JP5242009B2 - Photovoltaic device using carbon nanowall - Google Patents

Description

The present invention relates to a photovoltaic device using the carbon nano-wall.

A structure (carbon nanostructure) that is mainly composed of carbon and has a predetermined microstructure is known. Such carbon nanostructures include fullerenes, carbon nanotubes, carbon nanowalls, and the like. Patent Document 1 listed below describes carbon nanostructures called carbon nanowalls. In Patent Document 1, for example, a microwave is applied to a mixture of CH ₄ and H ₂ to form carbon nanowalls on a sapphire substrate coated with a nickel iron catalyst. Patent Document 2 below discloses a method for forming carbon nanowalls with high quality.
US Patent Application Publication No. 2003/0129305 PCT application publication WO2005 / 021430A1

Carbon nanotubes and carbon nanowalls are expected to be applied to electronic devices such as fuel cells and field emissions. However, the electrical properties regarding these carbon nanostructures are not known.
The present inventors, in certain bonding structure of the carbon nano-wall, was measured the change of voltage-current characteristics due to the presence or absence of light irradiation, and found that there is a photovoltaic characteristics.
The present invention has been made based on this discovery, and to realize the photovoltaic element using the carbon nano-wall. There is no prior art of the present invention.

The invention of claim 1 includes a p-conduction type semiconductor, an n-conduction type carbon nanowall having a wall composed of a single layer or multiple layers of a graphene sheet standing on the p-conduction type semiconductor, and an n-conduction type carbon A photovoltaic device comprising a first electrode connected to an upper end surface of a nanowall and a second electrode connected to a p-conduction type semiconductor .
The present invention is characterized that by forming a pn junction constitute a photovoltaic element by a p conductivity type semiconductor and an n conductivity type carbon nano-wall.
As the p-conduction type semiconductor, any semiconductor such as a III-V group compound semiconductor such as silicon or GaAs or a group III nitride semiconductor can be used. Further, the p-conduction type semiconductor may be bulk or may be a p-conduction type region by adding an acceptor impurity to a partial region of the substrate.
The first, the second electrode, n conductivity type carbon nano-wall, directly p conductivity type semiconductor, also be joined, the other conductive layer may be interposed between.

The invention of claim 2 comprises a substrate, an n-conducting carbon nanowall having a single-layered or multi-layered graphene sheet standing on the substrate, and an n-conducting carbon nanowall graphene sheet. A photovoltaic device having a p-conduction type carbon nanowall having a wall composed of a single layer or multiple layers of a graphene sheet formed so as to cover the wall surface along the surface of each wall surface .
The present invention includes an n-conduction-type carbon nano-wall, by its n p conductivity type carbon nano-wall formed on the surface of the conduction type carbon nano-wall, it is characterized that by forming a pn junction constitute a photovoltaic element It is.
The present invention is characterized by the pn junction, may be what things for supporting the n conductivity type carbon nano-wall.
The n conductivity type carbon nano-wall when grown on the substrate, the substrate is not particularly limited. A semiconductor substrate, a glass substrate, a metal, etc. are arbitrary. The substrate may be insulating or conductive. Further, it may be formed on a conductive diffusion region on the substrate, or may be formed on a conductive material such as a metal on an insulating substrate.

A third aspect of the present invention, according to claim 2, characterized in that it comprises a first electrode connected to the upper end surface of the p conductivity type carbon nano-wall, and a second electrode connected to the n conductivity type carbon nano-wall It is a photovoltaic element.
The present invention, the first electrode to the p conductivity type carbon nano-wall, it is a feature in which a second electrode connected to the n conductivity type carbon nano-wall.
Like the invention of claim 1, the first, second electrodes, p conductivity type carbon nano-wall, directly n conductivity type carbon nano-wall, also be joined, the other conductive layer is not interposed between May be.

The invention according to claim 4, board is an n conductivity type semiconductor, the second electrode is a photovoltaic element according to claim 3, characterized in that it is formed on the board.

The invention of claim 5, p conductivity type carbon nanowalls light according to any one of claims 1 to 4 the surface thereof characterized in that it is a carbon nano-wall that is terminated with fluorine atoms It is an electromotive force element.
The present invention is characterized in that the formation of the p conductivity type carbon nano-wall by terminating the carbon atoms on the surface of the carbon nano-wall with a fluorine atom.

