JP4514402B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a semiconductor element such as a photoelectric conversion element such as a solar cell, a light emitting element, a light receiving element, a diode, a transistor, a sensor, or an imaging element.
[0002]
[Prior art]
  In recent years, with the spread of mobile devices such as portable terminals and notebook computers and the seriousness of environmental problems such as reduction of energy consumption, there is an increasing demand for devices with high energy utilization efficiency. Also in a semiconductor device, efficient generation and efficient movement of charges are the most important elements for improving device performance. In addition, the price of electronic equipment has been reduced, and not only high-performance devices and systems have high efficiency and high functionality, but also there has been a great demand for technologies that can be produced at low cost.
[0003]
  Various techniques have been proposed for this purpose. Here, a solar cell that is a photoelectric conversion element will be described as an example.
[0004]
  The prior art discloses a heterojunction functional device (diode, solar cell) in which fullerene and a derivative are dispersed in a conjugated polymer (see Patent Document 1, page 14). Electron-hole pairs excited by incident light are generated by a structure in which an infinite number of bonding surfaces of electron-donating materials consisting of fullerenes and derivatives, which are electron-accepting materials, and conjugated polymers exist at intervals of nanometer order. The purpose is to efficiently separate and generate carriers. However, at present, the mobility of organic materials and fullerene aggregates is very small compared to inorganic materials, so when carriers generated in the semiconductor layer move to the electrode, there are large losses due to trapping and deactivation, The carrier is not being used effectively.
[0005]
  In addition, in order to efficiently collect photogenerated carriers and move them to the electrode, it is composed of at least an electron-accepting transport layer, a donating transport layer, and an intervening light absorbing layer. A technique is disclosed in which either of the transport layers itself is a semiconductor needle crystal (see Patent Document 2, page 4).
[0006]
  Furthermore, a technique is disclosed in which at least an electron-accepting transport layer, an electron-donating transport layer, and an intervening light absorption layer are formed, and either the electron-accepting transport layer or the electron-donating transport layer itself is a flaky semiconductor crystal. (See Patent Document 3, page 4).
[0007]
  Also disclosed is a technique for transporting the charge generated by the photoelectric conversion means by a needle-shaped semiconductor crystal connected to one of the electrodes, and forming the needle-shaped semiconductor crystal by an electrodeposition method. (See Patent Documents 4, 4 and 6-7).
[0008]
  In addition, it is a technique for transporting the charge generated by the photoelectric conversion means through a needle crystal connected to one of the electrodes, and the needle crystal is formed by an electrodeposition method, and the needle crystal has a granular semiconductor crystal. Is disclosed (see Patent Literature 5, pages 4 to 6).
[0009]
  Furthermore, similarly, a technique is disclosed in which a columnar film formed on a substrate and generated by the deposition of a vapor deposition material flying from a direction inclined at a predetermined angle from the normal direction of the substrate is used as a charge collection electrode ( (See Patent Document 6, pages 2 to 3).
[0010]
  These all have the effect that the effective surface area of the electrode is increased, and the device characteristics can be improved by improving the efficiency and speed of charge transfer.
[0011]
  However, the techniques disclosed in these Patent Documents 2 to 5 are characterized by using needle-like and flaky semiconductor crystals, but crystals having a large aspect ratio (ratio of length to diameter) are generally used. It is mechanically weak and easily broken by external stress during the manufacturing process of the device or after it becomes a product.
[0012]
  In addition, in the technology using the columnar film as the charge collection electrode, the columnar crystal is not a general vapor phase growth method such as PVD or CVD, but uses a unique columnar structure obtained by dynamic oblique deposition. (See Patent Document 6, page 2, [0011]). In this case, the method becomes complicated, for example, a special vapor deposition apparatus is required, and the manufacturing cost increases. In general, the vapor deposition method has a slow crystal growth rate and poor production efficiency. Further, in the vapor deposition method, the vaporized raw material is scattered over a wide range from the evaporation source, and even if it reaches the substrate, there is re-evaporation and the utilization efficiency of the material is poor.
[0013]
[Patent Document 1]
  JP-T 8-500701
[0014]
[Patent Document 2]
  JP 2001-93590 A
[0015]
[Patent Document 3]
  JP 2001-358347 A
[0016]
[Patent Document 4]
  JP 2002-93471 A
[0017]
[Patent Document 5]
  JP 2002-141115 A
[0018]
[Patent Document 6]
  JP 2002-170557 A
[0019]
[Problems to be solved by the invention]
  As described above, several technologies that enable efficient generation and efficient transfer of charges in semiconductor elements, particularly semiconductor elements using organic materials, have been proposed. Productivity could not be realized. The present invention provides the aboveProblems with conventional technologyIn view of the above, it is possible to efficiently generate and move charges, and to improve device performance such as conversion efficiency and luminous efficiency.ButAn object of the present invention is to provide a semiconductor element useful for realizing an electronic device that is excellent and can be easily manufactured at low cost, and a method for manufacturing the same.
[0020]
[Means for Solving the Problems]
  In order to solve the above problems, a semiconductor element of the present invention includes a first electrode, a nanotube electrically connected to the first electrode, a semiconductor layer in contact with the nanotube, and the semiconductor layer. Is a semiconductor element composed of a second electrode that is electrically connected to the nanotube and is not in direct contact with the nanotube.
[0021]
  The nanotube in the present invention means a tube-like or tube-filled structure, is conductive at least in the long axis direction, and has an outer diameter of about 1 nm to several hundred nm. Furthermore, the structure of a cylindrical structure in which sheets of atoms and molecules are rolled, and a structure in which structures of different diameters are concentrically overlapped, the outermost cylindrical structure has a diameter of about 1 nm to several hundred nm. Means things. As a suitable structure, there is a structure in which a graphite sheet structure made of carbon is formed into a cylindrical shape as a basic structure. Another suitable structure has a cylindrical structure of a sheet structure made of amorphous carbon as a basic structure. According to the present invention, since the distance until carriers existing (or generated) in the semiconductor layer move by diffusion or drift and reach the nanotube can be shortened, carriers generated in the semiconductor layer or generated in the semiconductor layer The carrier thus made can be efficiently and rapidly guided to the first electrode. Therefore, the device characteristics can be improved. In particular, when an organic semiconductor is used as the semiconductor layer, an organic semiconductor generally has a lower carrier mobility than an inorganic semiconductor. Therefore, when an organic semiconductor is used, the carrier movement distance can be shortened.
