JP2011187646A - Optical converter and electronic apparatus including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectrically converting device which widens a selection range of materials of a layer including a quantum dot, for example. <P>SOLUTION: The photoelectrically converting device is configured to include a p-type monocrystal silicon layer 100, an n-type semiconductor layer 120, a porous silicon layer 110 which is formed between the p-type monocrystal silicon layer 100 and the n-type semiconductor layer 120, and contains a plurality of quantum dots 112 in a hole 111. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical conversion device and the like, and more particularly to a photoelectric conversion device using quantum dots.

  BACKGROUND ART Solar cells (photoelectric conversion devices) are actively developed as energy sources that are energy-saving and resource-saving and clean. A solar cell is a power device that uses the photovoltaic effect to directly convert light energy into electric power. Various structures such as organic thin-film solar cells, dye-sensitized solar cells, and multi-junction structure solar cells have been studied for the configuration. Among them, a solar cell using quantum dots (nanoparticles) is drawing attention as a next-generation solar cell that theoretically enables a conversion efficiency of 60% or more.

  For example, Patent Document 1 below discloses a solar cell having a plurality of crystalline semiconductor material quantum dots separated by a thin dielectric material layer. Further, a solar cell using quantum dots is also disclosed in Non-Patent Document 1 below.

Special Table 2007-535806

Multiple Exciton Generation in Colloidal Silicon Nanocrystals, Nano Letters.vol. 7 (8), 2007 pp. 2506-2512.

  There are many theoretical explanations about the reason why the conversion efficiency of solar cells is improved by using quantum dots. For example, in Non-Patent Document 1 described above, the MEG (multiple exciton generation) effect of generating two or more excitons when absorbing a single high energy (having energy more than twice the band gap) is the effect of silicon. It has been reported that it occurs even in nanoparticles (quantum dots). In consideration of improving the efficiency of the solar cell mainly using such MEG effect, it is preferable to use a material having a small absorption coefficient and a large carrier mobility as the material of the layer including the quantum dots. . Examples of such a material include amorphous silicon and crystalline silicon (single crystal, polycrystal, or microcrystal), but crystalline silicon is superior in comparison. However, until now, it has been difficult to form a structure in which arbitrary quantum dots are dispersed in crystalline silicon.

  Therefore, a specific aspect of the present invention is to provide a photoelectric conversion device to which single crystal silicon or the like can be applied as a material of a layer including quantum dots. Another object is to widen the selection of materials for layers including quantum dots, not limited to single crystal silicon. Another object of the present invention is to broaden the choices of combinations of quantum dot materials and materials containing quantum dots.

  The inventor of the present application has studied the means for forming a layer made of crystalline silicon (single crystal, polycrystal, or microcrystal) containing quantum dots, for example, and applied a porous silicon layer. I came up with a way to do it. Furthermore, it has been found that if a layer made of a porous material is used, various materials can be applied in addition to crystalline silicon.

  The photoelectric conversion device of one embodiment of the present invention includes a first layer formed of one of p-type and n-type semiconductors, a second layer formed of either the p-type or n-type semiconductor, And a third layer formed between the first layer and the second layer and made of a porous material containing a plurality of nanoparticles in the pores.

  According to this configuration, the third layer is a layer made of a porous material, and a plurality of nanoparticles (quantum dots) are contained in the pores formed in this layer. Can be applied as the material of the third layer. Accordingly, the selection range of the material for the third layer is widened, and a photoelectric conversion device having a structure using a material according to the purpose can be provided.

  Alternatively, the photoelectric conversion device according to another embodiment of the present invention includes a first layer including any one of p-type and n-type semiconductors and a second layer including either the p-type and n-type semiconductors. A layer, and a third layer formed between the first layer and the second layer and made of a porous body containing a plurality of nanoparticles in the pores, and the nanoparticles Has a granular material and a coating material covering the granular material.

  According to such a configuration, the third layer is made of a porous material as described above, and a plurality of nanoparticles (quantum dots) are contained in the pores formed in this layer. A material that can be tempered can be applied as the material of the third layer. As a result, the range of selection of the material for the third layer is widened, and the range of selection of the material for the nanoparticles (quantum dots) is also widened, making it possible to use a combination of materials according to the purpose. Furthermore, the quantum effect can be easily generated by using the nanoparticles having the granular material and the coating material covering the granular material. As a result, the photoelectric conversion efficiency can be increased.

  Moreover, it is preferable that the band gap of the said coating material is larger than the band gap of the said granular material and the band gap of the said porous body.

  According to this, since the band gap of the coating material covering the granular material is larger than the band gap of the granular material and the porous body, a quantum well is formed, and by tunneling this coating material, Electric charges can be easily taken out. Therefore, a photoelectric conversion device with high photoelectric conversion efficiency can be configured.

  In the photoelectric conversion device, the first layer is formed of crystalline silicon (single crystal, polycrystal, or microcrystal), and the porous body is formed of porous silicon. Can do.

  According to this configuration, the porous body forming the third layer is porous silicon obtained by making crystalline silicon porous. Thereby, the material forming the third layer can be crystalline silicon having an absorption coefficient sufficiently smaller than that of the material forming the quantum dots and a high carrier mobility. As a result, the photoelectric conversion efficiency of the photoelectric conversion device can be further increased.

