TW201916398A - Method for manufacturing a solar cell - Google Patents

Abstract

A method for manufacturing a solar cell includes: forming a first metal layer on a light receiving surface exposed from an anti-reflective layer opening of the photoelectric transformation substrate, and forming a second metal layer on a back surface exposed from an passivation layer opening of the photoelectric transformation substrate, wherein the first and second metal layers are formed simultaneously by a first eletroless plating process, and the first eletroless plating process is an eletroless plating process with high selectivity; and forming a third metal layer on the passivation layer, wherein the third metal layer is formed by a second eletroless plating process, and the second eletroless plating process is an eletroless plating process with low selectivity.

Description

 Solar cell manufacturing method  

The present invention relates to a method for fabricating a solar cell, and more particularly to a method for fabricating an electrode for a solar cell, so that two electroless plating processes can be used for different characteristics of the surface of the photoelectric conversion substrate and the surface of the antireflection layer/passivation layer, respectively. The effect of each optimization.

A solar cell is a kind of photoelectric component that converts light energy into electrical energy. It is one of the important alternative energy sources due to low pollution, low cost and the use of endless solar energy as an energy source.

Referring to FIG. 1 , a conventional back passivation solar cell 9 includes a germanium substrate 91 , an anti-reflective layer 93 , a passivation layer 94 , a back electrode 96 , and a front electrode 97 . The germanium substrate 91 has an emitter. Layer 92 and a back electric field layer 95. The front surface electrode 97 of the solar cell 9 is a patterned conductor layer (only formed on the front surface of the battery substrate), and the back surface electrode 96 is a full-surface conductor layer, that is, the front surface electrode 97 is formed only at the opening of the anti-reflection layer 93. A region 931 is formed on the passivation layer 94 and the two regions of the open region 941 of the passivation layer 94.

When the back surface electrode 96 is formed on the passivation layer 94 and the two regions of the opening region 941, the base layer (for example, a nickel layer) of the back surface electrode 96 and the passivation layer 94 and the germanium substrate 91 are formed. The adhesion between the materials must be sufficient. However, the optimum parameter conditions of the process conditions corresponding to the two regions may be different, and the problem that the base layer (for example, the nickel layer) of the back surface electrode 96 attached to the partial region may fall off may occur in the future.

Therefore, there is a need for a method of manufacturing a solar cell that overcomes the above problems.

It is an object of the present invention to provide a method for fabricating a solar cell that achieves an effect that each of the two electroless plating processes can be optimized for different characteristics of the surface of the photoelectric conversion substrate and the surface of the antireflection layer/passivation layer, respectively.

According to the above object, the present invention provides a method for manufacturing a solar cell, comprising the steps of: preparing a battery substrate, wherein the battery substrate comprises a photoelectric conversion substrate, an anti-reflection layer and a passivation layer, the photoelectric conversion substrate having a light receiving And a back surface, the anti-reflection layer is located on the light receiving surface, the passivation layer is located on the back surface, the anti-reflection layer comprises an anti-reflection layer opening, and the passivation layer comprises a passivation layer opening; the anti-reflection layer opening The exposed light receiving surface forms a first metal layer, and a second metal layer is formed on the back surface exposed by the opening of the passivation layer, wherein the first metal layer and the second metal layer are formed in a first electroless plating process. The first electroless plating process is a high selective ratio electroless plating process; and a third metal layer is formed on the passivation layer, wherein the third metal layer is formed by a second electroless plating process, and the second electroless plating process For a low choice than the electroless plating process.

The invention completes the base layer of the front electrode (for example, the first metal layer) and the base layer of the back electrode (for example, the second and third metal layers) by a simple process, and forms the first and second with a high selection ratio of the electroless plating process. The metal layer is respectively disposed on the light-receiving surface and the back surface of the opening of the anti-reflection layer and the opening of the passivation layer, and the passivation layer is covered by the third metal layer on the back surface by a low-selection electroless plating process to achieve two electroless plating processes. The effects of different characteristics of the surface of the ruthenium substrate and the surface of the anti-reflection layer/passivation layer can be respectively optimized, and the adhesion of the base layer of the back electrode to the surface of the ruthenium substrate and the surface of the anti-reflection layer/passivation layer can also be optimized respectively, and the electrode material is optimized. The choice of elasticity can also be improved.