[0022]
  As still another embodiment, the semiconductor layer may be composed of two materials, an electron donating material and an electron accepting material. For example, since the distance until the carrier generated at the junction between the electron-donating organic material and the electron-accepting organic material reaches the nanotube can be shortened, the generated carrier can be efficiently and rapidly guided to the first electrode. become able to. Therefore, the device characteristics can be improved.
[0023]
  When the semiconductor layer is composed of two types of materials, an electron donating material and an electron accepting material, the electron donating region and the electron accepting region are mixed, and the contact surface (bonding surface) of both is complicated. It is also possible to have a structure in which nanotubes are formed so as to penetrate through the joint surface and are connected to electrodes. In this case, a very large bonding area can be obtained as compared with planar bonding simply parallel to the surface. In addition, since the carriers generated near the bonding surface or the carriers existing near the bonding surface reach the nanotube only by moving a short distance, the nanotube is excellent in conductivity, so that the carrier captured by the nanotube efficiently reaches the electrode. Can reach.
[0024]
  Moreover, the surface of the nanotube may be coated with either an electron-donating material or an electron-accepting material, and the other may be arranged so as to be in contact with the coated material. Since the aspect ratio of nanotubes is very large, by simply setting the distance from the bonding surface to the nanotubes (that is, the film thickness of the coating material) and the density of the nanotubes to an appropriate value, planar bonding that is only parallel to the surface can be achieved. In comparison, a very large bonding area can be obtained. In addition, carriers generated in the vicinity of the bonding surface or carriers existing in the vicinity of the bonding surface reach the nanotube only by moving the distance of the film thickness of the coating material. Can reach the electrode efficiently.
[0025]
  Further, the electron donating material or the electron accepting material constituting the semiconductor layer may be composed of fine particles, or the semiconductor layer may be manufactured using the starting material as fine particles. By using fine particles, a structure in which the region of the electron donating material and the region of the electron accepting material are complicated can be easily manufactured. In addition, for example, a material that does not have a suitable solvent and can be produced only by a normal vapor deposition method can be used to produce a thin film by, for example, applying a liquid or paste-like sample in which fine particles are dispersed in a solvent onto a substrate. Thus, the manufacturing method becomes simple.
[0026]
  You may comprise the said semiconductor layer with the material which forms a Schottky junction with respect to a nanotube. For example, the Schottky barrier region generated near the interface between the nanotube and the semiconductor layer functions to dissociate electron-hole pairs (excitons) generated by photoexcitation of the semiconductor layer into electrons and holes. Since the aspect ratio of nanotubes is very large, by setting the density of the nanotubes to an appropriate value, a very large bonding area can be obtained as compared with planar bonding simply parallel to the surface. Carriers generated in the vicinity of the bonding surface or carriers existing in the vicinity of the bonding surface are guided to the nanotube. Since the nanotube is excellent in conductivity and mobility, the carrier captured by the nanotube can efficiently reach the electrode.
[0027]
  The semiconductor layer may be in contact with the nanotube through a material that forms a Schottky junction with the semiconductor layer.
[0028]
  Since the aspect ratio of the nanotube is very large, the distance from the Schottky junction surface to the nanotube, that is, the thickness of the material forming the Schottky junction with respect to the semiconductor layer and the density of the nanotube are set to appropriate values. Compared with planar bonding that is simply parallel to the surface, a very large bonding area can be obtained. In addition, since nanotubes exist at a distance of the film thickness of the material that forms a Schottky junction with respect to the semiconductor layer with respect to any bonding surface, carriers generated near the bonding surface or carriers existing near the bonding surface are Just by moving a short distance, it is efficiently guided to the nanotube. Since the nanotubes are excellent in conductivity, carriers captured by the nanotubes can efficiently reach the electrodes.
[0029]
  Further, the material for forming the Schottky junction with the semiconductor layer may be made of fine particles, or the starting material may be made of fine particles. In addition, by using fine particles, for example, a material without an appropriate solvent, and a material in which a thin film can be formed only by a normal vapor deposition method, for example, a liquid or pasty sample in which fine particles are dispersed in a solvent is applied on a substrate. A thin film can be produced by this method, and the production method becomes simple.
[0030]
  A first electrode, a first nanotube electrically connected to the first electrode, a second electrode, a second nanotube electrically connected to the second electrode, a first nanotube, The semiconductor layer may include a semiconductor layer in which the second nanotube is embedded, and the first nanotube and the second nanotube may not be in contact with each other.
[0031]
  According to the present invention, since the distance until carriers existing (or generated) in the semiconductor layer move by diffusion or drift and reach the nanotube can be shortened, carriers generated in the semiconductor layer or generated in the semiconductor layer The carriers thus introduced can be efficiently and quickly guided to the first electrode and the second electrode. Therefore, the device characteristics can be improved. Since organic semiconductors generally have lower carrier mobility than inorganic semiconductors, the present invention is particularly effective when organic semiconductors are used.
[0032]
  A first electrode, a first nanotube electrically connected to the first electrode, a second electrode, a second nanotube electrically connected to the second electrode, a first nanotube, The semiconductor element may be composed of a semiconductor layer in which the second nanotube is embedded, and may include a support layer for implanting the nanotube in the semiconductor element that is not in contact with the first nanotube. With this configuration, the nanotube can be firmly fixed on the electrode. Further, by using a conductive material as the material for the nanotube support layer, the electrical contact between the nanotube and the electrode can be enhanced.
[0033]
  A first electrode, a first nanotube electrically connected to the first electrode, a second electrode, a second nanotube electrically connected to the second electrode, a first nanotube, In the semiconductor element comprising a semiconductor layer in which the second nanotube is embedded, and the first nanotube and the second nanotube are not in contact with each other, the semiconductor layer is divided into two types of an electron donating material and an electron accepting material. You may comprise from material. For example, since the distance at which the carriers generated at the junction between the electron-donating organic material and the electron-accepting organic material reach the nanotube can be shortened, the generated carriers can be efficiently and quickly transferred to the first electrode and the second electrode. It can be led to the electrode. Therefore, the device characteristics can be improved.