  Moreover, the said photoelectric conversion apparatus can be set as the structure by which the surface of the hole formed in the said porous body was formed with the silicon oxide.

  According to this configuration, even when there is no coating material covering the periphery of the nanoparticles arranged in the pores of the porous body, the silicon oxide film formed on the surface of the pores of the porous body is the same as the coating material. The structure is such that the electrons contained in the nanoparticles are confined by silicon oxide, and the quantum effect can be easily generated. As a result, the photoelectric conversion efficiency of the photoelectric conversion device can be further increased. In addition, the range of nanoparticle material selection can be widened.

  In the photoelectric conversion device, the first layer may be formed of amorphous silicon, and the porous body may be formed of porous amorphous silicon.

  One embodiment of the present invention includes an electronic device including any one of the above photoelectric conversion devices.

  On the other hand, in the method for manufacturing a photoelectric conversion device of one embodiment of the present invention, a step of forming a first layer made of one of a p-type semiconductor and an n-type semiconductor and a part of the first layer are made porous. To form a porous layer, to form a third layer by containing a plurality of nanoparticles in the pores of the porous layer, and to form a p-type layer on the third layer forming a second layer made of one of the n-type semiconductors.

  According to this method, since the third layer is a layer made of a porous material and a method in which a plurality of nanoparticles (quantum dots) are contained in pores formed in this layer, the method is made porous. Possible materials can be applied as the material of the third layer. As a result, the width of selection of the material for the third layer is widened and the width of selection of the material for the nanoparticles (quantum dots) is also widened, and a photoelectric conversion device is manufactured using a combination of materials according to the purpose Can do.

  According to another aspect of the present invention, there is provided a method for manufacturing a photoelectric conversion device, the step of forming a first layer made of any one of a p-type semiconductor and an n-type semiconductor, and a partial porosity of the first layer. To form a porous layer, to form a third layer by containing a plurality of nanoparticles in the pores of the porous layer, and to form a p-type layer on the third layer forming a second layer made of one of the n-type semiconductors, and the nanoparticles have a granular material and a coating material covering the granular material.

  According to another aspect of the present invention, there is provided a method for manufacturing a photoelectric conversion device, the step of forming a first layer made of one of a p-type semiconductor and an n-type semiconductor, and i on the first layer. A step of forming an i-type semiconductor layer made of a semiconductor of a type, a step of forming a porous body layer by making at least a part of the i-type semiconductor layer porous, and a plurality of nano-pores in pores of the porous body layer Forming a third layer containing particles, and forming a second layer made of either the p-type or n-type semiconductor on the third layer. Yes.

  The method for manufacturing a photoelectric conversion device of the present invention includes a step of oxidizing at least a part of the porous body layer between the step of forming the porous body layer and the step of forming the third layer. You may have.

  According to this method, the material around the nanoparticles arranged in the pores of the porous body is silicon oxide. Thus, a configuration in which electrons contained in the nanoparticles are confined by silicon oxide, and a photoelectric conversion device that easily causes a quantum effect can be manufactured. That is, a photoelectric conversion device with higher photoelectric conversion efficiency can be manufactured.

FIG. 3 is a cross-sectional view illustrating a structure of a photoelectric conversion device according to Embodiment 1. Sectional drawing which shows the structure of a quantum dot. 1 is a first cross-sectional view in a manufacturing process of a photoelectric conversion device according to Embodiment 1. FIG. FIG. 3 is a second cross-sectional view in the manufacturing process of the photoelectric conversion device according to Embodiment 1. FIG. 3 is a third cross-sectional view in the manufacturing process of the photoelectric conversion device according to the first embodiment. Sectional drawing which shows the structure of the photoelectric conversion apparatus in which the upper electrode and the lower electrode were formed. Sectional drawing which shows the structure of the photoelectric conversion apparatus in a comparative example. The 1st sectional view in the manufacturing process of the photoelectric conversion device in a comparative example. 2nd sectional drawing in the manufacturing process of the photoelectric conversion apparatus in a comparative example. Sectional drawing which shows the structure of the photoelectric conversion apparatus in Embodiment 2. FIG. FIG. 6 is a first cross-sectional view in the process of manufacturing a photoelectric conversion device according to Embodiment 2. FIG. 6 is a second cross-sectional view in the manufacturing process of the photoelectric conversion device according to the second embodiment. FIG. 9 is a third cross-sectional view in the manufacturing process of the photoelectric conversion device according to Embodiment 2. Sectional drawing which shows the structure of the photoelectric conversion apparatus in Embodiment 3. FIG. FIG. 10 is a first cross-sectional view in the process of manufacturing a photoelectric conversion device according to Embodiment 3. FIG. 6 is a second cross-sectional view in the manufacturing process of the photoelectric conversion device according to the second embodiment. FIG. 9 is a third cross-sectional view in the manufacturing process of the photoelectric conversion device according to the second embodiment. The top view which shows the calculator to which the photoelectric conversion apparatus of this invention is applied. The top view which shows the mobile telephone to which the photoelectric conversion apparatus of this invention is applied. The top view which shows the wristwatch to which the photoelectric conversion apparatus of this invention is applied.

