JP5733655B2 - Silicon nanoparticle / silicon nanowire composite material, solar cell, light emitting device, and manufacturing method - Google Patents

Description

  The present invention uses a silicon nanoparticle / silicon nanowire composite material in which silicon nanoparticles having a light-emitting function or a light absorption function by band gap modulation control and a silicon nanowire having a carrier transfer function are combined in a composite function, and this composite material is used. The present invention relates to a novel and highly efficient solar cell, a light emitting device, and a manufacturing method.

  Since silicon nanoparticles can freely modulate the band gap by changing the size (diameter), they can be applied to a full-color light emitting device utilizing a photoluminescence phenomenon or an electroluminescence phenomenon by an optical excitation method or an electric field excitation method. In addition, since the entire wavelength region of sunlight can be efficiently absorbed by band gap modulation, it can be adapted as a solar cell utilizing a light absorption phenomenon. However, conventional full-color light-emitting devices and solar cells using silicon nanoparticles have low carrier injection efficiency from the electrode to the particle and carrier extraction efficiency (transport efficiency) from the particle to the electrode, thus reducing the light emission efficiency and conversion efficiency. Was causing. On the other hand, silicon nanowires are used as electronic devices because they can obtain high conductivity. Therefore, by combining silicon nanoparticles having excellent light emitting function and light absorbing function and silicon nanowires having excellent conductivity, light emitting efficiency and conversion efficiency can be improved.

  An object of the present invention is to provide a method for producing a novel composite material in which silicon nanowires are covered with silicon nanoparticles for use in an active layer of a high-light-emitting efficiency light-emitting device or a high-conversion-efficiency solar cell. And

  According to one aspect of the present invention, a silicon nanoparticle / silicon nanowire composite material in which silicon nanowires are covered with silicon nanoparticles is provided.

  The silicon nanowire may be erected on a silicon substrate.

  The silicon nanowire may be grown from the silicon substrate.

  The silicon nanowire may be doped with impurities such as boron and phosphorus.

  The silicon nanowire may have a diameter of 5 to 100 nm and a length of 1000 to 50000 nm.

  An interval between the silicon nanowires may be 20 to 200 nm.

  The silicon nanowire may have a tapered structure.

  The silicon nanoparticles may be doped with impurities such as boron and phosphorus.

  The diameter of the silicon nanoparticles may be in the range of 1.5 to 3.0 nm.

  According to another aspect of the present invention, there is provided a light emitting device using the silicon nanoparticle / silicon nanowire composite material having a first electrode and a second electrode for applying a driving voltage to both ends of the silicon nanowire. .

  According to another aspect of the present invention, the first electrode provided on the silicon substrate, and a second electrode provided on a tip of the silicon nanowire opposite to the silicon substrate, There is provided a light emitting device using the silicon nanoparticle / silicon nanowire composite material, in which a driving voltage is applied between a first electrode and the second electrode.

  In the light emitting device, the second electrode may be made of a transparent conductive material.

  In the light emitting device, the silicon nanoparticles may have a diameter of 1.5 to 1.9 nm, and may emit blue light when the driving voltage is applied.

  In the light emitting device, the silicon nanoparticles may have a diameter of 2.0 to 2.4 nm, and may emit green light when the driving voltage is applied.

  In the light emitting device, the silicon nanoparticles may have a diameter of 2.5 to 3.0 nm, and may emit red light when the driving voltage is applied.

  According to still another aspect of the present invention, a first electrode and a second electrode are provided on both ends of the silicon nanowire, respectively, and the silicon nanoparticle / silicon nanowire composite material is irradiated with light, thereby providing the first electrode. A solar cell using the silicon nanoparticle / silicon nanowire composite material is provided that extracts output from between the second electrode and the second electrode.

