TW201545371A - Method of manufacturing solar cell - Google Patents

Abstract

A method of manufacturing a solar cell comprises: preparing a substrate and roughening a first surface of the substrate; simultaneously forming a p-n junction in the substrate and an oxide layer on the substrate; subjecting the substrate to a wet-process surface treatment; forming a passivation layer and an anti-reflective layer on the substrate; and forming an electrode on the substrate. The wet-process surface treatment includes: isolating an edge of the substrate using a first acid; neutralizing the substrate using a first alkaline solution; removing the oxide layer from the substrate using a second acid; and forming Si-OH groups on a second surface of the substrate using a second alkaline solution. The Si-OH groups are hydrophilic and stable, and can facilitate formation of a high quality passivation layer to passivative and protect the substrate. Therefore, the present invention can achieve the purpose of high photoelectric conversion efficiency.

Description

Solar cell manufacturing method

The present invention relates to a method of fabricating a solar cell, and more particularly to a method of fabricating a twinned solar cell.

In recent years, solar cells with high conversion efficiency have received increasing attention. Therefore, how to produce solar cells with high conversion efficiency and high energy output is an important issue. Among them, the solar cell of the type of Passivated Emitter and Rear Contact (PERC) can increase the photoelectric conversion efficiency to more than 20% after adopting appropriate back passivation technology. The reason is that if the surface of the silicon substrate which can generate a photovoltaic effect is passivated, for example, a passivation layer is formed on the back surface of one of the substrates, the passivation layer can be repaired and lowered. Defects on the surface or inside of the substrate, and can greatly reduce the chance of carrier recombination, thereby achieving high photoelectric conversion efficiency.

It can be seen that how to effectively reduce the recombination opportunity of the carrier at the back side of the substrate will determine the photoelectric conversion efficiency of the PERC solar cell. As for the method of forming the passivation layer, a vacuum coating method such as physical vapor deposition (PVD) or chemical vapor deposition (CVD) is generally employed. In addition to this In addition, some employers use atomic layer deposition (ALD) methods to deposit and deposit on the atomic scale to form the passivation layer, and have superior film quality.

However, in the manufacturing process of the existing PERC solar cell, especially when a diffusion doping process is formed on the substrate to form a PN junction, which is a source of photovoltaic effect, an oxide layer is formed on the substrate. Generally, the oxide layer is removed by a diluted hydrofluoric acid (HF) solution, but at the same time, the hydrofluoric acid solution also reacts with the ruthenium on the surface of the substrate to form Si on the back surface of the substrate. -H bond. Since the Si-H bond is hydrophobic, the Si-H bond is not easily reacted with the gas introduced in the process in the atomic layer deposition method, and the reaction efficiency is low, resulting in poor film formation of the passivation layer.

Regarding the problem of the above-mentioned atomic layer deposition method and the surface bonding of the substrate, since the Si-OH bond is hydrophilic, the Si-OH bond reacts with the gas in the atomic layer deposition method, so that the atomic layer deposition can be effectively utilized. The benefits of the law form a good quality passivation layer. For the above reasons, the present invention provides a method for treating Si-OH bonding on the surface of a substrate, thereby improving the passivation effect to increase the life cycle and open circuit voltage of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

Accordingly, it is an object of the present invention to provide a method of fabricating a solar cell that provides better passivation protection of the substrate, thereby improving the photoelectric conversion efficiency of the solar cell.

Thus, the method of manufacturing the solar cell of the present invention comprises: Providing a substrate, the substrate includes an opposite first surface and a second surface, and roughening the first surface of the substrate; forming a PN junction in the substrate, and forming an oxide layer on the substrate; The substrate is subjected to a wet process surface treatment; a passivation layer and an anti-reflection layer are formed on the substrate; and an electrode is formed on the substrate. Wherein the wet process surface treatment comprises: insulating the edge of the substrate with a first acid solution; neutralizing the substrate with a first alkali solution; and removing the oxide layer on the substrate by using a second acid solution And forming a Si-OH bond on the second surface of the substrate using a second lye.

The effect of the present invention is that the second surface is used to form Si-OH bonds on the second surface, and the Si-OH bond is hydrophilic and relatively stable, which contributes to the formation of the passivation layer of excellent quality. The substrate can be repaired by the passivation layer to reduce defects on the surface or the inside of the substrate, and the opportunity for recombination of the carrier can be greatly reduced, thereby improving the passivation effect to increase the life cycle and the open circuit voltage of the solar cell, thereby achieving high photoelectric conversion efficiency. .

