WO2016158906A1

WO2016158906A1 - Solar cell and method for manufacturing solar cell

Info

Publication number: WO2016158906A1
Application number: PCT/JP2016/060029
Authority: WO
Inventors: 小椋　厚志; ヒュンジュリー; 知京　豊裕
Original assignee: 国立研究開発法人物質・材料研究機構
Priority date: 2015-03-31
Filing date: 2016-03-29
Publication date: 2016-10-06
Also published as: JP2016192499A

Abstract

[Problem] To provide: a solar cell comprising a passivation layer, wherein the charge loss at the interface between a p-type semiconductor layer and the passivation layer is suppressed low; and a method for manufacturing a solar cell. [Solution] A solar cell (10) which is provided with: a p-type semiconductor layer (12); an n-type semiconductor layer (14); and a passivation layer (16) that is laminated on the p-type semiconductor layer (12). The passivation layer (16) comprises at least an aluminum oxide layer (18) and an aluminum nitride layer (20), which are sequentially laminated on the p-type semiconductor layer (12) in this order.

Description

Solar cell and method for manufacturing solar cell

The present invention relates to a solar cell including a p-type semiconductor layer, an n-type semiconductor layer, and a passivation layer stacked on the p-type semiconductor layer, and a method for manufacturing the solar cell.

Solar cells are widely desired to be used from the viewpoint of effectively using sunlight as an energy source. A solar cell is a semiconductor element that converts light energy of sunlight into electrical energy. When sunlight is incident on the solar cell, electron-hole pairs are generated in the solar cell. Electron / hole pairs generated by the light energy of sunlight are separated by an electric field in the vicinity of the junction surface between the p-type semiconductor layer and the n-type semiconductor layer, and electrons and holes are captured by different electrodes. An electromotive force is generated between the two electrodes.

However, most of the electrons and holes are lost due to recombination at the dangling bonds, defects, interface states, and the like generated at the interface between the semiconductor layer and the electrode, resulting in charge loss. This charge loss is known as a factor that hinders the improvement in power generation efficiency of solar cells.

In order to keep this charge loss low, a passivation layer is generally provided on the surface of the semiconductor layer or between the semiconductor layer and the electrode. By providing the passivation layer, the interface state density at the interface between the semiconductor layer and the passivation layer is suppressed to about 5 × 10 ¹¹ / cm ² eV, the interface recombination rate of charge is suppressed to about 300 cm / s, and charge loss is reduced. It can be kept low.

This passivation layer is required to have optical characteristics for efficiently taking incident light into the solar cell. Moreover, the physical property which suppresses the spiking of the electrode installed adjacent is also requested | required. Further, when the aluminum oxide layer is made thicker by 10 nm or more, there arises a problem that bubbles are generated in the aluminum oxide layer. In order to satisfy the restrictions on the optical characteristics, physical properties, and thickness of the aluminum oxide layer, a passivation layer in which a silicon nitride layer is laminated on an aluminum oxide layer has been often used (Patent Document 1).

Special table 2012-530361 gazette

However, in the solar cell disclosed in Patent Document 1, the electric field passivation effect of the negative fixed charge of the aluminum oxide layer is weakened by the positive fixed charge of the silicon nitride layer. As a result, the interface recombination speed at the interface between the p-type semiconductor layer and the passivation layer is increased, and the charge loss cannot be sufficiently suppressed. Moreover, in order to laminate | stack the said passivation layer, there existed a problem that a dangerous raw material gas was used, lamination | stacking took a long time, and the structure of a manufacturing apparatus became complicated.

Specifically, the aluminum oxide layer of the passivation layer is laminated by, for example, atomic layer deposition (ALD: Atomic Layer Deposition), and trimethylaluminum gas having high toxicity and flammability is used. For example, it takes about 20 to 40 minutes to stack an aluminum oxide layer of 20 nm.

In addition, the silicon nitride layer of the passivation layer is laminated by, for example, chemical vapor deposition (CVD: Chemical Vapor Deposition) using plasma, and silane gas having high toxicity and flammability and ammonia gas are used. For example, it takes about 10 to 30 minutes to stack a silicon nitride layer of 50 nm.

Further, the lamination of the aluminum oxide layer and the silicon nitride layer needs to be performed independently by separate apparatuses in order to avoid an explosion or contamination due to gas mixing, and the configuration of the manufacturing apparatus becomes complicated.

The present invention has been made in consideration of the above problems, and provides a solar cell including a passivation layer that suppresses charge loss at the interface between the p-type semiconductor layer and the passivation layer. In addition, the present invention provides a method for manufacturing a solar cell, which enables stacking with a simple device configuration in which this passivation layer can be continuously performed using the same manufacturing apparatus in a shorter time than that using a safe gas.

