JP2005159168A - Photoelectric conversion device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low conversion efficiency and low productivity in a conventional method for producing a photoelectric conversion device using crystalline semiconductor particles.
SOLUTION: In a partial region of a large number of one-conductivity-type crystalline semiconductor particles 3 in which a semiconductor portion 4 of the other conductivity type is formed on the surface of a substrate 1 serving as a lower electrode except for a partial region on the surface. In addition to being bonded, the substrate 1 and the semiconductor portion 4 are arranged in a separated state, cover the substrate 1 and the lower portion of the semiconductor portion 4 between the adjacent crystalline semiconductor particles 3, and the semiconductor portion 4. The insulator 2 is formed by exposing the upper portion of the semiconductor substrate 4, and the upper electrode 5 is formed so as to cover the insulator 2 and the upper portion of the semiconductor portion 4, so that the substrate 1 serving as the upper electrode 5 and the lower electrode by the semiconductor portion 4 is formed. Therefore, a photoelectric conversion device with high conversion efficiency and high productivity can be obtained.
[Selection] Figure 1

Description

  The present invention relates to a photoelectric conversion device such as a solar cell that converts light into electricity and a method for manufacturing the photoelectric conversion device, and more particularly to a photoelectric conversion device using crystalline semiconductor particles and a method for manufacturing the photoelectric conversion device.

  Conventionally, solar cells with high conversion efficiency using crystalline silicon wafers have been put into practical use. This crystalline silicon wafer is manufactured by cutting from a large single crystal silicon ingot having good crystallinity, low impurities, and no uneven distribution. However, large single crystal silicon ingots take a long time to produce, so the productivity is poor and this makes it expensive, so there is no need for large single crystal silicon ingots and the emergence of highly efficient next-generation solar cells Is strongly desired.

  As a photoelectric conversion device that does not require a large single crystal silicon ingot, for example, a photoelectric conversion device using silicon crystal particles as shown in FIG. 5 has been proposed (see Patent Document 1). In this photoelectric conversion device, a low-melting point metal layer 108 is formed on a substrate 101, and a large number of one-conductivity-type semiconductor particles 103 are disposed on the low-melting point metal layer 108, and the low-melting point metal layer 108 is heated. After these semiconductor particles 103 are fixed, the insulator 102 is formed so as to fill the space between the fixed semiconductor particles 103 and cover the semiconductor particles 103 and the low-melting-point metal layer 108, and then one conductivity type semiconductor. Part of the insulator 102 on the particle 103 is polished to expose the one conductive type semiconductor particle 103, and the other conductive type semiconductor portion 104 and the transparent conductive layer 106 are sequentially formed on the exposed surface. It is.

Similarly, a photoelectric conversion device as shown in FIG. 6 has been proposed as a photoelectric conversion device using silicon crystal particles (see Patent Document 2). In this photoelectric conversion device, an uncured insulator 102 is formed on a graphite substrate (not shown), and one conductive type semiconductor particle 103 is disposed on the graphite substrate (not shown) so that a part of the semiconductor particle 103 is buried. After being cured, a connection layer 110 made of aluminum paste is formed so as to cover the insulator 102 and the one conductive type semiconductor particle 103 exposed from the insulator 102, and further, a substrate 101 serving as a lower electrode is provided. Then, the graphite substrate (not shown) is peeled off, and the insulator 102 on the peeled surface is polished so as to expose the one conductive type semiconductor particle 103, and the other conductive type semiconductor portion 104 is exposed on the exposed surface. And a transparent conductive layer 106 are sequentially formed.
Japanese Patent No. 2641800 JP-A-3-228379

  However, in the conventional photoelectric conversion device shown in FIGS. 5 and 6, the other conductive type semiconductor portion 104 is formed on the surface of the one conductive type semiconductor particle 103 which is polished and exposed together with the insulator 102, thereby forming a pn junction. For this reason, damage such as crystal defects due to polishing remains at the pn junction interface, and the quality of the pn junction deteriorates. This is caused by crystal defects between the valence band and the conduction electron band of the pn junction. A new energy level is formed, resulting in a problem that the conversion efficiency is lowered. In addition, since a precise polishing process is required to form a good exposed surface by polishing on all the semiconductor particles 103, there is a problem that manufacturing is difficult and productivity is poor.

  The present invention has been made in view of these problems, and an object thereof is to provide a photoelectric conversion device having high conversion efficiency and high productivity and a method for manufacturing the same.

  In the photoelectric conversion device of the present invention, a plurality of one-conductivity-type crystalline semiconductor particles in which the other-conductivity-type semiconductor portion is formed on the surface, excluding a partial region, on the substrate serving as the lower electrode. The regions are bonded to each other, and the substrate and the semiconductor portion are arranged in a separated state, covering the substrate and the lower portion of the semiconductor portion between the adjacent crystalline semiconductor particles, and the An insulator is formed by exposing an upper portion of the semiconductor portion, and an upper electrode is formed to cover the insulator and the upper portion of the semiconductor portion.