  According to still another aspect of the present invention, the first electrode provided on the silicon substrate, and a second electrode provided on the tip of the silicon nanowire on the opposite side of the silicon substrate, A solar cell using the silicon nanoparticle / silicon nanowire composite material that takes out an output from between the first electrode and the second electrode by irradiating the silicon nanoparticle / silicon nanowire composite material with light. Given.

  In the solar cell, an amorphous silicon film may be provided between the silicon nanowire composite material and the second electrode.

  In the solar cell, the second electrode may be made of a transparent conductive material.

  In the solar cell, the silicon nanowire may have a tapered structure.

According to still another aspect of the present invention, there is provided a method for producing the silicon nanoparticle / silicon nanowire composite material provided with the following steps (a) to (d).
(A) A silicon nanowire is grown on a silicon substrate.
(A) Prepare a solution in which silicon nanoparticles are dispersed in an organic solvent mixed with hydrofluoric acid.
(C) The solution is applied to the silicon substrate on which the silicon nanowires are grown.
(D) The silicon substrate coated with the solution is heat-treated to adsorb the silicon nanoparticles to the silicon nanowires.

  In the method, the organic solvent may be a volatile organic solvent.

  In the method, the heat treatment may be performed in an inert gas atmosphere.

  In the method, the temperature of the heat treatment may be 100 to 500 ° C., and the time may be 10 to 60 minutes.

  According to the present invention, it has been possible to obtain an improvement in light emission efficiency due to an increase in carrier injection efficiency and an increase in conversion efficiency due to an increase in carrier extraction efficiency, which have been difficult to obtain with conventional techniques.

The manufacturing process of the silicon nanoparticle / silicon nanowire composite material of this invention. The adsorption process by the heat processing of the silicon nanowire which has the silicon nanoparticle / silicon nanowire of this invention, and a silicon nanoparticle / taper structure. 3 is a process for producing a silicon nanowire composite material having a silicon nanoparticle / taper structure according to the present invention; A manufacturing process of a light emitting device using the silicon nanoparticle / silicon nanowire composite material of the present invention. The current-voltage characteristic of the light-emitting device using the silicon nanoparticle / silicon nanowire composite material of this invention. The emission spectrum of the light-emitting device using the silicon nanoparticle / silicon nanowire composite material of this invention. The manufacturing process of the solar cell using the silicon nanoparticle / silicon nanowire composite material of this invention. The short circuit current-open circuit voltage characteristic before and behind irradiation of the pseudo-sunlight of the solar cell using the silicon nanoparticle / silicon nanowire composite material of the present invention.

  In the method for producing a silicon nanowire having a silicon nanoparticle / silicon nanowire composite material and a silicon nanoparticle / taper structure according to the present invention, the generation of silicon nanoparticles is described in Patent Documents 1 to 8 and Non-Patent Documents 1 to 3. Those in the category of conventional methods can be used. Moreover, the production | generation of a silicon nanowire can utilize the thing in the category of the conventional method of a nonpatent literature 4 and 5.

  First, a method for erecting silicon nanowires on a silicon substrate is illustrated.

Step 1

Method A
A mask (2) provided with pores at regular intervals is placed on a p-type or n-type silicon substrate (1), and (FIG. 1 (A-1)) the mask (2) The metal dots (3) evaporated from above and deposited through the holes are formed on the surface of the silicon substrate (1). (FIG. 1B) This metal dot becomes a catalyst for the growth of silicon nanowires.

Method B
Instead of Method A, the step can be completed by depositing a metal film (4) on the p-type or n-type silicon substrate (1) and placing a mask (2) thereon. It is. (Fig. 1 (A-2))

  Furthermore, metal nanocolloids can also be used as metal dots necessary for the growth of silicon nanowires.

