Solar cell and method for manufacturing the same

Abstract

The present invention provides a solar cell and a method for manufacturing the same, which enable the easy and rapid formation of a structure for separating carriers generated by light absorption. [Solution] A solar cell comprising an n-type silicon layer 1, a carbon black-containing layer 3 provided on the light-receiving side of the n-type silicon layer 1, and a negative electrode layer 2 provided on the back side opposite to the light-receiving side of the n-type silicon layer 1, wherein the carbon black-containing layer 3 is provided with an opening 4 that exposes the n-type silicon layer 1, and generates electricity when light is irradiated onto the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1 through the opening 4.

Description

Technical Field

[0001] The present invention relates to a solar cell and a method for manufacturing the same.

Background Art

[0002] In a conventional solar cell using semiconductor silicon, in order to separate electrons and holes, which are carriers generated by light absorption, a structure having an energy barrier on the junction surface, such as a pn junction or a Schottky junction, and causing a rectifying action is used.

[0003] As a method for forming a pn junction on a silicon substrate (silicon wafer), for example, in Patent Document 1, when using a p-type silicon substrate, POCl3 gas as a diffusion source of phosphorus (P), which is an n-type impurity, is introduced into a diffusion furnace together with the p-type silicon substrate, and heat treatment is performed at about 850 °C to diffuse phosphorus from the surface of the p-type silicon substrate, and the surface layer side of the p-type silicon substrate is inverted to n-type to form a pn junction. It is also disclosed that when using arsenic (As) instead of phosphorus as the n-type impurity, a pn junction is formed by using AsCl3 gas as the diffusion source.

[0004] Furthermore, when using an n-type silicon substrate, boron (B), which is a p-type impurity, is diffused from the surface of the n-type silicon substrate by performing heat treatment in a diffusion furnace using BCl3 gas or BBr3 gas as a diffusion source, and the surface layer side of the n-type silicon substrate is inverted to p-type to form a pn junction.

[0005] Also, as a method for forming a Schottky junction on a silicon substrate, for example, in Patent Document 2, after forming Ni on a silicon substrate by sputtering, heat treatment is performed at about 900 °C to form a silicide (NiSi2) of silicon and Ni, and a Schottky junction is formed between the silicon substrate and the silicide layer.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-178194 [Patent Document 2] Japanese Patent Publication No. 2010-219399 [Overview of the project] [Problems that the invention aims to solve]

[0007] As mentioned above, forming a pn junction requires heating to over 800°C to diffuse impurities into the silicon substrate and electrically activate it. This presents challenges, as it necessitates a special diffusion furnace and a long processing time of several hours.

[0008] Furthermore, forming a Schottky junction requires the light-receiving surface to be covered with metal, necessitating the metal film to be extremely thin (approximately 10 nm or less) to suppress light absorption and reflection by the metal. This presents challenges, as it necessitates special deposition equipment such as sputtering devices and long deposition processing times of several hours. Additionally, if the film is not extremely thin, patterning is required to create openings in the metal film to expose the silicon, complicating the manufacturing process.

[0009] The present invention has been made to solve the above-mentioned problems, and aims to provide a novel solar cell and a method for manufacturing the same, which has a structure that separates carriers generated by light absorption, which can replace pn junctions consisting of p-type silicon and n-type silicon, and Schottky junctions consisting of metal and silicon, and for example, can be easily and quickly formed by applying a solution containing carbon black to the surface of an n-type silicon substrate having conductive electrodes on its back surface, drying it, and then removing a part of the carbon black-containing layer. [Means for solving the problem]

[0010] The gist of the present invention will be explained with reference to the attached drawings.

[0011] n-type silicon layer 1 and A carbon black-containing layer 3 is provided on the light-receiving surface side of the n-type silicon layer 1, The n-type silicon layer 1 has a negative electrode layer 2 provided on the back side opposite to the light-receiving surface side, The carbon black-containing layer 3 is provided with an opening 4 that exposes the n-type silicon layer 1. This invention relates to a solar cell characterized by generating electricity when light is irradiated onto the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1 through the opening 4.