  Hereinafter, the one-conductivity-type crystalline semiconductor particles having the other-conductivity-type semiconductor portion formed on the surface excluding a partial region are referred to as semiconductor particles that perform photoelectric conversion. Here, the lower portion of the semiconductor portion refers to a portion in contact with the insulator.

  The first manufacturing method of the photoelectric conversion device of the present invention includes a step of bonding a part of a large number of one-conductivity type crystalline semiconductor particles onto a substrate serving as a lower electrode, and the crystalline semiconductor particles. Forming a semiconductor portion of the other conductivity type excluding the partial region on the surface of the substrate, a step of removing the outer periphery of the junction between the substrate and the crystalline semiconductor particles, and the adjacent crystalline semiconductor particles Forming an insulator between and covering the lower portion of the substrate and the semiconductor portion and exposing the upper portion of the semiconductor portion; and forming an upper electrode covering the insulator and the upper portion of the semiconductor portion; Are sequentially performed.

  Further, the second manufacturing method of the photoelectric conversion device of the present invention includes a step of forming a semiconductor portion of the other conductivity type on the entire surface of a large number of one-conductivity type crystalline semiconductor particles by a thermal diffusion method, a lower electrode, Bonding a large number of the crystalline semiconductor particles onto the substrate, removing the periphery of the outer periphery of the bonding portion between the substrate and the crystalline semiconductor particles, and between the adjacent crystalline semiconductor particles A step of forming an insulator that covers a substrate and a lower portion of the semiconductor portion and exposes an upper portion of the semiconductor portion, and a step of forming an upper electrode that covers the insulator and the upper portion of the semiconductor portion are sequentially performed. It is characterized by this.

  Further, in the method for manufacturing a photoelectric conversion device according to the present invention, in the first or second manufacturing method, the step of removing the periphery of the outer periphery of the bonding portion between the substrate and the crystalline semiconductor particles may be a wet etching process. It is characterized by including.

  According to the photoelectric conversion device of the present invention, a large number of one-conductivity-type crystalline semiconductor particles in which the other-conductivity-type semiconductor portion is formed on the surface excluding a partial region on the substrate serving as the lower electrode are The substrate and the semiconductor part are arranged in a state of being separated in each region, and the substrate and the lower part of the semiconductor part are covered between the adjacent crystalline semiconductor particles, In addition, since an insulator is formed by exposing the upper portion of the semiconductor portion, and an upper electrode is formed to cover the insulator and the upper portion of the semiconductor portion, pn is formed before forming the insulator. Since the bonding is formed, a polishing step is not necessary. This prevents the quality of the pn junction from deteriorating due to defects due to the removal of the insulator and contamination due to the insulator adhering to the surface of the crystalline semiconductor particles or the other conductivity type semiconductor portion. A photoelectric conversion device with high conversion efficiency and high productivity is obtained.

  In particular, when the other conductive type semiconductor portion and the first upper electrode are formed up to the vicinity of the junction with the substrate on the lower half surface of the crystalline semiconductor particles, the light transmitted through the insulator is reflected by the substrate. And since it irradiates to a pn junction part, since photoelectric conversion can be performed efficiently, it becomes a photoelectric conversion apparatus with high conversion efficiency.

  In addition, since the substrate serving as the lower electrode and the semiconductor portion are separated, it is possible to suppress a short circuit from the upper electrode through the semiconductor portion to the lower electrode, so that a photoelectric conversion device with high conversion efficiency is obtained.

  In addition, according to the first manufacturing method of the photoelectric conversion device of the present invention, the step of bonding a plurality of one-conductivity-type crystalline semiconductor particles to a substrate serving as a lower electrode, respectively, A step of forming a semiconductor portion of the other conductivity type excluding the partial region on the surface of the semiconductor particles, a step of removing the outer periphery of the joint portion between the substrate and the crystalline semiconductor particles, and the adjacent crystalline material Forming an insulator covering between the semiconductor particles and the lower portion of the semiconductor portion and exposing the upper portion of the semiconductor portion; and forming an upper electrode covering the insulator and the upper portion of the semiconductor portion. Are sequentially performed, the photoelectric conversion device of the present invention can be easily manufactured. In particular, the substrate and the semiconductor portion can be separated without reducing the area of the pn junction by removing the periphery of the substrate-side outer periphery of the junction between the substrate and the crystalline semiconductor particles, so that the photoelectric conversion device with high conversion efficiency Can be produced.

