TW201616664A - Solar cell and method for manufacturing the same - Google Patents

Abstract

A solar cell includes a semiconductor substrate, a boron back surface field (BSF) layer, a passivation layer, a back electrode layer and an aluminum local BSF layer. The semiconductor substrate has a front surface and a back surface opposite to each other. The boron BSF layer is disposed beneath the back surface in the semiconductor substrate. The passivation layer is disposed over the boron BSF layer and has an opening through the passivation layer. The back electrode layer is disposed in the opening. The aluminum local BSF layer is disposed beneath the opening in the semiconductor substrate and in contact with the boron BSF layer and the back electrode layer.

Description

Solar cell and method of manufacturing same

The present invention relates to a bismuth based solar cell and a method of fabricating the same.

Solar cells are an environmentally friendly source of energy that converts solar energy directly into electricity. Since no greenhouse gases such as carbon dioxide are generated during power generation, there is no environmental pollution. When light is irradiated on a solar cell, the characteristics of its optoelectronic semiconductor are utilized to cause photons to interact with free electrons in the conductor or semiconductor to generate a current. At present, existing solar cells can be classified into germanium-based semiconductor solar cells, dye-sensitized solar cells, and organic material solar cells depending on the main material. Among them, the photoelectric conversion efficiency of the germanium-based semiconductor solar cell is better, but there is still room for improvement.

Silicon-based semiconductor solar cells typically have a comprehensive aluminum back surface field (BSF) layer. However, the recombination speed of the aluminum back field layer of such a ruthenium-based solar cell is too fast, resulting in a decrease in battery conversion efficiency. In order to solve this problem, a germanium-based solar cell having a partial back surface field layer has been developed. However, the conductivity of the back side of such bismuth-based solar cells is poor. Therefore, the purpose There is a need for a novel solar cell and a method of manufacturing the same in order to improve the above problems.

It is an object of the present invention to provide a solar cell comprising a boron back surface field layer, an aluminum partial back surface field layer, and a passivation layer. The boron back field layer and the aluminum partial back field layer can improve the back surface conductivity and effectively increase the collection efficiency of the carrier; the passivation layer can improve the back passivation effect, thereby improving the battery conversion efficiency of the solar cell, and comprehensively solving the problems faced by the prior art. problem.

The invention provides a solar cell comprising a semiconductor substrate, a boron back surface field layer, a passivation layer, a back electrode layer and an aluminum partial back surface field layer. The semiconductor substrate has a front side and a back side oppositely disposed. The boron back surface layer is located within the semiconductor substrate below the back side. The passivation layer is over the boron back field layer and the passivation layer has an opening through the passivation layer. The back electrode layer is located within the opening. The aluminum partial back field layer is located within the semiconductor substrate below the opening and contacts the boron back surface layer and the back electrode layer.

According to an embodiment of the invention, the back electrode layer further covers the passivation layer.

According to an embodiment of the invention, the passivation layer is not completely covered by the back electrode layer.

In accordance with an embodiment of the invention, the boron back surface field layer has an opening, and the opening of the boron back surface field layer is substantially aligned with the opening of the passivation layer.

According to an embodiment of the invention, the passivation layer comprises a first passivation layer and a second passivation layer. The first passivation layer contacts the boron back surface field layer, and the first passivation layer comprises aluminum oxide, cerium oxide, cerium oxynitride or a combination thereof. The second passivation layer is located at Above the passivation layer, the second passivation layer comprises tantalum nitride.

According to an embodiment of the invention, the solar cell further includes a first doped layer, a second doped layer, and a front electrode layer. The first doped layer is located within the semiconductor substrate below the front side. The second doped layer is located within the semiconductor substrate below the front side and adjacent to the first doped layer. The first doped layer and the second doped layer have the same conductivity type, and the doping concentration of the second doped layer is greater than the doping concentration of the first doped layer. The front electrode layer contacts the second doped layer.

The invention further provides a method for manufacturing a solar cell, comprising: providing a semiconductor substrate having a front surface and a back surface oppositely disposed; forming a boron back surface field layer in the semiconductor substrate under the back surface; forming a passivation layer Above the boron back field layer; forming an opening through the passivation layer; providing aluminum paste in the opening; and sintering the aluminum paste to form an aluminum partial back surface field layer in the semiconductor substrate below the opening.