[0012] Furthermore, the present invention relates to a solar cell according to claim 1, characterized in that the n-type silicon layer 1 is an n-type silicon substrate and the carbon black-containing layer 3 is dried India ink.

[0013] Furthermore, the process involves forming a carbon black-containing layer 3 by applying a carbon black-containing solution to the light-receiving surface side of the n-type silicon layer 1 and drying it, A negative electrode arrangement step involves providing a negative electrode layer 2 on the back side of the n-type silicon layer 1 opposite to the light-receiving surface side, The present invention relates to a method for manufacturing a solar cell, characterized by including an opening forming step of forming an opening 4 in the carbon black-containing layer 3 that exposes the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1. [Effects of the Invention]

[0014] As described above, the present invention provides a novel solar cell and a method for manufacturing the same, which allows for the easy and rapid formation of a structure for separating carriers generated by light absorption. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram illustrating Example 1. [Figure 2] This is a graph of the voltage-current characteristics of an experimental example. [Figure 3]It is an explanatory diagram showing the resistivity of the carbon black-containing layer. [Figure 4] It is a graph showing the temperature dependence of the resistance of the carbon black-containing layer. [Figure 5] It is a schematic explanatory diagram of the hot probe method. [Figure 6] It is a schematic explanatory diagram showing the manufacturing process of Example 1. [Figure 7] It is a schematic explanatory diagram showing the manufacturing process of Example 2. [Figure 8] It is a schematic explanatory diagram showing the manufacturing process of Example 3. [Figure 9] It is a schematic explanatory diagram showing the manufacturing process of Example 4.

Mode for Carrying Out the Invention

[0016] Preferred embodiments of the present invention will be briefly described based on the drawings while showing the operation of the present invention.

[0017] Details will be described in the experimental examples described later. However, in the state where white light of 100 mW / cm 2 is irradiated (during light irradiation) and in the state where no light is irradiated (in the dark) to the solar cell having the configuration of the present invention as shown in FIG. 1, the voltage-current characteristics measured while maintaining the temperature at 25°C are shown in FIG. 2. As is clear from FIG. 2, in the dark, diode curve characteristics similar to those of a conventional pn junction solar cell or a Schottky type solar cell are obtained, and it can be seen that a rectifying action occurs when the carbon black-containing layer 3 is joined to the n-type silicon layer 1. Also, it can be seen that power generation is occurring due to light irradiation.

[0018] Figures 3 and 4 show the temperature dependence of the resistivity and resistance of carbon black-containing layer 3 (a carbon black-containing sheet formed by drying a carbon black-containing solution). The resistivity is 0.4 Ωcm, and Figure 3 shows that, according to the resistivity classification, it is a semiconductor (Source: Taro Hino et al., "Electrical and Electronic Materials", 1st edition, Morikita Publishing Co., Ltd., October 1991, p. 76). Furthermore, Figure 4 shows that the resistance of carbon black-containing layer 3 tends to decrease with increasing temperature. This indicates the characteristic of semiconductors where electrical resistance decreases at high temperatures.

[0019] In the case of semiconductors, it is possible to determine whether they are p-type or n-type using the hot probe method. By keeping the positive probe of the tester at room temperature and heating the negative probe, the majority carriers around the negative probe increase and become more concentrated than the majority carriers around the positive probe, causing the majority carriers around the negative probe to diffuse to the positive probe. At this time, if the majority carriers are positively charged holes, i.e., if it is a p-type semiconductor, the area around the positive probe becomes relatively positively charged, and a positive voltage is detected at the positive probe relative to the negative probe. In the case of an n-type semiconductor, the majority carriers are negatively charged electrons, so a negative voltage is detected at the positive probe relative to the negative probe. In this way, it is possible to determine whether the semiconductor is p-type or n-type based on whether the detected voltage is positive or negative. As shown in Figure 5, when the hot probe method was applied to the carbon black-containing layer 3, a positive voltage was detected. Therefore, it can be seen that the carbon black-containing layer 3 is a p-type semiconductor, and the junction between the carbon black-containing layer 3 and the n-type silicon layer 1 is a semiconductor pn junction.