  Further, according to the second manufacturing method of the photoelectric conversion device of the present invention, the step of forming the other conductive type semiconductor part on the entire surface of the many one conductive type crystalline semiconductor particles by the thermal diffusion method, A step of bonding a large number of the crystalline semiconductor particles to a substrate to be an electrode, a step of removing the periphery of the bonding portion between the substrate and the crystalline semiconductor particles, and a gap between the adjacent crystalline semiconductor particles. Forming an insulator covering the substrate and a lower portion of the semiconductor portion and exposing an upper portion of the semiconductor portion; and forming an upper electrode covering the insulator and the upper portion of the semiconductor portion. By sequentially performing, the photoelectric conversion device of the present invention can be easily produced, and the surface of the crystalline semiconductor particles can easily form a semiconductor portion without the need for a large vacuum device, It becomes good production properties. In particular, the substrate and the semiconductor part can be separated without reducing the area of the pn junction by removing the periphery of the substrate side of the junction part between the substrate and the crystalline semiconductor particles, so that a photoelectric conversion device with high conversion efficiency can be obtained. Can be produced.

  According to the method for manufacturing a photoelectric conversion device of the present invention, in the first or second manufacturing method, the step of removing the periphery of the outer periphery of the bonding portion between the substrate and the crystalline semiconductor particles may be performed by a wet process. Since the etching process is included, the semiconductor portion and the substrate can be separated easily and without requiring a large-scale device, and the photoelectric conversion device of the present invention can be manufactured.

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

  FIG. 1 is a cross-sectional view showing an example of an embodiment of a photoelectric conversion device of the present invention. In FIG. 1, 1 is a substrate, 2 is an insulator, 3 is a crystalline semiconductor particle, 4 is a semiconductor portion, 5 is an upper electrode, and 6 is a separation portion that separates the substrate 1 and the semiconductor portion 4.

  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 4 formed on a surface of a substrate 1 serving as a lower electrode, except for a partial region. The one-conductive type (for example, p-type) crystalline semiconductor particles 3 are bonded to each other in a partial region, and the substrate 1 and the semiconductor portion 4 are separated from each other by the separation portion 6. Between the adjacent conductive semiconductor particles 3, an insulator 2 is formed so as to cover the lower portion of the substrate 1 and the semiconductor portion 4 and to expose the upper portion of the semiconductor portion 4. An upper electrode 5 is formed so as to cover the upper part of the substrate. Here, in the photoelectric conversion device shown in FIG. 1, the semiconductor portion 4 is formed up to the vicinity of the junction with the substrate 1 also on the lower half side of the crystalline semiconductor particles 3.

  As the substrate 1, metal, glass, ceramic, resin, 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 semiconductor particles that perform 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 of the semiconductor particles that perform photoelectric conversion due to the presence of the conductive layer, the conductive layer has high light reflectivity such as silver, aluminum, copper, and the like and has good conductivity. It is preferable to form with the material which has a rate.

The insulator 2 is made of an insulator 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 , Low-temperature firing glass material mainly composed of an arbitrary component selected from ZnO, BaO, TiO _2, etc., a glass composition in which a filler composed of any combination of one or more of the above materials is combined, heat resistance of epoxy resin, etc. A resin material, an inorganic organic composite material, or the like may be used.

  The light transmittance of the insulator 2 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 semiconductor particles that perform photoelectric conversion decreases, and conversion efficiency decreases.

  The insulator 2 is formed on the substrate 1 so as to fill between the semiconductor particles that perform photoelectric conversion after the semiconductor portion 4 is formed. The semiconductor part 4 is merely formed independently on the crystalline semiconductor particles 3 and is connected to each other by the upper electrode 5. Since the pn junction is formed before the insulator 2 is formed, defects caused by a polishing process for removing the insulator 2 or the insulator 2 adheres to the surface of the crystalline semiconductor particles 3 or the semiconductor portion 4. High conversion efficiency can be realized because the quality of the pn junction is not deteriorated due to the contamination caused by. Further, the polishing step for removing the insulator 2 is not required, and the productivity is improved.

The crystalline semiconductor particles 3 are made of silicon (Si), germanium (Ge), etc., but added to the crystalline semiconductor particles 3 to form p-type boron (B), aluminum, antimony (Sb), or n-type. Phosphorus (P), arsenic (As), or the like may be included. For example, in the case where the crystalline semiconductor particles 3 are p-type, about 1 × 10 ¹⁴ to 10 ¹⁸ atoms / cm ^{3 of} p-type boron and aluminum are added to the semiconductor material. The crystalline semiconductor particles 3 can be formed by a vapor phase growth method, an atomization method, a direct current plasma method, a melt dropping method, etc., but because of high productivity and low cost, the melt is produced in a non-contact environment. The melt dropping method is preferred. The crystalline semiconductor particles 3 may be either single crystal or polycrystalline, but are preferably single crystal in order to increase the photoelectric conversion efficiency.