The invention of claim 6 includes a conductive region, and the n conductivity type carbon nano-wall having a single layer or wall made of multiple layers of graphene sheets erected on the conductive region, the n conductivity type carbon nano-wall A photovoltaic element having a first electrode formed on the upper end surface and a second electrode connected to the conductive region . │ invention, the n conductivity type carbon nano-wall erected on the conductive regions, in the first electrode formed on the upper end surface of the n conduction type carbon nano-wall, photoelectromotive to form a Schottky junction It is characterized by configuring a power element.
The conductive region is arbitrary, such as a conductive semiconductor region to which a metal or an impurity is added.
The invention of claim 7, the conductive region is a photovoltaic element according to claim 6, characterized in that it consists of n-type semiconductor.

The invention of claim 8, n conductivity type carbon nano-wall is according to any one of claims 1 to 7, characterized in that one formed by plasma CVD in an atmosphere in the presence of nitrogen plasma The photovoltaic element.
The present invention is an n conductivity type carbon nano-wall is characterized in that formed by plasma CVD in an atmosphere in the presence of nitrogen plasma.

The “carbon nanowall” according to this application is a carbon nanostructure having a two-dimensional extension. A graphene sheet having a two-dimensional extension is erected on the surface of a base material, and a wall is constituted by a single layer or multiple layers. The two-dimensional meaning is used in the sense that the vertical and horizontal lengths of the surface are sufficiently large compared to the wall thickness (width). The surface may be a multilayer, a single layer, or a pair of layers (a layer having voids therein). Moreover, the thing with which the upper surface was covered, and therefore a cavity inside may be used. For example, the wall thickness is about 0.05 to 30 nm, and the vertical and horizontal lengths of the surface are about 100 nm to 10 μm. In general, the vertical and horizontal directions of the surface are very large compared to the width and are expressed as two-dimensional because they are subject to control.

Typical examples of the carbon nano-wall obtained by the above production method is a carbon nano-wall having a substantially constant direction upstanding wall-like structure from the surface of the substrate. Note that fullerenes (C60 and the like) can be regarded as zero-dimensional carbon nanostructures, and carbon nanotubes can be regarded as one-dimensional carbon nanostructures.
Further, the carbon nanotube may have a single-layer structure or a multilayer structure including two or more layers.

In the structures of claims 1 and 2 , rectification characteristics were observed. Therefore, since this element has a band barrier, it can function as a photovoltaic element when irradiated with light. If the element of the present invention is used in the forward direction, it becomes a solar cell, and if it is used in the reverse direction, it becomes a light detection element.
In claim 5, by terminating the surface of the carbon nano-wall with fluorine, it may be a p-type conductivity.
In the structure of claim 6 , rectification characteristics are observed. That is, since the first electrode is a Schottky junction with the n conductivity type carbon nano-wall, it is possible to obtain a rectification property, it is possible to obtain a photovoltaic by light irradiation.
In the invention of claim 8, by plasma CVD in an atmosphere in the presence of nitrogen plasma, it is possible to produce the n-conducting carbon nano-wall.

  Hereinafter, preferred embodiments of the present invention will be described in detail. It should be noted that technical matters other than the contents particularly mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the technical contents disclosed in the present specification and the common general technical knowledge in the field.

As a raw material used for producing carbon nanostructures such as carbon nanowalls and carbon nanotubes, various substances having at least carbon as a constituent element can be selected. Examples of elements that can form the raw material together with carbon include one or more selected from hydrogen, fluorine, chlorine, bromine, nitrogen, oxygen, and the like. Examples of preferable source materials include source materials substantially composed of carbon and hydrogen, source materials substantially composed of carbon and fluorine, and source materials substantially composed of carbon, hydrogen and fluorine. . Saturated or unsaturated hydrocarbon (for example, CH ₄ ), fluorocarbon (for example, C ₂ F ₆ ), fluorohydrocarbon (for example, CHF ₃ ) and the like can be preferably used. A linear, branched or cyclic molecular structure can be used. Usually, it is preferable to use a source material (source gas) that exhibits a gaseous state at normal temperature and pressure. Only one type of material may be used as the source material, or two or more types of materials may be used in any proportion. The type (composition) of the raw material to be used may be constant throughout the production stage (for example, the growth process) of the carbon nanowall, or may vary depending on the production stage. Depending on the properties (for example, wall thickness) and / or characteristics (for example, electrical characteristics) of the target carbon nano, the type (composition) of the raw material used, the supply method, and the like can be appropriately selected.
A metal catalyst is not required to produce carbon nanowalls, but when producing carbon nanotubes, metal nanoparticles such as Co and Co—Ti are preferably deposited on the substrate.