[0020] In other words, when light is irradiated through the opening 4 at the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1, a rectifying effect occurs because the junction between the carbon black-containing layer 3 and the n-type silicon layer 1 is a semiconductor pn junction. This allows the carriers generated by receiving light to be separated, and power can be output to an external load with the carbon black-containing layer 3 as the positive electrode and the negative electrode layer 2 as the negative electrode (the carbon black-containing layer 3 itself may be used as the positive electrode, or a separate positive electrode layer 6 with lower electrical resistance than the carbon black-containing layer 3 may be provided).

[0021] Furthermore, the present invention can be formed, for example, by simply applying a carbon black-containing solution (e.g., India ink) to an n-type silicon substrate, drying it, and then removing a portion of the carbon black-containing layer. This makes it easier and quicker to form compared to conventional pn junctions or metal-silicon Schottky junctions. [Examples]

[0022] A specific embodiment of the present invention, Part 1, will be described with reference to Figures 1 and 6.

[0023] This embodiment is a solar cell having an n-type silicon layer 1, a carbon black-containing layer 3 provided on the light-receiving side of the n-type silicon layer 1, and a negative electrode layer 2 provided on the back side of the n-type silicon layer 1 opposite to the light-receiving side, as shown in Figure 1.

[0024] Specifically, the carbon black-containing layer 3 is provided with an opening 4 that exposes the n-type silicon layer 1, and electricity is generated when light is irradiated onto the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1 through the opening 4.

[0025] Let's explain each part in detail.

[0026] The n-type silicon layer 1 is an n-type silicon substrate (n-type silicon wafer) containing n-type impurities such as phosphorus (P) and arsenic (As). For example, it can have a thickness of 725 μm ± 25 μm and a resistivity in the range of 1 to 100 Ωcm. A silicon native oxide film (insulating film) with a thickness of 10 nm or less (preferably 5 nm or less) may be formed on the surface of the n-type silicon substrate.

[0027] A carbon black-containing layer 3 is provided on the light-receiving surface side of this n-type silicon substrate.

[0028] The carbon black-containing layer 3 is a carbon black-containing sheet obtained by coating it with a paint (carbon black-containing solution) consisting of a mixture of carbon black and an aqueous solution of a water-soluble resin, and then drying it. This paint may contain water, surfactants, and preservatives. For example, commercially available India ink (containing approximately 3-20% by weight of carbon black relative to the total amount of the India ink composition) can be used. As an example of India ink, one can be used that contains, by weight, 7 parts carbon black with an average particle size of 24 nm, 2.5 parts polyvinyl alcohol, 2.0 parts emulsion, 2.0 parts laponite, 1.2 parts activated carbon, and 85.3 parts water. The carbon black-containing layer 3 has a thickness of approximately 50 μm to 1 mm after drying.

[0029] The carbon black-containing layer 3 is provided with one or more openings 4 that expose the n-type silicon layer 1, and the junction 5 (light-receiving region) between the carbon black-containing layer 3 and the n-type silicon layer 1 is exposed to the openings 4. In other words, when light is irradiated, the junction 5 can receive light more directly.

[0030] In this embodiment, the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1 acts as a light-receiving area. A rectifying effect occurs at the junction (interface) between the carbon black-containing layer 3 and the n-type silicon substrate, allowing for the separation of carriers generated by light reception, and the carbon black-containing layer 3 side becomes the positive electrode. Therefore, by receiving light, including sunlight, at the junction 5, a photovoltaic power is generated such that the carbon black-containing layer 3 becomes highly potential relative to the negative electrode layer 2.