1‧‧‧Solar battery

11‧‧‧Substrate

110‧‧‧PN junction

111‧‧‧ first surface

112‧‧‧ second surface

113‧‧‧ side torus

114‧‧ ‧ emitter layer

12‧‧‧ Passivation layer

13‧‧‧Anti-reflective layer

14‧‧‧Electrode

141‧‧‧First electrode

142‧‧‧second electrode

5‧‧‧Oxide

6‧‧‧Doped layer

7‧‧‧Oxide layer

81~85‧‧‧Steps

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: Figure 1 is a side elevational view showing one of the preferred embodiments of the manufacturing method of the present invention. FIG. 2 is a schematic flow chart of one step of the manufacturing method; and FIG. 3 is a block flow diagram of one step of the manufacturing method.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 1, a preferred embodiment of the manufacturing method of the present invention is used to manufacture a solar cell 1. In the embodiment, the solar cell 1 is exemplified by a battery type of a Passivated Emitter and Rear Contact (PERC). But not limited to this. The solar cell 1 comprises a substrate 11, a passivation layer 12, an anti-reflection layer 13, and an electrode 14.

The substrate 11 can be a p-type or n-type single crystal or polycrystalline germanium substrate, and includes a first light-receiving first surface 111, a second surface 112 opposite to the first surface 111, and a first surface 111 connected thereto. A side annular surface 113 that is circumferential with the second surface 112 and has a circumferential shape, and an emitter layer 114 formed in the first surface 111. The first surface 111 has a roughened structure, thereby reducing the reflectance of the incident light to increase the amount of incident light. The emitter layer 114 is disposed in the first surface 111 in conjunction with the undulation of the first surface 111, and forms a PN junction 110 with the substrate 11 to generate a photovoltaic effect.

The passivation layer 12 is disposed on the second surface 112 and can be used for repairing and reducing defects on the surface or inside of the substrate 11, and can reduce the Surface Recombination Velocity (SRV) and improve the photoelectric conversion efficiency. The anti-reflective layer 13 is disposed on the first surface 111 in conjunction with the undulation of the first surface 111, and can be used to increase the amount of light incident and reduce the surface recombination rate of the carrier.

The electrode 14 includes a first electrode 141 and a second electrode 142. The first electrode 141 is located on the anti-reflection layer 13 and passes through the anti-reflection layer 13 to contact the first surface 111 of the substrate 11; the second electrode 142 is located on the passivation layer 12 and passes through the passivation layer 12 contacts the second surface 112 of the substrate 11.

Referring to Figures 1, 2 and 3, a preferred embodiment of the manufacturing method of the present invention comprises the following steps: Step 81: providing the substrate 11 and roughening the first surface 111 of the substrate 11 to make the first surface 111 rough Structure.

Step 82: The PN junction 110 is formed in the substrate 11, and an oxide layer 7 is formed on the substrate 11. In this embodiment, the substrate 11 is a p-type single crystal germanium substrate. Therefore, in step 82, the first surface 111 is subjected to a phosphorus diffusion doping process by using a high temperature furnace, so that the first surface 111 is A doped n-type semiconductor is formed therein, that is, the emitter layer 114 of the present embodiment. At the same time, a doped layer 6 is formed within the second surface 112 and the side annulus 113 (collectively referred to as the edge of the substrate 11) due to diffusion of phosphorus in the high temperature furnace. In addition, an outer oxide layer 7 is formed on the outer side of the substrate 11 (that is, the outer surface of the emitter layer 114 and the outer side of the doped layer 6), and the material of the oxide layer 7 is a bismuth glass containing phosphorus (or Phosphorus Silicon Glass (PSG).

In addition, in the implementation, the substrate 11 may also be an n-type single crystal germanium substrate. In step 82, the first surface 111 is subjected to a boron diffusion doping process to make the first surface 111. A doped p-type semiconductor is formed, that is, the emitter layer 114. The material of the oxide layer 7 formed on the outer periphery of the periphery of the substrate 11 is a neodymium glass containing boron. (or Boron Silicon Glass, or BSG for short).

Step 83: Performing a wet process surface treatment on the substrate 11 includes the following steps: Step 831: Insulating the edge of the substrate 11 with a first acid solution. Since the doping layer 6 is electrically conductive, the solar cell 1 is liable to cause a short circuit or a leakage current problem. Therefore, in the step 831, the first acid solution is brought into contact with the second surface 112 and the side annulus of the substrate 11. 113, without contacting the first surface 111 of the substrate 11, thereby removing the doped layer 6 and the oxide layer 7 on the second surface 112 and the side ring surface 113, and remaining on the first surface The oxide layer 7 on 111. This step can be generally referred to as an edge Isolation process of the edge of the substrate 11 (that is, the second surface 112 and the side ring surface 113) to avoid short circuit or leakage current. In practice, the first acid liquid may specifically be a hydrofluoric acid (HF) solution, a nitric acid (HNO ₃ ) solution, a sulfuric acid (H ₂ SO ₄ ) solution, or any combination thereof.