An embodiment according to the present invention will be specifically described according to the following configuration with reference to the drawings. However, the embodiment described below is merely an example of the present invention, and does not limit the technical scope of the present invention. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and the description may be abbreviate | omitted.
1. Definition 2. Embodiment 1
(1) Configuration example of photoelectric conversion device (2) Manufacturing method of photoelectric conversion device (3) Comparative example (4) Features of Embodiment 1 Embodiment 2
(1) Configuration example of photoelectric conversion device (2) Manufacturing method of photoelectric conversion device (3) Features of Embodiment 2 (4) Modifications Embodiment 3
(1) Configuration example of photoelectric conversion device (2) Manufacturing method of photoelectric conversion device (3) Features of Embodiment 3 Application example 6. Applicability of the present invention

<1. Definition>
First, terms used in this specification are defined as follows.
“Porous body”: porous material such as porous silicon (referred to as porous single crystal silicon or polycrystalline silicon, also referred to as porous silicon), porous silicon oxide, or porous amorphous silicon A substance made of qualitative material.
“Porosity”: refers to a state in which a plurality of pores are formed in a certain substance.
“Porosification”: A process of forming a porous body by forming a plurality of pores in a certain substance.

<2. Embodiment 1>
First, Embodiment 1 regarding the photoelectric conversion apparatus of this invention and the manufacturing method of a photoelectric conversion apparatus is demonstrated, referring drawings.

<(1) Configuration Example of Photoelectric Conversion Device>
FIG. 1 is a cross-sectional view illustrating a configuration of the photoelectric conversion apparatus according to the first embodiment. As shown in FIG. 1, the photoelectric conversion device includes a p-type single crystal silicon layer 100 that is a p-type (first conductivity type) semiconductor layer, an n-type (second conductivity type) semiconductor layer 120, and their p-type. A porous silicon layer 110 containing a plurality of quantum dots 112 (also referred to as nanoparticles) is provided in a hole 111 formed between the single crystal silicon layer 100 and the n-type semiconductor layer 120.

  The p-type single crystal silicon layer 100 is made of single crystal silicon and contains p-type impurities such as boron. The n-type semiconductor layer 120 is made of amorphous silicon and contains an n-type impurity such as phosphorus.

  As the quantum dots 112, the so-called core-shell structure shown in FIG. 3 can be used. As shown in FIG. 3, the quantum dot 112 has a core c that is a granular material and a shell s that is a coating material that covers the granular material. The core c is a fine particle made of, for example, a semiconductor (including a compound semiconductor), and is a collection of hundreds to millions of atoms. The core c has a particle size of 1 nm or more and 20 nm or less. Further, the crystalline state of the core c may be any of a single crystal, a polycrystal, or an amorphous state. The material of the shell s covering the core c may be any material that satisfies the band gap relationship described below, and for example, an insulator or the like can be used. The film thickness of the shell s is, for example, 0.5 nm to 10 nm, and is a film thickness that allows tunneling of charges (electrons or holes) in the quantum well.

For example, germanium (Ge) can be used as the core c, and SiO ₂ can be used as the shell s. Such quantum dots can be produced, for example, by using molecular beam epitaxy or chemical vapor deposition, or in-gas vapor deposition, hot soap, colloid wet chemical methods, etc. For example, quantum dot dispersions having a core-shell structure are manufactured and sold by Quantum Dot and Evident Technologies.

  The relationship between the band gap between the shell s and the core c included in the quantum dot 112 and the matrix layer (the porous silicon layer 110 in the first embodiment) surrounding the quantum dot 112 is as follows. is there. The band gap E3 of the shell s is larger than the band gap E1 of the matrix layer and larger than the band gap E2 of the core c (E3> E1, E3> E2).

<(2) Method for Manufacturing Photoelectric Conversion Device>
<Step of making the single crystal silicon layer porous>
FIG. 3 is a cross-sectional view of the p-type single crystal silicon layer 100 before being made porous. FIG. 4 is a cross-sectional view showing a state in which a part of the p-type single crystal silicon layer 100 is made porous to form a porous silicon layer 110. As shown in FIGS. 3 and 4, in this step, a hole 111 is formed in a part of the p-type single crystal silicon layer 100 to make it porous, thereby forming porous silicon. The layer in which the porous silicon is formed is referred to as a porous silicon layer 110. The thickness of the porous silicon layer 110 is about 50 nm to 1 μm.

An example of a specific method for forming porous silicon is an anodizing method. In the anodizing method, porous silicon is formed by energizing an electrolyte solution composed of HF, H ₂ O, and H ₅ OH using a silicon substrate as an anode and a platinum (Pt) electrode as a cathode. More specifically, for example, a silicon substrate serving as an anode electrode is immersed in a 5 to 50% HF aqueous solution at a temperature of 10 to 70 ° C., and an anode current in the range of several tens to several hundred mA / cm ² is applied. Thus, porous silicon can be formed.

