TW201511037A - Aluminum paste for silicon solar cell and method for manufacturing silicon solar cell - Google Patents

Abstract

An aluminum paste for silicon solar cell and a method for manufacturing silicon solar cell is provided by this invention. The aluminum paste for silicon solar cell contains an aluminum powder, a glass powder, an organic vehicle and an organic silicon-containing additive, wherein the organic silicon-containing additive has at least one silanol group.

Description

Aluminum paste for twinned solar cells and twin crystal solar cell manufacturing method

This invention relates to an aluminum paste, and more particularly to an aluminum paste for a twinned solar cell.

A solar cell is an energy-converting photovoltaic device. The basic structure of a typical solar cell can be divided into four main parts: a substrate, a P-N diode, an anti-reflection layer, and a metal electrode. Simply put, the working principle of a solar cell is that the P-N diode converts solar energy into an electron hole pair, and then conducts electric energy through the positive and negative electrodes.

In the prior art, a passivated emitter and rear contact solar cell (PERC) having high efficiency is proposed, which mainly forms a passivation layer on the back surface of the substrate, and the patterned region is formed. Al/Si alloy. However, in the aluminum bismuth eutectic, there is a problem that it is difficult to fill and cause voids. Specifically, the conversion efficiency (η) of the solar cell is an open circuit voltage (Voc), a short circuit current (Isc), and a fill. The product of the fill factor (FF), and the fill factor is positively correlated with the hole fill rate. If there is a hole in the aluminum ruthenium eutectic, the hole filling rate is low, which will lower the conversion efficiency of the solar cell.

In addition, solar cells tend to be thinner as technology advances. However, in the process of thinning, the manufacture of the conductive electrode is often caused by the warpage of the battery, which affects the manufacturing yield of the battery and the battery module. Generally, when a conventional screen printing process is used to manufacture an electrode, a high-temperature co-firing process is used to burn the conductive paste into a cured electrode. However, during the cooling process after co-firing, the battery warps due to the difference in thermal expansion coefficient between the crucible substrate and the electrode. Solar cells with a warpage of more than 2 mm are prone to cracking in subsequent packaging processes, affecting production yield.

The invention provides an aluminum paste for a twinned solar cell, which can effectively improve the hole filling rate of the aluminum-bismuth eutectic of the passivated emitter back electrode twin solar cell, and can reduce the warpage of the thinned twin solar cell.

The invention provides a method for fabricating a passivated emitter back electrode twinned solar cell, whereby the hole filling rate of the aluminum germanium eutectic structure in the formed twin solar cell can be effectively improved, and the post-sintering twin solar energy can be alleviated The problem of battery warpage.

The present invention provides an aluminum paste for a twinned solar cell comprising aluminum powder, glass frit, an organic vehicle, and an organic silicon-containing additive, wherein the organic germanium-containing additive has at least one decane An alcohol (silanol, -SiOH) functional group.

The present invention provides an aluminum paste for passivating an emitter back electrode twinned solar cell comprising aluminum powder, glass frit, an organic vehicle, and an organic cerium-containing additive, wherein the organic cerium-containing additive has at least one stanol functional group.

In an embodiment of the invention, the structural formula of the above organic cerium-containing additive is represented by, for example, formula (1):

In the formula (1), at least one of R ₁ , R ₂ and R ₃ represents a hydroxyl group, and R ₄ represents a specific substituent group such as thiophene, vinyl, phenyl or isopropyl. Isopropoxy, tolyl, tert-butyl-indole-1-carboxylate, propyl amine or N-(2-aminoethyl) )-3-aminopropyl (N-(ethylamino)-3-aminopropyl). The specific substituent groups listed above are merely examples and are not intended to limit the organic cerium-containing additives used in the present invention. Specifically, in an embodiment of the invention, the organic cerium-containing additive may be selected from at least one of the formulae (2) to (9):

In an embodiment of the invention, the organic cerium-containing additive is added in an amount of 0.001% to 40%.

In an embodiment of the invention, the glass frit is a lead-free material and comprises cerium oxide.

In an embodiment of the invention, the glass frit is a leaded material and comprises lead oxide.