1‧‧‧Solar battery

10‧‧‧ battery base

101‧‧‧Stained surface

101’‧‧‧ front side

102‧‧‧Back

102’‧‧‧ Back side

11‧‧‧Photoelectric conversion substrate

12‧‧ ‧ emitter layer

13‧‧‧Anti-reflective layer

131‧‧‧Anti-reflection layer opening

14‧‧‧ Passivation layer

141‧‧‧ Passivation layer opening

15‧‧‧ Back electric field layer

16‧‧‧Back electrode

161‧‧‧Second metal layer

162‧‧‧ Third metal layer

163‧‧‧Second conductive layer

17‧‧‧Front electrode

171‧‧‧First metal layer

172‧‧‧First conductive layer

2‧‧‧Processing tank group

21‧‧‧sensitization/activation tank group

22‧‧‧ plating bath

3‧‧‧Processing tank group

31‧‧‧ sensitizing/activated liquid tank group

32‧‧‧ plating bath

9‧‧‧Back passivated solar cells

91‧‧‧矽 substrate

92‧‧ ‧ emitter layer

93‧‧‧Anti-reflective layer

931‧‧‧Open area

94‧‧‧ Passivation layer

941‧‧‧Open area

95‧‧‧ Back electric field layer

96‧‧‧Back electrode

97‧‧‧Front electrode

S100~S400‧‧‧Steps

1 is a schematic cross-sectional view of a conventional back passivated solar cell.

2 is a flow chart of a method of manufacturing a solar cell according to an embodiment of the present invention.

3 is a schematic cross-sectional view showing a method of fabricating a solar cell according to an embodiment of the present invention, showing preparation of a battery substrate.

4 is a schematic cross-sectional view showing a method of fabricating a solar cell according to an embodiment of the present invention, showing formation of first and second metal layers.

Figure 5 is a cross-sectional view showing a first line-type processing liquid tank assembly according to an embodiment of the present invention.

Figure 6 is a schematic cross-sectional view showing a method of fabricating a solar cell according to an embodiment of the present invention, showing the formation of a third metal layer.

Figure 7 is a cross-sectional view showing a second pipeline type processing liquid tank assembly according to an embodiment of the present invention.

Figure 8 is a cross-sectional view showing a second in-line treatment liquid tank assembly according to another embodiment of the present invention.

Figure 9 is a cross-sectional view showing a method of fabricating a solar cell according to an embodiment of the present invention, showing the formation of first and second conductive layers.

The above described objects, features, and characteristics of the present invention will become more apparent from the aspects of the invention.

Please refer to FIG. 2, which is a flow chart of a method for manufacturing a solar cell according to an embodiment of the present invention. The method for manufacturing the solar cell includes the following steps: Referring to FIG. 3, in step S100, a battery substrate 10 is prepared. The battery substrate 10 includes a photoelectric conversion substrate 11, an anti-reflection layer 13, and a passivation layer 14, wherein The photoelectric conversion substrate 11 has a light-receiving surface 101 (also referred to as a front surface) and a back surface 102. The anti-reflection layer 13 is located on the light-receiving surface 101. The passivation layer 14 is located on the back surface 102. The anti-reflection layer 13 includes An anti-reflective layer opening 131, and the passivation layer 14 includes a passivation layer opening 141. For example, the anti-reflection layer opening 131 and the passivation layer opening 141 may be formed by a laser grooving method or a photolithography method, and the light-receiving surface 101 of the photoelectric conversion substrate 11 and a portion of the back surface 102 are respectively exposed. The number of the anti-reflection layer opening 131 and the passivation layer opening 141 may be one or more according to design requirements. The anti-reflection layer 13 may be a layer having a reduced reflectance of incident light, and may be a single layer or a multilayer structure, which may also have a passivation effect. The passivation layer 14 can also be a single layer or a multilayer structure and has a passivation effect. The anti-reflection layer 13 and the passivation layer 14 can be made of tantalum nitride.

