JP2013051318A - Process of manufacturing quantum dot structure, wavelength conversion element and photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of manufacturing a quantum dot structure capable of distributing quality quantum dots with small number of defects three-dimensionally and uniformly, and to provide a wavelength conversion element having a quantum dot structure manufactured by this manufacturing process, and a photoelectric conversion device.SOLUTION: A laminate is produced by mutually laminating: a first amorphous layer composed of two kinds or more of semiconductor or metal element and oxygen where the composition ratio of the two kinds or more of semiconductor or metal element is high for the oxygen; a stoichiometric dielectric material layer having a composition consisting of a first semiconductor or a first metal element and oxygen; and a second amorphous layer composed of a first semiconductor or a first metal element and oxygen where the composition ratio of the first semiconductor or the first metal element is high. When the laminate is heat-treated, a matrix is formed by the first semiconductor or the first metal element, and crystalline quantum dots consisting of second semiconductor or second metal element, or quantum dots of mixed crystal of two kinds or more of semiconductor or metal element are formed in the matrix.

Description

  The present invention relates to a method for producing a quantum dot structure having quantum dots, and a wavelength conversion element and a photoelectric conversion device having a quantum dot structure produced by this production method. The present invention relates to a manufacturing method of a quantum dot structure that can be uniformly distributed in a dimension, and a wavelength conversion element and a photoelectric conversion device having the quantum dot structure by the manufacturing method.

Currently, research is actively conducted on solar cells. Among solar cells, a PN junction solar cell configured by bonding a P-type semiconductor and an N-type semiconductor, and a PIN junction solar cell configured by bonding a P-type semiconductor, an I-type semiconductor, and an N-type semiconductor, , Absorbs sunlight having energy greater than the band gap (Eg) between the conduction band and the valence band of the constituting semiconductor, and excites electrons from the valence band to the conductor to enter the valence band. Holes are generated and an electromotive force is generated in the solar cell.
A PN junction solar cell and a PIN junction solar cell have a single band gap and are called single junction solar cells.

  In the PN junction solar cell and the PIN junction solar cell, light having energy smaller than the band gap is transmitted without being absorbed. On the other hand, energy larger than the band gap is absorbed, but of the absorbed energy, the energy larger than the band gap is consumed as thermal energy as phonons. For this reason, single band gap single junction solar cells such as PN junction solar cells and PIN junction solar cells have a problem of poor energy conversion efficiency.

In order to improve this problem, a plurality of PN junctions and PIN junctions having different band gaps are stacked, and a structure that absorbs sequentially from light having a large energy is absorbed in a wide wavelength range, and Multijunction solar cells have been developed that reduce losses to thermal energy and improve energy conversion efficiency.
However, since this multi-junction solar cell has a plurality of PN and PIN junctions electrically connected in series, the output current is the minimum current generated at each junction. For this reason, when the solar spectrum distribution is biased and the output of one PN junction or PIN junction is decreased, the output of the junction that is not affected by the bias of the solar spectrum distribution is also decreased, and the output of the entire solar cell is greatly decreased. In addition, it is necessary to select materials using materials with almost the same crystal lattice length, because it is necessary to join semiconductors with high crystal quality and different hand gaps with high crystal quality. Therefore, it is difficult to make a material with a narrow range of material selection.

As a next-generation solar cell that solves this problem, a solar cell using a quantum effect by quantum dots has been rapidly studied in recent years. Solar cells using quantum dots are roughly classified into four types: multi-junction, intermediate band type, multi-exton type, and hot carrier type.
In any method, the theoretical conversion efficiency is determined by the combination of the band caps of the materials, and in any method, it is desired to form a quantum dot having a relatively low band gap of 1.0 eV or less.

  For example, the relatively low band gap of 1.0 eV or less includes Ge, SiGe, InN, InAs, FeSi, PbS, PbSe, and the like. Among these, in the vapor phase forming method, Ge and SiGe materials have been studied from the viewpoint of consistency with existing Si technology (for example, see Patent Document 1). In addition, in terms of particle formation and application, research on photoelectric conversion films using PbS and PbSe, which are relatively easy to synthesize particles, has been actively studied.