The invention further provides a method for fabricating a passivated emitter back electrode (PERC) twinned solar cell comprising the following steps. N-type doping on the light-receiving surface of the P-type germanium wafer to form an N-type doped layer on the light-receiving surface; forming a first dielectric layer on the N-type doped layer on the light-receiving surface; on the back surface of the P-type germanium wafer Forming a second dielectric layer; patterning a second dielectric layer on the back surface to expose a back surface of the P-type germanium wafer; forming a first electrode composition on the light receiving surface; and forming a first dielectric layer on the second dielectric layer and the P-type germanium wafer Forming a second electrode composition and a third electrode composition on the back surface, wherein the second electrode composition comprises aluminum powder, glass frit, organic carrier and organic cerium-containing additive, and the organic cerium-containing additive comprises at least one stanol functional group; And performing a high-temperature co-firing process such that the first electrode composition on the light-receiving surface forms a front electrode, and the second electrode composition on the back surface and the third electrode composition form a back electrode.

In an embodiment of the invention, the first electrode composition and the third electrode in the method for fabricating the passivated emitter back electrode (PERC) twinned solar cell are The material is silver paste.

In an embodiment of the invention, the back electrode formed after the high temperature co-firing process in the method for fabricating the passivated emitter back electrode twinned solar cell comprises a silver electrode, an aluminum electrode, an aluminum germanium eutectic layer, and a P layer. ^a germanium layer, wherein the aluminum germanium eutectic layer is between the P ⁺ germanium layer and the aluminum electrode, and the silver electrode on the back side is electrically connected to the aluminum electrode.

Based on the above, by adding an organic cerium-containing additive having at least one stanol function to the aluminum paste, the cerium-containing functional group can fully utilize the organic cerium-containing additive as a binder and can inhibit the organic cerium. The additive reacts excessively with the organic vehicle in the process of the twinned solar cell, resulting in an unstable phenomenon such as an increase in viscosity. Therefore, the aluminum paste for the twinned solar cell of the present invention can effectively improve the aluminum lanthanum of the passivated emitter back electrode twin solar cell. The hole filling rate of the crystal. In addition, the aluminum paste for a twinned solar cell of the present invention can effectively reduce the coefficient of thermal expansion, thereby alleviating the problem of warpage of the twinned solar cell after high temperature sintering.

The above described features and advantages of the invention will be apparent from the following description.

100‧‧‧Silver solar cells

200‧‧‧ Passivated emitter back electrode twin solar cell

110, 210‧‧‧P type silicon wafer

110a, 210a‧‧‧P ⁺ layer

120, 220‧‧‧N type doped layer

130, 230‧‧‧ first dielectric layer

240‧‧‧First electrode composition

140a, 240a‧‧‧ front electrode

250‧‧‧Second electrode composition

150a, 250a‧‧‧ back electrode

152, 252‧‧‧ aluminum eutectic layer

154, 254‧‧‧ aluminum electrodes

256‧‧‧ Silver electrode

260‧‧‧Second dielectric layer

260a‧‧‧ patterned second dielectric layer

270‧‧‧ third electrode composition

L‧‧‧ line segment

Op‧‧‧ openings

B‧‧‧Back

R‧‧‧Glossy surface

1 is a cross-sectional view showing the structure of a conventional twinned solar cell in accordance with an embodiment of the present invention.

2A and 2B are schematic diagrams showing the structure of a passivated emitter back electrode twin solar cell at different positions, respectively, according to an embodiment of the invention.

3 is a top plan view of a passivated emitter back electrode twinned solar cell, in accordance with an embodiment of the present invention.

Fig. 4 is a schematic view taken along line AA' of Fig. 3.

Fig. 5 is a schematic view taken along line BB' of Fig. 3.

6A-6C are schematic diagrams showing a method of fabricating a passivated emitter back electrode twinned solar cell, in accordance with an embodiment of the invention.

In the following embodiments of the present invention, the aluminum paste of the present invention is applied to a conventional twinned solar cell as an example. However, the application of the present invention is not limited thereto, and the aluminum paste of the present invention can also be used. Different types of solar cells (eg, passivated emitter back electrode twinned solar cells). Of course, the aluminum paste of the present invention can be applied to various types of elements in addition to the solar cell, and the present invention is not particularly limited herein.