The solar cell of the present invention is a solar cell comprising a p-type semiconductor layer, an n-type semiconductor layer, and a passivation layer stacked on the p-type semiconductor layer, wherein the passivation layer is formed on the p-type semiconductor layer. On the other hand, it has at least a layer in which an aluminum oxide layer and an aluminum nitride layer are stacked in this order.

The solar cell includes a silicon oxide layer between the p-type semiconductor layer and the aluminum oxide layer.

In the solar cell, the aluminum oxide layer has a thickness of 1 nm to 20 nm.

In the solar cell, the silicon oxide layer has a thickness of 0.5 nm to 2 nm.

In the solar cell, the aluminum nitride layer has a thickness of 50 nm to 100 nm.

The solar cell is characterized in that the maximum interface recombination rate of charges at the interface between the p-type semiconductor layer and the passivation layer is 38 cm / s or less.

In the solar cell, an interface state density at an interface between the p-type semiconductor layer and the passivation layer is 4 × 10 ¹¹ / cm ² eV or less.

In the solar cell, the p-type semiconductor layer and the n-type semiconductor layer have a crystallinity of single crystal, polycrystal, or amorphous.

In the solar cell, a part or all of the p-type semiconductor layer and the n-type semiconductor layer are silicon.

The method for manufacturing a solar cell according to the present invention is a method for manufacturing a solar cell comprising a p-type semiconductor layer, an n-type semiconductor layer, and a passivation layer stacked on the p-type semiconductor layer, wherein the passivation layer includes: It includes at least a step of stacking and forming an aluminum oxide layer and an aluminum nitride layer in this order on the p-type semiconductor layer.

In the solar cell manufacturing method, the aluminum oxide layer is formed by any one of a CVD method, an ALD method, a plasma CVD method, a sputtering method, a reactive sputtering method, or a combination thereof. The thickness is 1 nm to 20 nm.

In the method for manufacturing a solar cell, a silicon oxide layer is formed between the p-type semiconductor layer and the aluminum oxide layer.

In the method for manufacturing a solar cell, the thickness of the silicon oxide layer is 0.5 nm to 2 nm.

In the method for manufacturing a solar cell, the aluminum nitride layer is formed by any one of a CVD method, an ALD method, a plasma CVD method, a sputtering method, a reactive sputtering method, or a combination thereof. The thickness is 50 nm to 100 nm.

In the method for manufacturing a solar cell, at least one of the aluminum oxide layer or the aluminum nitride layer is formed by a reactive sputtering method, and a partial pressure ratio is 10 as a reaction atmosphere for forming the aluminum oxide layer. % To 50% oxygen gas.

In the method for manufacturing a solar cell, at least one of the aluminum oxide layer or the aluminum nitride layer is formed by a reactive sputtering method, and a partial pressure ratio is 10 as a reaction atmosphere for forming the aluminum nitride layer. % To 70% nitrogen gas.

In the method for manufacturing a solar cell, the formation of the aluminum oxide layer and the formation of the aluminum nitride layer are continuously performed in the same hermetic container.

In the solar cell manufacturing method, the aluminum oxide layer and the aluminum nitride layer are formed by a reactive sputtering method, and the reaction atmosphere includes a rare gas and an oxygen gas having a partial pressure ratio of 10% to 50%. A step of forming the aluminum oxide layer using an aluminum target; and after the aluminum oxide layer is formed, the reaction atmosphere includes a rare gas and a nitrogen gas having a partial pressure ratio of 10% to 70%. And switching to a reaction atmosphere, and forming the aluminum nitride layer using the aluminum target.

In the method for manufacturing a solar cell, the solar cell is heated after the passivation layer is formed.

In the method for manufacturing a solar cell, a maximum interface recombination rate of charges at an interface between the p-type semiconductor layer and the passivation layer is 38 cm / s or less.

In the method for manufacturing a solar cell, an interface state density at an interface between the p-type semiconductor layer and the passivation layer is 4 × 10 ¹¹ / cm ² eV or less.

According to the solar cell of the present invention, there is at least a passivation layer in which an aluminum oxide layer and an aluminum nitride layer are laminated in this order with respect to the p-type semiconductor layer, so that charges at the interface between the p-type semiconductor layer and the passivation layer can be obtained. Loss can be kept low. In addition, according to the manufacturing method of the present invention, at least a step of stacking and forming an aluminum oxide layer and an aluminum nitride layer in this order on the p-type semiconductor layer is provided, so that a safe gas can be used and shorter than before. In time, it is possible to manufacture solar cells with a simple device configuration that can be continuously performed by the same manufacturing apparatus.