In accordance with an embodiment of the invention, the step of forming the boron back surface field layer in the semiconductor substrate below the back side is by diffusion or ion implantation of boron into the semiconductor substrate under the back side.

According to an embodiment of the invention, the step of forming a boron back surface field layer in the semiconductor substrate below the back surface comprises: forming a boron-containing passivation material layer over the back surface of the semiconductor substrate, the boron-containing passivation material layer comprising boron and a passivation material; The boron of the boron-containing passivation material layer is diffused into the semiconductor substrate under the back surface to form a boron back surface field layer.

In accordance with an embodiment of the invention, the step of diffusing the boron of the boron-containing passivation material layer to the underlying semiconductor substrate is performed simultaneously with the step of sintering the aluminum paste.

According to an embodiment of the invention, the step of forming a boron back surface field layer in the semiconductor substrate under the back surface comprises: forming a boron source layer over the back surface of the semiconductor substrate; diffusing boron of the boron source layer to the semiconductor substrate under the back surface Inside to form a boron back surface field; and to remove the boron source layer.

According to an embodiment of the invention, the boron source layer comprises borosilicate, borosilicate glass or a combination thereof.

In accordance with an embodiment of the invention, the method of fabrication further includes diffusing phosphorus into the semiconductor substrate below the front side.

In accordance with an embodiment of the invention, the step of diffusing the boron of the boron source layer into the semiconductor substrate below the backside and the step of diffusing the phosphor to the semiconductor substrate below the front side are performed in the same heat treatment procedure.

110‧‧‧Semiconductor substrate

110a‧‧‧ positive

110b‧‧‧Back

120‧‧ ‧ boron back field layer

120a‧‧‧ openings

130‧‧‧ Passivation layer

130a‧‧‧ openings

132‧‧‧First passivation layer

132a‧‧‧ openings

134‧‧‧second passivation layer

134a‧‧‧ openings

140‧‧‧Back electrode layer

142‧‧‧Aluminum adhesive

150‧‧‧Aluminum partial back field layer

160‧‧‧Doped layer

162‧‧‧First doped layer

164‧‧‧Second doped layer

170‧‧‧ front electrode layer

172‧‧‧Silver glue

180‧‧‧Anti-reflective layer

BPL‧‧‧ boron-containing passivation material layer

BSL‧‧‧ boron source layer

O‧‧‧ openings

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

2 is a schematic cross-sectional view showing a solar cell according to another embodiment of the present invention.

3A-3F are schematic views showing respective process stages of a method of manufacturing a solar cell according to an embodiment of the present invention.

4A-4F are schematic views showing respective process stages of a method of fabricating a solar cell according to another embodiment of the present invention.

5A-5F are schematic views showing respective process stages of a method of fabricating a solar cell according to still another embodiment of the present invention.

The description of the embodiments of the present invention is intended to be illustrative and not restrictive. The embodiments disclosed herein may be combined or substituted with each other in an advantageous manner, and other embodiments may be added to an embodiment without further description or description.

As used herein, "about", "about" or "roughly" is used to modify the amount of any slight change, but such slight changes do not alter its nature. In the embodiment, unless otherwise stated, the error range for the value modified by "about", "about" or "approximately" is generally allowed to be within 20%, preferably 10%. Within, and more preferably within five percent.

As described in the prior art, a germanium-based solar cell having a full aluminum back surface layer has a low composite conversion speed, resulting in low battery conversion efficiency, while a germanium-based solar cell having a partial back surface field layer has poor backside conductivity. The present invention therefore provides a solar cell comprising a boron back surface field layer, an aluminum partial back surface field layer, and a passivation layer. The boron back field layer and the aluminum partial back field layer can improve the back surface conductivity and effectively increase the collection efficiency of the carrier; the passivation layer can improve the back passivation effect, thereby improving the battery conversion efficiency of the solar cell, thereby comprehensively solving the problems faced by the prior art. .

1 is a schematic cross-sectional view showing a solar cell according to an embodiment of the present invention. The solar cell comprises a semiconductor substrate 110 and a boron back field Layer 120, passivation layer 130, back electrode layer 140, and aluminum partial back surface field layer 150.