The radical injected into the plasma atmosphere preferably contains at least a hydrogen radical (that is, a hydrogen atom; hereinafter, sometimes referred to as “H radical”). It is preferable to decompose a radical source material containing at least hydrogen as a constituent element to generate H radicals and inject the H radicals into a plasma atmosphere. Particularly preferred as such a radical source material is hydrogen gas (H ₂ ). As the radical source material, a material having at least hydrogen as a constituent element can be preferably used. It is preferable to use a radical source material (radical source gas) that exhibits a gaseous state at normal temperature and pressure. In addition, a substance that can generate H radicals by decomposition, such as hydrocarbon (CH ₄ or the like), can be used as the radical source substance. Only one type of material may be used as the radical source material, or two or more types of materials may be used in any proportion.
In particular, when only H radicals are supplied, carbon nanowalls and carbon nanotubes can be generated satisfactorily. In addition, when OH radicals or O radicals are present appropriately, the formation of carbon nanotubes is likely to be facilitated.

  Adjust at least one of the conditions for producing carbon nanowalls and carbon nanotubes based on the concentration of at least one radical in the reaction chamber (for example, the concentration of at least one radical of carbon radicals, hydrogen radicals, and fluorine radicals) It is desirable to do. Examples of production conditions that can be adjusted based on such radical concentration include the amount of raw material supplied, the intensity of plasma of the raw material (the severity of the plasma conditions), the amount of radicals (typically H radicals) injected, etc. Is mentioned. Such production conditions are preferably controlled by feeding back the radical concentration. According to such a production method, it is possible to more efficiently produce carbon nanowalls or carbon nanotubes having properties and / or characteristics according to the purpose.

As a manufacturing method, it is desirable to inject radicals into a plasma atmosphere in which the raw material is turned into plasma. As a result, the plasma of the raw material and radicals (typically H radicals) are mixed. That is, high-density radicals (H radicals) can be formed in the plasma atmosphere of the source material. Carbon nanowalls are formed (grown) by the carbon deposited on the base material from the mixed region. Examples of the substrate that can be used include a substrate in which at least a region where carbon nanowalls are formed is made of a material such as Si, SiO ₂ , Si ₃ N ₄ , GaAs, or Al ₂ O ₃ . In order to form an electrode for carbon nanowalls, in the case of an insulating substrate, impurities are added to form partly conductive regions, or metal wiring is formed on the surface, and carbon nanowalls are formed thereon. Will do. The whole base material may be comprised with the said material. In the said manufacturing method, carbon nanowall can be directly produced on the surface of the said base | substrate, without using especially catalysts, such as nickel iron. A catalyst (typically a transition metal catalyst) such as Ni, Fe, Co, Pd, or Pt may be used. For example, a thin film of the catalyst (for example, a film having a thickness of about 1 to 10 nm) may be formed on the surface of the substrate, and carbon nanowalls may be formed on the catalyst coating. When forming carbon nanotubes, these catalyst nanoparticles are deposited on a substrate. The external shape of the base material to be used is not particularly limited. Typically, a plate-like base material (substrate) is used.

  One structural example of the carbon nanowall (carbon nanostructure) manufacturing apparatus according to this application is shown in FIG. The apparatus 1 includes a reaction chamber 10, plasma discharge means 20 that generates plasma in the reaction chamber 10, and radical supply means 40 connected to the reaction chamber 10. The plasma discharge means 20 is configured as a parallel plate capacitively coupled plasma (CCP) generating mechanism. The first electrode 22 and the second electrode 24 constituting the plasma discharge means 20 of the present embodiment both have a substantially disc shape. These electrodes 22 and 24 are disposed in the reaction chamber 10 so as to be substantially parallel to each other. Typically, the first electrode 22 is disposed on the upper side and the second electrode 24 is disposed on the lower side thereof.