  The semiconductor part 4 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 3. For example, when the crystalline semiconductor particles 3 are p-type, the semiconductor portion 4 contains phosphorus and arsenic which are added to silicon and exhibit n-type.

  Moreover, it is preferable that the thickness of the semiconductor part 4 is 5 nm or more and 5000 nm or less. This is because if the thickness of the semiconductor part 4 is less than 5 nm, the semiconductor part 4 is formed in an island shape, and a defective portion of the semiconductor part 4 is generated. If the thickness of the semiconductor part 4 exceeds 5000 nm, This is because light absorption in the semiconductor portion 4 increases and conversion efficiency decreases. Note that the thickness of the semiconductor portion 4 may not be uniform.

  The semiconductor portion 4 may be any one of single crystalline, polycrystalline, amorphous, microcrystalline, and nanocrystalline. Here, the microcrystalline means, for example, a crystal grain having a crystal grain size of 0.1 μm or more and less than 50 μm, and the nanocrystalline means, for example, a crystal grain having a crystal grain diameter of 1 nm or more and less than 50 nm. If the semiconductor part 4 is monocrystalline or polycrystalline, it is preferable because light absorption in the semiconductor part 4 can be reduced and conversion efficiency is improved.

  The semiconductor portion 4 may be formed by using a method of forming a thin film on the crystalline semiconductor particles 3 by a plasma CVD (Chemical Vapor Deposition) method, a catalytic CVD method, a sputtering method, etc., an ion implantation method, a thermal diffusion method. Although it may be formed outside the crystalline semiconductor particles 3 by a method or the like, it is preferably formed by a thermal diffusion method. This is because the uniform semiconductor portion 4 can be formed on the outer periphery of the crystalline semiconductor particles 3 with high productivity without the need for a large vacuum device by the thermal diffusion method. In the thermal diffusion method, for example, the dopant may be thermally diffused into the crystalline semiconductor particles 3 by heating in a gas containing the dopant.

  In addition, the present invention is not limited to a single junction type photoelectric conversion device, and the same effect can be obtained in a photoelectric conversion device having a plurality of semiconductor junctions. As a photoelectric conversion device having a plurality of semiconductor junctions, for example, an n-type microcrystalline semiconductor layer is formed on p-type crystal semiconductor particles, and a p-type amorphous semiconductor layer or i-type non-layer is formed thereon via an intermediate layer. A tandem photoelectric conversion device or the like in which a crystalline semiconductor layer and an n-type amorphous semiconductor layer are sequentially formed may be used.

  The upper electrode 5 is preferably made of tin oxide, indium oxide, or the like, which is 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. The thickness of the upper electrode 5 is preferably 50 nm or more and 300 nm or less. This is because when the thickness of the upper electrode 5 is less than 50 nm, resistance increases and conversion efficiency decreases, which is not preferable. On the other hand, when the thickness of the upper electrode 5 exceeds 100 nm, light is absorbed by the upper electrode 5, the amount of light guided to the pn junction of the semiconductor particles that perform photoelectric conversion is reduced, and the conversion efficiency is increased. This is because it is not preferable. The upper electrode 5 may be formed of the above material by sputtering, plasma CVD, catalytic CVD, or the like. At this time, it is also possible to give an antireflection effect by adjusting the thickness and refractive index of the material.

  Furthermore, you may form an auxiliary electrode in the suitable pattern which used the silver paste or the copper paste on it.

  The separation part 6 is formed in an annular shape so as to surround the junction between the crystalline semiconductor particles 3 and the substrate 1 so as to separate the substrate 1 and the semiconductor part 4 to be the lower electrode. By forming the separation part 6, it is possible to prevent the upper electrode 5 and the substrate 1 serving as the lower electrode from being short-circuited by the semiconductor part 4, and this is preferable because conversion efficiency is improved. FIG. 2 is a cross-sectional view showing an example of formation of the separation portion 6 in the photoelectric conversion device of the present invention. As shown in FIG. 2A, the separation unit 6 joins the substrate 1 and a part of the crystalline semiconductor particle 3 near the center of the partial region, and joins the inner substrate 1 in the partial region. The part that does not exist may be formed as the separation part 6, or after the substrate 1 and the crystalline semiconductor particles 3 are joined, a part of the semiconductor part 4 may be removed and formed. Further, as shown in FIGS. 2B to 2D, if the separation part 6 is formed by removing the periphery of the outer periphery of the joint part between the substrate 1 and the crystalline semiconductor particles 3, the separation part can be surely and easily performed. 6 can be formed. In order to remove the periphery of the junction, as shown in FIG. 2 (b), the periphery of the junction on the semiconductor particle side that performs photoelectric conversion may be removed, or as shown in FIG. 2 (d). In addition, the outer peripheral periphery of the bonding portion on the substrate 1 side may be removed, or the outer peripheral periphery of both the semiconductor particle side and the substrate 1 side for photoelectric conversion of the bonding portion is removed as shown in FIG. May be. In particular, when the separation portion 6 is formed by removing the outer periphery of the bonding portion on the substrate side, it is not necessary to remove a part of the pn junction formed on the surface of the crystalline semiconductor particles 3, so that the pn junction area is increased. Therefore, a photoelectric conversion device having high conversion efficiency can be obtained. In order to form the separation part 6 more reliably, the surface layer of the substrate 1 may be removed together with the periphery of the joint part.