The semiconductor substrate 110 has a front surface 110a and a back surface 110b disposed opposite each other. Herein, the lower side of the back surface 110b shown in FIG. 1 is defined as a side facing the semiconductor substrate 110, and the upper side of the back surface 110b is defined as a side facing away from the semiconductor substrate 110, to clearly define the boron back surface field layer 120. The relative positions of the passivation layer 130, the back electrode layer 140, and the aluminum partial back surface field layer 150.

The semiconductor substrate 110 can be a tantalum substrate, such as a single crystal germanium substrate, a polycrystalline germanium substrate, or an amorphous germanium substrate. In one embodiment, the semiconductor substrate 110 is a P-type germanium substrate. In one embodiment, the front side 110a of the semiconductor substrate 110 is a roughened surface to reduce the reflectivity of incident light.

The boron back surface field layer 120 is located within the semiconductor substrate 110 below the back surface 110b. In the present embodiment, the boron back surface field layer 120 has an opening 120a extending through the boron back surface field layer 120. Of course, the boron back surface field layer 120 may have a plurality of openings 120a separated from each other and through the boron back surface field layer 120. In one embodiment, the boron back surface field layer 120 is formed using high temperature diffusion or ion implantation. In one embodiment, the boron back surface field layer 120 has a dopant concentration of from about 10 ¹⁵ atoms/cm ³ to about 5×10 ²² atoms/cm ³ . In one embodiment, the boron back surface field layer 120 has a resistance of from about 10 ohms/square to about 200 ohms/square.

The passivation layer 130 is located above the boron back surface field layer 120. The passivation layer 130 has an opening 130a penetrating the passivation layer 130. Of course, the passivation layer 130 may also have a plurality of openings 130a separated from each other and penetrating the passivation layer 130. In the present embodiment, the opening 130a of the passivation layer 130 is substantially aligned with the boron back surface field layer 120. Opening 120a. In an embodiment, the material of the passivation layer 130 comprises hafnium oxide, tantalum nitride, hafnium oxynitride, aluminum oxide, other suitable materials, or a combination thereof.

In an embodiment, the passivation layer 130 includes a first passivation layer 132 and a second passivation layer 134. The first passivation layer 132 contacts the boron back surface field layer 120, and the first passivation layer 132 comprises aluminum oxide, tantalum oxide, or a combination thereof. The second passivation layer 134 is located above the first passivation layer 132, and the second passivation layer 134 includes tantalum nitride. The first passivation layer 132 and the second passivation layer 134 may have an opening 132a and an opening 134a, respectively, and the opening 132a and the opening 134a constitute an opening 130a. The second passivation layer 134 may be used to protect the first passivation layer 132 from deterioration or corrosion of the first passivation layer 132 due to contact with the back electrode layer 140. In addition, the second passivation layer 134 may have a function of optical reflection, for example, reflecting long-wavelength light back.

The back electrode layer 140 is located within the opening 130a. In the present embodiment, the back electrode layer 140 is located in the opening 130a and the opening 120a. In an embodiment, back electrode layer 140 comprises any suitable metallic material, such as aluminum. In one embodiment, the back electrode layer 140 is obtained by sintering aluminum paste. It should be noted that in the present embodiment, the passivation layer 130 is not completely covered by the back electrode layer 140, and the solar cell has a large light receiving area, which can increase the absorption of light.

The aluminum partial back surface field layer 150 is located within the semiconductor substrate 110 below the opening 120a and contacts the boron back surface field layer 120 and the back electrode layer 140. In one embodiment, the back electrode layer 140 contains aluminum, and the aluminum ions can form an aluminum-bismuth alloy with germanium in the semiconductor substrate 110 at a high temperature to form an aluminum partial back surface field layer 150. In one embodiment, the dopant concentration of the aluminum partial back surface field layer 150 is greater than the dopant concentration of the boron back surface field layer 120. In one embodiment, the aluminum partial back surface field layer 150 has a dopant concentration of from about 10 ¹⁵ atoms/cm ³ to about 5 x 10 ²² atoms/cm ³ .