As a method for forming Ge and SiGe quantum dots in a gas phase, a plurality of stoichiometric dielectric material layers having a compound of a semiconductor material and a dielectric layer having a large semiconductor composition ratio as disclosed in Patent Document 1 are used. A method has been proposed in which an amorphous dielectric material is used as a matrix (energy barrier) by stacking and heating each other to form a photoelectric conversion film in which quantum dots of crystalline semiconductor are uniformly distributed in three dimensions. ing.
Patent Document 1 discloses that a photoelectric conversion film in which crystalline quantum dots of a Si alloy are uniformly distributed three-dimensionally in a SiO ₂ , Si ₃ N ₄ , or SiC matrix material is disclosed. Yes.
Further, in Patent Document 1, when forming Si quantum dots, a reaction of 2SiO → Si + SiO ₂ is used by annealing. Furthermore, in Patent Document 1, a reaction of GeO → Ge + GeO ₂ is used to form Ge quantum dots.

In the method of Patent Document 1, an interface between Ge and GeO ₂ is formed.
Here, Non-Patent Document 1 discloses that Ge nanocrystals are formed in a GeO ₂ matrix by dry-oxidizing a SiGe amorphous film. As the PL emission intensity and composition change depending on the dry oxidation conditions, and the annealing temperature increases, the Raman intensity changes in the order of Si—Si bond → Si—Ge bond → Ge—Ge bond, and the results of FTIR indicate that -Ge changes to Ge-O-Ge. Furthermore, it is disclosed that it is estimated that defects are formed at the Ge / GeO ₂ interface from the correspondence between the change from Ge—Ge to Ge—O—Ge and the PL intensity.
As disclosed in Non-Patent Document 1, it has been pointed out that a defect at the Ge / GeO ₂ interface causes a decrease in light-light conversion efficiency and a decrease in photoelectric conversion efficiency. For this reason, it has been proposed to use relatively stable SiO ₂ as a matrix instead of GeO ₂ , which is likely to cause defects (see Patent Document 2 and Non-Patent Document 2).

  Patent Document 2 describes a photoelectric conversion device having a photoelectric conversion unit and a wavelength conversion unit (wavelength conversion element). This wavelength conversion unit is disposed on the light incident side of the photoelectric conversion unit, and the wavelength conversion unit is composed of quantum dots d and a layer (“matrix”) surrounding the quantum dot d, and the matrix is made of a silicon oxide film. It is described that it becomes. This Patent Document 2 describes that quantum dots d may be regularly arranged vertically and horizontally and vertically, or quantum dots d may be randomly arranged in a plane between thin films.

Non-Patent Document 2 discloses a method of forming a thin film in which uniform Ge nanocrystals are dispersed in SiO ₂ by co-sputtering SiO ₂ and Ge and annealing at 700 to 900 ° C.

Special Table 2007-535806 JP 2010-118491 A

Solid state communications 136 (2005) 224-227 JOURNAL OF APPLIED PHYSICS 103, 103534 (2008) Nanotechnology 21 (2010) 505201

Here, there is a report that SiGeO is formed at the Si-Ge interface at a relatively low annealing temperature (“Annealing effects on Ge / SiO2 interface structure in wafer-bonded Ge-on-insulator substrates (Osamu Yoshitake, ets Osaka University "from SSDM 2010 Proceeding).
From this report, there is a concern that the composition changes with time and the light-light conversion efficiency is lowered or the photoelectric conversion efficiency is lowered.
The inventor forms a laminated film by laminating a Si _x GeyO _(1-xy) layer and a SiO ₂ layer, and anneals the laminated film to obtain Si _x GeyO _(1-xy) → When Ge quantum dots were formed using the reaction of Ge + SiO ₂ , a peak derived from the Ge crystal was confirmed by Raman spectroscopic measurement, and PL emission in the infrared was confirmed. However, it is confirmed that the film quality is changed by a time-test for about one month and that PL emission is not generated.