The aluminum paste of the present invention can be applied to various types of twinned solar cells. For example, FIG. 1 is a conventional twin solar cell (Al-BSF (back surface field) solar cell), and the aluminum paste of the present invention is used to form an electrode in the structure to reduce thinning. Warpage of crystalline solar cells. The structure of each part of the twinned solar cell and the composition of the aluminum paste are detailed below.

1 is a perspective view of a conventional twinned solar cell in accordance with an embodiment of the present invention. Referring to FIG. 1, the conventional twinned solar cell 100 of the present embodiment includes a germanium wafer 110, an N-type doped layer 120, a first dielectric layer 130, and a front surface. The electrode 140a and the back surface electrode 150a, wherein the germanium wafer 110 is, for example, a P-type germanium wafer 110. In detail, the P-type germanium wafer 110 has a light-receiving surface R and a back surface B facing each other, and sequentially includes an N-type doping layer 120 from the P-type germanium wafer 110 on the light-receiving surface R (hereinafter also referred to as a front surface). A dielectric layer 130 is on the front side of the electrode 140a and the back side electrode 150a is on the back side B.

In the present embodiment, the back surface electrode 150a includes an aluminum germanium eutectic layer 152 and an aluminum electrode 154, and the second electrode composition 250 can further form the back surface electrode 150a and between the back surface electrode 150a and the germanium wafer 110 after the sintering process. The P ⁺ germanium layer 110a is formed to increase the collection of carriers and improve conversion efficiency. Further, as shown in FIG. 1, the two front electrodes 140a are parallel to each other and are disposed on the N-type doping layer 120.

As shown in FIG. 1, in the structure of the present embodiment, the light-receiving surface R of the P-type germanium wafer 110 has a structure such as a rough surface, a pyramid texturing or an inverted-pyramid texturing to reduce The reflectivity of sunlight or light entering the twin solar cell 100 increases the utilization of sunlight. The N-type doped layer 120 can be formed by doping a P-type germanium wafer 110 with a group V element such as phosphorus (P) or arsenic (As). The first dielectric layer 130 may be a single layer or a multilayer structure of SiO ₂ , Si _x N _y , Si _x N _y H _z , Si _x O _y N _z , SiC, or a combination thereof.

It is to be noted that the back electrode 150a and the P ⁺ germanium layer 110a are formed by the high temperature co-firing process of the aluminum paste of the present invention, whereby the conversion efficiency can be further improved. The aluminum paste of the present invention is further explained below.

<Aluminum paste>

Specifically, the aluminum paste for the twinned solar cell 100 comprises aluminum powder, glass frit, an organic vehicle, and an organic cerium-containing additive, wherein the organic cerium-containing additive has at least one stanol functional group. The individual components are detailed below.

[1] aluminum powder

The material of the aluminum powder in the aluminum paste is selected from aluminum, which may be a collection of aluminum particles composed of a single metal, or may be formed by forming aluminum with other elements (such as gallium, zinc, magnesium, bismuth, etc.). The collection of aluminum alloy particles, or further combined with other metal particles, is not limited thereto. After the aluminum paste is sintered, the aluminum particles are in contact with each other to constitute a portion of the electrode that mainly transfers electrical energy. Generally, the particle size of the metal particles is 0.1 to 20 um.

[2] Glass powder

The glass frit in the aluminum paste includes an inorganic glass material containing lead, antimony or a combination thereof. Specifically, the above glass frit may be an inorganic glass including at least one of boron (B), aluminum (Al), Ga (gallium), In (indium), and Tl (铊), or may include An inorganic glass containing at least one of N (nitrogen), P (phosphorus), As (arsenic), Sb (bismuth), and Bi (bismuth). In the present embodiment, the glass frit may be a lead-free material containing no lead, and the material thereof is, for example, cerium oxide. Of course, the glass frit may also be a lead-containing lead material, such as lead oxide. The glass frit softens during high temperature sintering, providing a good adhesion of the aluminum in the electrode to the crucible of the germanium wafer.