Step 832: neutralizing the substrate 11 with a first lye. After the first acid solution is applied, an oxide 5 such as a black spot or a brown spot may be generated on the second surface 112 and the side ring surface 113, or a small amount of the doped layer 6 may not be removed. Therefore, in this step 832, the substrate 11 is neutralized by the first alkali solution to remove the oxide 5, and the doping layer 6 on the second surface 112 and the side ring surface 113 is completely removed. In order to avoid the problem of short circuit or leakage current of the solar cell 1, the second surface 112 and the side annular surface 113 of the substrate 11 are made relatively flat. In practice, the first alkali liquid may specifically be a sodium hydroxide (NaOH) solution, and the first alkali liquid The pH is greater than 9.

In addition, since the rate of etching the ruthenium layer and the doping layer 6 is faster than the rate of etching the oxide layer 7, the substrate 11 can be entirely immersed in the first base in this step 832. In the liquid, it can be protected by the oxide layer 7 at this time to prevent the roughened structure of the first surface 111 from being broken.

Step 833: removing the oxide layer 7 on the first surface 111 of the substrate 11 by using a second acid solution in an environment of a temperature of 25-27 °C. In practice, the second acid solution is a hydrofluoric acid solution, and the concentration of the second acid solution is about 5% by weight.

Step 834: Forming a second surface 112 of the substrate 11 with a second lye to form a Si-OH bond. Since the second acid solution acts on all surfaces of the substrate 11, the second acid solution removes the oxide layer 7 on the first surface 111, and the second acid solution also causes the second surface. 112 reacts with the crucible on the side annulus 113 such that the second surface 112 forms a Si-H bond with the side annulus 113. Therefore, in this step 834, the second lye is reacted with the Si-H bond to etch the substrate 11 in an environment having a temperature of 5 to 95 ° C, and further on the second surface 112 and the side. A Si-OH bond is formed on the toroid 113. In practice, the second lye may specifically be a sodium hydroxide solution, a potassium hydroxide (KOH) solution or a tetramethylammonium hydroxide (TMAH) solution, and the concentration of the second lye is 5 to 60% by weight.

Further, the substrate 11 is etched and the etching depth is less than 5 μm, and the etching depth is calculated by the weight method of the substrate 11. In this embodiment, the etching depth is preferably less than 5 μm, that is, As long as the second lye has etched the second surface 112 and the side annulus 113, thereby forming a Si-OH bond on the second surface 112 and the side annulus 113, the invention can be achieved. Therefore, when the etching depth is higher than 5 μm, the amount of the substrate 11 which is etched away is too high, thereby reducing the volume of the substrate 11 and reducing the photocurrent yield of the solar cell 1.

In the step 834, the working temperature is preferably 5 to 95 ° C, and when the working temperature is lower than 5 ° C, the reaction speed of the second alkali liquid is too slow to reduce the production efficiency; when the working temperature is higher than 95 ° C, the second alkali is used. The reaction speed of the liquid is too fast to easily overetch the substrate 11, which will excessively reduce the volume of the substrate 11 and reduce the photocurrent yield of the solar cell 1.

The concentration of the second lye is preferably 5 to 60 wt%, and when the concentration of the second lye is less than 5 wt%, the reaction rate of the second lye is too slow to reduce the production efficiency; the second lye is When the concentration is higher than 60% by weight, the reaction speed of the second alkali liquid is too fast and the substrate 11 is easily over-etched, resulting in a decrease in the volume of the substrate 11 and a decrease in the photocurrent yield of the solar cell 1.

Step 84: forming the passivation layer 12 and the anti-reflection layer 13 on the substrate 11. In this embodiment, after the step 834 is completed, the passivation layer 12 is deposited on the second surface 112 of the substrate 11 by atomic layer deposition (ALD), and the material of the passivation layer 12 is, for example, aluminum oxide (AlO _X ); The anti-reflective layer 13 is deposited on the first surface 111 of the substrate 11 by plasma-assisted chemical vapor deposition (PECVD), and the material of the anti-reflective layer 13 is, for example, tantalum nitride (SiN _X ).

Further, in the process of depositing the passivation layer 12 by atomic layer deposition, the embodiment is specifically a gas which is fed with trimethylaluminum (TMA). The trimethylaluminum is reacted with the Si-OH bond of the substrate 11, whereby aluminum and oxygen are deposited on the atomic scale stack to form the passivation layer 12 of alumina.