A power supply 28 is connected to the first electrode (cathode) 22 via a matching network 26. These power supply 28 and matching circuit 26 allow RF waves (for example, 13.56 MHz), UHF waves (for example, 500 MHz), VHF waves (for example, 27 MHz, 40 MHz, 60 MHz, 100 MHz, 150 MHz), or microwaves (for example, 2.45 GHz). ) Can be generated. In this embodiment, at least an RF wave can be generated.
The second electrode (anode) 24 is disposed in the reaction chamber 10 away from the first electrode 22. The distance between the electrodes 22 and 24 can be set to about 0.5 to 10 cm, for example. In this example, it was about 5 cm. The second electrode 24 is grounded. At the time of manufacturing the carbon nanowall, the substrate (base material) 5 is disposed on the second electrode 24. For example, the substrate 70 is disposed on the surface of the second electrode 24 such that the surface of the base material 5 on which the carbon nanowall is to be manufactured is exposed (opposite the first electrode 22). The second electrode 24 incorporates a heater 25 (for example, a carbon heater) as a substrate temperature adjusting means. The temperature of the substrate 70 can be adjusted by operating the heater 25 as necessary.

  The reaction chamber 10 is provided with a raw material inlet 12 through which a raw material (raw material gas) can be supplied from a supply source (not shown). In a preferred embodiment, the inlet 12 is arranged so that the source gas can be supplied between the first electrode (upper electrode) 22 and the second electrode (lower electrode) 24. Further, the reaction chamber 10 is provided with a radical inlet 14 through which radicals can be introduced from a radical supply means 40 described later. In a preferred embodiment, the inlet 14 is arranged so that radicals can be introduced between the first electrode 22 and the second electrode 24. Further, the reaction chamber 10 is provided with an exhaust port 16. The exhaust port 16 is connected to a vacuum pump (not shown) or the like as pressure adjusting means (pressure reducing means) for adjusting the pressure in the reaction chamber 10. In a preferred embodiment, the exhaust port 16 is disposed below the second electrode 24.

  The radical supply means 40 has a plasma generation chamber 46 above the reaction chamber 10. The plasma generation chamber 46 and the reaction chamber 10 are partitioned by a partition wall 44 provided to face the carbon nanowall formation surface of the substrate 70. A power source 28 is connected to the partition wall 44 via the matching circuit 26. That is, the partition wall 44 in this embodiment also functions as the first electrode 22. In addition, the apparatus 2 includes high-frequency applying means 60 that applies an RF wave, a VHF wave, or a UHF wave between the wall surface of the plasma generation chamber 46 and the partition wall 44. Thereby, the plasma 33 can be generated from the radical source gas 36. In the high-frequency applying means 60 shown in FIG. 1, reference numeral 62 indicates an AC power source, reference numeral 63 indicates a bias power source, and reference numeral 64 indicates a filter.

  Ions generated from the plasma 33 disappear at the partition walls 44 and are neutralized to become radicals 38. At this time, the neutralization rate can be increased by appropriately applying an electric field to the partition wall 44. Moreover, energy can also be given to the neutralized radical. A large number of through holes are dispersed in the partition wall 44. These through holes become a large number of radical inlets 14, radicals 38 are introduced into the reaction chamber 10, diffused as they are, and injected into the plasma atmosphere 34. As shown in the drawing, these inlets 14 are arranged so as to extend in the surface direction of the upper surface of the substrate 70 (the surface facing the first electrode 22, that is, the carbon nanowall forming surface). According to the apparatus 2 having such a configuration, the radicals 38 can be introduced more uniformly in a wider range in the reaction chamber 10. As a result, carbon nanowalls can be efficiently formed in a wider range (area) of the substrate 70. In addition, carbon nanowalls having a more uniform structure (properties, characteristics, etc.) at each part in the plane direction can be formed. According to the present embodiment, one or more of these effects can be realized.

  The partition wall 44 may be formed by coating a surface with a material having high catalytic function such as Pt, or such a material itself. By applying an electric field between the partition wall 44 and the plasma atmosphere 34 having such a configuration (typically, applying a negative bias to the partition wall 44), ions in the plasma atmosphere 34 are accelerated, and the partition wall 44 is sputtered. To do. Thereby, atoms (such as Pt) or clusters having a catalytic function can be injected into the plasma atmosphere 34. In the process of forming the carbon nanowall, radicals (typically H radicals) 38 injected from the plasma generation chamber 46, radicals and / or ions containing at least carbon generated in the plasma atmosphere 34, and as described above An atom or cluster having a catalytic function generated and injected by sputtering of the partition wall 44 is used. Thereby, atoms, clusters or fine particles having a catalytic function can be deposited inside and / or on the surface of the obtained carbon nanowall. Since carbon nanowalls having such atoms, clusters or fine particles can exhibit high catalytic performance, they can be applied as electrode materials for fuel cells.