It is explanatory drawing of the solar cell which concerns on embodiment of this invention. It is explanatory drawing of the procedure of the manufacturing method of the solar cell which concerns on embodiment of this invention. It is a figure which shows the relationship between the thickness of the aluminum nitride layer laminated | stacked on the silicon substrate, and the fixed charge density of the aluminum nitride layer. It is a figure which shows the relationship between the thickness of an aluminum oxide layer, and the largest interface recombination speed in the solar cell which concerns on embodiment of this invention. It is a figure which shows the relationship between the partial pressure ratio of nitrogen gas in the case of forming the aluminum nitride layer, and an interface state density in the solar cell which concerns on embodiment of invention. It is explanatory drawing which shows the cross section of the solar cell which concerns on the modification of embodiment of this invention. It is a figure which shows the relationship between the wavelength of the light which injects into a solar cell, and a reflectance.

<Configuration of Solar Cell 10 of the Present Embodiment>
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing a cross section of a solar cell 10 according to an embodiment of the present invention. The upper side of FIG. 1 is the front surface, and the lower side is the back surface.

The solar cell 10 includes a p-type semiconductor layer 12, an n-type semiconductor layer 14, a passivation layer 16, a silicon nitride layer 22, a front electrode 24, and a back electrode 26.

The p-type semiconductor layer 12 is a crystalline semiconductor layer containing charges mainly including holes. As an additive, boron (B) which is a p-type impurity is included. Note that the p-type impurity is not limited to boron (B). As the p-type semiconductor layer 12, single crystal silicon is used. The thickness of the p-type semiconductor layer 12 is, for example, 0.1 mm to 0.2 mm, and the electric resistivity is 10 Ω · cm to 20 Ω · cm.

The n-type semiconductor layer 14 is a crystalline semiconductor layer containing charges mainly composed of electrons. As an additive, phosphorus (P) which is an n-type impurity is included. Note that the n-type impurity is not limited to phosphorus (P). As the n-type semiconductor layer 14, crystalline silicon is used. The thickness of the n-type semiconductor layer 14 is, for example, 0.1 μm to 0.8 μm, and the surface resistivity is 80 to 120 Ω / sq. Further, the n-type semiconductor layer 14 is formed on the surface of the p-type semiconductor layer 12.

The passivation layer 16 includes an aluminum oxide layer 18 and an aluminum nitride layer 20. The passivation layer 16 is formed on the back surface of the p-type semiconductor layer 12.

The aluminum oxide layer 18 is a layer having a thickness of 1 nm to 20 nm. The aluminum oxide layer 18 is formed on the back surface of the p-type semiconductor layer 12.

The aluminum nitride layer 20 is a layer having a thickness of 50 nm to 100 nm. The aluminum nitride layer 20 is formed on the back surface of the aluminum oxide layer 18.

The back surface through-hole 28 is formed in the passivation layer 16 from the back surface to the front surface. The back surface through hole 28 is a hole through which the p-type semiconductor layer 12 is electrically connected to the back surface electrode 26.

The silicon nitride layer 22 is a layer having a thickness of 50 nm to 100 nm and has a light transmitting property. The silicon nitride layer 22 is formed on the surface of the n-type semiconductor layer 14. Further, the surface through hole 30 is formed in the silicon nitride layer 22 from the front surface to the back surface. The surface through hole 30 is a hole through which the n-type semiconductor layer 14 is electrically connected to the surface electrode 24.

The surface electrode 24 is an electrode formed of metal, and for example, silver is used as the metal. The thickness of the surface electrode 24 is, for example, 5 μm to 20 μm. The surface electrode 24 is formed on the surface side of the silicon nitride layer 22. The surface electrode 24 is electrically connected to the n-type semiconductor layer 14 through the surface through hole 30.

The back electrode 26 is an electrode formed of metal, and for example, aluminum is used as the metal. The thickness of the back electrode 26 is, for example, 2 μm to 30 μm. The back electrode 26 is formed on the back side of the aluminum nitride layer 20. On the front surface side of the back electrode 26, a back surface protrusion 32 is formed for electrical connection with the p-type semiconductor layer 12 through the back surface through hole 28.

<The manufacturing method of the solar cell 10 of this embodiment>
Next, the manufacturing method of the solar cell 10 is demonstrated using FIG. FIG. 2 is an explanatory diagram of the procedure of the method for manufacturing the solar cell 10 of the present embodiment.

First, a silicon wafer containing p-type impurities is prepared (step S1).

The silicon wafer is preliminarily processed (step S2). Specifically, the silicon wafer is immersed in dilute hydrofluoric acid, and the natural oxide film formed on the surface of the silicon wafer is removed. Next, the surface of the silicon wafer is textured by reactive ion etching or anisotropic wet etching. Thereafter, n-type impurities are diffused into the silicon wafer in the depth direction from the surface of the silicon wafer by a thermal diffusion method, whereby the n-type semiconductor layer 14 is formed. By these preliminary processes, the surface of the silicon wafer is textured, and a laminated body in which the n-type semiconductor layer 14 is formed on the surface side of the silicon wafer and the p-type semiconductor layer 12 is formed on the back surface side is obtained.