[0034]
  When the semiconductor layer is composed of two types of materials, an electron donating material and an electron accepting material, the electron donating region and the electron accepting region are mixed, and the contact surface (joint surface) of both is complicated. It may be a structure in which a structure is formed, and nanotubes existing so as to penetrate the joint surface are connected to electrodes. In this case, a very large bonding area can be obtained as compared with planar bonding simply parallel to the surface. In addition, since the carriers generated near the bonding surface or the carriers existing near the bonding surface reach the nanotube only by moving a short distance, the nanotube is excellent in conductivity, so that the carrier captured by the nanotube efficiently reaches the electrode. Can reach.
[0035]
  Alternatively, the surface of the nanotube may be coated with either an electron-donating material or an electron-accepting material, and the other material may be disposed in contact with the coated material. Since the aspect ratio of nanotubes is very large, by simply setting the distance from the bonding surface to the nanotubes (that is, the film thickness of the coating material) and the density of the nanotubes to an appropriate value, planar bonding that is only parallel to the surface can be achieved. In comparison, a very large bonding area can be obtained. In addition, carriers generated in the vicinity of the bonding surface or carriers existing in the vicinity of the bonding surface reach the nanotube only by moving the distance of the film thickness of the coating material. Can reach the electrode efficiently.
[0036]
  Further, the electron donating material or the electron accepting material constituting the semiconductor layer may be composed of fine particles, or the semiconductor layer may be manufactured using the starting material as fine particles. By using fine particles, a structure in which the region of the electron donating material and the region of the electron accepting material are complicated can be easily manufactured. In addition, for example, a material that does not have a suitable solvent and can be produced only by a normal vapor deposition method can be used to produce a thin film by, for example, applying a liquid or paste-like sample in which fine particles are dispersed in a solvent onto a substrate. Thus, the manufacturing method becomes simple.
[0037]
  You may comprise a semiconductor layer with the material which forms a Schottky junction with respect to a nanotube. For example, the Schottky barrier region generated near the interface between the nanotube and the semiconductor layer functions to dissociate electron-hole pairs (excitons) generated by photoexcitation of the semiconductor layer into electrons and holes. Since the aspect ratio of nanotubes is very large, by setting the density of the nanotubes to an appropriate value, a very large bonding area can be obtained as compared with planar bonding simply parallel to the surface. Carriers generated in the vicinity of the bonding surface or carriers existing in the vicinity of the bonding surface are guided to the nanotube. Since the nanotube is excellent in conductivity and mobility, the carrier captured by the nanotube can efficiently reach the electrode.
[0038]
  Since the work function of the nanotube can be controlled by the surface treatment of the nanotube, it is possible to make a difference between the work function of the first nanotube and the work function of the second nanotube. For example, by appropriately setting the work functions of the first nanotube, the second nanotube, and the semiconductor layer, the semiconductor layer forms a Schottky junction for one nanotube and an ohmic junction for the other. It is also possible to make it.
[0039]
  The semiconductor layer may be in contact with the nanotube through a material that forms a Schottky junction with the semiconductor layer. Since the aspect ratio of nanotubes is very large, by simply setting the distance from the bonding surface to the nanotubes (that is, the film thickness of the coating material) and the density of the nanotubes to an appropriate value, planar bonding that is only parallel to the surface can be achieved. In comparison, a very large bonding area can be obtained. In addition, carriers generated in the vicinity of the bonding surface or carriers existing in the vicinity of the bonding surface reach the nanotube only by moving the distance of the film thickness of the coating material. Can reach the electrode efficiently.
[0040]
  Further, the material for forming the Schottky junction with the semiconductor layer may be made of fine particles, or the starting material may be made of fine particles. In addition, by using fine particles, for example, a material without an appropriate solvent, and a material in which a thin film can be formed only by a normal vapor deposition method, for example, a liquid or pasty sample in which fine particles are dispersed in a solvent is applied on a substrate. A thin film can be produced by this method, and the production method becomes simple.
[0041]
  In the present invention, electrophoresis may be used as a method for arranging nanotubes (including first and second nanotubes) at predetermined positions. By using the electrophoresis method, an expensive facility such as a vacuum process, a heat treatment, or a plasma process is required, and a simple and low-cost manufacturing process can be realized without going through a process with high energy consumption. Since the electrophoresis method is a normal temperature process, nanotubes can be arranged on the surface of a structure including a material that is easily damaged by heat. In addition, according to the electrophoresis method, it is possible to align the nanotubes in almost one direction.
[0042]
  In the present invention, a CVD method may be used as a method for producing a nanotube. According to the CVD method, it is possible to grow the nanotubes so as to be substantially perpendicular to the substrate, and to easily control the density of the nanotubes. In the vacuum deposition method, atoms or molecules constituting a thin film to be produced are supplied onto the substrate, so that it is generally difficult to form nanotubes on the substrate surface. In contrast, the CVD method can produce nanotubes by supplying carbon-containing molecules to the substrate surface and using the thermally induced reaction, catalytic chemical reaction, plasma reaction, or a combination of these on the surface. As a method for performing this, it is a preferred method among vapor phase growth methods. A chemical reaction using a catalytic metal or the like that is arranged in advance on the substrate surface is mainly used.
[0043]
  The semiconductor layer, the region made of the electron donating material, and the region made of the electron accepting material can be formed by polymerization from a monomer. By supplying a monomer in the form of gas or solution to the surface of the nanotube and polymerizing it, a structure in which the polymer is coated on the surface of the nanotube or a structure in which the nanotube is embedded in the polymer can be easily produced. Of course, a polymer organic semiconductor solution may be supplied to the substrate on which the nanotubes are arranged to form a structure in which the polymer organic semiconductor is in contact with the nanotubes. Due to viscosity and surface tension, the polymer semiconductor may not sufficiently penetrate into the gap between the nanotubes. On the other hand, in the case of a monomer, since the monomer molecule is small, it can enter the gap between the nanotubes and easily reach the surface of the nanotube. Therefore, a method by polymerization from the monomer is preferable.