  In the mask (2), a plurality of holes are formed at predetermined intervals with a diameter and a distance corresponding to the diameter of the silicon nanowire (5) and the distance between the silicon wires (5) performed in step 2. The thickness of the mask (2) is set so that the length of the silicon nanowire (5) can be varied. Specifically, the pore diameter is preferably 50 to 100 nm. The interval is preferably 50 to 200 nm. The thickness is preferably 1000 to 5000 nm. The material of the mask (2) may be any material as long as it does not deform at the time of vapor deposition or does not chemically react with the metal to be vapor deposited, and alumina or the like is generally used. Moreover, it is preferable that the thickness of the said metal dot (3) and the said metal film (4) shall be 1-5 nm, and material is conventionally well-known, such as gold | metal | money, platinum, nickel, titanium, iron, copper, aluminum, etc. The thing used for the growth method of the silicon nanowire by a thermal CVD method can be used.

Step 2
Silicon nanowires (5) doped with p-type or n-type impurities having the same conductivity type as the substrate between the surface of the metal dots (3) or the metal film (4) and the silicon substrate (1) by thermal CVD. ) Was grown, and columnar impurity-doped silicon nanowires standing on the silicon substrate (1) at regular intervals were formed. Specifically, in the method A, the impurity-doped silicon nanowire (5) was grown between the metal dot (3) and the silicon substrate (1). (FIG. 1 (C-1)) In the method B, in the hole portion of the mask (2), the impurity-doped silicon nanowire (5) between the metal film (4) and the silicon substrate (1). Grew (FIG. 1 (C-2)).

The impurity-doped silicon nanowire (5) is very useful for carrier transfer from the electrode to the silicon nanoparticle (6) and carrier transfer from the silicon nanoparticle (6) to the electrode when used in a light emitting device or a solar cell. It plays an important role. Therefore, as an impurity element to be doped into the silicon nanowire (5), boron is used when p-type is formed, and phosphorus is used when n-type is formed. The carrier concentration is 10 ¹⁷ to 10 ²⁰ cm ⁻³ . High conductivity can be obtained from the silicon nanowire (5) doped with this impurity.

As a method for forming impurity-doped silicon nanowires, a Vapor-Liquid-Solid (VLS) growth mechanism based on a catalytic reaction with a metal was used. Specifically, a silane gas (monosilane gas, disilane gas, tetrachlorosilane gas) in which silicon and hydrogen are mixed as a reaction gas, and diborane gas or phosphine gas as an n-type impurity gas are used as a p-type impurity gas. The pressure of the mixed gas is 1 × 10 ^{−2 to} 20 torr, preferably 5 × 10 ^{−2 to} 15 torr, and more preferably 1 to 10 torr. These gases are decomposed by heat, and the metal dots (3) (the method A) or the mask (wherein the silicon atoms and boron atoms or phosphorus atoms in the gas state (V) are catalysts on the surface of the silicon substrate (1). It reacts with the metal film (4) in the hole part of 2) (the method B). At this time, when the reaction temperature of the silicon atom and the metal catalyst is equal to or higher than the eutectic temperature, the metal dot (3) (the method A) or the metal film (4) (the method B) is in a liquid state (L). In the liquid state, gaseous silicon atoms and boron atoms or phosphorus atoms are continuously taken in. In this process, when the ratio of silicon atoms to the metal catalyst reaches the eutectic point or more, the silicon atoms increase as a component in the metal catalyst and become supersaturated. In this state, silicon atoms are deposited (S) while taking in boron atoms or phosphorus atoms, and as a result of continuous deposition in one direction, the p-type or n-type silicon nanowire (5) is generated. The p-type or n-type silicon nanowire (5) has a diameter of 5 to 20 nm and a length of 1000 to 5000 nm.

Step 3
On another substrate, p-type or n-type silicon nanoparticles (6) were generated by a high-frequency sputtering method. Specifically, a silicon chip / boron chip (p-type impurity material) or a phosphorous pentoxide chip (n-type impurity material) / quartz disk glass mixed material is sputtered simultaneously as a sputtering target material, and boron atoms or phosphorus atoms and silicon are simultaneously sputtered. An amorphous silicon oxide film containing excess atoms was prepared. The amorphous silicon oxide film was heat-treated to produce the p-type or n-type silicon nanoparticles (6). Although the temperature of heat processing shall be 900-1200 degreeC, Preferably, it is 1000-1100 degreeC. The heat treatment time is 15 to 100 minutes, preferably 30 to 80 minutes, and more preferably 50 to 60 minutes.

