JP2005243872A - Photoelectric converter and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric converter having higher conversion efficiency. <P>SOLUTION: The photoelectric converter can provide higher conversion efficiency by joining many particle semiconductors 20 for photoelectric conversion on a substrate 1 working as a lower electrode, providing an insulator 4 to the lower portions among these particle semiconductors, providing an insulating film 6 including non-covering portion to the upper portions of the particle semiconductors 20, and forming a light transmissive conductive layer 5 working as an upper electrode on the insulator 4 and the insulating film 6 for electrical connection with the particle semiconductors 20 through the non-covering portion. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion device such as a solar cell that converts light into electricity, and more particularly to a photoelectric conversion device using a granular semiconductor.

  An example of a solar cell which is a photoelectric conversion device using a conventionally proposed granular semiconductor is shown in a sectional view in FIG.

That is, as shown in FIG. 4, a low melting point metal layer 108 is formed on a substrate 101, and a large number of one-conductivity type granular semiconductors 103 are disposed on the low melting point metal layer 108. These granular semiconductors 103 are fixed by heating, and the insulator 102 is formed so as to fill between the fixed granular semiconductors 103 and cover the granular semiconductors 103 and the low melting point metal 108, and then one conductivity type Part of the insulator 102 on the granular semiconductor 103 is polished to expose the one conductive type granular semiconductor 103, and the other conductive type semiconductor portion 104 and the transparent conductive layer 105 are sequentially formed on the exposed surface. A photoelectric conversion device is disclosed (see, for example, Patent Document 1).
Japanese Patent No. 2641800

  However, in the photoelectric conversion device illustrated in FIG. 4, the insulator 102 and the one-conductivity-type granular semiconductor 103 are polished, so that a portion with a small thickness of the insulator 102 is formed by the polishing process, or a hole or a peeling is formed in the insulator 102. As a result, there is a problem that the transparent conductive layer 105 and the low melting point metal layer 108 are short-circuited to reduce conversion efficiency.

  The present invention has been made in view of this problem, and an object thereof is to provide a photoelectric conversion device having high conversion efficiency.

  In the photoelectric conversion device of the present invention, a large number of granular semiconductors that perform photoelectric conversion are joined on a substrate that serves as a lower electrode, an insulator is provided between the granular semiconductors, and an uncoated portion is formed on the granular semiconductor. A transparent conductive layer serving as an upper electrode is formed on the insulator and the insulating film so as to be electrically connected to the granular semiconductor through the non-covering portion. It is characterized by.

  Further, the photoelectric conversion device of the present invention is provided with a plurality of granular semiconductors that perform photoelectric conversion on a substrate serving as a lower electrode, and a conductive protective layer is provided on the surface excluding the junction with the granular semiconductor substrate. An insulator is provided between the granular semiconductors on which the conductive protective layer is formed, and an insulating film having an uncoated portion is provided on the granular semiconductor on which the conductive protective layer is formed, A light-transmitting conductive layer serving as an upper electrode is formed on the insulator and the insulating film so as to be electrically connected to the conductive protective layer through the portion.

  The method for manufacturing a photoelectric conversion device of the present invention includes a step of bonding a number of granular semiconductors that perform photoelectric conversion on a substrate that serves as a lower electrode, and an insulator below the granular semiconductor, Forming an insulating film having an uncovered portion on the upper part, forming a light-transmitting conductive layer serving as an upper electrode on the insulator and the insulating film, and forming the granular semiconductor and the light-transmitting conductive layer And electrically connecting through the uncovered portion of the insulating film.

  Moreover, the manufacturing method of the photoelectric conversion device of the present invention is a mixed solution in which, in the above manufacturing method, two uncured insulating materials are mixed and dissolved in an organic solvent on the substrate and the plurality of granular semiconductors. And filling the mixed solution in the lower part between the granular semiconductors and forming a film of the mixed solution on the upper part of the granular semiconductor, followed by curing the mixed solution to obtain the insulator and the non- The insulating film having a covering portion is formed.

  In addition, the method for manufacturing a photoelectric conversion device of the present invention includes a step of bonding a number of granular semiconductors that perform photoelectric conversion on a substrate to be a lower electrode, and a conductive surface on a surface of the granular semiconductor excluding the junction with the substrate. Forming a conductive protective layer, forming an insulator below the granular semiconductor, forming an insulating film having an uncovered portion above the granular semiconductor on which the conductive protective layer is formed, and A transparent conductive layer serving as an upper electrode is formed on the insulator and the insulating film, and the conductive protective layer and the transparent conductive layer are electrically connected through the uncovered portion of the insulating film. And a step of causing the step to occur.

  Moreover, the method for manufacturing a photoelectric conversion device of the present invention is the method described above, wherein two uncured insulating materials are mixed on the substrate and the granular semiconductor on which the plurality of conductive protective layers are formed. After supplying a mixed solution dissolved in an organic solvent, filling the mixed solution in the lower part of the granular semiconductor and forming the film of the mixed solution on the upper part of the granular semiconductor on which the conductive protective layer is formed, The mixed solution is hardened to form the insulating film having the insulator and the non-covered portion.

  According to the photoelectric conversion device of the present invention, a large number of granular semiconductors that perform photoelectric conversion are joined on a substrate that serves as a lower electrode, an insulator is provided between the granular semiconductors, and the upper part of the granular semiconductor is not covered. A transparent conductive layer serving as an upper electrode is formed on the insulator and the insulating film so as to be electrically connected to the granular semiconductor through the non-covered portion. Since the granular semiconductor to be converted and the translucent conductive layer are electrically connected through the non-covering portion, a short circuit between the translucent conductive layer serving as the upper electrode and the substrate serving as the lower electrode can be prevented. Thus, a photoelectric conversion device with high conversion efficiency is obtained.