[0044]
  Among the methods of forming the semiconductor layer, the region made of the electron donating material, and the region made of the electron accepting material by polymerization from a monomer, the electric field polymerization method is more preferably used. The electropolymerization method is a method of generating a polymer on the surface of a nanotube by immersing an electrode substrate on which the nanotube is arranged in a solution of a monomer of an organic semiconductor and applying an electric field. According to this method, the monomer solution penetrates into the minute gaps of the nanotubes and forms a polymer on the surface of the nanotubes, so that the polymer can be formed on the entire surface of the nanotubes. Moreover, since the film thickness of the polymer can be controlled by controlling the growth time, for example, the nanotube surface can be coated with the polymer. Moreover, since the electric field is simply applied by immersing in the monomer solution, the apparatus is very simple as compared with a method such as vapor deposition.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the semiconductor device according to the present invention will be described.Basic form andEmbodiments will be described.
[0046]
  The present invention can be used for semiconductor elements in general, but can be suitably used for photovoltaic elements such as solar cells, photoelectric conversion elements used for optical sensors, photodiodes, and the like. Therefore, although embodiment of this invention is described in detail using the Example of a solar cell or a photoelectric conversion element, this invention is not limited to these Examples.
[0047]
  The photoelectric conversion elements of the following basic modes 1 and 2 are used in the second embodiment, but common portions with the second embodiment are also applied to the first embodiment.
[0048]
  (Basic form1)
  <Element structure>
  FIG. 1 shows a photoelectric conversion element according to the present invention.Part ofIt is sectional drawing. Formed in contact with the first electrode 12 formed on the substrate 11 and the nanotube 14 oriented and implanted in the nanotube support layer 13 formed thereon, the semiconductor layer 15 in which the nanotube is embedded, and the semiconductor layer 15 The second electrode 16 is formed. The nanotubes 14 are directly electrically connected to the first electrode 12 or are electrically connected to the first electrode 12 through the support layer 13 imparted with conductivity.
[0049]
  The length of the nanotube is used in the range of several tens of nm to several hundreds of μm, but the preferred length varies depending on the specifications required for each semiconductor element. For example, in the case of a photoelectric conversion element, light incident on the semiconductor layer of the photoelectric conversion element is absorbed and a charge is generated, so the thickness of the semiconductor layer defines the length of the nanotube. The thickness of the semiconductor layer needs to be a thickness that allows the incident light to be sufficiently absorbed from the aspect of efficiency of the element. Usually, the light absorption coefficient of the semiconductor layer is 10²cm^-1About 10 at most⁷cm^-1Therefore, for example, in order to absorb 99% of incident light, the thickness of the semiconductor layer needs to be about 500 μm to about 5 nm. When the linear nanotubes are oriented substantially parallel to the normal direction of the substrate 11, the length of the nanotubes is approximately the same as the film thickness of the semiconductor layer material. However, when the nanotubes are obliquely oriented or when the nanotubes are twisted, they may be longer as long as they do not deviate from the semiconductor layer.
[0050]
  Nanotubes having a diameter of about 1 nm to several hundreds nm are used, but a diameter of several nm to several tens of nm is preferable. For example, in the case of carbon nanotubes, the diameter increases from about 1 nm of the smallest single-walled nanotube by about 0.7 nm as the number of layers increases by one. Depending on the number of nanotube layers, a diameter of several nm to 100 nm is used, but a diameter of several nm to several tens of nm is preferable. If the density of the nanotubes is small, sufficient charge collection efficiency cannot be obtained, and if it is too large, the substantial volume of the semiconductor layer is reduced, the amount of charges is reduced, and as a result, sufficient charges cannot be collected. The optimum density is set according to the type of semiconductor material (in particular, electron-hole pair (exciton), electron and hole diffusion distance), the diameter of the nanotube, and the like. Specifically, the distance between the nanotubes is several nm to 1 μm, preferably several nm to several tens of nm.
[0051]
  Regarding the orientation (degree) of the nanotube, the linear nanotube may be oriented substantially parallel to the normal direction of the substrate 11 or may be oriented obliquely. Since it is desirable that the distance between the nanotubes is uniform, it is desirable that the orientation directions of the nanotubes are aligned, but they may not be aligned. Also, the nanotubes may be spiral or winding.
[0052]
  <Method of planting nanotubes>
  For example, the following method can be used as a method for producing a nanotube electrically connected to an electrode used in the present invention.
[0053]
  (1) A method in which an existing nanotube is cut into a desired length and placed on an electrode by electrophoresis.
[0054]
  In the electrophoresis method, when a voltage is applied between a substrate (electrode) on which nanotubes are to be arranged and a counter electrode arranged in parallel with the substrate, the nanotubes move along the electric field and move to the substrate (electrode). It uses the phenomenon that reaches In general, a support layer is used to align and fix the nanotubes. As the support layer, a layer having conductivity and having pores or fine gaps is preferably used. The support layer is preferably conductive. The electrode itself may also serve as the support layer.
[0055]
  Examples of the material for the support layer include a porous structure, for example, an anodized film such as silicon and aluminum, and an aggregate film of conductive fine particles such as gold and silver. In addition, a conductive polymer such as polysilane or PEDOT (polyethylenedioxythiophene) is also used as a material for the support layer. Also. A material in which fine particles of a good conductor are dispersed in a polymer or a conductive polymer may be used. Since the electrophoresis method is a room temperature process, it is desirable in terms of application to a substrate that is easily damaged by heat, production cost, and the like. In addition, since nanotubes mass-produced by an arc discharge method or the like can be used, production efficiency is good and production cost is low.
[0056]
  (2) A method in which a source gas containing carbon is supplied to the substrate surface by chemical vapor deposition (CVD), and nanotubes are grown by a chemical reaction on the substrate surface.
[0057]
  In the CVD method, a catalytic metal layer (such as discontinuous dots) such as Fe, Ni, Fe—Ni alloy, Co, and Pd is formed on a substrate, and acetylene (C₂H₂When a gaseous raw material such as) is supplied, a phenomenon in which nanotubes grow in a portion where a catalytic metal exists is utilized. The substrate temperature is preferably about 600 ° C. to 800 ° C. Hydrogen (H₂) Etc. may flow.
[0058]
  According to the CVD method, the density of the nanotubes can be controlled by the distribution state of the catalytic metal, and nanotubes with a high degree of orientation can be grown very densely. By making the distribution state of the catalyst metal into a desired pattern in advance, nanotubes can be produced only in the region of the pattern. The length of the nanotube can also be controlled by the growth time. Further, a catalyst metal plate or film may be used as the substrate.
[0059]
  <Constituent materials>
  Materials constituting the semiconductor layer
  The material constituting the semiconductor layer is not particularly limited as long as it is a material having an electron accepting function or a material having an electron accepting function. For example, the following materials can be used.