<Step of including quantum dots in pores of porous silicon layer>
Next, the quantum dots 112 are contained in the holes 111 of the porous silicon layer 110. This step is performed, for example, by preparing a liquid in which quantum dots are dispersed and immersing a wafer having a p-type single crystal silicon layer 100 and a porous silicon layer 110 as shown in FIG. 4 in this liquid for about 10 minutes. Is called. As this liquid, for example, an organic solvent dispersion in which the above-mentioned quantum dots having a core-shell structure are dispersed in toluene or cyclohexane at a concentration of 1 wt% (mass%) can be used. In this manner, as shown in FIG. 5, the quantum dots 112 can be contained in the holes 111 of the porous silicon layer 110.

<Step of forming an n-type semiconductor layer>
Next, the n-type semiconductor layer 120 is formed on the porous silicon layer 110 containing the quantum dots 112. As a material for forming the n-type semiconductor layer 120, for example, n-type amorphous silicon is used. The n-type semiconductor layer 120 can be formed by a conventional film formation method described in, for example, Japanese Patent Laid-Open No. 5-283723. That is, as an example, the substrate temperature is room temperature to 250 ° C., the SiH ₄ gas flow rate is 40 SCCM, the H ₂ gas flow rate is 100 SCCM, and the flow rate of PH ₃ gas diluted to 1000 ppm with H ₂ gas is 10 to 100 SCCM. A film can be formed by setting the density to 10 to 200 mW / cm ² .

  Through the above steps, a photoelectric conversion device as shown in FIG. 1 can be manufactured.

<Step of forming electrode>
Further, in order to use the photoelectric conversion device formed by the above process as a solar cell or the like, it is necessary to form the upper electrode 130 and the lower electrode 140 on the upper surface and the lower surface, respectively. FIG. 6 illustrates an example of a configuration of a photoelectric conversion device in which the upper electrode 130 and the lower electrode 140 are formed.

As shown in FIG. 6, the upper electrode 130 is formed as a transparent electrode on the n-type semiconductor layer 120. Examples of the material forming the upper electrode 130 which is a transparent electrode include indium-added tin oxide (ITO), fluorine-doped tin oxide (FTO), indium oxide (IO), or tin oxide (SnO ₂ ). Used.

  Further, as shown in FIG. 6, the lower electrode 140 is formed below the single crystal silicon layer 100. As a material for forming the lower electrode 140, for example, Al (aluminum) can be used. In addition, nickel (Ni), cobalt (Co), platinum (Pt), silver (Ag), gold (Au), copper (Cu), molybdenum (Mo), titanium (Ti), tantalum (Ta), etc. Metal materials can also be used.

<(3) Comparative example>
Here, as a comparative example of the present invention, a photoelectric conversion device having a so-called pin structure and an i-type amorphous silicon layer including quantum dots will be described. In the photoelectric conversion device of this comparative example, an example using quantum dots having a core-shell structure is shown. Note that the photoelectric conversion device described in the comparative example is described in detail in Japanese Patent Application No. 2009-050922 (not disclosed at the time of the present application) by the inventors of the present invention.

  FIG. 7 is a cross-sectional view illustrating a configuration of a photoelectric conversion device in this comparative example. FIG. 2 is a cross-sectional view showing the configuration of the quantum dot d in FIG. The photoelectric conversion device illustrated in FIG. 7 is a device having a so-called pin structure, and has a configuration in which a p layer, an i layer, and an n layer are sequentially stacked. Specifically, as shown in the figure, a transparent electrode 3, a p-type (first conductivity type) amorphous silicon layer 5, an i layer 7, and an n-type (second conductivity type) amorphous silicon layer 9 are formed on the substrate 1. The upper electrode 11 is sequentially stacked.

  The first and second conductivity types are p-type or n-type. In the case of p-type, p-type impurities such as boron and in the case of n-type have n-type impurities such as phosphorus. i-type (intrinsic) means a layer in which no impurity is implanted and has a lower impurity concentration than a p-type or n-type layer.

  As the substrate 1, for example, a light transmissive quartz glass substrate is used. In addition, another glass substrate such as a soda glass substrate, a resin substrate using a resin such as polycarbonate, polyethylene terephthalate, or a ceramic substrate may be used.

As the transparent electrode 3, for example, indium tin oxide (ITO) added with indium is used. In addition, other conductive metal oxides such as fluorine-doped tin oxide (FTO), indium oxide (IO), and tin oxide (SnO ₂ ) may be used. By using such a transparent electrode, the light transmittance from the back surface side (lower side in the figure) of the substrate 1 can be improved.

  The p-type (first conductivity type) amorphous silicon layer 5 is made of amorphous silicon having p-type impurities.

  The i layer (photoelectric conversion layer) 7 includes an i-type amorphous silicon layer 7a and quantum dots (nanoparticles) d contained therein in a dispersed state. As shown in FIG. 7, the quantum dot d has a core-shell structure, and includes a core c made of a granular material and a shell s made of a coating material covering the outer periphery of the core.

  The n-type (second conductivity type) amorphous silicon layer 9 is made of amorphous silicon having n-type impurities.