  In addition, according to the photoelectric conversion device of the present invention, a large number of granular semiconductors that perform photoelectric conversion are bonded onto a substrate that serves as a lower electrode, and a conductive protective layer is formed on the surface excluding the bonding portion between the granular semiconductor and the substrate. An insulating material is provided below the granular semiconductor between which the conductive protective layer is formed, and an insulating film having an uncovered portion is provided above the granular semiconductor on which the conductive protective layer is formed. Since the light-transmitting conductive layer that becomes the upper electrode is formed on the insulator and the insulating film so as to be electrically connected to the conductive protective layer, the light-transmitting layer that becomes the upper electrode from the place where the photocurrent is generated. Since resistance to the photocurrent in the path to the photoconductive layer is reduced and resistance loss of the generated photocurrent can be reduced, a photoelectric conversion device with high conversion efficiency is obtained.

  In addition, according to the method for manufacturing a photoelectric conversion device of the present invention, a step of joining a number of granular semiconductors that perform photoelectric conversion on a substrate that serves as a lower electrode, and an insulator is provided below the granular semiconductor, and the granular semiconductor Forming an insulating film having an uncovered portion on the upper portion of the substrate, and forming a light-transmitting conductive layer as an upper electrode on the insulator and the insulating film to insulate the granular semiconductor from the light-transmitting conductive layer Including a step of electrically connecting through a non-covering portion of the film, and thus a polishing step is not required, and a short circuit between the translucent conductive layer serving as the upper electrode and the substrate serving as the lower electrode can be reliably prevented. Thus, a photoelectric conversion device with high conversion efficiency can be manufactured with high productivity.

  Moreover, according to the method for manufacturing a photoelectric conversion device of the present invention, in the above manufacturing method, a mixed solution in which two uncured insulating materials are mixed and dissolved in an organic solvent on a substrate and a number of granular semiconductors. After filling the lower part between the granular semiconductors with the mixed solution and forming the mixed solution film on the upper part of the granular semiconductor, the mixed solution is cured to form an insulating film having an insulator and an uncoated portion. When formed, the photoelectric conversion device of the present invention can be easily manufactured because the insulator and the insulating film having the non-covering portion can be formed simultaneously in the same process.

  In addition, according to the method for manufacturing a photoelectric conversion device of the present invention, a step of bonding a large number of granular semiconductors that perform photoelectric conversion on a substrate serving as a lower electrode, and a surface excluding the bonding portion between these granular semiconductor substrates. A step of forming a conductive protective layer, a step of forming an insulator below the granular semiconductor, an insulating film having an uncovered portion above the granular semiconductor on which the conductive protective layer is formed, and an insulator and Forming a light-transmitting conductive layer to be an upper electrode on the insulating film, and electrically connecting the conductive protective layer and the light-transmitting conductive layer through the non-covered portion of the insulating film, A polishing step is not necessary, and it is possible to reliably prevent a short circuit between the translucent conductive layer serving as the upper electrode and the substrate serving as the lower electrode, and to reduce the resistance loss of the generated photocurrent, thereby reducing the conversion efficiency. Productive high photoelectric conversion device It can be.

  Moreover, according to the method for manufacturing a photoelectric conversion device of the present invention, in the above manufacturing method, two uncured insulating materials are mixed on the substrate and the granular semiconductor on which a large number of conductive protective layers are formed. After supplying a mixed solution dissolved in an organic solvent, filling the lower part of the granular semiconductor with the mixed solution and forming a film of the mixed solution on the upper part of the granular semiconductor, the mixed solution is cured, and the insulator When forming the insulating film having the covering portion, the insulator and the insulating film having the non-covering portion can be formed simultaneously in the same process, whereby the photoelectric conversion device of the present invention can be easily manufactured.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating an example of an embodiment of a photoelectric conversion device of the present invention. In FIG. 1, 1 is a substrate, 2 is a crystalline semiconductor particle, 3 is a semiconductor portion exhibiting a conductivity type opposite to that of the crystalline semiconductor particle 2, 4 is an insulator, 5 is a translucent conductive layer, and 6 is an uncoated portion. 10 is an alloy layer of the substrate 1 and the crystalline semiconductor particles 2, and 20 is a granular semiconductor that performs photoelectric conversion.

  Here, the granular semiconductor 20 that performs photoelectric conversion is obtained by forming the other-conductivity-type semiconductor portion 3 on the surface excluding a partial region of the one-conductivity-type crystalline semiconductor particles 2.

  As shown in FIG. 1, the photoelectric conversion device of the present invention has a large number of other conductive type (for example, n-type) semiconductor portions 3 formed on a surface of a substrate 1 serving as a lower electrode except for a partial region. Between the adjacent regions of the one-conductivity-type crystalline semiconductor particles 2 in which a part of the one-conductivity-type (for example, p-type) crystalline semiconductor particles 2 is joined and the other-conductivity-type semiconductor portion 3 is formed. The insulator 4 is formed so as to cover the substrate 1 and the lower part of the other conductive type semiconductor part 3 and to expose the upper part of the other conductive type semiconductor part 3 so as to cover the upper part of the other conductive type semiconductor part 3. An insulating film 6 having an uncovered portion is formed, and a transparent conductive layer 5 serving as an upper electrode is formed so as to cover the insulator 4 and the insulating film 6, and the other conductive type semiconductor portion is formed through the uncovered portion. 3 and the translucent conductive layer 5 are electrically connected. Here, the partial region of the crystalline semiconductor particle 2 is a minimum necessary region necessary for reliably joining the substrate 1, and the substrate 1 and the crystalline semiconductor particle 2 are a part of the crystalline semiconductor particle 2. Bonded over the entire area. For this reason, in the photoelectric conversion device shown in FIG. 1, the semiconductor portion 3 is formed up to the junction with the substrate 1 also on the lower half side of the crystalline semiconductor particles 2.