[0060]
  Examples of the electron-accepting material include oligomers and polymers having pyridine and its derivatives as a skeleton, oligomers and polymers having quinoline and its derivatives as a skeleton, ladder polymers made of benzophenanthrolines and derivatives thereof, and cyano-polyphenylene vinylene. Small molecules such as molecules, fluorinated metal-free phthalocyanines, fluorinated metal phthalocyanines and derivatives thereof, perylene and derivatives thereof (PTCDA, PTCDI, etc.), naphthalene derivatives (NTCDA, NTCDA, etc.), bathocuproin and derivatives thereof can be used.
[0061]
  As electron donating materials, oligomers and polymers having thiophene and its derivatives as a skeleton, oligomers and polymers having phenylene-vinylene and its derivatives as a skeleton, oligomers and polymers having thienylene-vinylene and its derivatives as a skeleton, carbazole and its derivatives Oligomers and polymers having skeletons, oligomers and polymers having skeletons of vinylcarbazole and derivatives thereof, oligomers and polymers having skeletons of pyrrole and derivatives thereof, oligomers and polymers having skeletons of acetylene and derivatives thereof, isothiaphene and its Oligomers and polymers with derivatives as skeletons, polymers such as oligomers and polymers with skeletons of heptadiene and derivatives thereof, metal-free phthalocyanines, metal phthalocyanines and their derivatives, diamines Phenyldiamines and derivatives thereof, acenes such as pentacene and derivatives thereof, porphyrin, tetramethylporphyrin, tetraphenylporphyrin, tetrabenzporphyrin, monoazotetrabenzporphyrin, diazotetrabenzporphine, triazotetrabenzporphyrin, octaethylporphyrin , Octaalkylthioporphyrazine, octaalkylaminoporphyrazine, hemiporphyrazine, metalloporphyrin and metalloporphyrin and their derivatives such as chlorophyll, cyanine dye, merocyanine dye, squarylium dye, quinacridone dye, azo dye, anthraquinone, benzoquinone, naphthoquinone Small molecules such as quinone dyes such as can be used. As the central metal of metal phthalocyanine and metal porphyrin, magnesium, zinc, copper, silver, aluminum, silicon, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, tin, platinum, lead and other metals, metal oxides, Metal halides are used.
[0062]
  As the semiconductor layer, the above materials can be used alone, but it is also possible to use a material obtained by dispersing and mixing the above materials in an appropriate binder material. Moreover, the material etc. which incorporated said low molecule in the principal chain or side chain of a suitable polymer are used. Examples of the binder material or the main chain polymer include polycarbonate resin, polyvinyl acetal resin, polyester resin, modified ether type polyester resin, polyarylate resin, phenoxy resin, polyvinyl chloride resin, polyvinyl acetate resin, poly Vinylidene chloride resin Polystyrene resin, acrylic resin, methacrylic resin, cellulose resin, urea resin, polyurethane resin, silicone resin, epoxy resin, polyamide resin, polyacrylamide resin, polyvinyl alcohol resin, etc., copolymers thereof, or polyvinyl carbazole And photoconductive polymers such as polysilane are used.
[0063]
  The semiconductor layer can be used as a single material or a uniform mixture of the above materials, but a junction structure of a region made of an electron donating material and a region made of an electron accepting material may be formed.
[0064]
  Here, the bonding structure has an interface (bonding surface) at which two or more different kinds of materials are in contact, and an electronic function generated at this interface (bonding surface) and its vicinity region (function unique to the element ( Rectification, photoelectric conversion, light emission, etc.).
[0065]
  Substrate material
  The material and thickness of the substrate are not particularly limited as long as the first electrode can be manufactured and can be stably held. Examples thereof include metals such as stainless steel, alloys, glass, resin, paper, and cloth. When light is incident from the substrate side, a material having a predetermined transparency in a wavelength range required by the element is used.
[0066]
  Material for first and second electrodes
  As materials of the first and second electrodes, metals such as gold, platinum, and aluminum, alloys, and as transparent electrodes, for example, indium tin oxide (ITO), fluorine-doped tin oxide, zinc oxide, oxidation A metal oxide such as tin is used. Conductive polymers such as polyacetylene, polypyrrole, and polythiazyl may be used. The electrode material is selected not only by transparency but also by electrical properties (such as ohmic property and Schottky property) with the semiconductor layer.
[0067]
  When a transparent conductive film is used as a material for the first and second electrodes in a solar cell or the like, it is usually necessary to make the work function on the cathode side smaller than that on the anode side. The conductive metal oxide having a small work function is, for example, a metal having a low work function such as aluminum (Al), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lithium (Li) (ie, 4.3 eV or less metal) or aluminum oxide (Al₂O_Three), Magnesium oxide (MgO), barium oxide (BaO), and other oxides are added as a dopant to a transparent conductive film such as ITO or ZnO.
[0068]
  <Production method>
  First, the first electrode 12 is formed on the substrate 11. For example, the materials described above are used. The thickness of the 1st electrode 12 should just be more than the thickness from which sufficient electroconductivity is acquired. The method for manufacturing the electrode is not particularly limited, and for example, an evaporation method, a sputtering method, a CVD method, a printing method, a spin coating method, or the like is used. For example, in the case of ITO, which is a typical transparent conductive film, it may be about 50 nm to 200 nm, and is produced by sputtering. If necessary, the electrode may be patterned by a known method such as photolithography. Next, the nanotube support layer 13 is formed on the surface of the first electrode 12, and the nanotubes 14 are implanted in the support layer 13. As a method for implanting the nanotubes 14, as described above, for example, electrophoresis or CVD is used. As the support layer in the case of electrophoresis, the above porous structure or conductive polymer is used. The porous structure is produced by anodic oxidation of silicon or aluminum, for example. A known method can be employed to produce the anodized film. For example, when a container is filled with a chemical conversion liquid, a semiconductor or metal or a semiconductor substrate or metal film formed on a substrate is used as an anode, a counter electrode is used as a cathode, and they are arranged in parallel to each other. Alternatively, an anodic oxide film having pores on the metal surface side is formed. The portion that is not anodized functions to electrically connect the nanotube and the electrode.