Next, the aluminum oxide layer 18 is laminated on the back surface of the p-type semiconductor layer 12 by reactive sputtering (step S3). Specifically, an aluminum target is first placed inside an airtight container. Next, the p-type semiconductor layer 12 is placed at a position facing the aluminum target side. Further, a reaction gas composed of argon gas and oxygen gas having a partial pressure ratio of 10% to 50% is filled as 3 mTorr as a reaction atmosphere. Next, an alternating electromagnetic field of 300 W is applied between the aluminum target and the laminate for 0.5 to 11 minutes. As a result, an aluminum oxide layer 18 having a thickness of 1 nm to 20 nm is stacked on the back surface of the p-type semiconductor layer 12 (step S3).

Next, the aluminum nitride layer 20 is laminated on the back surface of the aluminum oxide layer 18 by reactive sputtering (step S4). Specifically, the reaction gas is once exhausted from the airtight container. Next, the hermetic container is filled with 3 mTorr using a reaction gas composed of argon gas and nitrogen gas having a partial pressure ratio of 10% to 70% as a reaction atmosphere. Further, an alternating electromagnetic field of 300 W is applied between the aluminum target and the laminate for 5 to 10 minutes. As a result, an aluminum nitride layer 20 having a thickness of 50 nm to 100 nm is laminated on the back surface of the aluminum oxide layer 18 (step S4).

Next, the silicon nitride layer 22 is deposited on the surface of the n-type semiconductor layer 14 by chemical vapor deposition (step S5). Specifically, the n-type semiconductor layer 14 of the stacked body is remounted in another gastight container different from the gastight container so as to be in contact with the gas atmosphere. Next, in the airtight container, monosilane (SiH ₄ ) gas and ammonia (NH ₃ ) gas diluted with H ₂ gas or He gas to a partial pressure ratio of 1% to 50% are used as raw material gases from 1 Torr to atmospheric pressure. Filled. In this state, the laminate is heated at about 350 ° C. for 5 to 10 minutes. As a result, the silicon nitride layer 22 having a thickness of 50 nm to 100 nm is stacked on the surface of the n-type semiconductor layer 14 (step S5).

Next, an electrode is formed on the laminate (step S6). From the back surface side of the passivation layer 16, a pulsed DPSS (Diode-pumped solid state) laser with an output of 8 W and a wavelength of 266 nm is irradiated to form the back surface through hole 28. Thereafter, the back electrode 26 is formed on the back surface of the aluminum nitride layer 20 by screen printing. Further, a surface through hole 30 and a surface electrode 24 are formed on the surface of the silicon nitride layer 22 by a fire-through method. Specifically, an electrode material containing silver that corrodes silicon nitride is printed at a predetermined location where the electrode is formed and heated at 200 ° C. to 800 ° C. for 1 minute to 60 minutes, whereby the surface electrode 24 is formed. It is formed on the surface of silicon nitride layer 22. For the formation of the front electrode 24 and the back electrode 26, the front electrode 24 may be formed first.

Next, the laminate on which the front electrode 24 and the back electrode 26 are formed is heated in a nitrogen gas atmosphere at 200 ° C. to 800 ° C. for 1 minute to 60 minutes (step S7). By this heating, the front surface electrode 24, the back surface electrode 26, the aluminum oxide layer 18, the aluminum nitride layer 20, and the silicon nitride layer 22 are annealed. Density is lowered. In addition, you may perform the heat processing in step 6 in step 7.

The solar cell 10 is obtained by the above manufacturing process.

<Operation of Solar Cell 10 of the Present Embodiment>
Next, operation | movement of the solar cell 10 which concerns on embodiment of this invention is demonstrated.

Sunlight is incident on the p-type semiconductor layer 12 through the silicon nitride layer 22 and the n-type semiconductor layer 14. Electron / hole pairs are generated in the n-type semiconductor layer 14 and the p-type semiconductor layer 12 by the light energy of sunlight. Since the surface of the n-type semiconductor layer 14 is textured, the incident sunlight is repeatedly reflected in the n-type semiconductor layer 14 and the p-type semiconductor layer 12. As a result, electron / hole pairs are effectively generated. Electron / hole pairs generated by sunlight are separated by an electric field in the vicinity of the junction surface between the p-type semiconductor layer 12 and the n-type semiconductor layer 14, electrons are moved to the front electrode 24, and the positive holes are transferred to the back electrode. The electromotive force is generated between the front electrode 24 and the back electrode 26.