[3] Organic carrier

The organic vehicle in the aluminum paste may include a solvent, a binder or an organic additive, wherein the organic additive is, for example, a rocking aid (thixotropic agent), a thickener, Anti-settling agent, etc. The organic carrier functions to uniformly mix the aluminum powder, the glass powder, and the organic cerium-containing additive. Further, the organic carrier can help screen printing to proceed smoothly, and the organic carrier can be volatilized or burned off after sintering. In other words, the organic vehicle can be used as an adhesive for each component in the aluminum paste at normal temperature and is removed after sintering at a high temperature.

[4] Organic antimony additive

The organic cerium-containing additive of the present invention is different from the general inorganic cerium additive, and the use of the organic cerium-containing additive has an effect of further increasing the adhesion between aluminum and cerium compared to the inorganic cerium additive. Further, the organic cerium-containing additive of the present invention has at least one stanol functional group and is different from a general siloxane or an unhydrolyzed silane or a derivative thereof. The organic cerium-containing additive having at least one stanol function has problems such as preventing the aluminum paste from increasing in viscosity in the subsequent twinned solar cell process, resulting in poor screen printing, compared to the unhydrolyzed silane.

Specifically, the structural formula of the organic cerium-containing additive of the present invention is represented by the formula (1): In the formula (1), at least one of R ₁ , R ₂ and R ₃ represents a hydroxyl group, and R ₄ represents a specific substituent group such as thiophene, vinyl, phenyl or isopropyl. Isopropoxy, tolyl, tert-butyl-indole-1-carboxylate, propyl amine or N-(2-aminoethyl) )-3-aminopropyl (N-(ethylamino)-3-aminopropyl). Specifically, the organic cerium-containing additive may be at least one selected from the group consisting of formula (2) to formula (9): an organic cerium-containing additive represented by formula (2): In the formula (2), R ₁ , R ₂ and R ₃ each represent a hydroxyl group, and R ₄ represents a propyl amine. In other words, the organic cerium-containing additive represented by the formula (2) has three stanol functional groups.

Organic antimony additive represented by formula (3): In the formula (3), R ₁ , R ₂ and R ₃ represent a hydroxyl group, and R ₄ represents a vinyl group. In other words, the organic cerium-containing additive represented by the formula (3) has three stanol functional groups.

Organic antimony additive represented by formula (4): In the formula (4), R ₁ and R ₂ represent a hydroxyl group, and R ₃ and R ₄ represent a phenyl group. In other words, the organic cerium-containing additive represented by the formula (4) has two stanol functional groups.

An organic antimony additive represented by the formula (5): In the formula (5), R ₁ represents a hydroxyl group, and R ₂ , R ₃ and R ₄ represent an isopropoxy group. In other words, the organic cerium-containing additive represented by the formula (5) has one stanol function.

Organic antimony additive represented by formula (6): In the formula (6), R ₁ represents a hydroxyl group, R ₂ and R ₃ represent a methyl group, and R ₄ represents a thiophene. In other words, the organic cerium-containing additive represented by the formula (6) has one stanol functional group.

An organic antimony additive represented by the formula (7): In the formula (7), R ₁ represents a hydroxyl group, R ₂ and R ₃ represent a methyl group, and R ₄ represents a tolyl group. In other words, the organic cerium-containing additive represented by the formula (7) has one stanol function.

An organic antimony additive represented by the formula (8): In the formula (8), R ₁ represents a hydroxyl group, R ₂ and R ₃ represent a methyl group, and R ₄ represents a tert-butyl-indole-1-carboxylate. In other words, the organic cerium-containing additive represented by the formula (8) has one stanol functional group.

An organic antimony additive represented by the formula (9): In the formula (9), R ₁ , R ₂ and R ₃ represent a hydroxyl group, and R ₄ represents N-(2-aminoethyl)-3-aminopropyl. In other words, the organic cerium-containing additive represented by the formula (9) has three stanol functional groups.

In the composition of the aluminum paste of the present embodiment, the organic cerium-containing additive is added in an amount of 0.001% to 40% in terms of the total amount of the composition in the aluminum paste of 100%.