  Moreover, it is preferable that the area of this separation part 6 is 1/5 or less compared with the surface area of the semiconductor particle which performs photoelectric conversion. This is because, when the area of the separation part 6 exceeds 1/5 of the surface area of the semiconductor particles that perform photoelectric conversion, recombination on the surface proceeds due to dangling bonds formed on the surface of the separation part 6 and the characteristics are greatly deteriorated. Because. Further, even if the area of the separation portion 6 exceeds 1/5 of the surface area of the semiconductor particles that perform photoelectric conversion, the dangling bond is terminated by passivating the separation portion 6 with an oxide film or the like. As a result, recombination in the separation part 6 can be prevented and a high photoelectric conversion rate can be maintained.

  Next, the first manufacturing method of the photoelectric conversion device of the present invention will be described by taking the photoelectric conversion device shown in FIG. 1 as an example.

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

  First, as shown in FIG. 3A, a large number of crystalline semiconductor particles 3 are arranged densely on the substrate 1 and heated as a whole to bond the substrate 1 and the crystalline semiconductor particles 3 together. In addition, a load may be applied from a large number of crystalline semiconductor particles 3 arranged closely on the substrate 1 to mechanically join them.

  Next, as shown in FIG. 3B, the semiconductor portion 4 is formed on the surface of the crystalline semiconductor particles 3. At this time, if the crystalline semiconductor particles 3 are p-type, the semiconductor portion 4 is formed to be n-type, and if the crystalline semiconductor particles 3 are n-type, the semiconductor portion 4 is p-type. Form. The semiconductor portion 4 may not be formed on the crystalline semiconductor particles 3 but may be formed by injecting a dopant into the crystalline semiconductor particles 3.

  Next, as shown in FIG. 3C, the periphery of the outer periphery of the bonded portion between the substrate 1 and the crystalline semiconductor particles 3 is removed to form the separation portion 6. The periphery of the outer periphery of the bonding portion between the substrate 1 and the crystalline semiconductor particles 3 is removed to expose the crystalline semiconductor particles 3, and the exposed portion is used as a separation portion 6 to separate the substrate 1 and the semiconductor portion 4. it can. As a method for forming the separation portion 6, there are a wet etching treatment, a dry etching treatment performed by forming a mask with a photoresist, and the like. The periphery of the outer periphery of the joint portion between the substrate 1 and the crystalline semiconductor particles 3 is formed on the substrate 1. A method of removing by selective wet etching is preferable because of high productivity. The separating portion 6 is preferably formed by removing only the outer periphery of the bonding portion on the substrate 1 side without removing the semiconductor portion 4 near the bonding portion between the substrate 1 and the crystalline semiconductor particles 3. This is to increase the area of the pn junction. By forming the separation part 6 in this way, the substrate 1 and the crystalline semiconductor particles 3 are joined only at the central part of the joint part.

  The area of the separation portion 6 can be easily controlled from the etching rate of the substrate 1 that becomes the lower electrode. The etchant used in this wet etching process needs to have a higher etching rate for the substrate 1 than for the crystalline semiconductor particles 3 and the semiconductor portion 4. For example, when the crystalline semiconductor particles 3 and the semiconductor portion 4 are silicon and the substrate 1 is aluminum, hydrochloric acid, hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, sodium hydroxide or potassium hydroxide is preferable. Moreover, you may provide the protective layer for protecting the semiconductor part 4 from the damage and contamination by an etching at the time of this wet etching process. An oxide film, a nitride film, or the like may be formed as the protective layer.

  Next, as shown in FIG. 3D, an insulator 2 is formed on the substrate 1 so as to fill in the space between adjacent semiconductor particles that perform photoelectric conversion. At this time, the amount of the insulator 2 is adjusted so that the upper portion of the semiconductor portion 4 is exposed.

  Further, as shown in FIG. 3 (e), the upper electrode 5 is formed so as to cover the upper portions of the insulator 2 and the semiconductor portion 4, and the photoelectric conversion device of the present invention shown in FIG. 1 can be obtained.

  Next, an example of the second manufacturing method of the photoelectric conversion device of the present invention will be described with reference to FIG.