  As the substrate 1, metal, glass, ceramic, or the like is used. Preferably, a highly reflective metal such as silver (Ag), aluminum (Al), or copper (Cu) is used. This is because by using the substrate 1 having a high reflectance, a large amount of reflected light from the substrate 1 can be guided to the pn junction of the granular semiconductor 20 that performs photoelectric conversion, thereby improving the conversion efficiency. When an insulator is used as the substrate 1, it is necessary to form a conductive layer serving as a lower electrode on the surface of the substrate 1. In order to guide more reflected light from the substrate 1 to the pn junction part of the granular semiconductor 20 that performs photoelectric conversion due to the presence of this conductive layer, it has high light reflectivity such as silver, aluminum, copper, etc., and good conductivity. It is preferable to form with the material which has a rate. For example, a simple substance of aluminum or a composite in which a metal or ceramic having a melting point equal to or higher than that of aluminum is used as a base substrate and an electrode layer made of aluminum is formed thereon can be used.

  On the substrate 1, a large number of one-conductive type crystalline semiconductor particles 2 are arranged. The crystalline semiconductor particles 2 are made of silicon (Si), germanium (Ge), etc., but added to the crystalline semiconductor particles 2 to exhibit p-type boron (B), aluminum, antimony (Sb), n-type, and the like. Phosphorus (P), arsenic (As), or the like exhibiting The crystalline semiconductor particles 2 may have a polyhedral shape, rounded corners, or curved surfaces, and the particle size distribution may be uniform or non-uniform. Since a process for aligning the diameters is required, non-uniformity is advantageous in order to reduce the cost. Furthermore, by having a convex curved surface, the dependence of the light beam angle can be reduced.

  The particle size of the crystalline semiconductor particles 2 is preferably 0.2 mm or greater and 1.0 mm or less. This is because if the thickness exceeds 1.0 mm, the amount of raw material used in the conventional crystal plate type photoelectric conversion device including the cutting portion is not changed, and the merit of using crystalline semiconductor particles is lost. On the other hand, when the thickness is less than 0.2 mm, another problem that it is difficult to assemble the substrate 1 is not preferable. More preferably, the grain size of the crystalline semiconductor particles 2 is 0.2 mm or more and 0.6 mm or less because of the amount of raw material used.

  The crystalline semiconductor particles 2 may be either single crystal or polycrystalline, but are preferably single crystal in order to increase the photoelectric conversion efficiency.

After disposing a large number of these crystalline semiconductor particles 2 on the substrate 1, a certain load is applied on the crystalline semiconductor particles 2 to heat the substrate 1 and the crystalline semiconductor particles 2. The substrate 1 and the crystalline semiconductor particles 2 are bonded via the alloy layer 10 with the semiconductor particles 2. For example, when the substrate 1 made of aluminum and the crystalline semiconductor particles 2 made of silicon are bonded, heating to 577 ° C. or more, which is the eutectic temperature of aluminum and silicon, is sufficient to ensure bonding strength. When the conductivity type of the crystalline semiconductor particles 2 made of silicon is p-type, aluminum as the material of the substrate 1 diffuses in the region of the crystalline semiconductor particles 2 in contact with the alloy layer 10 and the p ⁺ layer. Form. For this reason, since it becomes a photoelectric conversion apparatus which has high conversion efficiency by a BSF effect (Back Surface Field), it is preferable.

A semiconductor portion 3 is formed on the surface of the crystalline semiconductor particle 2 excluding a partial region, and a granular semiconductor 20 that performs photoelectric conversion is formed. The semiconductor portion 3 is formed by adding a trace component to silicon, germanium or the like so as to have a conductivity type opposite to that of the crystalline semiconductor particles 2. For example, the semiconductor unit 3 is formed by introducing a small amount of a vapor phase of a phosphorus-based compound exhibiting n-type or a vapor phase of a boron-based compound exhibiting p-type into the vapor phase of a silane compound by a vapor deposition method or the like. Further, the semiconductor portion 3 may be formed outside the crystalline semiconductor particles 2 by an ion implantation method or a thermal diffusion method. The concentration of the trace element in the semiconductor portion 3 may be, for example, 1 × 10 ¹⁶ atoms / cm ³ or more and 1 × 10 ¹⁹ atoms / cm ³ or less. Since the semiconductor portion 3 is formed before the insulator 4 is formed, the pn junction can be protected from contamination due to the formation of the insulator 4.

  Further, according to the photoelectric conversion device shown in FIG. 1, the semiconductor portion 3 is also formed on the surface of the lower half side of the crystalline semiconductor particles 2. For this reason, the light transmitted through the insulator 4 is reflected by the substrate 1 and irradiated to the pn junction of the granular semiconductor 20 that performs photoelectric conversion, so that the light incident on the entire photoelectric conversion device is efficiently photoelectrically converted. It is possible to irradiate the pn junction of the granular semiconductor 20 that performs the above without waste. For this reason, it becomes photoelectric conversion with high conversion efficiency.

  The semiconductor portion 3 may be any of crystalline, amorphous, and a mixture of crystalline and amorphous, but considering the light transmittance, crystalline or a mixture of crystalline and amorphous Is good.

An insulator 4 is formed on the substrate 1 so as to fill between the adjacent granular semiconductors 20 that perform photoelectric conversion. The insulator 4 is made of an insulating material for separating the positive electrode and the negative electrode. For example, SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , CaO, MgO, P ₂ O ₅ , Li ₂ O, SnO ₂ , ZnO , BaO, TiO _2, etc., a glass material for low-temperature firing mainly composed of an arbitrary component selected from, for example, a glass composition in which a filler composed of any combination of one or more of the above materials is combined, epoxy resin, polyimide, etc. A heat-resistant resin material, an inorganic organic composite material, or the like may be used, but a polyimide having a curing temperature of 180 ° C. or higher and 250 ° C. or lower, more preferably a curing temperature of 220 ° C. or lower is preferable. This is because, by setting the heat treatment temperature for curing to 250 ° C. or less, an insulator is provided between the adjacent granular semiconductors 20 that perform photoelectric conversion without causing thermal damage to the pn junction of the granular semiconductor 20 that performs photoelectric conversion. This is because the pn junction can be kept in high quality and a photoelectric conversion device with high conversion efficiency can be manufactured. When the heat treatment temperature for curing is less than 180 ° C., an uncured portion remains, which is not preferable. In order to lower the curing temperature of polyimide, the skeleton of the raw acid component or amine component may be changed, or a basic low-temperature curing agent that promotes the imidization reaction may be added. If used, it is desirable to select one that can be volatilized and removed as much as possible during the polyimide curing process. In addition, although the curing temperature of a polyimide can be normally estimated by the imidation rate calculated | required from a thermal analysis or an infrared peak ratio, the temperature which becomes 99% or more of imidation rate can be considered substantially as a curing temperature.