The photoelectric conversion substrate 11 refers to a substrate that can convert light energy into electrical energy by a photovoltaic effect, such as a semiconductor germanium substrate having a PN junction (P/N junction) or a PIN junction. In the embodiment, the photoelectric conversion substrate 11 is a germanium substrate, such as a single crystal germanium or a polycrystalline germanium substrate, and the germanium substrate has an emitter layer 12 and a back electric field layer 15. The main body portion of the germanium substrate and the back electric field layer 15 are of a first conductivity type, and the emitter layer 12 is of a second conductivity type and located in the germanium substrate 11 near the light receiving surface 101, and the back electric field layer 15 is located The inside of the crucible substrate 11 is adjacent to the back surface 102.

Referring to FIG. 4, in step S200, a first metal layer 171 is formed on the light-receiving surface 101 exposed by the anti-reflection layer opening 131, and a second metal layer 161 is formed on the back surface 102 exposed in the passivation layer opening 141. The first metal layer 171 and the second metal layer 161 are formed synchronously in a first electroless plating process, and the first electroless plating process is a high selective ratio electroless plating process, and the first and second metal layers 171 161 can be made of nickel. For the purposes of the present invention, a high selectivity ratio electroless plating process means that the electroless plating process has a plating rate on the surface of the photoelectric conversion substrate 11 (for example, the germanium substrate) that is much larger than the electroless plating process on the antireflection layer 13 or the The plating rate on the surface of the passivation layer 14 is such that even if the light-receiving surface 101, the back surface 102, the anti-reflection layer 13, and the passivation layer 14 of the photoelectric conversion substrate 11 are simultaneously in contact with the plating solution, during the process, a plating layer (for example, The nickel layer is formed substantially only on the light-receiving surface 101 and the back surface 102 exposed by the photoelectric conversion substrate 11, and the deposition amount on the anti-reflection layer 13 and the passivation layer 14 is zero or less to no additional step. .

The first electroless plating process of step S200 can be carried out by a batch process, for example, coating a non-plated area of the surface of the battery substrate 10 with a fixture, and then immersing the relevant treatment liquid of the electroless plating process, however, the production thereof The speed is limited by the time of disassembly and assembly of the jig. In addition, when the jig is taken out of the treatment liquid, the jig itself will take away some of the liquid and increase the loss. Therefore, the present invention proposes an in-line process. Referring to FIG. 5, the first electroless plating process includes immersing the battery substrate 10 in a liquid in a whole piece and passing it through a first in-line process by pushing a plurality of rollers. Tank set 2. Preferably, the battery substrate 10 passes through the first in-line processing liquid tank group 2 in such a manner that the back side 102' is downward (ie, the back surface 102 of the photoelectric conversion substrate 11 is downward). The front side 101' of the battery base 10 is referred to as the side of the battery base 10 closer to the light receiving surface 101, and the back side 102' of the battery base 10 is referred to as the side closer to the back surface 102. The first pipelined treatment tank group 2 generally includes a sensitizing/activation liquid tank group 21 and a plating tank 22. Depending on the formulation, the sensitizing solution and the activation solution may be completed in the same tank or in two separate tanks, as shown in Figure 5 in the same tank. The treatment liquid suitable for the high-selection electroless plating process of the present invention, for example, the activation liquid is a product of Japan Uemura Corporation (Uemura Industrial Co., Ltd. - UYEMURA) (ACG-9), and the electroless nickel plating liquid is the Japanese company (Japan) Product of Kokumura Industrial Co., Ltd. - UYEMURA (KPD-9)". In contrast to the batch process in which the fixture covers the battery substrate 10, the production process of the in-line process is faster and the loss of the treatment liquid is less.

The first electroless plating process includes a sensitization and activation step of forming a plurality of seed particles (not shown) attached to the light receiving surface 101 and the back surface 102. The first electroless plating process is Autocatalytic Plating, which first forms a catalytic surface on the surface of the work object, or uses a catalytic action of the surface of the work object to chemically reduce the metal ions into a metal state. Precipitate. The first and second metal layers 171 and 161 are respectively attached to the light-receiving surface 101 and the back surface 102 by the seed particles.