In Non-Patent Document 3, a layered film of SiO ₂ layer, Si ₃ N ₄ layer and Si _x Ge _1-x layer is formed as a matrix material and quantum dot material, and silicon of Si _x Ge _1-x layer is selected A method is disclosed in which Ge quantum dots are formed in a Si ₃ N ₄ layer by selective oxidation.
However, in Non-Patent Document 3, however, a Ge quantum dot is formed by forming a laminated film of a SiO ₂ layer and a Si _x Ge _1-x layer and selectively oxidizing the silicon of the Si _x Ge _1-x layer. The possibility of formation was examined. As oxidation progressed from the surface, a difference in oxidation degree occurred in the depth direction. From this, it is considered that when the number of layers is relatively large, it is difficult to uniformly distribute the Ge quantum dots in a three-dimensional manner and it is not possible to arrange them at high density.
Further, since the matrix material surrounding the Ge quantum dots is different from SiO ₂ and Si ₃ N _{4 in} the horizontal direction and in the vertical direction, the photoelectric conversion film in which the quantum dots are uniformly distributed three-dimensionally is defined in the horizontal direction, A difference in the hand barrier occurs in the vertical direction, which makes it easy for the charge to move in the horizontal direction but not in the vertical direction, so that it is difficult to pass a current in the vertical direction, and the device application is limited.

  An object of the present invention is to solve the problems based on the prior art and to produce a quantum dot structure capable of three-dimensionally uniformly distributing high-quality quantum dots with few defects, and a quantum dot produced by this production method It is providing the wavelength conversion element and photoelectric conversion apparatus which have a structure.

  In order to achieve the above object, the present invention has a composition composed of oxygen of first and second semiconductors or metal elements and oxygen, and the first and second kinds of oxygen with respect to the oxygen. A first amorphous layer having a high composition ratio of the semiconductor or metal element; a stoichiometric dielectric material layer having a composition comprising the first semiconductor or the first metal element and oxygen; And a first amorphous element or a second amorphous layer having a composition ratio of the first metal element and a high composition ratio of the first semiconductor element and the first metal element. A step of obtaining, a heat treatment of the stacked body, a matrix is formed of the first semiconductor or the first metal element, and a crystal composed of the second semiconductor or the second metal element in the matrix Quality quantum dots Is to provide a method of manufacturing a quantum dot structure, characterized by a step of forming the first, quantum dots mixed crystal of the second of two or more semiconductor or metallic elements.

The stacked body includes a first amorphous layer adjacent to the first amorphous layer or the second amorphous layer, the stoichiometric dielectric material layer being formed, and the first amorphous layer being adjacent to the first amorphous layer. It is preferable that at least one second amorphous layer is present between the layers.
Further, in the heat treatment step of the stacked body, the second semiconductor or the second metal element of the first amorphous layer forms quantum dots in the first amorphous layer, and the second semiconductor element. The first semiconductor or the first metal element contained in the second amorphous layer is oxidized, and the second semiconductor or the second metal element is a main component. It is preferable to form quantum dots.

When the electronegativity of the first semiconductor or the first metal element is A1, and the electronegativity of the second semiconductor or the second metal element is A2, it is preferable that A1> A2.
When the first semiconductor or the first metal element has a melting point M1, and the melting point of the second semiconductor or the second metal element is M2, it is preferable that M1> M2.
The first amorphous layer is preferably composed of a Si _x Ge _y O _(1-xy) layer.
Preferably, the stoichiometric dielectric material layer is composed of a SiO ₂ layer, and the second amorphous layer is composed of a SiO _x layer.
The SiO _x layer is preferably formed by reactive sputtering of Si.

  This invention has the quantum dot structure manufactured by the manufacturing method of the quantum dot structure of the said invention, The said quantum dot is lower than the said absorbed light with respect to the specific wavelength range of the absorbed light A wavelength conversion element comprising a wavelength conversion composition for wavelength conversion to energy light, wherein the quantum dots are arranged such that an interval between adjacent particles is equal to or smaller than a particle size of the quantum dots. It is.

In the present invention, the wavelength conversion element of the present invention is disposed on the incident light side of the photoelectric conversion layer, and the wavelength conversion element has an effective refractive index of the refractive index of the photoelectric conversion layer and the refractive index of air. A photoelectric conversion device having an intermediate refractive index is provided.
The wavelength conversion element preferably has an effective refractive index n at a wavelength of 533 nm of 1.7 <n <3.0.