Herein, the lower side of the front surface 110a of the semiconductor substrate 110 is defined as a side facing the semiconductor substrate 110, and the upper side of the front surface 110a of the semiconductor substrate 110 is defined as a side facing away from the semiconductor substrate 110. In an embodiment, the solar cell further includes a first doped layer 162, a second doped layer 164, and a front electrode layer 170. The first doped layer 162 is located within the semiconductor substrate 110 below the front side 110a. The second doped layer 164 is located within the semiconductor substrate 110 below the front side 110a and is adjacent to the first doped layer 162. The first doped layer 162 and the second doped layer 164 have the same conductivity type. In an embodiment, the conductivity patterns of the first doping layer 162 and the second doping layer 164 are opposite to those of the semiconductor substrate 110. In an embodiment, the front electrode layer 170 comprises any suitable metallic material, such as silver. In one embodiment, the front electrode layer 170 is obtained by sintering silver paste.

In one embodiment, the dopant concentration of the second doped layer 164 is greater than the dopant concentration of the first doped layer 162. In one embodiment, the dopant concentration of the first doped layer 162 is from about 10 ¹⁵ atoms/cm ³ to about 5×10 ²² atoms/cm ³ . In one embodiment, the dopant concentration of the second doped layer 164 is from about 10 ¹⁵ atoms/cm ³ to about 5×10 ²² atoms/cm ³ . In one embodiment, the first doped layer 162 has a resistance of from about 10 ohms/square to about 200 ohms/square. In one embodiment, the second doped layer 164 has a resistance of from about 10 ohms/square to about 200 ohms/square. That is, the resistance of the second doping layer 164 is lower than that of the first doping layer 162, and thus the front electrode layer 170 may contact the second doping layer 164 to lower the contact resistance.

In an embodiment, the solar cell further includes an anti-reflection layer 180 disposed above the first doped layer 162 and the second doped layer 164 to reduce the reflectivity of the incident light. In an embodiment, the material of the anti-reflective layer 180 comprises tantalum nitride.

2 is a schematic cross-sectional view showing a solar cell according to another embodiment of the present invention. The difference between FIG. 2 and FIG. 1 is that the back electrode layer 140 of the solar cell of FIG. 2 further covers the passivation layer 130. In other words, the back electrode layer 140 completely covers the passivation layer 130.

Several methods of manufacturing the above solar cell will be described below. 3A-3F are schematic views showing respective process stages of a method of manufacturing a solar cell according to an embodiment of the present invention. First, as shown in FIG. 3A, a semiconductor substrate 110 is provided. The semiconductor substrate 110 has a front surface 110a and a back surface 110b disposed opposite each other.

Then, as shown in FIG. 3B, boron is driven into the semiconductor substrate 110 under the back surface 110b by diffusion or ion implantation to form a boron back surface field layer 120. Before diffusion or ion implantation of boron, a mask (not shown) may be formed to cover the front surface 110a to prevent boron from entering the semiconductor substrate 110 under the front surface 110a. After the boron back surface field layer 120 is formed, the accompanying formed boron germanium glass (not shown) and the mask can be removed.

As shown in FIG. 3C, the front surface 110a is subjected to a roughening process, and then the doped layer 160 is formed in the semiconductor substrate 110 below the front surface 110a. In detail, a mask (not shown) may be formed before the roughening process. The back side 110b protects the boron back surface field layer 120. A roughening process is then performed to form a rough front surface 110a. The dopant is diffused into the semiconductor substrate 110 under the front surface 110a to form a doped layer 160. The dopant can be, for example, phosphorus or other suitable dopant.

As shown in FIG. 3D, a passivation layer 130 is formed over the boron back surface field layer 120. In this embodiment, the first passivation layer 132 and the second passivation layer 134 are sequentially formed over the boron back surface field layer 120. In an embodiment, the first passivation layer 132 comprises aluminum oxide, tantalum oxide or a combination thereof, and the second passivation layer 134 comprises tantalum nitride, but is not limited thereto. The first passivation layer 132 and the second passivation layer 134 may be formed by chemical vapor deposition. In addition, an anti-reflection layer 180 may be formed over the doped layer 160 to reduce the reflectance of incident light. In an embodiment, the material of the anti-reflective layer 180 comprises tantalum nitride.