  FIG. 4 is a cross-sectional view showing the steps of the second manufacturing method of the photoelectric conversion device of the present invention.

  First, as shown in FIG. 4A, the crystalline semiconductor particles 3 are heated in a gas containing a dopant so as to have conductivity opposite to that of the crystalline semiconductor particles 3, and the dopant is converted into crystalline semiconductor particles. Then, the semiconductor portion 4 is formed outside the crystalline semiconductor particles 3 by thermal diffusion into the inside. Here, the thickness of the semiconductor part 4 can be controlled by the heating temperature and the processing time.

  Next, as shown in FIG. 4B, a large number of crystalline semiconductor particles 3 are arranged densely on the substrate 1 and heated as a whole to join the substrate 1 and the crystalline semiconductor particles 3 together. By heating and bonding the substrate 1 and the crystalline semiconductor 3, an alloy of the substrate 1 and the crystalline semiconductor particles 3 is formed at the bonded portion. Therefore, at the bonded portion between the substrate 1 and the crystalline semiconductor particles 3. The semiconductor part 4 is eliminated. The substrate 1 and the crystalline semiconductor particles 3 can be bonded after the semiconductor portion 4 is removed in a partial region of the crystalline semiconductor particles 3.

  Thus, as shown in FIGS. 4C to 4E, the semiconductor particles bonded to the substrate 1 that perform photoelectric conversion are separated as in the above-described first manufacturing method of the photoelectric conversion device of the present invention. 6, the insulator 2 and the upper electrode 5 are formed, and the photoelectric conversion device of the present invention shown in FIG. 1 can be obtained.

  As described above, according to the photoelectric conversion device of the present invention shown in FIG. 1, on the substrate 1 serving as the lower electrode, a large number of other-conductivity-type semiconductor portions 4 are formed on the surface except for a partial region. On the other hand, conductive crystalline semiconductor particles 3 are bonded in a part of the region, and the substrate 1 and the semiconductor portion 4 are arranged in a separated state, and between the adjacent crystalline semiconductor particles 3 on the substrate 1. And the insulator 2 is formed by covering the lower part of the semiconductor part 4 and exposing the upper part of the semiconductor part 4, and the upper electrode 5 is formed so as to cover the upper part of the insulator 2 and the semiconductor part 4. Since the pn junction part of the semiconductor particle which performs photoelectric conversion can be protected, it can be set as the photoelectric conversion apparatus with high conversion efficiency. In addition, since a polishing step is unnecessary, a photoelectric conversion device with high productivity can be obtained.

  In the configuration of FIG. 1, since the semiconductor portion 4 is also formed on the surface of the lower half of the crystalline semiconductor particles 3, the area of the pn junction for performing photoelectric conversion can be increased, and thus high conversion is achieved. An efficient photoelectric conversion device can be obtained.

  Further, in the configuration of FIG. 1, by forming the separation part 6, it is possible to prevent a short circuit from the upper electrode 5 to the substrate 1 that passes through the semiconductor part 4 and serves as the lower electrode, and thus a photoelectric conversion device having high conversion efficiency. It can be.

  Moreover, in the structure of FIG. 1, the influence of the recombination in the isolation | separation part 6 can be made small by making the area of the isolation | separation part 6 into 1/5 or less of the surface area of the semiconductor particle which performs photoelectric conversion, and high conversion efficiency The photoelectric conversion device having

  Further, in the configuration of FIG. 1, by using a material having high reflectivity for the substrate 1, a large amount of reflected light from the substrate 1 can be guided to the pn junction portion of the semiconductor particle that performs photoelectric conversion, thereby achieving high conversion efficiency. It can be set as a photoelectric conversion device.

  In the configuration of FIG. 1, since the insulator 2 is formed of a material having a high light transmittance, light can be efficiently guided to the pn junction of the semiconductor particle that performs photoelectric conversion. It can be a conversion device.

  In the configuration of FIG. 1, by using a single crystal for the crystalline semiconductor particles 3, a photoelectric conversion device having high conversion efficiency can be obtained.

  Further, in the configuration of FIG. 1, by forming the semiconductor portion 4 with a thickness of 5 nm or more and 5000 nm or less, a pn junction can be formed without gaps in the semiconductor particles, and light absorption can be reduced, leading to the pn junction. Since light can be guided efficiently, a photoelectric conversion device having high conversion efficiency can be obtained. Further, since the semiconductor portion 4 is formed of a single crystal and a polycrystal, light absorption can be reduced, and light can be efficiently guided to a pn junction of a semiconductor particle that performs photoelectric conversion. An efficient photoelectric conversion device can be obtained.

  Further, in the configuration of FIG. 1, the upper electrode 5 is formed of a material having a high light transmittance, and the thickness of the upper electrode 5 is formed to be 50 nm or more and 300 nm or less, so that the pn junction portion of the semiconductor particle that performs photoelectric conversion Therefore, it is possible to guide light efficiently and reduce the resistance, so that a photoelectric conversion device having high conversion efficiency can be obtained.