  According to the present invention, high-quality crystalline quantum dots with few defects can be generated in a matrix. In this case, since the quantum dots are distributed three-dimensionally uniformly and at a high density, a quantum dot structure having a three-dimensional periodicity and having quantum dots uniformly distributed at a high density is obtained. be able to. According to the wavelength conversion element and the photoelectric conversion device having the quantum dot structure, a decrease in light-light conversion efficiency and a decrease in photoelectric conversion efficiency due to deterioration with time are suppressed.

(A)-(c) is typical sectional drawing which shows the manufacturing method of the quantum dot structure of the 1st Embodiment of this invention in order of a process. (A) is drawing substitute photograph which shows the whole TEM image of the quantum dot structure of the 1st Embodiment of this invention, (b) is the quantum dot structure of the 1st Embodiment of this invention. It is a drawing substitute photograph which shows the TEM image of the principal part, (c) is a graph which shows the result of the Raman measurement of the quantum dot structure of the 1st Embodiment of this invention. It is a graph which shows the emission spectrum of the quantum dot structure of the 1st Embodiment of this invention, and the emission spectrum of the conventional quantum dot structure. It is a graph which shows the emission spectrum (PL wavelength dispersion characteristic) at the time of progress after one month of the quantum dot structure of the 1st Embodiment of this invention. (A) is a drawing-substituting photograph showing a TEM image of a laminated film, and (b) is a drawing-substituting photograph showing a TEM image after heat-treating the laminated film of FIG. 5 (a). (A) is typical sectional drawing which shows the laminated body for manufacturing the quantum dot structure of the 2nd Embodiment of this invention, (b) is the quantum dot of the 2nd Embodiment of this invention. It is typical sectional drawing which shows the principal part of a structure. (A) is a schematic diagram which shows the energy band structure of the quantum dot structure of the 2nd Embodiment of this invention, (b) is a schematic diagram which shows the energy band structure of the conventional quantum dot structure. . (A) is a graph which shows the emission spectrum of the quantum dot structure of the 2nd Embodiment of this invention, (b) is a graph which shows the emission spectrum of the conventional quantum dot structure. It is typical sectional drawing which shows the wavelength conversion element of embodiment of this invention. It is a schematic diagram for demonstrating the multi exciton effect. It is a schematic diagram which shows a sunlight spectrum and the spectral sensitivity curve of crystalline Si. It is a graph which shows the difference in the reflectance by the difference in the structure of an antireflection film. (A) is a graph showing the relationship between the content of the Si quantum dots in the SiO ₂ matrix and the refractive index, and (b) is the spacing and refractive index of the Si quantum dots in the SiO ₂ matrix. It is a graph which shows the relationship. It is a graph showing the SiO ₂ film / wavelength converting element (Si quantum dots _{/ SiO} 2Mat) _/ Si substrate reflectivity, a wavelength conversion element has a refractive index of 1.80. It is a graph showing the SiO ₂ film / wavelength converting element (Si quantum dots _{/ SiO} 2Mat) _/ Si substrate reflectivity, a wavelength conversion element has a refractive index of 2.35. It is a typical sectional view showing a photoelectric conversion device which has a wavelength conversion element of an embodiment of the present invention. It is typical sectional drawing which shows the structure of the other photoelectric conversion apparatus of embodiment of this invention. It is a typical perspective view which shows the light absorption layer of the photoelectric conversion apparatus of FIG. (A), (b) is typical sectional drawing which shows the manufacturing method of the conventional quantum dot structure in order of a process, (c) is drawing substitute which shows the TEM image of the principal part of the conventional quantum dot structure. It is a photograph.

Below, based on the preferred embodiment shown in an accompanying drawing, the manufacturing method of the quantum dot structure of the present invention, a wavelength conversion element, and a photoelectric conversion device are explained in detail.
FIG. 1A to FIG. 1C are schematic cross-sectional views showing a method of manufacturing the quantum dot structure according to the first embodiment of the present invention in the order of steps.