Next, carbon nanowalls were produced using the apparatus 1 described above.
As shown in FIG. 2, a 0.5 mm p-type silicon substrate 70 was used as the substrate. An n-type carbon nanowall 73 was grown on the substrate 70. In this experimental example, C ₂ F ₆ was used as the source gas 32. Hydrogen gas (H ₂ ) and nitrogen gas (N ₂ ) were used as the radical source gas 36. In addition, the catalyst (metal catalyst etc.) does not substantially exist on the substrate surface on which the carbon nanowall is deposited.

The silicon substrate 70 was set on the second electrode 24 so that the (100) surface thereof faced the first electrode 22 side. C ₂ F ₆ (raw material gas) 32 was supplied from the raw material inlet 12 to the reaction chamber 10, and hydrogen gas and nitrogen gas (radical source gas) 36 were supplied from the radical source inlet 42. Further, the gas in the reaction chamber 10 was exhausted from the exhaust port 16. The supply amounts (flow rates) of the source gas 32 and the radical source gas 36 are set so that the partial pressure of C ₂ F ₆ in the reaction chamber 10 is about 20 mTorr, the partial pressure of H ₂ is about 80 mTorr, and the total pressure is about 100 mTorr. ) And exhaust conditions were adjusted. C ₂ F ₆ is 50 sccm, H ₂ is 100 sccm, and N ₂ is 20 sccm.

While supplying the raw material gas 32 under these conditions, RF power of 13.56 MHz and 100 W is input from the power source 28 to the first electrode 22, and the raw material gas (C ₂ F ₆ ) 32 in the reaction chamber 10 is irradiated with RF waves. did. As a result, the source gas 32 was turned into plasma, and a plasma atmosphere 34 was formed between the first electrode 22 and the second electrode 24. Further, while supplying the radical source gas 36 under the above conditions, 13.56 MHz and 50 W of RF power is input from the power source 58 to the coil 52, and the radical source gas (H ₂ and N ₂ ) 36 in the radical generation chamber 40 is input. Irradiated with RF waves. H radicals and N radicals generated thereby were introduced into the reaction chamber 10 from the radical inlet 14. In this way, carbon nanowalls were grown (deposited) on the (100) surface of the silicon substrate 70. In this experimental example, the growth time of the carbon nanowall was 2 hours. Meanwhile, the temperature of the substrate 70 was maintained at about 550 ° C. by using the heater 25 and a cooling device (not shown) as necessary. The growth time is 3 hours. The carbon nanowalls 73 and 74 have a height of 530 nm and a thickness of 30 nm.

  An n-conducting carbon nanowall 73 was formed as described above. Next, gold was deposited on the end face of the n-conducting carbon nanowall 73 by EB vapor deposition to form the first electrode 75. Also, gold was deposited on the back surface of the p-conductivity type silicon substrate 70 by EB vapor deposition to form the second electrode 76. In this way, a pn junction was formed by joining the p-conduction type silicon substrate 70 and the n-conduction type carbon nanowall 73, thereby forming a photovoltaic device.

  The voltage-current characteristics of the photovoltaic element thus formed were measured. The result is shown in FIG. In FIG. 3, the direction in which the potential of the first electrode 73 is higher than the potential of the second electrode 76 is the positive direction of the voltage. When the second electrode 76 is positive and the first electrode 73 is a negative potential, it was observed that the current increases exponentially as the voltage increases. On the other hand, when the first electrode 73 is positive and the second electrode 76 is negative, no current flows even when the voltage is increased. Thus, the photovoltaic device of this example showed typical rectification characteristics.

  This photovoltaic element was irradiated with visible light. The voltage-current characteristic at that time is shown in FIG. A curve A is a voltage-current characteristic when light is irradiated, and a curve B is a voltage-current characteristic when light is not irradiated, which is measurement data shown in FIG. In reverse bias, the current clearly increases at the same voltage, and it is understood that the present device functions as a photovoltaic device.