  In addition, according to the first and second manufacturing methods of the photoelectric conversion device of the present invention, after separating the crystalline semiconductor particles 3 in which the semiconductor portion 4 is formed except the partial region on the surface and the substrate 1, the separating portion 6 is joined. Therefore, a short circuit between the upper electrode 5 and the substrate 1 serving as the lower electrode can be prevented reliably and easily, and a photoelectric conversion device with high conversion efficiency can be manufactured. In addition, the peripheral portion on the substrate 1 side of the bonding portion between the substrate 1 and the crystalline semiconductor particles 3 is removed to form the separation portion 6 without reducing the area of the pn junction, so that the photoelectric conversion device having high conversion efficiency Can be produced.

  Further, according to the second method for manufacturing a photoelectric conversion device of the present invention, since the semiconductor portion 4 is formed by a thermal diffusion method, a uniform semiconductor portion 4 can be formed without requiring a large vacuum device. The photoelectric conversion device of the present invention can be manufactured with good performance.

  Further, the separation portion 6 is formed by wet etching treatment with hydrochloric acid, hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, sodium hydroxide or potassium hydroxide, thereby removing the outer periphery of the bonding portion on the substrate 1 side. Since the substrate 1 and the semiconductor portion 4 can be reliably and easily separated, a photoelectric conversion device having high conversion efficiency can be easily manufactured.

  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.

  For example, in the example of the above embodiment, the crystalline semiconductor particles 3 are spherical, but may be cylindrical. The surface of the crystalline semiconductor particles 3 may be a rough surface. In this case, the irradiated light is multiply reflected and can be efficiently taken into the semiconductor particles that perform photoelectric conversion, resulting in high conversion efficiency and improved adhesion due to the anchor effect. Since it becomes a converter, it is preferable. Here, the anchor effect is that the insulator 2 enters the recesses on the surface of the semiconductor particles that perform photoelectric conversion, and the adhesion is improved by taking a shape as if a wedge is driven into the semiconductor particles that perform photoelectric conversion. Say effect.

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

  First, crystalline semiconductor particles 3 made of p-type silicon, which is a granular crystal having an average particle diameter of 700 μm, are heated in a mixed gas of phosphorus oxychloride, oxygen and nitrogen at 850 ° C. for 40 minutes to thermally diffuse phosphorus, An n-type semiconductor portion 4 having a thickness of 500 nm was formed on the outer periphery of the crystalline semiconductor particles 3.

  Next, the crystalline semiconductor particles 3 are densely arranged in a single layer on the substrate 1 made of aluminum, and heated to 577 ° C. or more, which is the eutectic temperature of aluminum and silicon. Particles 3 were joined.

  Next, wet etching is performed by immersing the substrate 1 in which a large number of semiconductor particles for photoelectric conversion are bonded in a 10% by mass aqueous sodium hydroxide solution heated to 70 ° C. for 1 minute. 3, the periphery of the outer periphery on the side of the substrate 1, which is a part of the bonding portion with the substrate 3, and the surface layer portion of the substrate 1 were removed to form the separation portion 6. At this time, the etching conditions were adjusted so that the area of the separation part 6 would be 1/5 or less of the surface area of the semiconductor particles for photoelectric conversion.

  Next, the insulator 2 made of an epoxy resin is filled between semiconductor particles that perform photoelectric conversion so that the upper surface of the semiconductor portion 4 is exposed and then cured, and then DC using a tin-added indium oxide (ITO) target is used. An upper electrode 5 made of ITO was formed to a thickness of 100 nm on the upper part of the semiconductor part 4 and the insulator 2 by putting in a sputtering apparatus.

  Next, an auxiliary electrode was formed using silver paste, and the electrical characteristics were evaluated. As a result, the conversion efficiency was 14.4%.

  In addition, as a first comparative example, a photoelectric conversion device in which the separation unit 6 was formed by a different method was evaluated. Specifically, as in the above embodiment, after the semiconductor portion 4 is formed on the outer periphery of the crystalline semiconductor particles 3, a resist is applied to the surface of the semiconductor portion 4 except for a partial region, and a sodium hydroxide aqueous solution is used. Etching was performed to remove a part of the semiconductor portion 4 and expose the p-type portion of the crystalline semiconductor particles 3. Next, the vicinity of the central part of the partial region of the crystalline semiconductor particles 3 where the p-type part was exposed and the substrate 1 were heated to a temperature equal to or higher than the eutectic temperature of aluminum and silicon of 577 ° C. or more. Next, as in the above example, the insulator 2, the upper electrode 5 and the auxiliary electrode were formed and the electrical characteristics were evaluated. As a result, the conversion efficiency was 9.3%.