Referring to FIG. 6, in step S300, a third metal layer 162 is formed on the passivation layer 14, wherein the third metal layer 162 is formed by a second electroless plating process, and the second electroless plating process is a low selection. Than the electroless plating process. For the purposes of the present invention, the low selectivity ratio electroless plating process refers to the plating rate of the electroless plating process on the surface of the photoelectric conversion substrate 11 (for example, the germanium substrate) and the electroless plating process in the antireflection layer 13 or the passivation. The plating rate on the surface of the layer 14 is equivalent, so that if the light-receiving surface 101, the back surface 102, the anti-reflection layer 13 and the passivation layer 14 of the photoelectric conversion substrate 11 are in contact with the plating solution, the plating solution is used during the process. A plating layer (for example, a nickel layer) can be effectively formed on the surface of the photoelectric conversion substrate 11 exposed, the antireflection layer 13 and the passivation layer 14. It should be noted that the above-mentioned "plating rate equivalent" does not mean that the plating rate is the same, that is, the thickness of the plating layer formed on each of the light-receiving surface 101, the back surface 102, the reflective layer 13, and the passivation layer 14 exposed by the photoelectric conversion substrate 11 is still There may be differences. In this embodiment, since the second metal layer 161 and the third metal layer 162 are made of the same material, the third metal layer 162 is also formed on the second metal layer 161. In addition, if the second metal layer 161 and The third metal layer 162 is different, and the third metal layer 162 may or may not be formed on the second metal layer 161 depending on the processing liquid formulation.

The second electroless plating process of step S300 can be performed by a batch process, or the second electroless process of step S300 can be performed by a pipeline process. Referring to FIG. 7, in the embodiment, the second electroless plating process includes The battery base 10 is passed through a second in-line treatment tank group 3 by pushing a plurality of rollers. For example, the second pipelined treatment tank group 3 includes a sensitizing/activated liquid tank group 31 and a plating bath 32. The battery base 10 has a liquid on the front side 101' and a liquid on the back side 102'. The water-repellent process is performed by the sensitization/activation liquid tank group 31 and the plating bath 32, and the third metal layer 162 is formed on the passivation layer 14 and the second metal layer 161. If the material of the third metal layer 162 is the same as the material of the second metal layer 161, the third metal layer 162 is formed on the second metal layer 161 to thicken the second metal layer 161. In addition, when the pipeline process is performed by the water drifting method, only one side (the back side 102' in the embodiment) is in contact with the liquid, and the selective deposition effect is achieved without the fixture, and The loss of the treatment fluid is less than the streamlined process of immersing the entire substrate in the liquid.

The second electroless plating process includes a sensitization and activation step of forming a plurality of seed particles (not shown) attached to the surface of the passivation layer 14. The second electroless plating process described above is also a self-catalytic plating process. The third metal layer 162 is attached to the surface of the passivation layer 14 through the seed particles.

Referring to FIG. 8 , in another embodiment, the second electroless plating process includes passing the battery substrate 10 through a second in-line processing liquid tank group, and the second pipeline processing liquid tank group 3 The difference between the embodiment shown in FIG. 7 and the embodiment shown in FIG. 7 is that the battery substrate 10 in this embodiment passes through the plating bath 32 in a manner of immersing the whole piece in a liquid. . The mode shown in Fig. 7 consumes less sensitizing liquid and activation liquid; while the whole piece is immersed in liquid as shown in Fig. 8, the control accuracy of the liquid level is lower than that of the water floating method. In addition, when the entire metal layer 162 is made of the same material as the material of the first metal layer 171, the third metal layer 162 is formed in the first layer. A metal layer 171 (not shown) corresponds to thickening the first metal layer 171 as well.