The impurity concentration doped in the silicon nanoparticles (6) is about 10 at%, and the carrier concentration is 10 ¹⁹ to 10 ²⁰ cm ⁻³ . The diameter of the particles can be controlled in the range of 1.5 to 3.0 nm by changing the area ratio of the silicon chip as the sputtering target material and the quartz disk glass. This area ratio is 1 to 50%. Further, the diameter of the particles can be controlled even by changing the high-frequency power and gas pressure, which are sputtering conditions. At this time, the high-frequency power is changed within a range of 10 to 500 W, and the gas pressure is changed within a range of 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ torr.

  The p-type or n-type silicon nanoparticles (6) generated in the amorphous silicon oxide film are subjected to hydrofluoric acid vapor treatment, ultrasonic treatment, and ultracentrifugation to remove amorphous silicon oxide, and the remaining The p-type or n-type silicon nanoparticles (6) were dispersed in an organic solvent such as ethanol or acetone mixed with hydrofluoric acid (use a highly volatile substance in the atmosphere). At this time, the solution concentration of the hydrofluoric acid vapor treatment is 20 to 40%, the treatment temperature is 40 ° C., and the treatment time is 30 to 60 minutes. The temperature of ultrasonic treatment is 20 ° C., and the treatment time is 30 to 60 minutes. The number of rotations of the ultracentrifugation process is 10,000 rpm, and the time is 30 to 60 minutes.

Step 4
An organic solvent in which the p-type or n-type silicon nanoparticles (6) are dispersed is extracted with a micropipette and applied to the silicon substrate (1) on which the p-type or n-type silicon nanowire (5) is grown, The p-type or n-type silicon nanowires (6) are infiltrated between the p-type or n-type silicon nanowires (5) (FIGS. 1 (D-1), (D-2), and FIG. 2 (A)). .

  At this time, since hydrofluoric acid is mixed in the organic solvent in which the p-type or n-type silicon nanoparticles (6) are dispersed, the p-type or n-type silicon nanoparticles (6) and the p-type or The surface oxide layer of the n-type silicon nanowire (5) is completely removed, and the surface thereof is terminated with hydrogen (FIG. 2B).

  Then, the organic solvent is evaporated by heat-treating the p-type or n-type silicon nanoparticles (6) terminated with hydrogen and the p-type or n-type silicon nanowire (5) in an argon gas atmosphere, and at the same time, The hydrogen which terminated the surface of the p-type or n-type silicon nanoparticle (6) and the p-type or n-type silicon nanowire (5) is also released (FIG. 2C). Since a dangling bond is formed in a portion where hydrogen is released, the p-type or n-type silicon nanoparticle (6) and the p-type or n-type silicon nanowire (5) or the p-type or n-type silicon nanoparticle (6 ) Are chemically adsorbed in a self-organized manner, so that silicon nanoparticles are densely and uniformly adsorbed around the silicon nanowires. The heat treatment temperature at this time is 100 to 500 ° C., and the heat treatment time is 10 to 60 minutes.

Step 5
The mask (2) disposed on the silicon substrate (1) is completely removed with a chemical such as phosphoric acid. (See FIG. 1 (E)) Further, the uppermost metal dot (3) of the p-type or n-type silicon nanowire (5) or the metal dot (3) remaining on the surface of the silicon substrate (1). (Method A) or the metal film (4) (Method B) is completely removed with a chemical solution such as a mixed solution of potassium iodide and iodine or aqua regia (see FIG. 1E).