  The thickness of the insulator 4 is desirably 1 μm or more. This is because if the thickness is less than 1 μm, the insulation becomes unstable, and therefore a short-circuit current easily flows from the translucent conductive layer 5 serving as the upper electrode to the substrate 1 serving as the lower electrode, thereby reducing the conversion efficiency. It is because it is not preferable. In addition, it is not preferable that a short-circuit current easily flows from the light-transmitting conductive layer 5 serving as the upper electrode to the substrate 1 serving as the lower electrode because the insulating material changes in quality and the weather resistance and adhesion are deteriorated. For example, when polyimide is used as the insulator 4, the carbonization of the polyimide is promoted and the weather resistance and adhesion are deteriorated.

  The light transmittance of the insulator 4 at a wavelength of 400 nm to 1200 nm is preferably 70% or more. This is because when the light transmittance is less than 70%, the amount of light guided to the pn junction of the granular semiconductor 20 that performs photoelectric conversion decreases, and conversion efficiency decreases.

  The insulator 4 is formed on the substrate 1 so as to fill the space between the granular semiconductors 20 that perform photoelectric conversion after the semiconductor portion 3 is formed. The semiconductor portions 3 are merely formed independently on the crystalline semiconductor particles 2 and are connected to each other by the translucent conductive layer 5. For this reason, a polishing process for removing a part of the insulator 4 is not required, and as a result, defects caused by a polishing process for removing a part of the insulator 4 as in the conventional photoelectric conversion device, or the insulator 4 is crystallized. Since the quality of the pn junction is not deteriorated due to the contamination due to adhering to the surface of the crystalline semiconductor particle 2, high conversion efficiency can be realized. Furthermore, the polishing step for removing the insulator 4 is not required, and the productivity is improved.

  The insulator 4 is formed by a dipping method, a spin coating method, a spray method, a screen printing method, a method using a capillary phenomenon, or the like. Here, the method using the capillary phenomenon is to apply an uncured insulating material on the substrate 1 and automatically fill the gap between the granular semiconductors 20 that perform photoelectric conversion by the capillary phenomenon. After being moved and spread, the substrate 1 and the gap between the plurality of granular semiconductors 20 that perform photoelectric conversion are filled, and then heat treatment is performed and cured. This method is preferable because the insulator 4 can be formed without using a large-scale apparatus.

  A case where the insulator 4 made of polyimide is formed by a method using a capillary phenomenon will be described. First, uncured polyimide is dissolved in an organic solvent to prepare a polyimide solution. As the organic solvent, N-methylpyrrolidone, N, N′-dimethylformamide, N, N′-dimethylacetamide, o, m, p-methylphenol and the like can be used, but they have high solubility and low toxicity. N-methylpyrrolidone and N, N′-dimethylacetamide are preferable because of low cost. The polyimide solution thus prepared is used, for example, by using a dispenser so that the upper part of the granular semiconductor 20 that performs photoelectric conversion is exposed in a spot shape or a line shape at specific positions on the substrate 1 at equal intervals. Adjust the supply amount. The polyimide solution on the substrate 1 moves between the granular semiconductors 20 that automatically perform photoelectric conversion by capillary action, and fills the entire area between adjacent granular semiconductors 20 that perform photoelectric conversion on the substrate 1. Here, in order to easily move the polyimide solution by capillary action and form the insulator 4 with high productivity, when the viscosity of the polyimide solution is 10% by mass, preferably 100 mPa · s or less at 25 ° C. Is preferably 60 mPa · s or less, more preferably 40 mPa · s or less. When the viscosity is 60 mPa · s or less, since the insulating material can move over a wide range by capillary action, the number of locations where the insulating material is supplied onto the substrate 1 and the granular semiconductor 20 that performs photoelectric conversion can be reduced. This is preferable because of improved properties. Furthermore, in the case of 40 mPa · s or less, it is possible to quickly fill the uncured insulating material between the granular semiconductors 20 that perform photoelectric conversion, and reduce the amount of uncured insulating material used as a raw material to the minimum necessary level. This is preferable. Moreover, in order to make the thickness of the insulator 4 1 μm or more, the concentration of the polyimide solution is preferably 10% by mass or more. In this way, the polyimide solution filled on the entire substrate 1 is heated and cured to form the insulator 4. The heat treatment for curing is preferably performed in a non-oxidizing atmosphere such as a nitrogen or argon atmosphere. This is because heat treatment in a non-oxidizing atmosphere increases the light transmittance of the insulator 4 made of polyimide and improves the adhesion to the substrate.

  An insulating film 6 is formed along the surface of the portion of the granular semiconductor 20 that performs photoelectric conversion that is not in contact with the insulator 4. The insulating film 6 can be made of the same material as that of the insulator 4, but it is preferable to use a material in which two kinds of insulating materials are mixed while being separated from each other. For example, a mixture of an uncured alkaline insulating material and an acidic or neutral insulating material may be used. This is because an uncured insulating material obtained by mixing an alkaline insulating material and an acidic or neutral insulating material is dissolved in an organic solvent, and a thin film is formed on the surface of the granular semiconductor 20 that performs photoelectric conversion. This is because when the thin insulating film 6 is formed, an uncovered portion is automatically formed, so that the uncovered portion can be formed on the insulating film 6 with high productivity.