As shown in FIG. 3E, the opening O is formed to penetrate the passivation layer 130. In detail, the opening O penetrates the first passivation layer 132, the second passivation layer 134, and the boron back surface field layer 120. For example, the opening O can be formed using a laser or other suitable means.

As shown in FIG. 3F, an aluminum paste 142 is disposed in the opening O. Silver paste 172 may also be formed on anti-reflective layer 180 before or after aluminum paste 142 is formed. Finally, a sintering step is performed to sinter the aluminum paste 142 and the silver paste 172 to form an aluminum partial back surface field layer 150, a back electrode layer 140 and a front electrode layer 170 as shown in FIG. 2, and the aluminum partial back surface layer 150 is located at the opening. In the semiconductor substrate 110 under the 130a, 120a.

4A-4F are schematic views showing respective process stages of a method of fabricating a solar cell according to an embodiment of the present invention. First, as in the first As shown in FIG. 4A, a semiconductor substrate 110 is provided. The semiconductor substrate 110 has a front surface 110a and a back surface 110b disposed opposite each other.

Then, as shown in FIG. 4B, the front surface 110a is subjected to a roughening process, and a boron source layer BSL is formed over the back surface 110b of the semiconductor substrate 110. In an embodiment, the boron source layer BSL comprises borosilicate, borosilicate glass, or a combination thereof. Boron glue can be formed by coating or printing. Boron bismuth glass can be formed by chemical vapor deposition, such as atmospheric pressure chemical vapor deposition (APCVD).

Next, as shown in FIG. 4B-4C, the boron of the boron source layer BSL is diffused into the semiconductor substrate 110 under the back surface 110b to form the boron back surface field layer 120 in the semiconductor substrate 110 under the back surface 110b. After the boron back surface field layer 120 is formed, the boron source layer BSL is removed. In one embodiment, the step of diffusing the boron of the boron source layer BSL to the semiconductor substrate 110 under the back surface 110b and diffusing the phosphor to the semiconductor substrate 110 under the front surface 110a to form the doped layer 160 are subjected to the same heat treatment process. In progress. In this way, the process steps can be reduced. Specifically, the structure as shown in FIG. 4B can be placed in a high temperature furnace tube, and phosphorus oxychloride (POCl ₃ ) and oxygen gas can be introduced to form a doped layer in the semiconductor substrate 110 under the front surface 110a. 160, a boron back surface field layer 120 is formed in the semiconductor substrate 110 under the back surface 110b. Finally, the boron source layer BSL is removed, as well as the phosphorous glass (not shown) produced when the phosphorus is diffused.

As shown in FIG. 4D, a passivation layer 130 is formed over the boron back surface field layer 120. In this embodiment, the first passivation layer 132 and the second passivation layer 134 are sequentially formed over the boron back surface field layer 120. In addition, it can form anti-reverse The shot layer 180 is over the doped layer 160 to reduce the reflectivity of the incident light. In an embodiment, the anti-reflective layer 180 comprises tantalum nitride.

As shown in FIG. 4E, the opening O is formed to penetrate the passivation layer 130. In detail, the opening O penetrates the first passivation layer 132, the second passivation layer 134, and the boron back surface field layer 120. For example, the opening O can be formed using a laser or other suitable means.

As shown in FIG. 4F, an aluminum paste 142 is disposed in the opening O. Silver paste 172 may also be formed on the anti-reflective layer 180. Finally, a sintering step is performed to sinter the aluminum paste 142 and the silver paste 172 to form an aluminum partial back surface field layer 150, a back electrode layer 140 and a front electrode layer 170 as shown in FIG. 2, and the aluminum partial back surface layer 150 is located at the opening. In the semiconductor substrate 110 under the 130a, 120a.

5A-5F are schematic views showing respective process stages of a method of manufacturing a solar cell according to an embodiment of the present invention. First, as shown in FIG. 5A, a semiconductor substrate 110 is provided. The semiconductor substrate 110 has a front surface 110a and a back surface 110b disposed opposite each other.

Then, as shown in FIG. 5B, the front surface 110a is subjected to a roughening process, and the doped layer 160 is formed in the semiconductor substrate 110 below the front surface 110a. For example, the dopant layer 160 can be formed by diffusing the dopant into the semiconductor substrate 110 under the front surface 110a using high temperature diffusion.

