oxide layer 30, silicon nitride layer 32 and aluminum oxide layer 34 are sequentially formed. The front electrode 10 is formed on the upper surface of the wafer 20 to be adjacent to the silicon oxide layer 30, the silicon nitride layer 32, and the aluminum oxide layer 34. The front electrode 10 may be formed of the composition used for solar cell electrodes according to the present invention.

Although the silicon oxide layer 30, the silicon nitride layer 32, and the aluminum oxide layer 34 are shown in FIG. 1 as being formed on the upper surface of the wafer 20 in this order, it should be understood that the present invention is not limited to this, and these layers The stacking order can be changed as needed. For example, the silicon oxide layer 30, the aluminum oxide layer 34, and the silicon nitride layer 32 may be stacked on the upper surface of the wafer 20 in this order.

The lower surface of the wafer 20 corresponds to the rear side of the solar cell, and the back electrode 40 is formed on the lower surface of the wafer 20.

Although not shown in FIG. 1, at least one of the silicon oxide layer 30, the silicon nitride layer 32, and the aluminum oxide layer 34 may have a textured structure.

In addition, although not shown in FIG. 1, at least one of the silicon oxide layer 30, the silicon nitride layer 32 and the aluminum oxide layer 34 may be further formed on the lower surface of the wafer 20 to abut the back electrode 40.

For example, the preliminary process of preparing the front electrode 10 can be performed by depositing a composition for solar cell electrodes on the front surface of the wafer 20 by printing, and then drying at about 200°C to about 400°C. 10 seconds to 60 seconds. Then, the dried composition may be subjected to baking at 400° C. to 950° C., preferably at 600° C. to 850° C., for about 30 seconds to 210 seconds, thereby preparing the front electrode 10.

Next, the present invention will be explained in more detail with reference to examples. However, should Note that these examples are provided for illustration only, and should not be construed as limiting the present invention in any way.

Table 1 shows the composition details of the glass frit used in the Examples and Comparative Examples. Each glass frit is prepared in the following way: According to the different combinations of metal oxides listed in Table 1, the components are mixed in the amounts listed in Table 1 (unit: parts by weight), and used at 800°C to 1300°C. The obtained glass frit is melted, and the molten composition is quenched to 25°C, and then the obtained product is pulverized using a disc mill or the like.

[Example 1]

As an organic binder, 2.0 parts by weight of ethyl cellulose (STD4, Dow Chemical Company) was fully dissolved in 6.75 parts by weight of terpineol at 60°C, and then added to the binder solution 90.0 parts by weight of spherical silver powder (AG-4-8, Dowa Hightech Co., Ltd.) with an average particle diameter of 2.0 μm and 1.25 parts by weight of glass frit A shown in Table 1 were added, and then 3 Roll Mixing and kneading are performed in a 3-roll kneader to prepare a composition for solar cell electrodes.

[Example 2 to Example 9]

A composition for solar cell electrodes was prepared in the same manner as in Example 1, except that the kind of glass frit used was changed as listed in Table 2.

[Comparative Example 1 to Comparative Example 8]

A composition for solar cell electrodes was prepared in the same manner as in Example 1, except that the kind of glass frit used was changed as listed in Table 2.

[Production and evaluation of solar cells]

Solar cells were fabricated using each composition prepared in the Examples and Comparative Examples, and then evaluated as described below, and the results are shown in Table 2.

Each of the compositions for solar cell electrodes prepared in the Examples and Comparative Examples was deposited on the wafer by screen printing in a predetermined pattern and then drying in an infrared drying oven at 300°C for 1 minute (Prepared by texturing the front surface of a p-type wafer doped with boron (B), forming _{an n+ layer of POCl 3} on the textured surface, and sequentially forming an aluminum oxide layer and a silicon oxide layer on the n+ layer Single crystal wafer) above the front surface. Next, the aluminum paste is printed on the back surface of the wafer and dried in the same manner as described above, thereby forming finger electrodes and bus bar electrode patterns. The battery formed according to this procedure was baked in a belt-type baking furnace at 800° C. for 50 seconds to produce a solar cell.

Use the h.a.l.m. solar cell performance tester to test the short-circuit current (Isc, unit: A), open circuit voltage (Voc, unit: mV), and series resistance (Rs, unit: The manufactured solar cells were evaluated in terms of mΩ), conversion efficiency (Eff, unit: %), and fill factor (FF, unit: %).

As shown in Table 2, it can be seen that the electrode formed from the composition for the solar cell electrode according to the present invention can exhibit reduced series resistance when forming the electrode of the solar cell including the aluminum oxide layer, while improving The conversion efficiency of solar cells.

It should be understood that those skilled in the art can make various modifications, changes, alterations and equivalent examples without departing from the spirit and scope of the present invention.

10: Front electrode

20: chip

30: Silicon oxide layer

32: silicon nitride layer

34: Alumina layer

40: back electrode

Claims (9)

A composition for a solar cell electrode including an aluminum oxide layer. The composition includes: conductive powder; glass frit; and an organic carrier; wherein the glass frit includes lead, bismuth, tungsten, and alkali metals, and the In terms of content, tungsten is present in the glass frit in an amount of 0.1% to 7% by weight, and in terms of oxide content, the alkali metal is present in the glass frit in an amount of 5% to 8% by weight, And based on the oxide content, the weight ratio of the alkali metal to tungsten is 0.8 or greater. The composition as described in item 1 of the scope of patent application, wherein, based on the oxide content, there is lead in the glass frit in an amount of 1% to 30% by weight, and based on the oxide content, the lead is present in the glass frit. Bismuth is present in an amount of 1% to 25% by weight. The composition according to item 1 of the scope of patent application, wherein the alkali metal is lithium. The composition according to claim 1, wherein the glass frit further includes at least one metal or metal oxide selected from the group consisting of boron, magnesium, tellurium, phosphorus, gallium, cerium, iron , Silicon, cesium, strontium, molybdenum, titanium, tin, indium, vanadium, barium, nickel, copper, sodium, potassium, arsenic, cobalt, zirconium, manganese, aluminum, zinc and their oxides. The composition according to item 4 of the scope of patent application, wherein the at least one metal or metal oxide is present in the glass frit in an amount of 30% to 80% by weight based on the oxide content. The composition according to item 1 of the scope of the patent application, wherein the glass frit further includes 10% to 60% by weight tellurium, 0% to 30% by weight or less than 30% by weight of zinc based on the oxide content. And 0% to 10% by weight or less than 10% by weight of molybdenum. The composition as described in item 1 of the scope of the patent application includes: 60% to 95% by weight of the conductive powder; 0.1% to 20% by weight of the glass frit; and the balance of the organic carrier. The composition as described in item 1 of the scope of the patent application further includes: at least one additive selected from the group consisting of dispersant, thixotropic agent, plasticizer, viscosity stabilizer, defoamer, pigment, ultraviolet stabilizer, anti- Oxidizing agent and coupling agent. A solar cell includes: a wafer; an aluminum oxide layer formed on at least one surface of the wafer; and an electrode adjacent to the aluminum oxide layer, wherein the electrode is used as in the scope of the patent application item 1 to item 8. It is formed from the composition for solar cell electrodes described in any one of the items.

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