[0031] The negative electrode layer 2 (the electrode layer that serves as the negative electrode) is provided on the back side of the n-type silicon substrate, that is, on the side opposite to the side on which the carbon black-containing layer 3 is provided. The carbon black-containing layer 3 and the negative electrode layer 2 are provided so that they do not come into direct contact with each other.

[0032] The negative electrode layer 2 is composed of a metal electrode made of, for example, aluminum (Al). Specifically, it is provided by forming a thin metal film, such as an Al thin film with a thickness of 300 nm or more, on part or all of the back surface of the n-type silicon substrate using an appropriate film deposition method such as sputtering. In this embodiment, the negative electrode layer 2 is provided by depositing an Al thin film with a thickness of 600 nm on the entire back surface of the n-type silicon substrate.

[0033] Furthermore, the negative electrode layer 2 may be provided not only by forming a thin metal film, but also, for example, by placing a commercially available Al foil in physical contact with the back surface of an n-type silicon substrate and fixing the n-type silicon substrate and the Al foil with an insulating adhesive tape 30.

[0034] Furthermore, while the carbon black-containing layer 3 has low resistance and can act as an electrode, a metal electrode with even lower resistance may be formed on the carbon black-containing layer 3 as the positive electrode layer 6. In this case, the positive electrode layer 6 is formed only on a portion of the carbon black-containing layer 3 so that light is irradiated onto the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1. For example, similar to the negative electrode layer 2, a thin metal film such as an Al thin film with a thickness of 300 nm to 1 μm (preferably 600 nm or more) is formed by an appropriate film deposition method such as sputtering. In this case, the shape of the metal thin film can be made comb-like to minimize light obstruction.

[0035] A method for manufacturing a solar cell according to this embodiment having the above configuration will now be described.

[0036] First, a cleaning process is performed to remove organic matter (contaminants) from the n-type silicon substrate. Specifically, the n-type silicon substrate is immersed in ethanol, ultrasonically cleaned for 10 minutes, and then air-dried.

[0037] Next, a negative electrode preparation process is performed to form the negative electrode layer 2 on the back side of the n-type silicon substrate (Figure 6(a)→(b)). Specifically, a thin Al film is formed on the back side of the n-type silicon substrate using a DC sputtering apparatus.

[0038] Next, a carbon black-containing layer formation process is performed to form a carbon black-containing layer 3 on the light-receiving surface side of the n-type silicon substrate (Figure 6(b)→(c)). Specifically, a carbon black-containing solution (ink) is dropped onto the light-receiving surface side of the n-type silicon substrate, then spread thinly with a brush to cover the light-receiving surface side of the n-type silicon substrate to a thickness of 1 mm or less, and the carbon black-containing layer 3 can be formed by drying it naturally. In other words, the carbon black-containing layer formation process can be completed in a short time, less than 30 minutes.

[0039] Furthermore, in the carbon black-containing layer formation process, the material may be spread thinly to a thickness of 1 mm or less by means other than a brush, such as a spin coater. Also, drying may be done not only by natural drying, but also by heating on a hot plate heated to 50°C for about 5 minutes.

[0040] Next, an opening formation process is performed in which an opening 4 is formed in a part of the carbon black-containing layer 3, exposing the joint 5 between the carbon black-containing layer 3 and the n-type silicon layer 1 to the opening 4 (Figure 6(c)→(d)). Specifically, the carbon black-containing layer 3 is physically peeled off by rubbing it with a jig that has a rod-shaped tip. For example, a pair of stainless steel tweezers can be used as the jig. Preferably, the material of the jig should be a material that does not cause physical damage to the surface of the n-type silicon layer 1, and it is not limited to stainless steel; it may also be resin or fiber.

[0041] Furthermore, when forming the openings 4, it is preferable to form them so that the carbon black-containing layer 3 remaining after the formation of the openings 4 is in contact with the entire solar cell element (so that in a plan view the carbon black-containing layer 3 does not separate into two or more regions but remains as one continuous unit). For example, it is preferable to form multiple openings 4 in a dispersed manner. By doing so, the area of ​​the junction 5 exposed to the openings 4 can be increased, and the current density can be improved.