As shown in FIG. 5C, a boron-contained passivation layer BPL is formed over the back surface 110b of the semiconductor substrate 110, and then a second passivation layer 134 is formed over the boron-containing passivation material layer BPL. Boron-containing passivation material layer BPL contains boron and passivation material material. In one embodiment, a boron-containing passivation material layer BPL is formed over the back surface 110b by a coating process, such as a spray coating method. In an embodiment, the passivation material comprises, but is not limited to, aluminum oxide, cerium oxide, cerium oxynitride or a combination thereof. In an embodiment, the second passivation layer 134 comprises tantalum nitride. In addition, an anti-reflection layer 180 may be formed over the doped layer 160 to reduce the reflectance of incident light.

As shown in FIG. 5D, the opening O is formed to penetrate the second passivation layer 134 and the boron-containing passivation material layer BPL. For example, the opening O can be formed using a laser or other suitable means.

As shown in FIG. 5E, an aluminum paste 142 is disposed in the opening O. Silver paste 172 may also be formed on the anti-reflective layer 180. Then, a sintering step is performed to sinter the aluminum paste 142 and the silver paste 172 to form an aluminum partial back surface field layer 150, a back electrode layer 140 and a front electrode layer 170 as shown in FIG. 5F, and the aluminum partial back surface layer 150 is located at the opening. Inside the semiconductor substrate 110 under O. It should be noted that when the aluminum paste 142 and the silver paste 172 are sintered, the boron of the boron-containing passivation material layer BPL as shown in FIG. 5E diffuses into the semiconductor substrate 110 under the back surface 110b to form a 5F. The boron back surface field layer 120 is shown. After the boron of the boron-containing passivation material layer BPL is released, the first passivation layer 132 as shown in FIG. 5F is formed. That is to say, in the present embodiment, the boron-containing passivation material layer BPL is not required to be removed, so that the process steps can be reduced.

According to the above, the manufacturing method of the present invention can produce the boron back surface field layer and the aluminum partial back surface field layer without using the lithography etching technology of the semiconductor process. Therefore, the manufacturing method of the present invention can greatly reduce the manufacturing process relative to the manufacturing method for forming a solar cell by using a lithography etching technique. This is extremely practical.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

110‧‧‧Semiconductor substrate

110a‧‧‧ positive

110b‧‧‧Back

120‧‧ ‧ boron back field layer

120a‧‧‧ openings

130‧‧‧ Passivation layer

130a‧‧‧ openings

132‧‧‧First passivation layer

132a‧‧‧ openings

134‧‧‧second passivation layer

134a‧‧‧ openings

140‧‧‧Back electrode layer

150‧‧‧Aluminum partial back field layer

160‧‧‧Doped layer

162‧‧‧First doped layer

164‧‧‧Second doped layer

170‧‧‧ front electrode layer

180‧‧‧Anti-reflective layer

Claims (6)

A solar cell comprising: a semiconductor substrate having a front surface and a back surface opposite; a boron back surface layer in the semiconductor substrate below the back surface; a passivation layer over the boron back surface layer The passivation layer has an opening extending through the passivation layer; a back electrode layer is located in the opening; and an aluminum partial back surface field layer in the semiconductor substrate under the opening and contacting the boron back surface layer and the back surface Electrode layer. The solar cell of claim 1, wherein the back electrode layer further covers the passivation layer. The solar cell of claim 1, wherein the passivation layer is not completely covered by the back electrode layer. The solar cell of claim 1, wherein the boron back surface field layer has an opening, the opening of the boron back surface field layer being substantially aligned with the opening of the passivation layer. The solar cell of claim 1, wherein the passivation layer comprises: a first passivation layer contacting the boron back surface field layer, the first passivation layer comprising aluminum oxide, cerium oxide, cerium oxynitride or a combination thereof; A second passivation layer is disposed above the first passivation layer, and the second passivation layer comprises tantalum nitride. The solar cell of claim 1, further comprising: a first doped layer in the semiconductor substrate under the front surface; a second doped layer in the semiconductor substrate under the front surface, and Adjacent to the first doped layer, the first doped layer and the second doped layer have the same conductivity type, and the second doped layer has a dopant concentration greater than a dopant concentration of the first doped layer; A front electrode layer contacts the second doped layer.