In addition, the first pipelined treatment tank group 2 and the second pipelined treatment tank group 3 can be connected to each other to form a large streamlined treatment tank group (not shown), if the battery substrate 10 is a front side The first pipeline type processing liquid tank group 2 passes through the side of the first pipelined processing liquid tank group 2, and then needs to be turned over by a substrate before passing through the second pipeline type processing liquid tank group 3. The surface of the battery substrate 10 is turned over by a surface device (not shown), and this is not necessary when the battery substrate 10 is passed through a first line-type processing liquid tank group 2 with the back side facing downward.

In this embodiment, the third metal layer 162 may be the same material as the second metal layer 161. For example, the third metal layer 162 may be made of nickel. In another embodiment, the third metal 162 may be different from the material of the second metal layer 161, for example, electrical conductivity or reflectivity may be considered, and the effect thereof is, for example, optimizing the internal reflection efficiency or electrical property of the single-sided light-receiving solar cell. .

The treatment liquid suitable for the low selection ratio electroless plating process of the present invention, for example, the main component of the sensitizing liquid is SnCl ₂ , the main component of the activation liquid is PdCl ₂ , and the main component of the electroless nickel plating liquid is NiSO ₄ (nickel sulfate) / NaH ₂ PO ₂ (sodium hypophosphite) / Na ₂ H ₄ C ₄ O ₄ (sodium succinate) / H ₂ O.

In this embodiment, the third metal layer 162 and the second metal layer 161 substantially completely cover the back surface 102, and can be applied to the back surface electrode of the single-sided light-receiving solar cell. The above "substantially complete coverage" means that: (1) covers the entire back surface 102, or (2) covers most of the area of the back surface 102, but a small portion is not covered by the second metal layer 161 or the third metal. The layer 162 covers, for example, near the edge of the battery substrate 10, or a marking area that remains due to, for example, alignment.

Referring to FIG. 9 , in step S400 , a first conductive layer 172 is formed on the first metal layer 171 , and a second conductive layer 163 is formed on the third metal layer 162 . The forming step of the first conductive layer 172 may be electroplating, and the first metal layer 171 is a seed layer. The forming step of the second conductive layer 163 may be electroplating, and the lamination of the second and third metal layers 161, 162 is a seed layer. In this embodiment, the first conductive layer 172 and the second conductive layer 163 are formed synchronously in the same plating process. In another embodiment, the first conductive layer 172 and the second conductive layer 163 are formed by different electroplating processes. The first metal layer 171 and the first conductive layer 172 are combined to form the front surface electrode 17, and the second and third metal layers 161 and 162 and the second conductive layer 163 are combined to form a back surface electrode 16. The material of the first conductive layer 172 and the second conductive layer 163 is, for example, copper.

The plating manners of the first and second conductive layers 172 and 163 are not intended to limit the present invention. The present invention may be used in other manners, for example, the first and second conductive layers may be formed by screen printing, physical vapor deposition (PVD) or the like. Layers 172, 163. However, the current combination of an electroless process metal layer and an electroplated metal layer is currently considered to be more commercially viable.

After the step S400, the front electrode 17 and the back electrode 16 are annealed, and then a tin layer (not shown) is formed as a protective layer of the front electrode 17 and a protective layer of the back electrode 16, to complete the single Mono-facial light-receiving solar cell 1. Alternatively, in other embodiments, a silver layer (not shown) may be separately formed as a protective layer of the front surface electrode 17 and a protective layer of the back surface electrode 16, and then the front surface electrode 17, the back surface electrode 16, and The protective layer is annealed to complete a mono-facial light-receiving solar cell 1.

For each of the pipelined embodiments of the present invention, one or both of the anti-reflective layer 13 and the passivation layer 14 may be used to cover the sidewall of the photoelectric conversion substrate 11 (not shown), and then the relevant electrode is performed. A forming step is formed to avoid electrical contact between the back electrode and the front electrode. If the sidewall of the photoelectric conversion substrate 11 is not covered by either of the anti-reflection layer 13 or the passivation layer 14, the back electric field layer (which is electrically connected to the back electrode) and the emitter may be additionally stepped after the electrode is formed. The layer (which is electrically connected to the front electrode) is electrically isolated, for example, by cutting the appropriate position of the front or back electrode or cutting off the portion of the battery substrate. For example, cleaning tanks, water jets, and air knives may be provided between the tanks depending on actual needs. In the present specification, the emitter layer is on the light-receiving surface side and the electric field layer is on the back side. However, the present invention can also be applied to the case where the emitter layer is on the back side and the electric field layer is on the light-receiving side. The former electric field layer).