The aluminum nitride layer 20 of the passivation layer 16 prevents the back electrode 26 from being scratched called spiking.

Also, the passivation layer 16 provides an electric field passivation effect. Specifically, the electron is moved away from the interface between the passivation layer 16 and the p-type semiconductor layer 12 by the high-density negative fixed charge electric field of the passivation layer 16, and the electrons are separated from the dangling bonds, defects, and interface states at the interface. The rate of loss due to the position is kept low, and the charge loss is kept low.

FIG. 3 is a diagram showing the relationship between the thickness of the aluminum nitride layer stacked on the silicon substrate and the fixed charge density of the aluminum nitride layer. The horizontal axis represents the thickness of the aluminum nitride layer (Thickness of AlN _x ), and the vertical axis represents the fixed charge density (Q _eff ) of the aluminum nitride layer. A white circle plot (◯) represents a fixed charge density when measured by sweeping from reverse bias to forward bias in CV measurement. The black circle plot (●) is the fixed charge density when measured by sweeping from forward bias to reverse bias.

In order for the passivation layer 16 to exhibit the electric field passivation effect, the sum of the charge density of the fixed charge of the aluminum oxide layer 18 and the charge density of the fixed charge of the aluminum nitride layer 20 on the back surface of the aluminum oxide layer 18 has a negative value. Must have. Here, the fixed charge density of the aluminum oxide layer 18 is −3.0 × 10 ¹² / cm ² to −5.0 × 10 ¹² / cm ² . For this reason, if the fixed charge density of the aluminum nitride layer 20 is 3.0 × 10 ¹² / cm ² or less, the sum of the charge densities becomes a negative value. From FIG. 3, when the thickness of the aluminum nitride layer is 50 nm or more, the fixed charge density is 2.0 × 10 ¹² / cm ² or less. That is, if the thickness of the aluminum nitride layer is 50 nm or more, the passivation layer 16 exhibits an electric field passivation effect.

FIG. 4 is a diagram showing the relationship between the thickness of the aluminum oxide layer 18 and the maximum interface recombination rate in the solar cell 10 according to the embodiment of the present invention. The horizontal axis represents the thickness (Thickness 層 of AlOx) of the aluminum oxide layer 18, and the horizontal axis represents the maximum interface recombination velocity (Smax) at the interface between the p-type semiconductor layer 12 and the aluminum oxide layer 18. When the thickness of the aluminum nitride layer 20 is 70 nm, the thickness of the aluminum oxide layer 18 is changed.

When the thickness of the aluminum oxide layer 18 is 5 nm to 20 nm, the maximum interface recombination rate is constant at 38 cm / s or less, and both are lower than the maximum interface recombination rate of the prior art, about 300 cm / s. This tendency does not change even when the thickness of the aluminum oxide layer 18 is 5 nm or less. From the viewpoint of reliability, the thickness of the aluminum oxide layer 18 is desirably 1 nm or more. Therefore, if the thickness of the aluminum oxide layer 18 is 1 nm to 20 nm, the maximum interface recombination rate is 38 cm / s or less, and charge loss at the interface between the p-type semiconductor layer 12 and the passivation layer 16 can be kept low. .

FIG. 5 is a diagram showing the relationship between the partial pressure ratio of nitrogen gas and the interface state density when forming the aluminum nitride layer 20 in the solar cell 10 according to the embodiment of the present invention. The horizontal axis shows the partial pressure ratio of nitrogen gas, and the vertical axis shows the relationship of the interface state density (D _it ) at the interface between the p-type semiconductor layer 12 and the aluminum oxide layer 18. In the case of forming the aluminum oxide layer 18 with a thickness of 5 nm and the aluminum nitride layer 20 with a thickness of 70 nm, the partial pressure ratio of the nitrogen gas is changed.

The interface state density at the interface between the p-type semiconductor layer 12 and the aluminum oxide layer 18 is an index of a chemical passivation effect that reduces the density of dangling bonds, defects, and interface states at the interface. It can be kept low. When the partial pressure ratio of nitrogen gas was 10% or more, the interface state density was 4 × 10 ¹¹ / cm ² eV or less. In the conventional technique including a silicon nitride layer terminated with hydrogen in the passivation layer, the interface state density at the interface between the p-type semiconductor layer and the aluminum oxide layer is about 5 × 10 ¹¹ / cm ² eV. For economic reasons, it is not practical to make the partial pressure ratio of nitrogen gas higher than 70%. When the partial pressure ratio of nitrogen gas is 10% to 70%, the interface state density is suppressed to 4 × 10 ¹¹ / cm ² eV or less, and the chemical passivation effect is about the same or higher than that of the prior art.