  The reason why such an uncovered portion is formed is not yet clear, but it is presumed that it is formed by the following mechanism. That is, when an alkaline, acidic or neutral uncured insulating material is mixed and dissolved in an organic solvent to prepare a mixed solution, the alkaline insulating material and the acidic or neutral insulating material are mixed in the mixed solution. , Exist in a state separated from each other. Using such a mixed solution, for example, when a thin film having a thickness of about 10 nm is formed and cured, the organic solvent evaporates, and the alkaline insulating material and the acidic or neutral insulating material are cured. However, since it exists in the state isolate | separated from each other, it is guessed that a clearance gap will generate | occur | produce between both and an uncovered part will be formed. As a combination of insulating materials having such characteristics, for example, there is a combination of polyimide and silicone resin. By mixing silicone resin with respect to polyimide at a ratio of 5% to 40% and dissolving in an organic solvent to produce a mixed solution, a non-coated part is automatically formed when a thin film is formed and cured. The Here, the curing temperature of each insulating material, the organic solvent that dissolves each insulating material, the concentration of the mixed solution, the viscosity of the mixed solution, and the light transmittance when each insulating material is cured are in the case of the insulator 4 made of polyimide. You can do it in the same way.

  Further, by reducing the film thickness of the insulating film 6, it is possible to easily fill a non-covered portion of the insulating film 6 and form a material having a good conductivity. The photoconductive layer 5 can be electrically connected. For example, the same material as the conductive translucent conductive layer 5 may be used as the material having good conductivity.

  The insulating film 6 may be formed by a dipping method, a spin coating method, a spray method, a screen printing method, a method using a capillary phenomenon, etc., as in the case of the insulator 4, but it does not require a large-scale device, so that the capillary phenomenon is prevented. It is preferable to form by the method to utilize.

  The number, size, and shape of the non-covered portion of the insulating film 6 can be freely designed as long as the granular semiconductor 20 that performs photoelectric conversion and the translucent conductive layer 5 can be electrically connected. The uncovered portion is formed by removing a part of the insulating film 6 near the zenith of the granular semiconductor 20 that performs photoelectric conversion after the insulating film 6 is formed, or by using two types of uncured insulating materials. Using a mixed solution that is mixed in a state separated from each other and dissolved in an organic solvent, a thin film may be formed on the surface of the granular semiconductor 20 that performs photoelectric conversion, and then cured to form automatically. . Here, the zenith portion refers to the highest position of the granular semiconductor 20 that performs photoelectric conversion.

  By forming the insulating film 6 having the uncovered portion between the semiconductor portion 3 and the translucent conductive layer 5 in this way, the granular semiconductor 20 that performs photoelectric conversion with the translucent conductive layer 5 through the uncovered portion, and Are electrically connected to each other, but a short circuit between the translucent conductive layer 5 and the substrate 1 serving as the lower electrode can be surely prevented by the insulating film 6 in addition to the insulator 4. Can be obtained.

A translucent conductive layer 5 is formed so as to cover the insulator 4 and the insulating film 6. The translucent conductive layer 5 is formed of one or more oxides selected from SnO ₂ , In ₂ O ₃ , ITO, ZnO, TiO _{2 and the} like by a film forming method such as a sputtering method or a vapor phase growth method or a coating baking method. A material film or one or more metal films selected from Ti, Pt, Au and the like are formed. In addition, it is necessary to form such a translucent conductive layer 5 with a material having a high light transmittance at a wavelength of 400 nm to 1200 nm so as not to absorb light. Here, the material having a high light transmittance means, for example, a material having a light transmittance of 70% or more, and ITO or the like is preferable. This is because the loss of the amount of light guided to the pn junction of the granular semiconductor 20 that performs photoelectric conversion can be reduced by forming the translucent conductive layer 5 with a material having high light transmissivity. Moreover, the translucent conductive layer 5 can be expected to have an effect as an antireflection film by adjusting the film thickness and refractive index.

  Furthermore, pattern electrodes (not shown) such as fingers and bus bars at regular intervals may be provided on the translucent conductive layer 5 in order to reduce the series resistance value.

A protective film (not shown) may be formed on the translucent conductive layer 5. The protective film is preferably light-transmitting and having dielectric properties, such as silicon oxide, cesium oxide, aluminum oxide, nitride by CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition). Silicon, titanium oxide, SiO ₂ —TiO ₂ , tantalum oxide, yttrium oxide, or the like may be formed as a single layer or a combination of a single composition or a plurality of compositions. Since this protective film is disposed on the light incident surface, it needs to be translucent, and it needs to be a dielectric material to prevent leakage of current obtained by photoelectric conversion. Furthermore, if the thickness of the protective film is optimized, a function as an antireflection film can be expected.

  Further, as shown in FIG. 2, it is preferable to provide a conductive protective layer 7 between the granular semiconductor 20 that performs photoelectric conversion and the insulating film 6. FIG. 2 shows that the conductive protective layer 7 is formed on the surface of the granular semiconductor 20 that performs photoelectric conversion, excluding the junction with the substrate 1, so that the conductivity is between the granular semiconductor 20 that performs photoelectric conversion and the insulating film 6. It is sectional drawing which shows an example of the photoelectric conversion apparatus which interposed the protective layer. By providing the conductive protective layer 7 between the granular semiconductor 20 that performs photoelectric conversion and the insulating film 6, the light-transmitting conductive layer 5 and the electricity through the non-covered portion of the insulating film 6 of the granular semiconductor 20 that performs photoelectric conversion. The photocurrent generated at a site distant from the connected site (hereinafter referred to as the connection site) is collected to the connection site through the conductive protective layer 7 having a low resistance, and the translucent conductive material serving as the upper electrode The loss of photocurrent generated in the granular semiconductor 20 that can be transmitted to the layer 5 and that performs photoelectric conversion can be reduced. Here, as long as the conductive protective layer 7 covers the upper part of the granular semiconductor 20 that performs photoelectric conversion, the conductive protective layer 7 may be formed on the entire surface of the granular semiconductor 20 that performs photoelectric conversion, excluding the junction with the substrate 1. , A portion not formed may be provided.