As shown in FIG. 5, an n-conducting carbon nanowall 81 was formed on an n-conducting silicon substrate 80 in the same manner as in Example 1. Next, the supply of N ₂ gas and H ₂ gas was stopped, the radical source gas 36 was also turned off, and discharge was performed only with C ₂ F ₆ gas. In this way, the p-conduction type carbon nanowall 82 was grown on the surface of the n-conduction type carbon nanowall 81 so as to cover it.

  Next, gold was deposited on the end surface of the p-conduction type carbon nanowall 82 by EB vapor deposition to form the first electrode 85. Further, gold was deposited on the back surface of the n-conductivity type silicon substrate 80 by EB vapor deposition to form the second electrode 86. In this way, a pn junction was formed by joining the p-conduction type carbon nanowall 82 and the n-conduction type carbon nanowall 81 to form a photovoltaic device.

  The voltage-current characteristics of the photovoltaic element thus formed were measured. The result is shown in FIG. In FIG. 6, the direction in which the potential of the first electrode 85 is higher than the potential of the second electrode 86 is the positive direction of the voltage. When the first electrode 85 is positive and the second electrode 86 is negative potential, it is observed that the current increases exponentially as the voltage increases. On the other hand, when the second electrode 86 is positive and the first electrode 85 is negative, no current flows even when the voltage is increased. Thus, the photovoltaic device of this example showed typical rectification characteristics. Due to this rectification characteristic, there is a band barrier, and a photovoltaic force is generated during light irradiation.

  As shown in FIG. 7, an n-conducting carbon nanowall 91 was formed on an n-conducting silicon substrate 90 in the same manner as in Example 1. Next, gold was deposited on the end face of the n-conduction type carbon nanowall 91 by EB vapor deposition to form the first electrode 95. In addition, gold was deposited on the back surface of the n-conductivity type silicon substrate 90 by EB vapor deposition to form a second electrode 96. In this way, a Schottky barrier was formed at the interface between the n-conducting carbon nanowall 91 and the first electrode 95 made of gold. A photovoltaic element having the first electrode 95 as an anode and the second electrode 96 as a cathode was formed by this Schottky barrier. The voltage-current characteristics of this photovoltaic element were measured. The result is shown by curve A in FIG.

  In FIG. 8, the direction in which the potential of the first electrode 95 is higher than the potential of the second electrode 96 is the positive direction of the voltage. When the first electrode 95 is positive and the second electrode 96 is negative potential, it was observed that the current increases exponentially as the voltage increases. On the other hand, when the second electrode 96 is positive and the first electrode 95 is negative, the current does not increase greatly even when the voltage is increased. Thus, the photovoltaic device of this example showed typical rectification characteristics. From this, it is understood that there is a Schottky barrier, whereby a photovoltaic device using the Schottky barrier can be realized.

  When the first electrode 95 is made of aluminum instead of gold, the voltage-current characteristic has no rectification characteristic as shown by the curve B in FIG. That is, aluminum having a small work function has better ohmic properties than gold having a large work function. For an n-type semiconductor, a metal having a smaller work function has better ohmic properties, and it can be seen from the characteristics of FIG. 8 that the carbon nanowall 91 is n-conductive.

[Comparative Example]
In Example 1, carbon nanowalls were grown on an n-type silicon substrate and a p-type silicon substrate without introducing nitrogen radicals. FIG. 9 shows the voltage-current characteristics in this case. When carbon nanowalls are grown on an n-type silicon substrate, the characteristics as shown by curve A in FIG. 9 are exhibited, and when carbon nanowalls are grown on a p-type silicon substrate, curves shown in FIG. B-like characteristics were exhibited. The former resistivity was 1.5 × 10 ⁴ Ω · cm, and the latter resistivity was 4.1 × 10 ⁴ Ω · cm, indicating a high resistivity.

  In the photovoltaic device, as shown in FIG. 10A, the surface of the n-silicon substrate 100 is doped with an acceptor to form a p-type region 102, and an n conductivity type is formed on the p-type region 102. A carbon nanowall 105 may be formed to form a photovoltaic element. In this case, the first electrode 103 is formed on the upper end surface of the n-conducting carbon nanowall 105, and the second electrode 104 is formed in the p-type region 102.