Next, a modification of the embodiment of the present invention will be described with reference to the drawings. FIG. 6 is an explanatory diagram showing a cross section of a solar cell 50 according to a modification of the embodiment of the present invention.

The solar cell 50 includes a p-type semiconductor layer 52, an n-type semiconductor layer 54, a passivation layer 56, a silicon nitride layer 62, a front electrode 64 and a back electrode 66.

In the solar cell 50, the p-type semiconductor layer 52 is basically the same as the p-type semiconductor layer 12 in the solar cell 10, and the same description is omitted. Hereinafter, the n-type semiconductor layer 54 is the n-type semiconductor layer 14, the passivation layer 56 is the passivation layer 16, the silicon nitride layer 62 is the silicon nitride layer 22, the surface electrode 64 is the back electrode 26, and the back electrode 66 is Similar to the surface electrode 24.

In the solar cell 50, the p-type semiconductor layer 52 has a thickness of 0.1 μm to 0.8 μm, and the n-type semiconductor layer 54 has a thickness of 0.1 mm to 0.2 mm. A p-type semiconductor layer 52 is formed on the surface of the n-type semiconductor layer 54.

The passivation layer 56 includes an aluminum oxide layer 58 and an aluminum nitride layer 60. The passivation layer 56 is formed on the surface of the p-type semiconductor layer 52.

The aluminum oxide layer 58 is formed on the surface of the p-type semiconductor layer 52. The aluminum nitride layer 60 is formed on the surface of the aluminum oxide layer 58.

In the passivation layer 56, front surface through holes 70 are formed from the front surface to the back surface. The surface through hole 70 is a hole through which the p-type semiconductor layer 52 is electrically connected to the surface electrode 64.

The silicon nitride layer 62 is formed on the back surface of the n-type semiconductor layer 54. Further, a back surface through hole 68 is formed in the silicon nitride layer 62 from the back surface to the front surface. The back surface through hole 68 is a hole through which the n-type semiconductor layer 54 is electrically connected to the back surface electrode 66.

The surface electrode 64 is formed on the surface side of the aluminum nitride layer 60. On the back side of the surface electrode 64, a surface protrusion 72 is formed for electrical connection with the p-type semiconductor layer 52 through the surface through hole 70.

The back electrode 66 is formed on the back side of the silicon nitride layer 62. The back electrode 66 is electrically connected to the n-type semiconductor layer 54 through the back surface through hole 68.

The manufacturing method of the solar cell 50 is the same as the manufacturing method of the solar cell 10.

FIG. 7 is a diagram showing the relationship between the wavelength of light incident on the solar cell and the reflectance. The horizontal axis indicates the wavelength (Wavelength) of light, and the vertical axis indicates the reflectance (Reflectance). The solid line represents the reflectance of the stacked body in which the p-type semiconductor layer, the aluminum oxide layer, and the aluminum nitride layer are formed in order from the bottom with respect to the surface of the n-type silicon layer. The thickness of the aluminum oxide layer of the laminate is 20 nm, and the thickness of the aluminum nitride layer is 70 nm. The dotted line is the reflectivity of the polished silicon crystal surface.

The reflectance of light by the laminate is 0.1% to 51.0% when the wavelength of light is between 400 nm and 1050 nm. On the other hand, the reflectance of the polished silicon crystal surface is 32.5% to 50.6% when the wavelength of light is between 400 nm and 1050 nm. When the wavelength of light is around 400 nm, the reflectivity is almost 50%, but the difference in reflectivity opens up to about 680 nm from the long wavelength side, and at 683 nm, the reflectivity of the laminate is 0.1%. On the other hand, the reflectance of the polished silicon crystal surface is 35.4%. On the longer wavelength side, the difference is greatly widened. When the wavelength of light is around 1050 nm, the reflectance of the laminate is 19.5%, whereas the reflectance of the polished silicon crystal surface is 37.4. %.

Thus, in the laminate, the reflectance is significantly lower than the polished silicon crystal when the wavelength of light is between 400 nm and 1050 nm. This indicates that the aluminum oxide layer and the aluminum nitride layer included in the passivation layer can incorporate light having a wavelength capable of effectively generating power into the stacked body as incident light in silicon-based solar power generation.

The solar cell 10 is a solar cell 10 including a p-type semiconductor layer 12, an n-type semiconductor layer 14, and a passivation layer 16 stacked on the p-type semiconductor layer 12, and the passivation layer 16 includes the p-type semiconductor layer 12. At least a layer in which an aluminum oxide layer 18 and an aluminum nitride layer 20 are stacked in this order on the type semiconductor layer 12 is provided.

The thickness of the aluminum oxide layer 18 is 1 nm to 20 nm.

The thickness of the aluminum nitride layer 20 is 50 nm to 100 nm.

The maximum interface recombination rate of charges at the interface between the p-type semiconductor layer 12 and the passivation layer 16 is 38 cm / s or less.