  Furthermore, as a second comparative example, the semiconductor portion 4 is formed on the outer periphery of the crystalline semiconductor particles 3 and the substrate 1 and the crystalline semiconductor particles 3 are bonded together, and then the separation portion 6 is formed. The insulator 2, the upper electrode 5 and the auxiliary electrode were formed without forming them, and the electrical characteristics were evaluated. As a result, the conversion efficiency was 1.8%.

  The photoelectric conversion device of the example in which the separation unit 6 was formed and the first comparative example had higher conversion efficiency than the photoelectric conversion device of the second comparative example in which the separation unit 6 was not formed. This is presumably because the short circuit from the upper electrode 5 to the substrate 1 serving as the lower electrode through the semiconductor part 4 can be effectively prevented by forming the separation part 6.

  In addition, the photoelectric conversion device of the example had higher conversion efficiency than the photoelectric conversion device of the first comparative example. This is because the photoelectric conversion device of the first comparative example is bonded in the vicinity of the central portion of the partial region where the semiconductor portion 4 of the crystalline semiconductor particles is removed when the substrate 1 and the crystalline semiconductor particles 3 are bonded. However, this alignment is shifted and the conversion efficiency is lowered because the substrate 1 and the semiconductor part 4 are in contact with each other and short-circuited. The apparatus is presumed to have obtained a high conversion efficiency because the separation part 6 is reliably formed between the substrate 1 and the semiconductor part 4.

  As can be seen from the above results, it was possible to obtain a photoelectric conversion device with high conversion efficiency by separating the substrate 1 and the semiconductor portion 4 by the separation portion 6. Furthermore, the method of forming the separation part 6 between the substrate 1 and the semiconductor part 4 by removing the peripheral periphery of the joint part between the substrate 1 and the crystalline semiconductor particles 3 makes it possible to simplify a photoelectric conversion device having high conversion efficiency. It was possible to produce with good productivity.

It is sectional drawing which shows an example of embodiment of the photoelectric conversion apparatus of this invention. (A)-(d) is sectional drawing which shows the example of formation of the isolation | separation part in the photoelectric conversion apparatus of this invention, respectively. (A)-(e) is sectional drawing explaining each process of the 1st manufacturing method of the photoelectric conversion apparatus of this invention. (A)-(e) is sectional drawing explaining each process of the 2nd manufacturing method of the photoelectric conversion apparatus of this invention. It is sectional drawing which shows the conventional photoelectric conversion apparatus. It is sectional drawing which shows the other conventional photoelectric conversion apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... substrate 2 ... insulator 3 ... crystalline semiconductor particle 4 ... semiconductor part 5 ... upper electrode 6 ... separation part

Claims (4)

A plurality of one-conductivity-type crystalline semiconductor particles, each of which has a semiconductor region of the other conductivity type formed on the surface, excluding a partial region, are bonded to each other in the partial region. The substrate and the semiconductor portion are arranged in a separated state, covering the substrate and the lower portion of the semiconductor portion between the adjacent crystalline semiconductor particles, and exposing the upper portion of the semiconductor portion. A photoelectric conversion device, wherein an insulator is formed, and an upper electrode is formed to cover the insulator and the upper portion of the semiconductor portion. A step of bonding partial regions of a large number of one-conductivity type crystalline semiconductor particles to a substrate serving as a lower electrode, respectively, and the other conductive-type semiconductor portion excluding the partial region on the surface of the crystalline semiconductor particles Forming a step, removing the periphery of the outer periphery of the junction between the substrate and the crystalline semiconductor particles, covering the lower portion of the substrate and the semiconductor portion between the adjacent crystalline semiconductor particles, and the semiconductor A method of manufacturing a photoelectric conversion device comprising: sequentially forming a step of forming an insulator that exposes an upper portion of a portion; and forming a top electrode that covers the upper portion of the insulator and the semiconductor portion. A step of forming a semiconductor portion of the other conductivity type on the entire surface of a large number of one-conductivity type crystalline semiconductor particles by a thermal diffusion method, and joining a plurality of the crystalline semiconductor particles on a substrate to be a lower electrode. A step of removing an outer periphery of a bonding portion between the substrate and the crystalline semiconductor particles, covering a lower portion of the substrate and the semiconductor portion between the adjacent crystalline semiconductor particles, and an upper portion of the semiconductor portion A method of manufacturing a photoelectric conversion device, comprising: sequentially forming an insulator that exposes the substrate; and forming an upper electrode that covers the insulator and the upper portion of the semiconductor portion. 4. The method for manufacturing a photoelectric conversion device according to claim 2, wherein the step of removing the periphery of the outer periphery of the joint portion between the substrate and the crystalline semiconductor particles includes a wet etching process. 5.

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