  As a material of the upper electrode 11, for example, Al (aluminum) is used. Other metals such as nickel (Ni), cobalt (Co), platinum (Pt), silver (Ag), gold (Au), copper (Cu), molybdenum (Mo), titanium (Ti), and tantalum (Ta) Materials can be used. Moreover, you may use these alloys. Alternatively, the above conductive metal oxide may be used.

  Thus, in this comparative example, quantum dots d are contained in the i-type amorphous silicon layer (also referred to as matrix layer) 7a.

  Here, in this comparative example, the i-type amorphous silicon layer 7a containing the quantum dots d is formed by the following method.

  That is, as shown in FIG. 8, after forming the substrate 1, the transparent electrode 3, and the p-type amorphous silicon layer 5, the silicon precursor liquid L7 in which the quantum dots d are dispersed is adjusted to adjust the p-type amorphous silicon layer. 5 is applied by spin coating, for example. Next, heat treatment is performed to make the silicon precursor liquid L7 amorphous. In addition to the spin coating method, other discharge methods such as a spray method and an ink jet method may be used. As a result, as shown in FIG. 9, an i-type amorphous silicon layer 7a containing the quantum dots d having a core-shell structure in a dispersed state is formed.

<(4) Features of Embodiment 1>
When comparing the first embodiment and the comparative example, one of the features of the first embodiment is that the layer containing the quantum dots d is the porous silicon layer 110. In the comparative example, since the method using the silicon precursor liquid L7 in which the quantum dots d are dispersed in the manufacturing process is adopted, the material of the layer containing the quantum dots d is limited. For example, single crystal silicon can be adopted. could not.

  On the other hand, the photoelectric conversion device according to the first embodiment has a configuration in which the porous silicon layer 110 is provided and the quantum dots 112 are contained in the holes 111. According to this configuration, the range of selection of the material for forming the layer containing the quantum dots 112 is widened, and it is possible to provide a photoelectric conversion device having a configuration using a material according to the purpose.

  Further, according to the photoelectric conversion device using the core-shell structured quantum dots 112 as described above, the quantum well is formed by the band gap of the coating material (shell s) covering the granular material (core c). By tunneling this coating material, the charge in the quantum well can be easily taken out. Therefore, a photoelectric conversion device with high photoelectric conversion efficiency can be configured.

  Here, when comparing amorphous silicon and single crystal silicon, amorphous silicon may be preferable in terms of ease of processing, but single crystal silicon has an absorption coefficient that is 100 times smaller than that of amorphous silicon. When single crystal silicon is used as the layer containing dots, the proportion of light absorbed by the quantum dots increases. In addition, since single crystal silicon has a carrier mobility of 100 times or more higher than that of amorphous silicon, it is possible to carry charges generated in the quantum dots to the electrode more efficiently. As a result, as the material of the layer containing the quantum dots d, the use of single crystal silicon is superior in photoelectric conversion efficiency compared to the case where amorphous silicon is used. However, as described above, in the comparative example, single crystal silicon could not be adopted as the material of the layer containing the quantum dots d.

  That is, according to the configuration of the first embodiment, the porous material forming the layer containing the quantum dots 112 is porous silicon obtained by making single crystal silicon porous. Thereby, the material for forming the layer containing the quantum dots 112 can be single crystal silicon whose absorption coefficient is sufficiently smaller than that of the material forming the quantum dots and whose carrier mobility is large. As a result, the photoelectric conversion efficiency of the photoelectric conversion device can be further increased.

<3. Second Embodiment>
Next, Embodiment 2 regarding the photoelectric conversion apparatus of this invention and the manufacturing method of a photoelectric conversion apparatus is demonstrated, referring drawings.

<(1) Configuration Example of Photoelectric Conversion Device>
FIG. 10 is a cross-sectional view illustrating a configuration of the photoelectric conversion apparatus according to the second embodiment. As illustrated in FIG. 10, the photoelectric conversion device includes a single crystal silicon layer 100 that is a p-type (first conductivity type) semiconductor layer, an n-type (second conductivity type) semiconductor layer 120, and p-type single crystals thereof. A porous silicon oxide layer 150 containing a plurality of quantum dots 112 is provided in the hole 111 formed between the silicon layer 100 and the n-type semiconductor layer 120.

  When Embodiment 2 is compared with Embodiment 1, the layers containing the quantum dots 112 are different. That is, in the first embodiment, the quantum dots 112 are contained in the holes 111 formed in the porous silicon layer 110, whereas in the second embodiment, the quantum dots 112 are formed in the porous silicon oxide layer 150. Contained in the formed holes 111. In the porous silicon oxide layer 150, the interface between the hole 111 and single crystal silicon (the surface of the hole 111) is oxidized to form a silicon oxide film 113. The second embodiment is also different from the core / shell structure described in the first embodiment as the quantum dots 112 in that a single particle material is used.

<(2) Method for Manufacturing Photoelectric Conversion Device>
<Step of making the single crystal silicon layer porous>
FIG. 11 is a cross-sectional view showing a state in which a part of the p-type single crystal silicon layer 100 is made porous to form a porous silicon layer 110. This step can be performed by the same method as in the first embodiment.