The interface state density at the interface between the p-type semiconductor layer 12 and the passivation layer 16 is 4 × 10 ¹¹ / cm ² eV or less.

The p-type semiconductor layer 12 and the n-type semiconductor layer 14 have single crystallinity.

The p-type semiconductor layer 12 and the n-type semiconductor layer 14 are all silicon.

The manufacturing method of the solar cell 10 is a manufacturing method of the solar cell 10 including the p-type semiconductor layer 12, the n-type semiconductor layer 14, and the passivation layer 16 stacked on the p-type semiconductor layer 12. The layer 16 includes at least a step of forming the aluminum oxide layer 18 and the aluminum nitride layer 20 in this order on the p-type semiconductor layer 12.

At least one of the aluminum oxide layer 18 or the aluminum nitride layer 20 is formed by a reactive sputtering method, and a rare gas as a reaction atmosphere for forming the aluminum oxide layer 18 has a partial pressure ratio of 10% to 50%. Oxygen gas.

At least one of the aluminum oxide layer 18 or the aluminum nitride layer 20 is formed by a reactive sputtering method, and a rare gas as a reaction atmosphere for forming the aluminum nitride layer 20 has a partial pressure ratio of 10% to 70%. Nitrogen gas.

The formation of the aluminum oxide layer 18 and the formation of the aluminum nitride layer 20 are continuously performed in the same hermetic container.

The aluminum oxide layer 18 and the aluminum nitride layer 20 are formed by a reactive sputtering method, and an aluminum target is used in a reaction atmosphere containing a rare gas and an oxygen gas having a partial pressure ratio of 10% to 50% as a reaction atmosphere. A step of forming the aluminum oxide layer 18, and after the aluminum oxide layer 18 is formed, the reaction atmosphere is switched to a reaction atmosphere containing a rare gas and a nitrogen gas having a partial pressure ratio of 10% to 70%. And forming the aluminum nitride layer 20 using the aluminum target.

After the passivation layer 16 is formed, it is heated.

It should be noted that the present invention is not limited to the above-described embodiment, and various configurations can be taken without departing from the spirit of the present invention.

In the above embodiment, the p-type semiconductor layer 12 and the n-type semiconductor layer 14 are formed of a single crystal, but are not limited thereto. For example, in consideration of economy, the p-type semiconductor layer 12 and the n-type semiconductor layer 14 may be formed of either polycrystalline or amorphous crystallinity.

In the above embodiment, the p-type semiconductor layer 12 and the n-type semiconductor layer 14 are all formed of silicon, but a part thereof is formed of silicon and the other part is formed of another semiconductor material. May be.

In the above embodiment, in the solar cell 10, the presence or absence of a layer between the p-type semiconductor layer 12 and the aluminum oxide layer 18 is not mentioned, but a silicon oxide layer may be formed. In such a case, in step S3, an oxygen gas having a partial pressure ratio of 0% to 15% may be added as an atmospheric gas to form a silicon oxide layer of 0.5 nm to 2 nm. Further, in step S3 or S7, an oxidizing species such as H ₂ O or O ₃ (ozone) is introduced as an atmospheric gas, or before step S3, the back surface of the p-type semiconductor layer 12 becomes an oxidizing species. A silicon oxide layer with a thickness of 0.5 nm to 2 nm may be formed by exposure.

In the above embodiment, the aluminum oxide layer 18, the aluminum nitride layer 20, and the silicon nitride layer 22 are formed by a reactive sputtering method, but are not limited thereto. For example, it may be formed by a CVD method, an ALD method, a plasma CVD method, a sputtering method, or a combination of these methods including a reactive sputtering method.

In the above embodiment, the formation of the aluminum oxide layer 18 and the formation of the aluminum nitride layer 20 are continuously performed in the same hermetic container, but may be performed in different hermetic containers.

DESCRIPTION OF

SYMBOLS

10, 50 ...

Solar cell

12, 52 ... p-

type semiconductor layer

14, 54 ... n-

type semiconductor layer

16, 56 ...

Passivation layer

18, 58 ...

Aluminum oxide layer

20, 60 ...

Aluminum nitride layer

22, 62 ...

Silicon nitride layer

24 , 64...

Surface electrodes

26 and 66... Back

surface electrodes

28 and 68... Back surface through-

holes

30 and 70.