  As shown in FIG. 1C, the quantum dot structure 20 of the present embodiment is provided on a substrate 12, for example, and includes a matrix (matrix layer) 22 and quantum dots provided in the matrix 22. 24. The quantum dots 24 have a three-dimensional periodicity in the matrix 22 and are uniformly arranged with high density, and the quantum dots 24 are arranged so as to constitute a multiple quantum well structure. Specifically, the quantum dot structure 20 has a structure as shown in FIGS. 2 (a) and 2 (b), for example.

Next, the manufacturing method of the quantum dot structure 20 of this embodiment is demonstrated.
First, as shown in FIG. 1A, a SiO ₂ layer 14 (stoichiometric dielectric material layer), a SiGeO layer 16 (first amorphous layer), a SiO ₂ layer 14 and a SiOx layer 18 are formed on a substrate 12. (0 <X <2), SiO ₂ layer 14, SiGeO layer 16, SiO ₂ layer 14, SiOx layer 18 (second amorphous layer), SiO ₂ layer 14, SiGeO layer 16, SiO ₂ layer 14 in this order. To obtain a laminate 10.
The thicknesses of the SiO ₂ layer 14, the SiGeO layer 16, and the SiOx layer 18 are, for example, 3 to 6 nm.
The SiO ₂ layer 14 corresponds to a stoichiometric dielectric material layer having a composition composed of the first semiconductor or the first metal element and oxygen. The SiOx layer 18 has a composition composed of the first semiconductor or the first metal element and oxygen, and corresponds to the second amorphous layer having a high composition ratio of the first semiconductor or the first metal element. .
The SiGeO layer 16 has a composition of Si _x Ge _y O _(1-xy) , has a composition composed of first and second semiconductors or metal elements and oxygen, and oxygen. On the other hand, it corresponds to the first amorphous layer having a high elemental composition ratio of the first or second semiconductor or the metal element.
In the present embodiment, the first semiconductor or the first metal element is, for example, Si, and the second semiconductor or the second metal element is, for example, Ge.

In the stacked body 10, Si _x Ge _y O _(1-xy) and SiO _z layers may be alternately or periodically arranged in the SiO ₂ layer.
In the stacked body 10, an SiO ₂ layer 14 (stoichiometric dielectric material layer) is formed adjacent to the SiGeO layer 16 (first amorphous layer) or the SiOx layer 18 (second amorphous layer). In addition, at least one SiOx layer 18 may be disposed between the SiGeO layer 16 and the adjacent SiGeO layer 16.

The SiO ₂ layer 14 is formed, for example, by RF sputtering using SiO ₂ as a target. The SiGeO layer 16 is formed by, for example, co-reactive sputtering of Si and Ge. The SiOx layer 18 is formed, for example, by oxidizing Si by reactive sputtering.

Next, the laminated body 10 is subjected to nitriding and crystallization by performing a heat treatment (annealing treatment) at, for example, 900 ° C. for 1 minute in an atmosphere in which a nitrogen gas is flowed. In this case, as shown in FIG. 1B, Ge quantum dots (quantum dots 24) are formed in the SiGeO layer 16 (first amorphous layer) (Si _x Ge _y O _(1-xy)). → Ge + GeO _z1 + SiO _z2 ). At this time, GeOx 17 (GeO _z1 ) diffuses from the SiGeO layer 16 (first amorphous layer) to the SiOx layer 18 (second amorphous layer). The diffused GeOx 19 reacts with the SiOx layer 18 to form Ge quantum dots (quantum dots 24). At this time, taking advantage of the property that Si is more easily oxidized than Ge by making the diffused GeO _z1 react with SiO _z2 + GeO _z1 → SiO ₂ + Ge, the generation of GeO _z is suppressed, and GeO _z diffuses over time, It is possible to suppress the defect film quality change at the Ge / GeO ₂ interface.
By this heat treatment, for example, an amorphous SiOx (x≈2) matrix 22 is formed by the SiO ₂ layer 14, the SiGeO layer 16 and the SiOx layer 18.

The SiO ₂ layer 14, the SiGeO layer 16, and the SiOx layer 18 are stacked on each other and subjected to heat treatment, whereby crystalline quantum dots 24 are three-dimensionally formed in the matrix 22 as disclosed in Patent Document 1. Uniformly distributed. In the present embodiment, the quantum dots 24 are further formed with high density. The generated quantum dots 24 have a three-dimensional periodicity in the matrix 22 and are uniformly distributed at a high density.