<Step of oxidizing the porous silicon layer>
Next, an oxide film is formed on the surface of the hole of the porous silicon layer 110. Specifically, for example, after anodizing by the anodizing method in the above-described porosification step and washing, an electrolyte is exchanged with 1 M sulfuric acid, and a voltage is applied between the electrodes in the same manner as in the anodizing method. As a result, a silicon oxide film 113 is formed on the surface of the hole 111 of the porous silicon layer 110.

<Step of including quantum dots in pores of porous silicon oxide layer>
Next, the quantum dots 112 are contained in the porous silicon oxide layer 150. This step is performed by the same method as in the first embodiment, and as shown in FIG. 13, the quantum dots 112 can be contained in the holes 111 of the porous silicon oxide layer 150.

  The quantum dots 112 used in the second embodiment are minute particles made of a semiconductor material (including a compound semiconductor), and are formed by collecting hundreds to millions of atoms. Further, the quantum dots 112 have a particle size of 1 nm or more and 20 nm or less and are made of a single particle material.

  In order to produce a quantum effect in the photoelectric conversion device, the band gap of the particle material constituting the quantum dot 112 is smaller than the band gap of the single crystal silicon constituting the porous silicon layer 110. As the particle material constituting the quantum dots 112, for example, lead sulfide (PbS), germanium (Ge), lead selenide (PbSe), or the like is used.

<Step of forming an n-type semiconductor layer>
Next, the n-type semiconductor layer 120 is formed on the porous silicon oxide layer 150 containing the quantum dots 112. This step is also performed by the same method as in the first embodiment. In this way, the photoelectric conversion device as shown in FIG. 10 can be manufactured.

<Step of forming electrode>
Similarly to Embodiment 1, in order to use the photoelectric conversion device formed by the above process as a solar cell or the like, it is necessary to form the upper electrode 130 and the lower electrode 140 on the upper surface and the lower surface, respectively. This step can also be performed by the same method as in the first embodiment.

<(3) Features of Embodiment 2>
In the photoelectric conversion device of Embodiment 2, the surface of the hole 111 is oxidized. As a result, a silicon oxide film 113 is formed at the interface between the hole 111 and the single crystal silicon. According to the photoelectric conversion device thus configured, the silicon oxide film 113 functions in the same manner as the shell of a quantum dot having a core / shell structure, and the electrons contained in the quantum dot 112 are confined by the silicon oxide film 113. Since the configuration is such that the quantum dot shell can be omitted, the range of choice of material for the quantum dots is widened.

<(4) Modification>
In the second embodiment, the core-shell structure as described in the first embodiment may be used as the quantum dots. In that case, both the silicon oxide film and the quantum dot shell serve as a barrier to confine electrons, and the required barrier height can be controlled more precisely.

<4. Embodiment 3>
Next, Embodiment 3 regarding the photoelectric conversion apparatus of this invention and the manufacturing method of a photoelectric conversion apparatus is demonstrated, referring drawings.

<(1) Configuration Example of Photoelectric Conversion Device>
The photoelectric conversion device of Embodiment 3 has a so-called pin structure, and has a configuration in which a p layer, an i layer, and an n layer are sequentially stacked. FIG. 14 is a cross-sectional view illustrating a configuration of the photoelectric conversion device according to the third embodiment. As shown in FIG. 14, the photoelectric conversion device includes a p-type amorphous silicon layer 160, which is a p-type (first conductivity type) semiconductor layer, an n-type (second conductivity type) semiconductor layer 180, and p-type amorphous layers thereof. An i-type amorphous silicon layer 170 that is an i-type semiconductor layer formed between the silicon layer 160 and the n-type semiconductor layer 180 is provided. A porous amorphous silicon layer 190 in which holes 111 are formed is formed on a part of the i-type semiconductor layer on the n-type semiconductor layer 180 side. A plurality of quantum dots 112 are contained in the holes 111 formed in the porous amorphous silicon layer 190. In the third embodiment, the quantum dots 112 having the same core-shell structure as in the first embodiment are used, and detailed description of the quantum dots is omitted.

  The photoelectric conversion device according to the third embodiment is characterized in that it has a pin structure and that the quantum dots 112 are contained in the holes 111 formed in the i-type amorphous silicon layer 170. Further, although the substrate and the electrode described in the comparative example having the same pin structure are not illustrated in the third embodiment, the same substrate and electrode as in the comparative example may be provided in the third embodiment.

  Here, when the photoelectric conversion device of the present embodiment includes a substrate, a light-transmitting quartz glass substrate or the like is used as the material of the substrate. In addition, another glass substrate such as a soda glass substrate, a resin substrate using a resin such as polycarbonate, polyethylene terephthalate, or a ceramic substrate may be used.

As the transparent electrode formed between the substrate and the p-type amorphous silicon layer 160, for example, indium tin oxide (ITO) to which indium is added is used. In addition, other conductive metal oxides such as fluorine-doped tin oxide (FTO), indium oxide (IO), and tin oxide (SnO ₂ ) may be used. If such a transparent electrode is used, the light transmittance from the back side (lower side in the figure) of the substrate can be improved.

<(2) Method for Manufacturing Photoelectric Conversion Device>
<Step of forming p-type amorphous silicon layer and i-type amorphous silicon layer>
First, as shown in FIG. 15, a p-type amorphous silicon layer (p-type semiconductor layer) 160 and an i-type amorphous silicon layer (i-type semiconductor layer) 170 are formed.