Step 85: The electrode 14 is formed on the substrate 11. Specifically, the conductive paste can be separately printed on the anti-reflective layer 13 and the passivation layer 12, and the conductive paste is separately sintered into the first electrode 141 and the second electrode 142 by heat treatment. 141 will burn through the anti-reflective layer 13 to contact the first surface 111, and the second electrode 142 will burn through the passivation layer 12 to contact the second surface 112. In practice, the specific structure of the first electrode 141 and the second electrode 142 need not be limited, as long as it can be used to derive the electrical energy generated by the substrate 11.

As apparent from the above description, in the manufacturing method of the present invention, in the step 834, the second surface 112 is formed into a Si-OH bond by the second alkali solution, and the Si-OH bond is hydrophilic and stable. In the atomic layer deposition method of 84, the Si-OH bond can produce a higher reaction efficiency with the gas of trimethylaluminum (TMA), and can be deposited on the atomic scale to form the passivation layer 12 of excellent quality. Therefore, the second surface 112 of the substrate 11 of the solar cell 1 produced by the manufacturing method of the present invention can be repaired through the passivation layer 12, reducing surface or internal defects, and greatly reducing the chance of carrier recombination. The passivation effect is increased to increase the life cycle and open circuit voltage of the solar cell 1 to achieve high photoelectric conversion efficiency.

It is further noted that the manufacturing method of the present invention is carried out in an environment of a temperature of 5 to 95 ° C in the step 834, and the low temperature process is in the flow. The process is relatively simple, and steps such as heating and cooling can be omitted, thereby improving production efficiency and reducing equipment costs. In addition, it is easy to form a defect in the substrate 11 and increase the composite probability of the carrier in the substrate 11 with respect to the high temperature process. The present invention can maintain the material quality of the substrate 11 by the low temperature process. The doping depth and range of the PN junction 110 formed in step 82 are prevented from being affected, thereby providing the substrate 11 with better service life and stability. Therefore, the above-described improvement in the properties of the substrate 11 is combined with the excellent passivation effect of the passivation layer 12, so that the photoelectric conversion efficiency of the solar cell 1 can be further improved.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

1‧‧‧Solar battery

11‧‧‧Substrate

110‧‧‧PN junction

111‧‧‧ first surface

112‧‧‧ second surface

113‧‧‧ side torus

114‧‧ ‧ emitter layer

12‧‧‧ Passivation layer

13‧‧‧Anti-reflective layer

14‧‧‧Electrode

141‧‧‧First electrode

142‧‧‧second electrode

5‧‧‧Oxide

6‧‧‧Doped layer

7‧‧‧Oxide layer

Claims (10)

A method of manufacturing a solar cell, comprising: providing a substrate, the substrate includes an opposite first surface and a second surface, and roughening the first surface of the substrate; forming a PN junction in the substrate, and the Forming an oxide layer on the substrate; performing a wet process surface treatment on the substrate comprises: insulating the edge of the substrate with a first acid solution; neutralizing the substrate with a first alkali solution; using a second An acid solution removes the oxide layer on the substrate; and a second alkali solution is used to form a Si-OH bond on the second surface of the substrate; a passivation layer and an anti-reflection layer are formed on the substrate; and the substrate is formed on the substrate An electrode is formed on the upper surface. The method for producing a solar cell according to claim 1, wherein the second alkali solution is a sodium hydroxide solution, a potassium hydroxide solution or a tetramethylammonium hydroxide solution. The method for producing a solar cell according to claim 1, wherein the concentration of the second alkali solution is 5 to 60% by weight. The method for producing a solar cell according to claim 1, wherein the second surface is Si-OH-bonded by the second alkali solution in an environment having a temperature of 5 to 95 °C. The method of manufacturing a solar cell according to claim 1, wherein the second alkali liquid causes the second surface to form a Si-OH bond, the substrate Etched and etched to a depth of less than 5 μm. The method of manufacturing a solar cell according to claim 1, wherein the passivation layer is deposited on the second surface of the substrate by an atomic layer deposition method. The method of manufacturing a solar cell according to claim 1, wherein the antireflection layer is deposited on the first surface of the substrate by plasma assisted chemical vapor deposition. The method for manufacturing a solar cell according to claim 1, wherein the first acid solution is a hydrofluoric acid solution, a nitric acid solution, a sulfuric acid solution, or any combination thereof; the first alkali solution is a sodium hydroxide solution. The second acid solution is a hydrofluoric acid solution. The method of manufacturing a solar cell according to claim 1, wherein the passivation layer is deposited on the second surface of the substrate after the second surface is formed into a Si-OH bond by the second alkali solution. The method of manufacturing a solar cell according to claim 9, wherein the passivation layer is deposited on the second surface by an atomic layer deposition method.