A composite material using a silicon nanowire (7) having a tapered structure can also be produced by the process of FIG. 1 (FIG. 3). The difference is that the flow rate of the dopant gas during the growth of the silicon nanowire is higher than that in the above case so that the silicon nanowire has a tapered structure in the growth axis direction. Specifically, when the carrier concentration approaches 10 ²⁰ cm ⁻³ , the growth of the silicon nanowire in the radial direction is promoted, and as a result, the silicon nanowire having a tapered structure in the growth axis direction grows. The upper limit of the carrier concentration is determined by the solid solubility of each impurity atom doped into the silicon nanowire. A silicon nanoparticle / silicon nanowire composite material using a nanowire having a tapered structure can further improve the conversion efficiency, for example, by using it in a solar cell, and details will be described in Example 3.

  The composite material of the p-type or n-type silicon nanoparticles (6) and the p-type or n-type silicon nanowire (5) produced in this way can be obtained from the electrode, which has been a problem in the prior art, from the p-type or n-type. Carrier injection efficiency into the p-type silicon nanoparticles (6) and carrier extraction efficiency from the p-type or n-type silicon nanoparticles (6) to the electrode are improved.

  Using the silicon nanoparticle / silicon nanowire composite material obtained in Example 1, a light emitting device was manufactured as follows. FIG. 4 shows the manufacturing process.

Step 1
A composite material of the p-type or n-type silicon nanoparticles (6) and the p-type or n-type silicon nanowire (5) was formed on the silicon substrate (1) by the manufacturing process. (FIG. 4A) The silicon substrate (1) has a resistivity of 0.01 Ωcm or less, and the type is p-type or n-type. In addition, the p-type or n-type silicon nanoparticles (6) have a band gap width (as a guide, the band gap width when the diameter is 1.5 to 1.9 nm is 4.3 to 3.1 eV) due to the difference in diameter. The band gap width at 2.0 to 2.4 nm is 2.9 to 2.3 eV, and the band gap width at 2.5 to 3.0 nm is 2.25 to 1.9 eV. .) Can be changed, the emission wavelength can be controlled by using the p-type or n-type silicon nanoparticles (6) having different diameters.

Step 2
A surface electrode is formed on the outermost surface of the composite material of the p-type or n-type silicon nanoparticles (6) and the p-type or n-type silicon nanowire (5) by a high-frequency sputtering method, and a back electrode is formed on the rear surface of the silicon substrate (1). (FIG. 4B). An ITO film (8) having a thickness of 100 nm is used for the surface electrode. An aluminum film (9) having a thickness of 100 nm is used for the back electrode. Then, a lead wire is bonded to the ITO film (8) and the aluminum film (9) with a silver paste, and a low driving voltage is applied between both electrodes, whereby the p-type or n-type silicon nanowire (5 ), The carriers are injected with high injection efficiency into the p-type or n-type silicon nanoparticles (6), so that a light emitting device exhibiting high light emission efficiency can be manufactured.

  FIG. 5 shows current-voltage characteristics of the light-emitting device manufactured as described above. The current-voltage characteristic was defined as a forward direction when a drive voltage was applied with the ITO film (8) side negative and the aluminum film (9) side positive. The light emitting device of the present invention exhibited rectifying properties, and carrier injection into the p-type or n-type silicon nanoparticles (6) occurred when the forward voltage was 2.0 V or more. After carrier injection, light emission of any one of blue, green and red depending on the diameter of the p-type or n-type silicon nanoparticles (6) was confirmed.

  FIG. 6 shows an emission spectrum obtained from the light-emitting device. When a forward voltage of 3.0 V or more is applied, the p-type or n-type silicon nanoparticles (6) having a diameter of 1.5 to 1.9 nm to blue light having a light emission wavelength of 400 nm, 2.0 to 2 A green light emission having a light emission wavelength of 560 nm can be obtained from a light emission wavelength of 4 nm, and a red light emission having a light emission wavelength of 670 nm can be obtained from a light emission wavelength of 2.5 to 3.0 nm. The difference in emission color is due to the difference in the band gap width due to the diameter change of the p-type or n-type silicon nanoparticles (6) as described above. The luminance of each luminescent color was so strong that it could be clearly seen with the driving voltage of 7.0 V under room lighting, and the emission life was stable enough to enable continuous driving for a long time.