Claims

A solar cell comprising a p-type semiconductor layer, an n-type semiconductor layer, and a passivation layer stacked on the p-type semiconductor layer,
The said passivation layer has at least the layer laminated | stacked in order of the aluminum oxide layer and the aluminum nitride layer with respect to the said p-type semiconductor layer, The solar cell characterized by the above-mentioned.
The solar cell according to claim 1,
A solar cell comprising a silicon oxide layer between the p-type semiconductor layer and the aluminum oxide layer.
The solar cell according to claim 1 or 2,
A solar cell, wherein the aluminum oxide layer has a thickness of 1 nm to 20 nm.
The solar cell according to claim 2,
A solar cell, wherein the silicon oxide layer has a thickness of 0.5 nm to 2 nm.
The solar cell according to any one of claims 1 to 4,
A solar cell, wherein the aluminum nitride layer has a thickness of 50 nm to 100 nm.
The solar cell according to any one of claims 1 to 5,
A solar cell, wherein a maximum interface recombination velocity of charges at an interface between the p-type semiconductor layer and the passivation layer is 38 cm / s or less.
The solar cell according to any one of claims 1 to 6,
A solar cell, wherein an interface state density at an interface between the p-type semiconductor layer and the passivation layer is 4 × 10 11 / cm 2 eV or less.
The solar cell according to any one of claims 1 to 7,
The solar cell, wherein the p-type semiconductor layer and the n-type semiconductor layer have a crystallinity of single crystal, polycrystal, or amorphous.
The solar cell according to any one of claims 1 to 8,
Part or all of the p-type semiconductor layer and the n-type semiconductor layer is silicon.
A method for manufacturing a solar cell comprising a p-type semiconductor layer, an n-type semiconductor layer, and a passivation layer stacked on the p-type semiconductor layer,
The passivation layer comprises at least a step of forming an aluminum oxide layer and an aluminum nitride layer in this order on the p-type semiconductor layer.
In the manufacturing method of the solar cell of Claim 10,
The aluminum oxide layer is formed by a CVD method, an ALD method, a plasma CVD method, a sputtering method, a reactive sputtering method, or a combination thereof,
A method for producing a solar cell, wherein the aluminum oxide layer has a thickness of 1 nm to 20 nm.
In the manufacturing method of the solar cell of Claim 10 or 11,
A method for manufacturing a solar cell, wherein a silicon oxide layer is formed between the p-type semiconductor layer and the aluminum oxide layer.
In the manufacturing method of the solar cell of Claim 12,
A method for producing a solar cell, wherein the silicon oxide layer has a thickness of 0.5 nm to 2 nm.
The method for manufacturing a solar cell according to any one of claims 10 to 13,
The aluminum nitride layer is formed by a CVD method, an ALD method, a plasma CVD method, a sputtering method, a reactive sputtering method, or a combination thereof,
A method for producing a solar cell, wherein the aluminum nitride layer has a thickness of 50 nm to 100 nm.
The method for manufacturing a solar cell according to any one of claims 10 to 14,
At least one of the aluminum oxide layer or the aluminum nitride layer is formed by a reactive sputtering method. As a reaction atmosphere for forming the aluminum oxide layer, a rare gas and an oxygen gas having a partial pressure ratio of 10% to 50% are used. A method for producing a solar cell, comprising:
The method for manufacturing a solar cell according to any one of claims 10 to 15,
At least one of the aluminum oxide layer or the aluminum nitride layer is formed by a reactive sputtering method, and a noble gas as a reaction atmosphere for forming the aluminum nitride layer and a nitrogen gas having a partial pressure ratio of 10% to 70% A method for producing a solar cell, comprising:
The method for manufacturing a solar cell according to any one of claims 10 to 14,
The method for producing a solar cell, wherein the formation of the aluminum oxide layer and the formation of the aluminum nitride layer are continuously performed in the same hermetic container.
The method for manufacturing a solar cell according to any one of claims 10 to 17,
The aluminum oxide layer and the aluminum nitride layer are formed by a reactive sputtering method, and the reaction atmosphere includes a rare gas and an oxygen gas having a partial pressure ratio of 10% to 50% using an aluminum target. Forming an aluminum oxide layer;
After the aluminum oxide layer is formed, the reaction atmosphere is switched to a reaction atmosphere containing a rare gas and a nitrogen gas having a partial pressure ratio of 10% to 70%, and the aluminum nitride layer is formed using the aluminum target. Forming a step;
A method for producing a solar cell, comprising:
The method for manufacturing a solar cell according to any one of claims 10 to 18,
A method of manufacturing a solar cell, wherein the solar cell is heated after the passivation layer is formed.
The method for manufacturing a solar cell according to any one of claims 10 to 19,
The method for manufacturing a solar cell, wherein a maximum interface recombination rate of charges at an interface between the p-type semiconductor layer and the passivation layer is 38 cm / s or less.
The method for manufacturing a solar cell according to any one of claims 10 to 20,
A method for manufacturing a solar cell, wherein an interface state density at an interface between the p-type semiconductor layer and the passivation layer is 4 × 10 11 / cm 2 eV or less.