[0042] Furthermore, in the opening formation process, peeling is not limited to using a jig. For example, before applying the carbon black-containing solution onto the n-type silicon layer 1, adhesive tape may be applied to the area that will later become the opening. After the carbon black-containing layer 3 is formed, the adhesive tape can be peeled off to create the opening 4. Alternatively, before applying the carbon black-containing solution onto the n-type silicon layer 1, transparent adhesive tape may be applied to the area that will later become the opening. The carbon black-containing solution may then be applied to the surface of the n-type silicon layer 1 other than the adhesive tape, and dried to form an optically opened substantial opening 4 using the transparent adhesive tape.

[0043] In this embodiment, the process is carried out in the order described above, but the carbon black-containing layer formation step may be performed before the negative electrode placement step. Furthermore, in order to further improve the electrical contact between the n-type silicon substrate and the carbon black-containing layer 3 and the electrode layer, a step to remove the native oxide film from the light-receiving side and the back side of the n-type silicon substrate may be included before the carbon black-containing layer formation step and the negative electrode placement step. In this case, the cleaning step is performed after the native oxide film removal step.

[0044] By following the above steps, the solar cell according to this embodiment can be manufactured.

[0045] As this embodiment is configured as described above, the carriers generated by receiving light at the joint 5 through the opening 4 can be separated, and power can be output to an external load with the carbon black-containing layer 3 as the positive electrode and the negative electrode layer 2 as the negative electrode.

[0046] Furthermore, the light-absorbing layer in this embodiment can be formed simply by applying a carbon black-containing solution (ink) to an n-type silicon substrate, drying it, and then removing a portion of it. This allows for easier and faster formation compared to conventional pn junctions or metal-silicon Schottky junctions.

[0047] Therefore, this embodiment provides a novel solar cell that allows for the easy and rapid formation of a structure for separating carriers generated by light absorption. [Examples]

[0048] A specific embodiment of the present invention, Part 2, will be described with reference to Figure 7.

[0049] Example 2 is an example in which a positive electrode layer 6, which plays a role in reducing contact resistance when connecting to an external load, is provided on the carbon black-containing layer 3 of the solar cell according to Example 1 (see Figure 7(e)).

[0050] The positive electrode layer 6 (the electrode layer that serves as the positive electrode) is provided on a portion of the carbon black-containing layer 3.

[0051] The positive electrode layer 6 is composed of a metal electrode made of, for example, aluminum (Al). Specifically, it is provided by forming a thin metal film, such as an Al thin film with a thickness of 300 nm or more, on a part of the light-receiving surface side of the carbon black-containing layer 3 using an appropriate film deposition method such as sputtering.

[0052] In this embodiment, the positive electrode layer 6 is provided by depositing a 600 nm thick Al thin film on the carbon black-containing layer 3 using the same method as for the negative electrode layer 2. However, the positive electrode layer 6 is provided in a comb-like shape so as not to block sunlight as much as possible, while exposing the junction 5 (light-receiving region) between the carbon black-containing layer 3 and the n-type silicon layer 1 and exposing most of the carbon black-containing layer 3 (e.g., 80% or more). Specifically, the positive electrode preparation process involves depositing aluminum by DC sputtering in the same manner as for the negative electrode layer 2 described above, with a comb-shaped opening mask in contact with the carbon black-containing layer 3, and then removing the mask to form the positive electrode layer 6.

[0053] After providing the positive electrode layer 6, an opening 4 is formed in a part of the carbon black-containing layer 3, and an opening formation process is performed to expose the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1 to the opening 4 (Figure 7(d)→(e)).

[0054] In the opening formation process, the opening 4 can be formed by rubbing the carbon black-containing layer 3 with a jig such as stainless steel tweezers, similar to Example 1.