The p-type amorphous silicon layer 160 is formed using, for example, an impurity-added precursor liquid obtained by adding a p-type impurity such as boron to a silicon precursor liquid (liquid silicon material). The “precursor liquid” refers to a substance in a previous stage for obtaining a specific substance, and here, it refers to a liquid silicon material for obtaining a silicon layer. As the silicon precursor solution, for example, a solution obtained by diluting a cyclosilane silane (Si ₅ H ₁₀ ) with an organic solvent by polymerizing polysilane by irradiating it with ultraviolet rays is used. This impurity-added precursor liquid is applied onto the transparent electrode 3 by spin coating. Next, heat treatment is performed to make it amorphous (solidify and fire). In addition to the spin coating method, other discharge methods such as a spray method and an ink jet method may be used.

  The i-type amorphous silicon layer 170 can also be formed by the same method as the p-type amorphous silicon layer 160, but a precursor liquid to which no impurity is added is used. That is, a silicon precursor solution that does not contain impurities is applied on the p-type amorphous silicon layer 160 by spin coating or the like, and then heat-treated to make it amorphous.

<Step of making i-type amorphous silicon layer porous>
Next, as shown in FIG. 16, a hole 111 is formed in a part of the i-type amorphous silicon layer 170 by the same method as in the first embodiment to make it porous, and a porous amorphous silicon layer 190 is formed. To do. The i-type amorphous silicon layer 170 has a thickness of about 300 nm, and the porous amorphous silicon layer 190 has a thickness of about 75 nm to 150 nm, which is about 1/4 to 1/2 of the i-type amorphous silicon layer 170.

<Step of including quantum dots in pores of porous silicon layer>
Next, as shown in FIG. 17, quantum dots 112 are contained in the holes 111 formed in the porous amorphous silicon layer 190. As a method for causing the holes 111 to contain the quantum dots 112, the same method as in the first embodiment is used.

<Step of forming an n-type semiconductor layer>
Next, an n-type semiconductor layer 180 is formed on the porous amorphous silicon layer 190. As a material for forming the n-type semiconductor layer 180, for example, n-type amorphous silicon is used. The n-type semiconductor layer 180 can be formed by the same method as in the first embodiment.

<Step of forming electrode>
Similarly to Embodiment 1, in order to use the photoelectric conversion device formed by the above steps as a solar cell or the like, it is necessary to form an upper electrode and a lower electrode on the upper surface and the lower surface, respectively. This step can be formed by the same method as in the first embodiment.

<(3) Features of Embodiment 3>
In the photoelectric conversion device of Embodiment 3, a part of the i-type semiconductor layer (i-type amorphous silicon layer 170) in the pin structure is made porous to form a porous body layer (porous amorphous silicon layer 190), It was set as the structure which contains the quantum dot 112 in the formed hole 111. FIG. Compared to the first embodiment, the p-type semiconductor layer and the porous body layer have different configurations in the third embodiment because of the pin structure, but the quantum dots 112 are contained in the holes 111 of the porous body layer. The configuration to be shared is common. As described above, the material for forming the layer containing the quantum dots 112 can selectively use the single crystal silicon of the first embodiment, the i-type amorphous silicon of the third embodiment, or the like. That is, as a material for the layer containing the quantum dots 112 in the photoelectric conversion device, it is possible to use a material according to the purpose, such as cost reduction and improvement in power generation efficiency.

<5. Application example>
The photoelectric conversion device can be incorporated into various electronic devices. There is no limitation on applicable electronic devices, but an example thereof will be described.

  18 is a plan view showing a calculator to which the solar cell (photoelectric conversion device) of the present invention is applied, and FIG. 19 is a perspective view showing a mobile phone (including PHS) to which the solar cell (photoelectric conversion device) of the present invention is applied. FIG.

  A calculator 200 illustrated in FIG. 18 includes a main body 201, a display unit 202 provided on the upper surface (front surface) of the main body 201, a plurality of operation buttons 203, and a photoelectric conversion element installation unit 204.

  In the configuration shown in FIG. 18, five photoelectric conversion elements 20 are connected in series and arranged in the photoelectric conversion element installation unit 204. The photoelectric conversion device can be incorporated as the photoelectric conversion element 20.

  A cellular phone 300 illustrated in FIG. 19 includes a main body portion 301, a display portion 302 provided on the front surface of the main body portion 301, a plurality of operation buttons 303, an earpiece 304, a mouthpiece 305, and a photoelectric conversion element installation portion 306. I have.

  In the configuration illustrated in FIG. 19, the photoelectric conversion element installation unit 306 is provided so as to surround the display unit 302, and a plurality of photoelectric conversion elements 20 are connected in series. The photoelectric conversion device can be incorporated as the photoelectric conversion element 20.

  FIG. 20 is a perspective view illustrating a wrist watch that is an example of an electronic apparatus. The wristwatch 400 includes a display unit 401. For example, the photoelectric conversion device can be incorporated in the outer periphery of the display unit 401.