The conductive protective layer 7 is formed of SnO ₂ , In ₂ O ₃ , ITO, ZnO, TiO ₂ by a film forming method such as sputtering or vapor phase growth, or a coating / firing method, as with the light-transmitting conductive layer 5. One or more oxide-based films selected from the above, or one or more metal-based films selected from Ti, Pt, Au, or the like are formed. Such a conductive protective layer 7 needs to be formed of a material having a high light transmittance at a wavelength of 400 nm to 1200 nm so as not to absorb light. Here, the material having a high light transmittance means, for example, a material having a light transmittance of 70% or more, and ITO is preferable. This is because the loss of the amount of light guided to the pn junction of the granular semiconductor 20 that performs photoelectric conversion can be reduced by forming the conductive protective layer 7 with a material having high light transmittance.

  The conductive protective layer 7 is preferably formed before forming the insulator 4 so as to cover the semiconductor portion 3 formed on the surface excluding a partial region of the crystalline semiconductor particles 2. This is because, since the conductive protective layer 7 is formed before the insulator 4 is formed, the insulator 4 and the insulating film 6 can be formed at the same time as described later, and the productivity is improved. Further, according to the photoelectric conversion device shown in FIG. 2, the semiconductor portion 3 and the conductive protective layer 7 are also formed on the surface of the lower half side of the crystalline semiconductor particles 2. For this reason, the light transmitted through the insulator 4 is reflected by the substrate 1 and irradiated to the pn junction of the granular semiconductor 20 that performs photoelectric conversion, so that the light incident on the entire photoelectric conversion device is efficiently photoelectrically converted. It is possible to irradiate the pn junction of the granular semiconductor 20 that performs the above without waste. For this reason, photoelectric conversion can be performed efficiently, and the generated photocurrent can be led to the junction site with little resistance loss.

  Here, it is preferable that the thickness of the zenith part of the granular semiconductor 20 which performs photoelectric conversion of the conductive protective layer 7 is 3 nm or more and 30 nm or less. This is because if the thickness of the zenith portion of the granular semiconductor 20 that performs photoelectric conversion of the conductive protective layer 7 is less than 3 nm, the contact resistance with the translucent conductive layer 5 increases, which is not preferable. On the other hand, when the thickness of the top of the granular semiconductor 20 that performs photoelectric conversion of the conductive protective layer 7 exceeds 30 nm, the pn junction of the granular semiconductor 20 that absorbs light by the conductive protective layer 7 and performs photoelectric conversion The amount of light guided to the portion is reduced. In particular, when the conductive protective layer 7 is also formed below the granular semiconductor 20 that performs photoelectric conversion, it flows through the conductive protective layer 7 to the substrate 1 serving as the lower electrode. This is not preferable because leakage current increases and conversion efficiency decreases.

  Next, a method for manufacturing a photoelectric conversion device according to the present invention will be described using the photoelectric conversion device shown in FIG. 1 as an example.

  FIG. 3 is a cross-sectional view showing the steps of the method for producing a photoelectric conversion device of the present invention.

  First, as shown in FIG. 3A, a large number of crystalline semiconductor particles 2 are densely arranged on the substrate, and the whole is heated while applying a load from above the crystalline semiconductor particles. The crystalline semiconductor particles 2 are joined via an alloy layer 10 of the substrate 1 and the crystalline semiconductor particles 2.

  Next, as shown in FIG. 3B, the semiconductor portion 3 is formed on the surface of the crystalline semiconductor particles 2 to produce a granular semiconductor 20 that performs photoelectric conversion. At this time, if the crystalline semiconductor particles 2 are p-type, the semiconductor portion 3 is formed to be n-type, and if the crystalline semiconductor particles 2 are n-type, the semiconductor portion 3 is p-type. Form. The semiconductor portion 3 may not be formed on the crystalline semiconductor particles 2 but may be formed by injecting a dopant into the crystalline semiconductor particles 2. Alternatively, the semiconductor portion 3 may be formed by thermally diffusing the dopant into the crystalline semiconductor particles 2, and then the substrate 1 and the crystalline semiconductor particles 2 may be joined.

  Next, as shown in FIG. 3C, the insulator 4 is filled so as to fill in the space between adjacent granular semiconductors 20 that perform photoelectric conversion, and the insulating film 6 is formed on the upper surface of the granular semiconductor 20 that performs photoelectric conversion. Form. The insulator 4 and the insulating film 6 may be formed separately or at the same time, but are preferably formed at the same time because the manufacturing process is simplified and the productivity is improved.

  When the insulator 2 and the insulating film 6 are formed of the same material at the same time, the insulator 2 and the insulating film 6 are integrated. At this time, the portion formed along the granular semiconductor 20 that performs photoelectric conversion and in contact with the translucent conductive layer 5 becomes the insulating film 6, and the remaining portion becomes the insulator 4.

  The uncovered portion of the insulating film 6 may be formed by removing a part of the insulating film 6 by etching or the like after the insulating film 6 is formed, or may be formed at the same time as the insulating film 6 is formed. In order to form an uncovered portion at the same time as the formation of the insulating film 6, for example, photoelectric conversion is performed using a mixed solution in which two uncured insulating materials are mixed while being separated from each other and dissolved in an organic solvent. A thin film is formed on the surface of the granular semiconductor 20 to be subjected to the curing process, and the insulating film 6 is formed by performing a curing process, so that the uncovered portion may be automatically formed.