[0069]
  As the porous structure, for example, an aggregate film of conductive fine particles can be used. A well-known method can be adopted to produce an aggregate film of conductive fine particles. For example, it can be produced by applying fine particles of metal such as gold, silver, nickel, etc. on the first electrode in the form of a paste. The strength of the aggregate film of fine particles can be increased and the adhesion to the electrode can be increased by heat treatment or a method such as mixing a polymer such as an epoxy resin or an acrylic resin with the paste.
[0070]
  As the porous structure, for example, a conductive polymer such as polysilane or PEDOT is also used as a material for the support layer. Further, a material in which fine particles of a good conductor are dispersed in a polymer or a conductive polymer may be used. These support layers can be formed on the electrode surface by applying a polymer material dissolved in a solvent or a mixture of polymer and fine particles of a good conductor by a spin coating method, screen printing or the like. These polymer films, polymers and good conductors can function as a support layer as they are, but by irradiating them with ultraviolet rays or electron beams, some bonds in the polymer chains are cut to form fine gaps. Can also be used as a support layer. When the support layer is formed using a polymer dissolved in a solvent, heat treatment may be performed in order to remove the solvent from the polymer film. The temperature is preferably about the boiling point of the solvent or higher. The treatment time depends on the thickness of the support layer using the polymer, and is desirably the time until the solvent in the membrane is sufficiently removed.
[0071]
  In the case of the CVD method, the catalytic metal layer formed on the surface of the first electrode 12 functions as a support layer. In the case of a CVD method using a catalytic metal, the nanotube is grown with fine particles of the catalytic metal as growth points, and thus the nanotube is bonded to the catalytic metal.
[0072]
  A known technique is used to form the semiconductor layer 15. For example, vapor deposition, sputtering, CVD, printing, spin coating, etc. are used. In addition, the semiconductor layer 15 may be formed by applying a liquid in which micelles or fine particles are dispersed in a solvent and evaporating the solvent. For the production of the fine particles, known methods such as a vapor phase growth method, a pulverization method, a reprecipitation method, and an acid pasting method can be used. In addition, an electric field polymerization method may be used for forming the semiconductor layer 15. A structure in which the nanotubes are implanted is immersed in a solution in which a monomer or oligomer that is a raw material of a semiconductor material is dissolved, and the first electrode is connected to one terminal of the power source, and the opposite is immersed in the solution. When the electrode is connected to the other terminal of the power source and applied while sweeping the voltage within a range of plus or minus several V, the dissolved monomer or oligomer is polymerized and adheres to the nanotube surface, and the semiconductor layer 15 is formed. It is formed.
[0073]
  As a method for forming the second electrode 16 on the surface of the semiconductor layer 15, for example, a vapor deposition method, a sputtering method, a CVD method, a printing method, a spin coating method, or the like is used. When an organic material is used for the semiconductor layer 15, it is desirable to prevent damage to the surface of the semiconductor layer when forming the second electrode. For example, the cause of damage when the second electrode 16 is formed is heat, but the semiconductor layer 15 may be cooled when the second electrode 16 is formed. Further, when there is a heat source near the semiconductor layer 15 as in a vapor deposition source in the vapor deposition method, a shielding plate for shielding radiant heat from the heat source may be disposed between the heat source and the semiconductor layer 15. In this case, the second electrode is formed by the substance that has reached the semiconductor layer 15 around the shielding plate. A layer that mediates charge transfer between the second electrode 16 and the semiconductor layer 15 may be formed between the second electrode 16 and the semiconductor layer 15.
[0074]
  (Basic form2)
  The first electrode may also serve as a nanotube support layer. A cross-sectional view of an example configuration is shown in FIG.
[0075]
  <Element structure>
  The first electrode 22 formed on the substrate 21, the nanotube 24 oriented and implanted thereon, the semiconductor layer 25 in which the nanotube is embedded, and the second electrode 26 formed in contact with the semiconductor layer. The The nanotube 24 is connected to the first electrode 22. This embodiment isBasic form1 except that the support layer 13 is not provided and the nanotube 24 is directly implanted in the first electrode 22. The substrate, nanotube, semiconductor layer, and second electrode are both in the material and the manufacturing method.Basic form1 is the same as described above.
[0076]
  <Production method>
  Basic form1 is different in that the support layer 13 is not provided and the nanotube 24 is directly disposed on the first electrode 22, and therefore, only a method for implanting the nanotube 24 directly on the first electrode 22 will be described. The manufacturing method of other components is as follows:Basic formSame as 1.
[0077]
  As a method of implanting nanotubes directly on the first electrode 22, for example, a source gas containing carbon is supplied to the substrate surface by chemical vapor deposition (CVD), and the nanotube is formed by a chemical reaction on the substrate surface. The method of growing can be used. In the CVD method, it is necessary that a catalytic metal layer such as Fe, Ni, Fe—Ni alloy, Co, or Pd exists on the growth surface. Since these metals usually exhibit good conductivity, the catalyst metal layer formed on the substrate can be used as the first electrode 22. While heating a substrate 21 having a catalyst metal layer formed as a first electrode 22 on a substrate 21, acetylene (C₂H₂When a gaseous raw material such as) is supplied, nanotubes 24 grow on the catalytic metal layer. The substrate temperature is preferably about 600 ° C. to 800 ° C. Inert gas and hydrogen (H₂) Etc. may flow.
[0078]
  <Effect>
  BookBasic formAccording to the method, it is not necessary to separately provide a nanotube support layer, and thus the process is simplified. According to the CVD method, the density of the nanotubes can be controlled by the distribution state of the catalytic metal, and nanotubes with a high degree of orientation can be grown very densely. By making the distribution state of the catalyst metal into a desired pattern in advance, nanotubes can be produced only in the region of the pattern. The length of the nanotube can also be controlled by the growth time.
[0079]
  (Embodiment1)
  <Element structure>
  In the solar cell in which the semiconductor layer is composed of two materials of an electron donating material and an electron accepting material, a structure in which a nanotube is coated with an electron donating material or an electron accepting material may be used. A cross-sectional view showing an example3Shown in A first electrode 52 formed on a substrate 51, a nanotube support layer 53 formed thereon, a nanotube 54 implanted in the nanotube support layer 53, and an electron donating property for coating the nanotube 54 A region 551 made of a material, a region 552 made of an electron-accepting material in contact with the region 551 made of the electron-donating material, and a region 552 made of the electron-accepting material, but directly in contact with the nanotube. The second electrode 56 is not formed. The nanotube 54 is directly connected to the first electrode 52 or is electrically connected to the first electrode 52 via a nanotube support layer 53 imparted with conductivity.