It is worth noting that by adding an organic cerium-containing additive having at least one stanol function to the aluminum paste, the organic cerium-containing additive can be sufficiently and uniformly mixed with the aluminum powder, the glass powder and the organic vehicle, thereby sufficiently It functions as a sealant. In addition, the organic rhodium-containing additive has been previously hydrolyzed prior to addition to the aluminum paste to produce a functional group having at least one stanol. By making the organic cerium-containing additive have at least one stanol functional group, the organic cerium-containing additive can be inhibited from being formed in a twin solar cell. The process reacts excessively with the organic carrier, resulting in instability such as increased viscosity. Specifically, if an unhydrolyzed methoxy or methoxy alkoxysilane or decane is used as the organic cerium-containing additive, the unhydrolyzed organic cerium-containing additive is, for example, ethyl cellulose. The organic carrier of (ethyl cellulose) is excessively polymerized, resulting in an increase in viscosity and instability of the aluminum paste. Therefore, in the aluminum paste of the present invention, since the organic cerium-containing additive having at least one stanol function is used, the above problem of an increase in viscosity can be avoided.

Based on the above, the aluminum paste for a twinned solar cell of the present invention can effectively increase the adhesion between the electrode and the substrate and reduce the coefficient of thermal expansion, thereby alleviating the problem of warpage of the twinned solar cell after high temperature sintering.

Of course, the aluminum paste of the present invention can be applied not only to the conventional twinned solar cell 100 as in the foregoing FIG. 1, but also to the passivated emitter back electrode twinned solar cell 200 shown in FIGS. 2A and 2B (hereinafter referred to as For the twinned solar cell 200), the invention is not limited thereto.

2A and FIG. 2B are schematic diagrams showing the structure of a passivated emitter back electrode twin solar cell at different positions according to an embodiment of the present invention, wherein FIG. 2A is a bus bar along the front electrode. FIG. 2B is a schematic cross-sectional view of the bus electrode. 3 is a top plan view of the back side of the twinned solar cell of FIGS. 2A and 2B. Please refer to FIG. 2A, FIG. 2B and FIG. The structure of the twinned solar cell 200 is similar to that of the conventional twinned solar cell 100. In detail, the N-type doping layer 220, the first dielectric layer 230 and the front surface electrode 240a are sequentially included on the light-receiving surface R (hereinafter also referred to as the front surface) from the P-type germanium wafer 210, and on the back surface B. The P-type germanium wafer 210 sequentially includes a patterned second dielectric layer 260a, a back surface electrode 250a, and a P ⁺ germanium layer 210a. The back electrode 250a includes an aluminum germanium eutectic layer 252, an aluminum electrode 254, and a silver electrode 256, and the back electrode 250a of FIG. 2B has only an aluminum germanium eutectic layer 252 and an aluminum electrode 254.

Specifically, as shown in FIGS. 2A and 2B, the back surface B of the P-type germanium wafer 210 includes a back surface electrode 250a and a patterned second dielectric layer 260a between the P-type germanium wafer 210 and the back surface electrode 250a. As shown in FIG. 2A and FIG. 2B, the patterned second dielectric layer 260a has an opening Op, and a portion of the back surface electrode 250a forms an aluminum crucible with the P-type germanium wafer 210 in the opening Op of the patterned second dielectric layer 260a. The eutectic layer 252 is connected to the P-type germanium wafer 210, and a P ⁺ germanium layer 210a is formed between the aluminum germanium eutectic layer 252 and the p-type germanium wafer 210.

The relative positional relationship between the silver electrode 256 and the aluminum electrode 254 is as shown in FIG. 3. In the present embodiment, the silver electrode 256 is electrically connected to a part of the aluminum electrode 254. The silver electrode 256 is formed as a plurality of line segments L.

It is worth noting that the line segments L formed by the silver electrodes 256 have a certain spacing, thereby avoiding warpage of the battery due to the difference in thermal expansion coefficient between the ruthenium substrate and the electrodes during the cooling process after high temperature co-firing.

The cross-sectional structure of the twinned solar cell 200 will be described in detail below.

More specifically, please refer to FIG. 4 and FIG. 5, which is a schematic view taken along line AA' of FIG. Fig. 5 is a schematic view taken along line BB' of Fig. 3.

On the light-receiving surface R of the twinned solar cell 200, the high-temperature sintered front electrode 240a passes through the first dielectric layer 230 (indicated by a broken line) and N due to sintering. The doped layer 220 is in contact.