  High luminance and stable blue, green, and red light emission at such a low driving voltage can be obtained for the first time by the method of the present invention. This is possible because carriers injected from both electrode sides are efficiently transferred into the p-type or n-type silicon nanoparticles (6) via the p-type or n-type silicon nanowire (5). ing.

  Using the silicon nanoparticle / silicon nanowire composite material obtained in Example 1, a solar cell was manufactured as follows. FIG. 7 shows the manufacturing process.

Step 1
A composite material of the p-type or n-type silicon nanoparticles (6) and the p-type or n-type silicon nanowire (5) was formed on the silicon substrate (1) by the manufacturing process (FIG. 7A). The silicon substrate (1) has a resistivity of 0.1 Ωcm or less, and the type is p-type or n-type. In addition, the p-type or n-type silicon nanoparticles (6) have a band gap width (as a guide, the band gap width when the diameter is 1.5 to 1.9 nm is 4.3 to 3.1 eV) due to the difference in diameter. The band gap width at 2.0 to 2.4 nm is 2.9 to 2.3 eV, and the band gap width at 2.5 to 3.0 nm is 2.25 to 1.9 eV. .) Can be changed. If the band gap width of the material can be modulated, sunlight having a wide wavelength distribution can be absorbed without waste. Therefore, by combining the p-type or n-type silicon nanoparticles (6) with different diameters (different band gaps), it is possible to effectively absorb all sunlight without waste and convert it into large-capacity electricity. can do.

Step 2
On the outermost surface of the composite material of the p-type or n-type silicon nanoparticles (6) and the p-type or n-type silicon nanowires (5) by plasma CVD, the silicon nanoparticles and the silicon nanowires have different conductivity types. A p-type amorphous silicon film (10) was formed. (FIG. 7B) The reason why the amorphous silicon films (10) having different conductivity types are formed is to form the pn junction necessary for the solar cell. At this time, the n-type or p-type amorphous silicon film (10) is formed by using silane-based gas (monosilane gas, disilane gas, tetrachlorosilane gas) as a reactive gas, hydrogen gas, phosphine gas as n-type impurity gas, or diborane gas as p-type impurity gas. Generated using. The high frequency power is 50 to 400 W, preferably 100 to 300 W, and more preferably 200 W. The gas pressure is 1 × 10 ^{−2 to 1} torr, preferably 5 × 10 ^{−2 to} 5 × 10 ⁻¹ torr, and more preferably 1.5 × 10 ⁻¹ torr. Further, the deposition time is 1 to 60 minutes, preferably 5 to 30 minutes, and more preferably 10 minutes. The film thickness of the n-type or p-type amorphous silicon film (10) formed under these conditions is 100 to 1000 nm.

Step 3
A surface electrode and a back electrode were formed on the surface of the n-type or p-type amorphous silicon film (10) and the back surface of the silicon substrate (1) by high-frequency sputtering, respectively. (FIG. 7C) An ITO film (8) having a film thickness of 100 nm is used for the surface electrode. An aluminum film (9) having a thickness of 100 nm is used for the back electrode. Then, by irradiating pseudo sunlight from the surface electrode side, the carrier is transferred from the p-type or n-type silicon nanoparticle (6) side to the electrode via the p-type or n-type silicon nanowire (5) with high efficiency. Therefore, a solar cell exhibiting high conversion efficiency can be manufactured.