[0080]
  Figure3In the above example, the region 551 made of the electron-donating material is coated with the nanotube 54, but the region 552 made of the electron-accepting material may be coated with the nanotube.
[0081]
  The material in this embodiment isBasic form1 is the same as described above. Further, the nanotubes may be directly implanted in the first electrode as shown in FIG. The form and method of implanting the nanotubes directly on the first electrode is:Basic form2 as described.
[0082]
  The thickness for coating the nanotube is determined by the function required for the semiconductor element. For example, in the photoelectric conversion element, the wavelength distribution of incident light, the light absorption coefficient of the coating material, the charge in the coating material, It is determined in consideration of exciton's movable distance (free path) and the like, and is in the range of about 1 nm to several hundred nm.
[0083]
  <Production method>
  In the semiconductor element of the present invention, the manufacturing method other than the semiconductor layer is as follows:Basic formSame as 1 and 2. The nanotube 54 of the present embodiment is coated with an electron donating organic material or an electron accepting organic material. As a method for coating nanotubes with an electron-donating organic material or an electron-accepting organic material, known methods such as vapor deposition, sputtering, CVD, and electric field polymerization are used. Legal methods are preferably used. The electropolymerization method is as described in the first embodiment. The growth rate of the electrolytic polymer film can be controlled by the concentration of the monomer solution, and the coating thickness can be controlled by the time of electric field polymerization.
[0084]
  <Effect>
  The aspect ratio of the nanotube is so large that the distance from the joint surface to the nanotube, that is, the thickness of the coating material, and the density of the nanotube are set to appropriate values, compared with a flat joint that is simply parallel to the surface. Thus, a very large bonding area can be obtained. Further, the carrier generated in the vicinity of the bonding surface or the carrier existing in the vicinity of the bonding surface is guided to the nanotube only by moving the film thickness distance of the coating material. Since the nanotube is excellent in conductivity, the carrier that has reached the nanotube and is captured can efficiently reach the electrode.
[0085]
  (Embodiment2)
  <Element structure>
  HalfThe conductor layer may have a structure in which a layer made of an electron donating material and a layer made of an electron accepting material are laminated. A sectional view showing an example4Shown in. HalfThe conductor layer is composed of a laminated structure of a region 951 layer made of an electron donating material and a region 952 layer made of an electron accepting material.It is characterized by.
[0086]
  <Production method>
  The element of the configuration of the present embodiment isBasic formTwo structures in which the semiconductor layer is formed by the method according to 1 or 2Half as followsIt is produced by bonding the surfaces of the conductor layer together.
[0087]
  When the semiconductor layer is a polymer, the surface of the semiconductor layers of the two structures is brought into close contact with each other, and the temperature is raised to a temperature near the glass transition point or melting point of the semiconductor composed of the polymer. The two structures can be bonded to each other by press-bonding for a certain period of time with fluidity and lowering to room temperature. The process of raising the temperature to a temperature near the glass transition point or melting point of a polymer semiconductor, holding it, and lowering it to room temperature is preferably an inert gas atmosphere, a vacuum state or a reducing atmosphere, and also blocks light. It is also desirable that As another bonding method, a cross-linking agent is mixed in a material constituting the semiconductor layer or a cross-linkable functional group is introduced so that the surfaces of the semiconductor layers of the two structures are brought into close contact with each other. In this state, it is possible to give energy necessary for crosslinking such as heat and light to bond two semiconductors. Further, in the case of crosslinking by light, light may be irradiated while being pressed for a certain period of time while the temperature is raised to a temperature near the glass transition point or melting point of the semiconductor. As another bonding method, a layer for adhering both may be interposed between the surfaces of the semiconductor layers of the two structures.
[0088]
  <Effect>
  According to the present invention, since the distance until carriers existing (or generated) in the semiconductor layer move by diffusion or drift and reach the nanotube can be shortened, carriers generated in the semiconductor layer or generated in the semiconductor layer The carriers thus introduced can be efficiently and quickly guided to the first electrode and the second electrode. Therefore, the device characteristics can be improved. Organic semiconductors generally have lower carrier mobility than inorganic semiconductors, but the present invention is particularly effective because it can shorten the carrier movement distance. In the photoelectric conversion element according to this embodiment, electric charges can be efficiently generated by an internal potential difference (built-in electric field) generated near the interface due to the energy level difference between the electron donating material and the electron accepting material. The magnitude of the internal potential difference necessary for generating the charge can be controlled by a combination of the electron donating material and the electron accepting material. Further, since the wavelength distribution of incident light can be complementarily covered with two kinds of materials, an electron donating material and an electron accepting material, the utilization efficiency of incident light is increased.
[0089]
【Example】
  Hereinafter, Embodiments 1 to2This will be described more specifically with reference to examples.
[0090]
  (Example1)
  Embodiment1A specific example is shown.
[0091]
  Figure3In this case, glass is used as the substrate 51, and ITO as the first electrode 52 is formed on the surface by a sputtering method to a film thickness of about 50 nm. A highly conductive PEDOT film having a thickness of about 50 nm is formed on the ITO surface as a nanotube support layer 53 by spin coating. This is heat-treated at 90 ° C. for about 20 minutes in an inert gas (in this example, nitrogen gas). After the heat treatment, the nanotubes (about 1 μm in length) are immersed in a liquid dispersed in isopropyl alcohol, a voltage (about 2 KV / cm) is applied between the opposite electrodes arranged in parallel, and the nanotubes 54 are placed on the PEDOT. A structure in which is oriented almost perpendicular to the surface is obtained.
[0092]
  This structure was combined with 0.05M tetrabromo-p-xylene and 0.1M TEABF._FourWhen immersed in a DMF solution of 0.2% water and subjected to electric field polymerization, polyphenylene vinylene is formed as an electron donating material region 551 on the surface of the nanotube 54 and the exposed portion of the support layer 53. In this example, the film thickness is approximately 5 nm, but by appropriately controlling the time of electropolymerization, polyphenylene vinylene coats the entire surface of the nanotube 54 or a part thereof, and is adjacent to the nanotube 54. It is possible to form a structure in which the gaps between the nanotubes are not filled.