The aluminum electrode 254 covers the portion of the patterned second dielectric layer 260a that is covered with the silver electrode 256. Specifically, the aluminum electrode 254 covers the exposed portion of the patterned second dielectric layer 260a and is adjacent to the aluminum germanium eutectic layer 252.

The aluminum germanium eutectic layer 252 is located between the P ⁺ germanium layer 210a and the aluminum electrode 254, and the aluminum germanium eutectic layer 252 is distributed along with the aluminum electrode 254 along the position corresponding to the exposed portion of the patterned second dielectric layer 260a. .

In particular, the aluminum electrode 254, the aluminum ruthenium eutectic layer 252, and the P ⁺ ruthenium layer 210a are all formed by sintering the second electrode composition 250 of the present invention at a high temperature.

<Method of Manufacturing Solar Cell>

6A through 6C are schematic views of a method of fabricating a twinned solar cell 200 in accordance with the above-described embodiments of the present invention. Referring to FIG. 6A, first, a P-type germanium wafer 210 is provided, wherein the P-type germanium wafer 210 is, for example, a boron doped or gallium doped wafer. Then, doping (for example, phosphorus doping or arsenic doping) on the light receiving surface R of the P-type germanium wafer 210 by, for example, thermal diffusion or ion implantation, thereby being applied to the light receiving surface R An N-type doped layer 220 is formed.

Then, a first dielectric layer 230 is formed on the N-type doped layer 220 of the light receiving surface R, and a second dielectric layer 260 is formed on the back surface B of the P-type germanium wafer 210 with respect to the light receiving surface R. Specifically, the first dielectric layer 230 may be a single layer or a multilayer structure of SiO ₂ , Si _x N _y , Si _x N _y H _z , Si _x O _y N _z , SiC, or a combination thereof, and the second dielectric Layer 260 may be a single layer or a multilayer structure of a combination of Al _x O _y , SiO ₂ , Si _x N _y , Si _x N _y H _z , Si _x O _y N _z , SiC. In addition, the method for forming the first dielectric layer 230 and the second dielectric layer 260 is, for example, a chemical vapor deposition (CVD) or a plasma enhanced chemical vapor deposition (Plasma Enhanced Chemical Vapor Deposition). , PECVD) or Thermal oxidation or Atomic Layer Deposition (ALD).

Next, referring to FIG. 6B, the second dielectric layer 260 is patterned to expose the back surface B of the P-type germanium wafer 210 to form the patterned second dielectric layer 260a. The patterning step can be formed by photolithography, directly using an etching paste, or by a laser etch.

Then, referring to FIG. 6C, a first electrode composition 240 is formed on the light receiving surface R of the P-type germanium wafer 210, for example, a screen printing first electrode composition 240, wherein the first electrode composition 240 is, for example, It is a silver paste. Of course, the aluminum paste of the present invention or the aluminum paste and the silver paste may be used to form the front electrode, and the invention is not limited thereto.

Next, a second electrode composition 250 and a third electrode composition 270 are formed on the patterned second dielectric layer 260a and the back surface B of the P-type germanium wafer 210. In particular, the second electrode composition 250 uses the present invention. The above aluminum paste can thereby provide conversion efficiency and reduce the phenomenon of thinning of the twinned solar cell. Further, the third electrode composition 270 is formed, for example, by screen printing to form a silver paste.

Specifically, the second electrode composition 250 and the third electrode composition 270 described above are screen printed on the patterned second dielectric layer 260a and the P-type germanium wafer 210. The back side B, whereby the second electrode composition 250 can cover the exposed portions of the patterned second dielectric layer 260a and the P-type germanium wafer 210.