The invention completes the base layer of the front electrode (for example, the first metal layer) and the base layer of the back electrode (for example, the second and third metal layers) by a simple process, and forms the first and second with a high selection ratio of the electroless plating process. The metal layer is respectively disposed on the light-receiving surface and the back surface of the opening of the anti-reflection layer and the opening of the passivation layer, and the passivation layer is covered by the third metal layer on the back surface by a low-selection electroless plating process to achieve two electroless plating processes. The effects of different characteristics of the surface of the ruthenium substrate and the surface of the anti-reflection layer/passivation layer can be respectively optimized, and the adhesion of the base layer of the back electrode to the surface of the ruthenium substrate and the surface of the anti-reflection layer/passivation layer can also be optimized respectively, and the electrode material is optimized. The choice of elasticity can also be improved.

In summary, the present invention is only described as a preferred embodiment or embodiment of the technical means for solving the problem, and is not intended to limit the scope of the invention. That is, the equivalent changes and modifications made in accordance with the scope of the patent application of the present invention or the scope of the invention are covered by the scope of the invention.

Claims (10)

 A method for manufacturing a solar cell, comprising the steps of: preparing a battery substrate, wherein the battery substrate comprises a photoelectric conversion substrate, an anti-reflection layer and a passivation layer, the photoelectric conversion substrate having a light receiving surface and a back surface, the anti-reflection a layer is located on the light receiving surface, the passivation layer is located on the back surface, the anti-reflective layer includes an anti-reflection layer opening, and the passivation layer includes a passivation layer opening; the light receiving surface exposed at the opening of the anti-reflection layer forms a first a metal layer, and a second metal layer is formed on the back surface exposed by the opening of the passivation layer, wherein the first metal layer and the second metal layer are simultaneously formed by a first electroless plating process, and the first electroless plating process is a high selectivity is compared to the electroless plating process; and a third metal layer is formed on the passivation layer, wherein the third metal layer is formed by a second electroless plating process, and the second electroless plating process is a low selectivity ratio electroless plating process .    The method of manufacturing a solar cell according to claim 1, wherein the second metal layer and the third metal layer collectively completely cover the back surface.    The method for manufacturing a solar cell according to claim 2, wherein the material of the third metal layer and the second metal layer are different.    The method for manufacturing a solar cell according to the first, second or third aspect of the invention, further comprising: forming a first conductive layer on the first metal layer and forming a second conductive layer on the third metal layer a layer, and the first conductive layer and the second conductive layer are formed synchronously in the same plating process.    The method for manufacturing a solar cell according to claim 1, wherein the first electroless plating process comprises: passing the battery substrate in a liquid immersion manner through a first pipeline processing liquid tank group; .    The method of manufacturing a solar cell according to claim 1, wherein the second electroless plating process comprises passing the battery substrate through a second pipeline processing liquid tank group.    The method for manufacturing a solar cell according to claim 6, wherein the second pipelined treatment tank group comprises a sensitizing/activating liquid tank group and a plating bath, the battery substrate being immersed in the liquid on the back side. The sensitizing/activating liquid tank group is passed through the liquid on the front side.    The method for producing a solar cell according to claim 7, wherein the battery substrate passes through the plating bath so that the liquid is immersed in the back side and the liquid is exposed on the front side.    The method of manufacturing a solar cell according to claim 7, wherein the battery substrate passes through the plating bath in such a manner that the entire substrate is immersed in a liquid.    The method of manufacturing a solar cell according to claim 6, wherein the first electroless plating process comprises passing the battery substrate through a first pipeline processing liquid tank in a back side downward direction. The group is then subjected to the second electroless plating process.