[0093]
  When a liquid in which fine particles of perylene (particle diameter of several nm to several tens of nm) are dispersed is applied to this structure and dried, the perylene fine particles are formed in the gaps between the nanotubes coated with polyphenylene vinylene. Filling and depositing perylene fine particles on the tip side of the nanotube also forms an electron-accepting material region 552.
[0094]
  The second electrode 56 is formed by forming AlLi or LiF with a thickness of several に on the surface of the electron-accepting material region 552 by a vacuum deposition method, and then depositing an Al electrode by about 50 nm without breaking the vacuum. Composed of structure. A photoelectric conversion element is formed through the above process.
[0095]
  (Example2)
  Embodiment2A specific example is shown.
[0096]
  Figure4In FIG. 2, glass is used as the substrate 91, and ITO as the first electrode 92 is formed on the surface by a sputtering method to a film thickness of about 50 nm. A highly conductive PEDOT film having a thickness of about 50 nm is formed on the ITO surface as the first nanotube support layer 93 by spin coating. This is heat-treated at 90 ° C. for about 20 minutes in an inert gas (in this example, nitrogen gas). After the heat treatment, the nanotubes (about 1 μm in length) are immersed in a liquid dispersed in isopropyl alcohol, and an electric field (about 2 KV / cm) is applied between the opposite electrodes arranged in parallel with each other, the first PEDOT is formed on the PEDOT. A structure in which the nanotubes 941 are oriented substantially perpendicular to the surface is obtained. On this structure, an MEH-PPV thin film is formed by spin coating using a solution (about 0.5% by weight) of a derivative MEH-PPV of polyphenylene vinylene, which is an electron donating organic material, in xylene. Make it.
[0097]
  An Fe—Ni alloy substrate is used as the second electrode 96, which is heated to about 700 ° C., and acetylene (C₂H₂) And hydrogen (H₂), The second nanotube 942 grows in a substantially vertical alignment with the substrate.
[0098]
  A thin film of CN-PPV is spin-coated by using a solution (about 0.5% by weight) of CN-PPV, which is a derivative of polyphenylenevinylene, which is an electron-accepting organic material, dissolved in xylene on the structure. Is made.
[0099]
  The structure on the substrate 91 and the structure on the second electrode 96 are brought into contact with each other on the surfaces of the MEH-PPV and CN-PPV films and heated to near the glass transition temperature in a nitrogen atmosphere. Then, MEH-PPV and CN-PPV are in close contact with each other.4An element having the structure shown in FIG.
[0100]
【The invention's effect】
  According to the present invention, carriers generated in the semiconductor layer can be efficiently and rapidly guided to the electrode. Therefore, the device characteristics can be improved. In general, organic semiconductors have lower carrier mobility than inorganic semiconductors. However, according to the present invention, since the carrier movement distance can be shortened, the present invention is particularly effective when an organic semiconductor is used as a semiconductor layer.
[0101]
  Further, by using an organic material, a process for forming a device using the structure according to the present invention can be simplified and reduced in cost.
[Brief description of the drawings]
FIG. 1 is a photoelectric conversion element according to an embodiment of the present invention.Part ofIt is sectional drawing.
FIG. 2 is a photoelectric conversion element according to an embodiment of the present invention.Part ofIt is sectional drawing.
FIG. 3 is a cross-sectional view of a photoelectric conversion element according to an embodiment of the present invention.
FIG. 4 is a cross-sectional view of a photoelectric conversion element according to an embodiment of the present invention.
[Explanation of symbols]
  11, 21, 51, 91 Substrate, 12, 22, 52, 92 First electrode, 13, 53, 93 Support layer, 14, 24, 54 Nanotube, 941 First nanotube, 942 Second nanotube, 15, 25 Semiconductor Layer, 551,951 region made of electron donating material, 552,952 region made of electron accepting material, 16, 26, 56, 96 second electrode.

Claims (11)

A first electrode, a nanotube electrically connected to the first electrode and having conductivity in a major axis direction, a semiconductor layer embedded with the nanotube, and electrically connected to the semiconductor layer, and The second electrode is not in contact with the nanotube, the nanotube is implanted in a support layer of the nanotube in contact with the first electrode, and the semiconductor layer includes both an electron donating material and an electron accepting material. A semiconductor element comprising a material . A first electrode, a nanotube electrically connected to the first electrode and having conductivity in a major axis direction, a semiconductor layer embedded with the nanotube, and electrically connected to the semiconductor layer, and The second electrode is not in contact with the nanotube, the nanotube is implanted in the nanotube support layer in contact with the first electrode, and the semiconductor layer forms a Schottky junction with the nanotube. A featured semiconductor element. 3. The semiconductor element according to claim 2, wherein the semiconductor layer is in contact with the nanotube through a material that forms a Schottky junction with the semiconductor layer. A first nanotube electrically connected to the first electrode; a second electrode; a second nanotube electrically connected to the second electrode; and the first nanotube. and a second nanotube is a semiconductor device comprising a semiconductor layer which is buried, the semiconductor device according to claim 1, characterized in that said first nanotube, and the second nanotube are not in contact. A first support layer in which the first nanotube is implanted and in contact with the first electrode; or a second support layer in which the second nanotube is implanted and in contact with the second electrode. 5. The semiconductor element according to claim 4 , wherein Semiconductor layer, the semiconductor device according to claim 4 or 5, wherein it is composed of both an electron donating material and an electron-accepting material material. The semiconductor device according to claim 4 or 5, wherein the semiconductor layer is characterized by forming a Schottky junction with the nanotubes. Semiconductor layer semiconductor device according to claim 4 or 5, wherein the in contact with the nanotubes through a material forming a Schottky junction with the semiconductor layer. Method of manufacturing a semiconductor device nanotubes in a manufacturing method of a semiconductor device according to any one of claims 1 to 8, characterized in that it comprises a step to be implanted in the electrode or support layer using an electrophoresis. Method of manufacturing a semiconductor device in which a semiconductor layer in the manufacturing method of a semiconductor device according to any one of claims 1 to 8, characterized in that it comprises a step which is formed by polymerization of monomer. Method of manufacturing a semiconductor device in which a semiconductor layer in the manufacturing method of a semiconductor device according to any one of claims 1 to 8, characterized in that it comprises a step which is formed microparticles as a starting material.

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