  FIG. 8 shows short-circuit current-open-circuit voltage characteristics before and after irradiation with pseudo sunlight (AM1.5G) for the solar cell thus manufactured. The solar cell of the present invention has high conversion efficiency by pseudo-sunlight irradiation (the ratio of how much electric energy (W) is converted by the solar cell out of the light energy (P) hitting the solar cell: conversion efficiency = (output electric energy (W) / solar energy (P)) × 100).

  Such high conversion efficiency can be obtained for the first time by using a novel functional composite material in which silicon nanoparticles are densely and uniformly adhered around the silicon nanowire proposed in the present invention. The use of the p-type or n-type silicon nanoparticles (6) that effectively absorbs all sunlight without waste and the carriers generated in the p-type or n-type silicon nanoparticles (6) are the p-type or It is possible by efficiently transmitting to both electrodes via the n-type silicon nanowire (5).

  In the solar cell manufactured as shown in FIG. 7, light having a wide spectrum such as incident sunlight is obtained by using a nanowire having a tapered structure as shown in FIG. 3 as the n-type silicon nanowire (5). The utilization efficiency can be further improved. Specifically, by providing a tapered structure, the band gap of the nanowire itself can be lowered stepwise from the light incident surface, and the nanowire itself can absorb sunlight light without waste. Thereby, the expansion of the wavelength band of light-electrical energy conversion target in the silicon nanoparticles realized by giving the width of the diameter of the silicon nanoparticles in Step 1 of the present embodiment is also achieved on the nanowire side. This leads to higher efficiency. That is, in the solar cell using the silicon nanoparticle / silicon nanowire composite material of the present invention, light incident on the silicon nanowire is also converted into electric energy. Also for the above, by converting a wide wavelength range to be converted, the effect of increasing the aperture ratio of the solar cell of the present invention over a wide wavelength range of incident light can be obtained.

  The present invention uses a novel material that can be described as a sea grape shape, in which impurity-doped silicon nanoparticles are compounded in a densely and uniformly attached shape around the impurity-doped silicon nanowires. Since it is possible to realize luminous efficiency and high conversion efficiency, it is a foundation for developing new light-emitting light source materials or photovoltaic power generation materials. In addition, since silicon nanoparticles and silicon nanowires are harmless to the global environment and are harmless materials, they can be applied to technologies for commercializing new display devices and solar power generation. Therefore, the present invention is highly likely to be used in an innovative light-emitting light source and solar cell manufacturing technology in the 21st century in the industrial field, industrial field, and other fields.

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Mask 3 Metal dot 4 Metal film 5 Silicon nanowire 6 Silicon nanoparticle 7 Silicon nanowire 8 which has a taper structure ITO film 9 Aluminum film 10 Amorphous silicon film

Patent No. 4336133 JP 2005-268337 JP2006-070089 JP 2006-071330 JP2007-063378 JP2007-067104 JP2007-246329 WO2007 / 026533A1

K. Sato, N. Fukata, K. Hirakuri, Appl. Phys. Lett. 94, 161902 (2009) K. Sato, K. Niino, N. Fukata, K. Hirakuri, Y. Yamauchi, Nanotechnology 20, 365207 (2009) K. Sato, N. Fukata, K. Hirakuri, M. Murakami, T. Shimizu, Y. Yamauchi, Chem. Asia J. 5, 50-55 (2010) N. Fukata, J. Chen, T. Sekiguchi, S. Matsushita, T. Oshima, N. Uchida, K. Murakami, T. Tsurui, S. Ito, Appl. Phys. Lett. 90, 153117 (2007) N. Fukata, M. Mitome, Y. Bando, M. Seoka, S. Matsushita, K. Murakami, J. Chen, T. Sekiguchi, Appl. Phys. Lett. 93, 203106 (2008)

Claims (24)