  In order to form the insulator 4 and the insulating film 6 at the same time and simultaneously form the non-covered portion when the insulating film 6 is formed, for example, the following may be performed. Using a dipping method, spin coating method, spray method, method using capillary action, etc., a mixed solution in which an alkaline insulating material and acid and neutral insulating materials are mixed in an uncured state and dissolved in an organic solvent Supply to the substrate 1 and the granular semiconductor 20 that performs photoelectric conversion, fill the upper surface of the granular semiconductor 20 that performs photoelectric conversion and the lower portion between the granular semiconductor 20 that performs photoelectric conversion, and then heat and mix as a whole The solution is cured to form the insulator 4 and the insulating film 6. Here, the insulating film 6 is formed so as to cover the surface of the granular semiconductor 20 that performs photoelectric conversion. If the thickness of the insulating film 6 is reduced to, for example, 10 nm, an uncovered portion is automatically formed. The thickness of the insulating film 6 can be freely adjusted by the viscosity and concentration of the mixed solution. In the case where the insulator 4 and the insulating film 6 are formed by a method utilizing the capillary phenomenon, even if the thickness of the mixed solution on the granular semiconductor 20 that performs photoelectric conversion when the mixed solution is supplied is increased. However, there is no problem because the thickness of the upper part of the granular semiconductor 20 that performs photoelectric conversion becomes thin and an uncoated portion is formed. Further, the supply amount of the mixed solution is adjusted so that the thickness of the insulator 4 is thinner than the height of the granular semiconductor 20 that performs photoelectric conversion.

  Next, as shown in FIG. 3D, the translucent conductive layer 5 is formed so as to cover the insulator 4 and the insulating film 6, and the photoelectric conversion device of the present invention shown in FIG. 1 can be obtained. . Here, by filling the uncovered portion of the insulating film 6 to form the light-transmitting conductive layer 5, the granular semiconductor 20 that performs photoelectric conversion and the light-transmitting conductive layer 5 are in an electrically connected state. be able to.

  Next, a method for manufacturing the photoelectric conversion device of the present invention will be described using the photoelectric conversion device shown in FIG. 2 as an example.

  First, in the same manner as in the above manufacturing method, the crystalline semiconductor particles 2 are bonded onto the substrate 1, the semiconductor portion 3 is formed on the surface of the crystalline semiconductor particles 2 excluding the bonding portion with the substrate 1, and the photoelectric conversion is performed. The semiconductor 20 is manufactured. Next, the conductive protective layer 7 is formed on the surface of the granular semiconductor 20 that performs photoelectric conversion, excluding the joint portion with the substrate 1. Next, similarly to the above manufacturing method, the insulator 4, the insulating film 6, and the light-transmitting conductive layer 5 can be formed to obtain the photoelectric conversion device of the present invention shown in FIG.

  The photoelectric conversion device of the present invention is not limited to the above-described embodiment, and various changes and improvements can be added without departing from the gist of the present invention.

  Next, a specific first embodiment of the photoelectric conversion device of the present invention will be described with reference to the photoelectric conversion device shown in FIG.

After a large number of crystalline semiconductor particles 2 made of p-type silicon having a particle size of 0.3 mm or more and 0.5 mm or less are placed on a substrate 1 made of aluminum, the crystalline semiconductor particles 2 are fixed from above so that they do not move. The substrate 1 and the crystalline semiconductor particles 2 are heated in a N ₂ —H ₂ atmosphere at 630 ° C. for 10 minutes while being pressed under a load, and the alloy layer 10 between the substrate 1 and the crystalline semiconductor particles 2 is heated. It joined via.

  Next, in order to clean the surface of the crystalline semiconductor particles 2, the substrate 1 to which the crystalline semiconductor particles 2 are bonded is immersed in a hydrofluoric nitric acid mixed solution in which the mixing ratio of hydrofluoric acid to nitric acid is 0.05 for 1 minute. And then thoroughly washed with pure water. Next, the semiconductor portion 3 made of n-type amorphous silicon is formed to a thickness of 20 nm on the surface excluding a partial region of the crystalline semiconductor particles 2 by plasma CVD using a mixed gas consisting of silane gas and a small amount of phosphorus compound. Formed with.

  Next, a polyimide resin having a curing temperature of 230 ° C. and a silicone resin were mixed at a ratio of the silicone resin to the polyimide of 15% and dissolved in an N-methylpyrrolidone solution to prepare a mixed solution. The concentration of the mixed solution was 12% by mass, and the viscosity at 25 ° C. when the concentration of the mixed solution was 10% by mass was 50 mPa · s. This mixed solution was supplied onto the granular semiconductor 20 that performs photoelectric conversion and the substrate 1 using a dispenser, and filled in the lower part between adjacent granular semiconductors 20 that perform photoelectric conversion by a method utilizing capillary action. Next, it heated at 250 degreeC in nitrogen atmosphere for 1 hour, the mixed solution of the polyimide and the silicone resin was hardened, and the insulator 4 and the insulating film 6 were formed. The thickness of the insulator 4 was formed in the range of 1 μm or more and 5 μm or less. Further, the film thickness of the insulating film 6 is 5 nm, and several tens of uncovered portions having a circle-equivalent diameter of several hundred nm are formed on the insulating film 6. Here, the equivalent circle diameter indicates the diameter of a circle assumed to be a circle having an area equal to the area when the non-covered portion is viewed from above. When the insulating film 6 is viewed from above, the non-covered portion includes various shapes such as a circle, an ellipse, and a polygon with a blunt corner. The mixed solution was applied to a glass substrate, heat-treated at 250 ° C. for 1 hour in a nitrogen atmosphere, and the light absorptivity was measured. It was 1% at 500 nm, and had good light transmission at a wavelength of 400 nm to 1200 nm.

  Next, it is put into a DC sputtering apparatus using an ITO target, and the transparent conductive layer 5 made of ITO is formed to a thickness of 100 nm so as to cover the insulator 4 and the insulating film 6 and fill the uncovered portion of the insulating film. Formed.