[0055] Alternatively, before applying the carbon black-containing solution onto the n-type silicon layer 1, adhesive tape may be attached to the area that will later become an opening, and the opening 4 may be created by peeling off the adhesive tape after the carbon black-containing layer 3 is formed. Alternatively, before applying the carbon black-containing solution onto the n-type silicon layer 1, transparent adhesive tape may be attached to the area that will later become an opening, and the carbon black-containing solution may be applied to the surface of the n-type silicon layer 1 other than the adhesive tape and dried to form an optically opened substantial opening 4 with the transparent adhesive tape. However, when creating the opening 4 by peeling off the adhesive tape or when creating the opening 4 with transparent adhesive tape, it is necessary to form the positive electrode layer 6 on the carbon black-containing layer 3 other than on the adhesive tape (or transparent adhesive tape) during the positive electrode placement process.

[0056] In other words, this embodiment is manufactured by following the above-described cleaning step, negative electrode placement step (Figure 7(a)→(b)), and carbon black-containing layer formation step (Figure 7(b)→(c)), followed by a positive electrode placement step (Figure 7(c)→(d)) in which an Al thin film is formed on the carbon black-containing layer 3 using a DC sputtering apparatus, and then an opening formation step (Figure 7(d)→(e)) in which an opening is formed to expose the junction 5 between the carbon black-containing layer 3 and the n-type silicon layer 1.

[0057] In this embodiment, the opening formation process is performed after the positive electrode placement process, but the opening formation process may be performed before the positive electrode placement process.

[0058] The remaining aspects are the same as in Example 1. [Examples]

[0059] A specific embodiment of the present invention, Part 3, will be described with reference to Figure 8.

[0060] Example 3 is an example in which the negative electrode layer 2 of the solar cell according to Example 1 is made of aluminum foil, and this aluminum foil is fixed with adhesive tape 30 (see Figure 8(c)).

[0061] In this embodiment, the negative electrode is arranged by physically fixing aluminum foil to the back surface of the n-type silicon substrate, which makes it possible to shorten the manufacturing time compared to Embodiment 1.

[0062] In other words, this embodiment is manufactured by performing the above-described cleaning step, then a negative electrode placement step (Figure 8(a)→(b)) in which aluminum foil is fixed to the n-type silicon substrate with adhesive tape 30, then the above-described carbon black-containing layer formation step (Figure 8(b)→(c)), and finally an opening formation step (Figure 8(c)→(d)) in which a part of the carbon black-containing layer 3 is removed to expose the joint 5 between the carbon black-containing layer 3 and the n-type silicon layer 1.

[0063] Specifically, the negative electrode placement process in this embodiment involves placing an n-type silicon substrate on aluminum foil and attaching adhesive tape 30 from the surface of the aluminum foil to the side and light-receiving surface (periphery of the light-receiving surface) of the n-type silicon substrate. Commercially available aluminum foil can be used as the aluminum foil, and its surface should not be covered with non-conductive materials. The adhesive tape 30 is provided to fix the aluminum foil, which is the negative electrode layer 2, and the n-type silicon substrate in a state where the upper surface of the aluminum foil and the back surface of the n-type silicon substrate are in contact, and it is desirable to provide it so as not to adhere to the light-receiving surface side of the n-type silicon substrate as possible. Specifically, it is desirable to provide it so that the light-receiving surface side of the n-type silicon substrate is open by 50% or more due to the adhesive tape 30.

[0064] The remaining aspects are the same as in Example 1. [Examples]

[0065] A specific embodiment of the present invention, specifically embodiment 4, will be described with reference to Figure 9.

[0066] Example 4 is an example in which a positive electrode layer 6, which plays a role in reducing contact resistance when connecting to an external load, is provided on the carbon black-containing layer 3 of the solar cell according to Example 3 (see Figure 9(e)).