Then, the above structure in which the first electrode composition 240, the second electrode composition 250, and the third electrode composition 270 have been formed is subjected to a high-temperature co-firing process to form the front surface electrode 240a, the back surface electrode 250a, and the P ⁺矽 layer 210a. The overall structure of the twinned solar cell 200 shown in the above FIGS. 2-5 is constructed. It is to be noted that the highest temperature of the high temperature process is, for example, greater than 600 ° C, whereby the first electrode composition 240 is sintered at a high temperature to form the front electrode 240a, and the front electrode 240a traverses the first dielectric layer 230 due to high temperature sintering ( Indicated by a broken line) is in contact with the N-type doping layer 220. In addition, since the aluminum-germanium eutectic temperature is about 577 ° C, a layer of aluminum germanium eutectic layer 252 is formed between the p-type germanium wafer 210 and the aluminum electrode 254. In addition, the aluminum of the group III element easily diffuses into the lanthanum of the group IV element. Therefore, during cooling to room temperature after high-temperature sintering, a P ⁺ germanium layer 210a (shown in FIG. 4) may be formed on the back surface B of the P-type germanium wafer 210, and the P ⁺ germanium layer 210a may be bonded to the P-type germanium wafer. 210 forms a high-low concentration difference P ⁺ -P junction, and generates a local back surface field (LBSF), which increases the collection of carriers in the P-type wafer 210, and reduces the recombination of carriers on the back surface. The opportunity to increase the conversion efficiency of the twin solar cell 200. Moreover, since the aluminum paste of the second electrode composition 250 contains an organic antimony additive having at least one stanol function, the hole filling rate of the aluminum eutectic eutectic can be maintained at a high level, the conversion efficiency is effectively improved, and the warpage is avoided. Qu and other issues.

<Solar cell evaluation method>

[efficiency and fill factor]

Cell efficiency and fill factor measurements were performed on twin solar cells of different embodiments using a solar cell efficiency measuring machine. The solar cell efficiency measuring machine is a QuickSun-120CA solar cell efficiency measuring machine manufactured by Endeas.

[warpage amount]

The twinned solar cells of different embodiments after sintering are placed on the platform with the light-receiving surface facing up, and then the thickness gauges of the edges of the twin crystal solar cells are measured at the highest warpage between the edges of the twin crystal solar cells.

[filling rate]

After passivating the emitter back electrode twin crystal solar cell of different examples after high temperature sintering, the scanning electron microscope (SEM) was used to observe that the aluminum ruthenium eutectic layer was completely filled, that is, the non-porous aluminum ruthenium eutectic layer occupied. proportion.

<Solar cell evaluation result>

In the following examples, the aluminum paste of the present invention can be applied to the conventional twinned solar cell of FIG. 1 described above and the passivated emitter back electrode twinned solar cell of FIGS. 2A and 2B, respectively. Further, the composition ratios and evaluation results of the aluminum paste are shown in Tables 1 and 2, respectively. It is to be noted that the experimental values of Tables 1 and 2 have been normalized to Comparative Example 1 and Comparative Example 2, respectively, that is, the evaluation values in Comparative Examples 1 and 2 are set to 1, and the respective examples are converted. The value of each item.

In detail, Table 1 shows the effect of changing the type of organic cerium-containing additive and its content in the aluminum paste on the efficiency of the twinned solar cell and the amount of warpage. value It is to be noted that in each of the first to the thirteenth embodiments, decyl alcohol is added as an organic cerium-containing additive to the aluminum paste, so that the amount of warpage of the twinned solar cell can be effectively reduced, and the twinned solar cell can be increased. effectiveness. Moreover, when the organic cerium-containing additive is tris(isopropoxy) decyl alcohol, the amount of warpage decreases as the content of the organic cerium-containing additive increases, especially when the content is 30%, the warpage of the twinned solar cell The amount is reduced to about 60% of Comparative Example 1 in which no organic cerium-containing additive is added; in addition, the conversion efficiency of the twinned solar cell can be effectively controlled by changing the content of the organic cerium-containing additive, especially when the content is 1%. The conversion efficiency of the twin solar cell can be effectively improved.

Table 2 shows the effect of changing the content of the organic cerium-containing additive in the aluminum paste, the hole filling ratio of the aluminum bismuth eutectic, the filling factor of the passivated emitter back electrode twin solar cell, and the conversion efficiency. It is worth noting that in Examples 1 to 4, since the aluminum paste contains tris(isopropoxy) stanol as an organic cerium-containing additive, the void filling ratio of the aluminum cerium eutectic can be increased, wherein the filling factor It also increases, which in turn increases the efficiency of the passivated emitter back electrode twinned solar cell.