  Note that the electronic device of the present invention is applicable to, for example, an optical sensor, an optical switch, an electronic notebook, an electronic dictionary, a clock, etc. in addition to the calculator shown in FIG. 18, the mobile phone shown in FIG. 19, and the wristwatch shown in FIG. You can also

<6. Applicability of the present invention>
The above embodiment is merely one embodiment of the present invention, and the present invention includes inventions in a range that can be conceived by those skilled in the art based on these embodiments.

  For example, Embodiments 1 to 3 can be combined in a range that does not contradict each other as long as those skilled in the art can conceive. For example, although not limited to these, the so-called core-shell structure quantum dots 112 may be used in the configuration of the second embodiment, or an oxide film is formed on the surface of the hole 111 in the configuration of the third embodiment. May be.

  In the embodiment, the n-type semiconductor layer 120 (or 180) is formed of n-type amorphous silicon, but may be formed of other n-type semiconductor materials.

In the embodiment, cyclopentasilane (Si ₅ H ₁₀ ) is used as the silicon precursor liquid, but other silicon compounds may be polymerized.

  In the embodiment, the p-type semiconductor layer is provided on the lower layer side and the n-type semiconductor layer is provided on the upper layer side. However, these may be reversed. That is, an n-type semiconductor layer may be provided on the lower layer side and a p-type semiconductor layer may be provided on the rising side.

  Further, in the embodiment, specific numerical conditions and the like are shown in each step in the manufacturing method, but these numerical conditions and the like are merely examples, and are not limited to these conditions. That is, the present invention includes those that can be conceived by those skilled in the art based on these descriptions.

c ... core, d ... quantum dot, L7 ... precursor liquid, s ... shell, 1 ... substrate, 3 ... transparent electrode, 5 ... amorphous silicon layer, 7 ... i layer, 7a ... i Type amorphous silicon layer, 9 ... n-type amorphous silicon layer, 11 ... upper electrode (metal electrode), 20 ... photoelectric conversion element, 100 ... p-type single crystal silicon layer, 110 ... porous silicon layer , 111... Hole, 112... Quantum dot, 113... Silicon oxide film, 120... N-type semiconductor layer, 130... Upper electrode, 140. -Type amorphous silicon layer, 170 ... n-type amorphous silicon layer, 180 ... n-type semiconductor layer, 190 ... porous amorphous silicon layer, 200 ... calculator, 201 ... body part, 202 ... display part, 03 …… Operating buttons, 204 …… Photoelectric conversion element installation section, 300 …… Mobile phone, 301 …… Main body section, 302 …… Display section, 303 …… Operation buttons, 304 …… Entrance, 305 …… Transmission Mouth, 306... Photoelectric conversion element installation section, 400... Wristwatch, 401.

Claims (11)

a first layer made of either p-type or n-type semiconductor;
a second layer made of either the p-type or n-type semiconductor;
A third layer formed between the first layer and the second layer and made of a porous body containing a plurality of nanoparticles in the pores,
Photoelectric conversion device. a first layer made of either p-type or n-type semiconductor;
a second layer made of either the p-type or n-type semiconductor;
A third layer formed between the first layer and the second layer and made of a porous body containing a plurality of nanoparticles in the pores, and
The nanoparticles have a particulate material and a coating material that coats the particulate material,
Photoelectric conversion device. The band gap of the coating material is larger than the band gap of the granular material and the band gap of the porous body,
The photoelectric conversion device according to claim 2. The first layer is formed of single crystal silicon or polycrystalline silicon;
The porous body is made of porous silicon;
The photoelectric conversion device according to claim 1. Having a silicon oxide film on the surface of the hole formed in the porous body,
The photoelectric conversion device according to claim 4. The first layer is formed of amorphous silicon;
The porous body is formed of porous amorphous silicon,
The photoelectric conversion device according to claim 1.   The electronic device which has a photoelectric conversion apparatus of any one of Claims 1 thru | or 6. forming a first layer made of either p-type or n-type semiconductor;
Making a part of the first layer porous to form a porous body layer;
Including a plurality of nanoparticles in the pores of the porous body layer to form a third layer;
Forming a second layer made of either the p-type or n-type semiconductor on the third layer.
A method for manufacturing a photoelectric conversion device. forming a first layer made of either p-type or n-type semiconductor;
Forming a porous body layer by partially making the first layer porous;
Including a plurality of nanoparticles in the pores of the porous body layer to form a third layer;
Forming a second layer made of one of the p-type and n-type semiconductors on the third layer, and
The nanoparticles have a particulate material and a coating material that coats the particulate material,
A method for manufacturing a photoelectric conversion device. forming a first layer made of either p-type or n-type semiconductor;
Forming an i-type semiconductor layer made of an i-type semiconductor on the first layer;
Forming a porous body layer by making at least a part of the i-type semiconductor layer porous;
Including a plurality of nanoparticles in the pores of the porous body layer to form a third layer;
Forming a second layer made of either the p-type or n-type semiconductor on the third layer.
A method for manufacturing a photoelectric conversion device. Oxidizing at least part of the porous body layer between the step of forming the porous body layer and the step of forming the third layer;
The manufacturing method of the photoelectric conversion apparatus of Claim 8 or 9.

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