A silicon nanoparticle / silicon nanowire composite material in which silicon nanowires having silicon nanoparticles with a diameter in the range of 1.5 to 3.0 nm attached thereto are erected on a silicon substrate. The silicon nanoparticle / silicon nanowire composite material according to claim 1, wherein the silicon nanoparticle has a light emitting function . The silicon nanoparticle / silicon nanowire composite material according to claim 1 , wherein the silicon nanowire is grown from the silicon substrate . The silicon nanowire / silicon nanowire composite material according to claim 1 , wherein the silicon nanowire is doped with an impurity such as boron or phosphorus . 5. The silicon nanoparticle / silicon nanowire composite material according to claim 1 , wherein the silicon nanowire has a diameter of 5 to 100 nm and a length of 1000 to 50000 nm . The silicon nanoparticle / silicon nanowire composite material according to claim 1, wherein a plurality of the silicon nanowires are erected on the silicon substrate . The silicon nanoparticle / silicon nanowire composite material according to claim 5 , wherein an interval between the silicon nanowires is 20 to 200 nm . The silicon nanoparticle / silicon nanowire composite material according to claim 1 , wherein the silicon nanowire has a tapered structure . The silicon nanoparticle / silicon nanowire composite material according to claim 1 , wherein the silicon nanoparticle is doped with an impurity such as boron or phosphorus .   The light emitting device using the silicon nanoparticle / silicon nanowire composite material according to any one of claims 1 to 9, comprising a first electrode and a second electrode for applying a driving voltage to both ends of the silicon nanowire. A first electrode provided on the silicon substrate; and a second electrode provided on a tip of the silicon nanowire opposite to the silicon substrate;
Applying a driving voltage between the first electrode and the second electrode;
A light-emitting device using the silicon nanoparticle / silicon nanowire composite material according to claim 2.   The light emitting device according to claim 10 or 11, wherein the second electrode is made of a transparent conductive material.   The light emitting device according to claim 10, wherein the silicon nanoparticles have a diameter of 1.5 to 1.9 nm and emit blue light when the driving voltage is applied.   The light-emitting device according to claim 10, wherein the silicon nanoparticles have a diameter of 2.0 to 2.4 nm and emit green light when the driving voltage is applied.   The light emitting device according to any one of claims 10 to 12, wherein the silicon nanoparticles have a diameter of 2.5 to 3.0 nm and emit red light when the driving voltage is applied. A first electrode and a second electrode are provided at both ends of the silicon nanowire,
By irradiating the silicon nanoparticle / silicon nanowire composite material with light, an output is extracted from between the first electrode and the second electrode.
A solar cell using the silicon nanoparticle / silicon nanowire composite material according to claim 1. A first electrode provided on the silicon substrate; and a second electrode provided on a tip of the silicon nanowire opposite to the silicon substrate;
By irradiating the silicon nanoparticle / silicon nanowire composite material with light, an output is extracted from between the first electrode and the second electrode.
A solar cell using the silicon nanoparticle / silicon nanowire composite material according to claim 1.   The solar cell according to claim 16 or 17, wherein an amorphous silicon film is provided between the silicon nanowire composite material and the second electrode.   The solar cell according to claim 16, wherein the second electrode is made of a transparent conductive material.   The solar cell according to claim 16, wherein the silicon nanowire has a tapered structure. The method for producing a silicon nanoparticle / silicon nanowire composite material according to any one of claims 1 to 9, wherein the following steps (a) to (d) are provided.
(A) A silicon nanowire is grown on a silicon substrate.
(A) Prepare a solution in which silicon nanoparticles are dispersed in an organic solvent mixed with hydrofluoric acid.
(C) The solution is applied to the silicon substrate on which the silicon nanowires are grown.
(D) The silicon substrate coated with the solution is heat-treated to adsorb the silicon nanoparticles to the silicon nanowires.   The method according to claim 21, wherein the organic solvent is a volatile organic solvent.   The method according to claim 21 or 22, wherein the heat treatment is performed in an inert gas atmosphere. The method according to any one of claims 21 to 23, wherein the temperature of the heat treatment is 100 to 500 ° C and the time is 10 to 60 minutes.