[0067] In other words, Example 4 is a configuration that reduces the contact resistance with the carbon black-containing layer 3 in addition to the configuration of Example 3. Therefore, since the negative electrode is arranged by physically fixing the aluminum foil, it is possible to shorten the manufacturing time in the same way as in Example 3, and the manufacturing time is shortened following that of Example 3.

[0068] This embodiment is manufactured by following the above-described cleaning step, the negative electrode placement step using the above-described aluminum foil and adhesive tape 30 (Figure 9(a)→(b)), and the carbon black-containing layer formation step (Figure 9(b)→(c)), followed by a positive electrode placement step (Figure 9(c)→(d)), and then an opening formation step (Figure 9(d)→(e)) to expose the joint 5 between the carbon black-containing layer 3 and the n-type silicon layer 1.

[0069] The remaining points are the same as in Examples 1 to 3.

[0070] The configurations described above are illustrative examples, and the present invention is not limited to these configurations.

[0071] [Example of experiment] We will now describe experimental examples that support the effects of the above-described embodiments.

[0072] A solar cell according to Example 3 was manufactured by sequentially performing the above-described cleaning process, negative electrode placement process, carbon black-containing layer formation process, and aperture formation process on a 2cm x 2cm n-type silicon substrate.

[0073] Specifically, in the negative electrode placement process, the cleaned n-type silicon substrate was shaped into a 5cm x 5cm piece of commercially available aluminum foil, and the four sides of the aluminum foil were fixed to the foil with transparent adhesive tape so that the center 1cm x 1cm of the n-type silicon substrate was exposed, and the n-type silicon substrate was placed so that the back surface of the n-type silicon substrate was in physical contact with the aluminum foil.

[0074] Furthermore, in the carbon black-containing layer formation process, after dropping the aforementioned components of India ink onto the exposed portion of the n-type silicon substrate, the ink was spread thinly with a brush to a thickness of 1 mm or less, covering the exposed portion of the n-type silicon substrate, ensuring that no India ink was applied to the transparent adhesive tape. The carbon black-containing layer 3 was then formed by natural drying.

[0075] Furthermore, in the opening formation process, three openings 4 measuring approximately 1 mm x 8 mm were formed by scraping and removing a portion of the carbon black layer 3 using stainless steel tweezers.

[0076] The solar cell manufactured in the manner described above has a power output of 100 mW / cm². 2 Figure 2 shows the voltage-current characteristics measured under illumination with white light and while maintaining the temperature at 25°C. From Figure 2, the open-circuit voltage is 0.341V and the short-circuit current density is 0.10mA / cm². 2 It can be confirmed that power is being generated. In other words, diode curve characteristics similar to those of conventional pn-junction solar cells and Schottky solar cells are obtained, and it has been confirmed that a rectifying effect occurs when the carbon black-containing layer 3 is bonded to the n-type silicon substrate. [Explanation of Symbols]

[0077] 1 n-type silicon layer 2. Negative electrode layer 3. Carbon black-containing layer 4 openings 5 Joint 6. Positive electrode layer

Claims

1. n-type silicon layer, A carbon black-containing layer provided on the light-receiving surface side of the n-type silicon layer, The n-type silicon layer has a negative electrode layer provided on the back side opposite to the light-receiving side, The carbon black-containing layer is provided with an opening that exposes the n-type silicon layer. A solar cell characterized by generating electricity when light is irradiated onto the junction between the carbon black-containing layer and the n-type silicon layer through the aforementioned opening.

2. A solar cell according to claim 1, characterized in that the n-type silicon layer is an n-type silicon substrate and the carbon black-containing layer is dried India ink.

3. A carbon black-containing layer formation process involves applying a carbon black-containing solution to the light-receiving surface side of an n-type silicon layer and drying it to form a carbon black-containing layer, A negative electrode arrangement step involves providing a negative electrode layer on the back side of the n-type silicon layer opposite to the light-receiving surface side, A method for manufacturing a solar cell, comprising a step of forming an opening in the carbon black-containing layer to expose the junction between the carbon black-containing layer and the n-type silicon layer.

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