  Further, in the photovoltaic element, as shown in FIG. 10B, the metal wiring layer 112 is formed on the silicon oxide film 111 on the n-silicon substrate 100, and the structure of the second embodiment is formed thereon. The photovoltaic element 115 may be formed by joining the n-conductivity type carbon nanowall of the p-conduction type carbon nanowall formed on the surface layer. Then, the first electrode 113 may be formed on the p-conduction type carbon nanowall, and the second electrode 114 may be formed on the metal wiring layer 112. Further, as shown in FIGS. 10A and 10B, a transistor Tr can be formed on the silicon substrate 110 to form an integrated circuit together with the photovoltaic element of this embodiment.

  In the above embodiment, the photovoltaic device using the carbon nanowall has been described. However, it is considered that the photovoltaic device can be configured similarly even if the carbon nanotube is used. N atoms were used to make carbon nanostructures such as carbon nanowalls n-type, but other group V elements such as P, As, Sb and Bi, and group VI elements such as O, S and Se were used. Can be used. Also, F was used for the p-conductivity type, but other halogen atoms, group III elements such as B, Al, Ga, In, and Tl, group II elements such as Be, Mg, Ca, Sr, and Ba Can be used. For the production, plasma CVD using an organometallic gas containing these elements is used.

  The present invention is a photovoltaic device having a novel structure. It can be used for solar cells and electronic circuits.

It is a schematic diagram which shows the manufacturing apparatus which manufactures the carbon nanowall of the photovoltaic element of this invention. The side view which showed the structure of the photovoltaic element which concerns on the specific Example 1 of this invention. FIG. 3 is a measurement diagram showing rectification characteristics of the photovoltaic element of Example 1. The measurement figure which shows the rectification | straightening characteristic at the time of light irradiation of the photovoltaic element of Example 1. FIG. The side view which showed the structure of the photovoltaic element concerning the specific Example 2 of this invention. FIG. 5 is a measurement diagram showing rectification characteristics of the photovoltaic element of Example 2. The side view which showed the structure of the photovoltaic element concerning the specific Example 3 of this invention. FIG. 5 is a measurement diagram showing rectification characteristics of the photovoltaic element of Example 2. The measurement figure which shows the rectification | straightening characteristic of the photovoltaic element which concerns on a comparative example. The side view which showed the structure of the photovoltaic element which concerns on another Example.

DESCRIPTION OF SYMBOLS 2 ... Carbon nanowall manufacturing apparatus 70 ... p conductive silicon substrate 80 ... n conductive silicon substrate 73,81,91 ... n conductive carbon nanowall 82 ... p conductive carbon nanowall 10 ... reaction chamber 14 ... radical introduction port 20 ... Plasma discharge means 75, 85, 95 ... First electrode 76, 86, 96 ... Second electrode

Claims (8)

a p-conduction type semiconductor, and an n-conduction type carbon nanowall having a wall made of a single layer or multiple layers of a graphene sheet standing on the p-conduction type semiconductor,
A first electrode connected to an upper end surface of the n-conducting carbon nanowall;
And a second electrode connected to the p-conduction type semiconductor. A substrate,
An n-conducting carbon nanowall having a wall composed of a single layer or multiple layers of a graphene sheet erected on the substrate;
A p-conduction type carbon nanowall having a wall made of a single layer or multiple layers of a graphene sheet formed so as to cover the wall surface along the surface of each wall surface made of the graphene sheet of the n-conduction type carbon nanowall; A photovoltaic device having: A first electrode connected to an upper end surface of the p-conduction type carbon nanowall;
The photovoltaic device according to claim 2, further comprising: a second electrode connected to the n-conducting carbon nanowall. The photovoltaic device according to claim 3, wherein the substrate is an n- conduction type semiconductor, and the second electrode is formed on the substrate.   The photovoltaic device according to any one of claims 2 to 4, wherein the surface of the p-conduction type carbon nanowall is terminated with a fluorine atom. A conductive region;
An n-conducting carbon nanowall having a wall composed of a single layer or multiple layers of a graphene sheet erected on the conductive region;
A first electrode formed on an upper end surface of the n-conducting carbon nanowall;
A photovoltaic device comprising: a second electrode connected to the conductive region.   The photovoltaic element according to claim 6, wherein the conductive region is made of an n-type semiconductor.   The photovoltaic element according to any one of claims 1 to 7, wherein the n-conducting carbon nanowall is formed by plasma CVD in an atmosphere in which nitrogen plasma is present.

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