  Next, after providing the pattern electrode which consists of a finger and a bus bar on the translucent conductive layer 5, when the photoelectric conversion rate was measured, it was 8.3%. Further, after 500 cycles of a temperature cycle test from −40 ° C. to 90 ° C. were performed on this photoelectric conversion device, the conversion efficiency was measured and found to be 8.1%.

  Next, as a second embodiment of the photoelectric conversion device of the present invention, the photoelectric conversion device shown in FIG. 2 will be described as an example. As in the first embodiment, after bonding the crystalline semiconductor particles 2 on the substrate 1 and forming the semiconductor part 3, the semiconductor part 3 is put into a DC sputtering apparatus using an ITO target. A conductive protective layer 7 was formed with a thickness at the zenith portion of 10 nm. Thereafter, as in the first example, an insulator 4, an insulating film 6, a light-transmitting conductive layer 5, and a pattern electrode were formed to produce a photoelectric conversion device, and the conversion efficiency was measured. It was. Further, when 500 cycles of a temperature cycle test from −40 ° C. to 90 ° C. were performed on this sample, the conversion efficiency was 8.4%. A number of uncovered portions were automatically formed on the insulating film 6 formed on the conductive protective layer 7.

  Both the first embodiment and the second embodiment have high conversion efficiency and high reliability. This is because an insulating film 6 having an uncovered portion is formed between the semiconductor portion 3 and the translucent conductive layer 5 to insulate a short circuit between the translucent conductive layer 5 and the substrate 1 that becomes the lower electrode. Since it was reliably prevented by the insulating film 6 in addition to the body 4, it is presumed that high conversion efficiency and high reliability were obtained. Moreover, it has confirmed that the semiconductor part 3 and the translucent conductive layer 6 were able to be electrically connected reliably through the non-coating part from having high conversion efficiency. Further, the conversion efficiency of the second example was higher than that of the first example. This is presumably because the conductive protective layer 7 and the translucent conductive layer 5 are electrically connected to reduce the resistance and reduce the resistance loss of the generated photocurrent.

  As can be seen from the above results, by forming the insulating film 6 having an uncovered portion between the semiconductor portion 3 and the translucent conductive layer 5, the translucent conductive layer 5 and the substrate 1 serving as the lower electrode, It was possible to obtain a photoelectric conversion device having high conversion efficiency by reliably preventing the short circuit. In addition, since the conductive protective layer 7 is formed between the insulating film 6 and the semiconductor portion 3, the resistance loss of the generated photocurrent can be reduced, so that a photoelectric conversion device having higher conversion efficiency is obtained. I was able to.

It is sectional drawing which shows an example of embodiment of the photoelectric conversion apparatus of this invention. It is sectional drawing which shows the other example of embodiment of the photoelectric conversion apparatus of this invention. (A)-(d) is sectional drawing explaining each process of the manufacturing method of the photoelectric conversion apparatus of this invention. It is sectional drawing which shows the conventional photoelectric conversion apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... substrate 2 ... crystalline semiconductor particle 3 ... semiconductor part 4 ... insulator 5 ... translucent conductive layer 6 ... insulating film 7 ...・ Conductive protective layer
10 ... Alloy layer
20 ... Granular semiconductor

Claims (6)

A plurality of granular semiconductors that perform photoelectric conversion are joined on a substrate that serves as a lower electrode, an insulator is provided between the granular semiconductors, and an insulating film having an uncoated portion is provided on the granular semiconductor. A photoelectric conversion device, wherein a translucent conductive layer serving as an upper electrode is formed on the insulator and the insulating film so as to be electrically connected to the granular semiconductor through an uncovered portion. A large number of granular semiconductors that perform photoelectric conversion are bonded onto a substrate that serves as a lower electrode, and a conductive protective layer is provided on the surface of the granular semiconductor excluding the bonded portion, whereby the conductive protective layer is formed. An insulator is provided between the granular semiconductors, an insulating film having an uncovered portion is provided on the granular semiconductor on which the conductive protective layer is formed, and the conductive protective layer is electrically connected to the conductive layer through the non-covered portion. A light-transmitting conductive layer serving as an upper electrode is formed on the insulator and the insulating film so as to be connected to the photoelectric conversion device. A step of bonding a large number of granular semiconductors that perform photoelectric conversion on a substrate to be a lower electrode, and forming an insulator below the granular semiconductor and an insulating film having an uncoated portion above the granular semiconductor. Forming a translucent conductive layer to be an upper electrode on the insulator and the insulating film, and electrically connecting the granular semiconductor and the translucent conductive layer through the uncovered portion of the insulating film. And a step of connecting to the photoelectric conversion device. Supplying a mixed solution in which two uncured insulating materials are mixed and dissolved in an organic solvent on the substrate and a large number of the granular semiconductors, and filling the mixed solution in the lower part between the granular semiconductors 4. The film of the mixed solution is formed on the granular semiconductor, and then the mixed solution is cured to form the insulating film having the insulator and the non-covered portion. The manufacturing method of the photoelectric conversion apparatus of description. A step of bonding a number of granular semiconductors that perform photoelectric conversion on a substrate to be a lower electrode; a step of forming a conductive protective layer on a surface of the granular semiconductor excluding a bonding portion with the substrate; and between the granular semiconductors Forming an insulator on the bottom of the substrate, forming an insulating film having an uncovered portion on the granular semiconductor on which the conductive protective layer is formed, and forming an upper electrode on the insulator and the insulating film. Forming a light-transmitting conductive layer, and electrically connecting the conductive protective layer and the light-transmitting conductive layer through the non-covering portion of the insulating film. Manufacturing method. A mixed solution in which two uncured insulating materials are mixed and dissolved in an organic solvent is supplied to the lower part of the granular semiconductor on the substrate and the granular semiconductor on which the plurality of conductive protective layers are formed. After forming the film of the mixed solution on the granular semiconductor in which the mixed solution is filled and the conductive protective layer is formed, the mixed solution is cured to form the insulator and the non-covered portion. The method for manufacturing a photoelectric conversion device according to claim 5, wherein the insulating film is formed.

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