In summary, the aluminum paste of the present invention and the method of manufacturing the passivated emitter back electrode twinned solar cell using the aluminum paste have the following advantages:

(1) By adding an organic cerium-containing additive having at least one stanol function to an aluminum paste, the organic cerium-containing additive can be sufficiently and uniformly mixed with the glass powder, the aluminum powder, and the organic vehicle, thereby functioning as a dense The function of the agent, therefore, the aluminum paste for the twinned solar cell of the present invention can effectively increase the hole filling rate of the aluminum-bismuth eutectic of the twinned solar cell, so as to improve the cell efficiency.

(2) By adding an organic antimony additive having at least one stanol function to the aluminum paste, the organic antimony additive can also be inhibited from excessively reacting with the organic vehicle in the process of the twin solar cell, resulting in instability such as an increase in viscosity. phenomenon.

(3) The aluminum paste for a twinned solar cell of the present invention can effectively increase the adhesion between the electrode and the substrate, thereby alleviating the problem of warpage of the twinned solar cell after high temperature sintering.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Silver solar cells

110‧‧‧P type silicon wafer

110a‧‧‧P ⁺ layer

120‧‧‧N-doped layer

130‧‧‧First dielectric layer

140a‧‧‧front electrode

150a‧‧‧ back electrode

152‧‧‧Aluminum bismuth eutectic layer

154‧‧‧Aluminum electrode

B‧‧‧Back

R‧‧‧Glossy surface

Claims (10)

An aluminum paste for a twinned solar cell comprising: aluminum powder; glass frit; an organic vehicle; and an organic cerium-containing additive, wherein the organic cerium-containing additive has at least one stanol functional group. An aluminum paste for passivating an emitter back electrode twinned solar cell, comprising: aluminum powder; glass frit; an organic carrier; and an organic germanium-containing additive, wherein the organic germanium-containing additive has at least one stanol functional group. The aluminum paste according to claim 1 or 2, wherein the structural formula of the organic cerium-containing additive is represented by the formula (1): In the formula (1), at least one of R ₁ , R ₂ and R ₃ represents a hydroxyl group, and R ₄ represents a thiophene group, a vinyl group, a phenyl group, an isopropoxy group, a tolyl group, and a tertiary butyl-derived carboxylic acid. Ester, propylamine or N-(2-aminoethyl)-3-aminopropyl. The aluminum paste according to claim 1 or 2, wherein the organic cerium-containing additive is selected from at least one of the formulae (2) to (9): The aluminum paste according to claim 1 or 2, wherein the organic cerium-containing additive is added in an amount of 0.001% to 40%. The aluminum paste according to claim 1 or 2, wherein the glass frit is a lead-free material and contains cerium oxide. The aluminum paste according to claim 1 or 2, wherein the glass frit is a lead material and contains lead oxide. A method for fabricating a passivated emitter back electrode twinned solar cell, comprising: performing N-type doping on the light-receiving surface of a P-type germanium wafer to form an N-type doped layer on the light-receiving surface; Forming a first dielectric layer on the N-type doped layer; forming a second dielectric layer on a back surface of the P-type germanium wafer; and patterning the second dielectric layer on the back surface to expose Forming the back surface of the P-type germanium wafer; forming a first electrode composition on the light receiving surface; forming a second electrode composition on the second dielectric layer and the back surface of the P-type germanium wafer a third electrode composition, wherein the second electrode composition comprises aluminum powder, glass frit, an organic vehicle, and an organic cerium-containing additive, and the organic cerium-containing additive includes at least one stanol functional group; and performing a high-temperature co-firing process The first electrode composition on the light-receiving surface forms a front electrode, and the second electrode composition on the back surface and the third electrode composition form a back electrode. The method for fabricating a passivated emitter back electrode twinned solar cell according to claim 8, wherein the first electrode composition and the third electrode composition are silver paste. The method for fabricating a passivated emitter back electrode twinned solar cell according to claim 9, wherein after the high temperature co-firing process, the back electrode comprises a silver electrode, an aluminum electrode, an aluminum germanium eutectic layer, and P ⁺ a germanium layer, wherein the aluminum germanium eutectic layer is between the P ⁺ germanium layer and the aluminum electrode, and the silver electrode is electrically connected to the aluminum electrode.