In this way, as shown in FIG. 1C, a quantum dot structure 20 in which the quantum dots 24 have a three-dimensional periodicity and are uniformly arranged at high density in the matrix 22 is obtained. Can do.
Further, when the manufactured quantum dot structure 20 was subjected to Raman spectroscopic analysis, a result as shown in FIG. 2C was obtained. From this result, it is confirmed that only Ge—Ge bonds are observed, Si—Ge bonds and Si—Si bonds are not observed, and only Ge quantum dots are formed.

In addition, in the quantum dot structure 20, in order to prevent generation | occurrence | production of the defect of the interface of the quantum dot 24 and the matrix 22, and the matrix 22, it is preferable to have a passivation process in the manufacturing process. In this case, in the passivation step, the quantum dot structure 20 is immersed in an ammonium sulfide solution or a cyan solution, or the quantum dot structure 20 is gas atmosphere of hydrogen gas, hydrogen fluoride gas, hydrogen bromide gas, or hydrogen phosphide gas. By heat treatment.
For example, when performing hydrogen termination in plasma hydrogen treatment, the treatment conditions are H ₂ flow rate 300 l / min, vacuum degree 0.9 Torr, microwave 2.5 KW, substrate temperature 300 ° C., treatment time 30 minutes.

Conventionally, it has been difficult to process at a relatively high temperature, but in the present invention, a structure in which diffused GeOx reacts with the SiOx layer 18 to form Ge quantum dots (quantum dots 24) is compared. It is possible to perform heat treatment (annealing) at a high temperature, for example, 800 ° C. or more, and to suppress the diffusion of GeO _z that has been diffused in the matrix 22 so far, the defect suppression can be enhanced. Thereby, the quantum dot structure 20 of the present invention has a PL intensity (symbol α ₁ shown in FIG. 3) immediately after formation, and a PL intensity (symbol α ₂ shown in FIG. 3) immediately after formation of the conventional quantum dot structure. Higher, the PL strength was improved. Furthermore, for example, with respect to the PL emission characteristics after one month, as shown in FIG. 4, it has also been confirmed that the PL wavelength dispersion characteristics do not change with time, and the emission lifetime is improved.

Hereinafter will be described with reference to FIG. 19 (a) ~ (c) the conventional quantum dot structures PL intensity code alpha ₂ shown in FIG. 3 is obtained.
A conventional quantum dot structure 110 shown in FIG. 19B has Ge quantum dots 112 formed in a matrix 114 made of SiO ₂ on a substrate 12. Specifically, the conventional quantum dot structure 110 is as shown in FIG.
When manufacturing the quantum dot structure 110, as shown in FIG. 19 (a), to obtain a laminate 100 by laminating a SiO ₂ layer 102, SiGeO layer 104 alternately on the substrate 12. The SiO ₂ layer 102 uses an ultimate vacuum of 3 × 10 ⁻⁴ Pa or less, a substrate temperature of room temperature (RT), Si as a target, an input power of 100 W, a deposition pressure of 0.3 Pa, and a gas flow rate of Ar. A film was formed under the conditions of 15 sccm for gas and 1 sccm for O ₂ gas.

The SiGeO layer 104 is amorphous, the ultimate vacuum is 3 × 10 ⁻⁴ Pa or less, the substrate temperature is room temperature (RT), Ge and Si are used as targets, the input power is 50 W for Ge, and Si is The film was formed under the film forming conditions of 100 W, a film forming pressure of 0.3 Pa, and a gas flow rate of 15 sccm for Ar gas and 0.5 sccm for O ₂ gas.
The stacked body 100 is annealed at 650 ° C. for 10 minutes in a nitrogen atmosphere. Thereby, Ge quantum dots 112 are formed, and the quantum dot structure 110 is manufactured.

As shown in FIG. 5A, the present inventor selectively oxidizes the silicon in the Si _x Ge _1-x layer after forming the laminated film 26 of SiO ₂ and Si _x Ge _1-x . Thus, the possibility of forming Ge quantum dots was investigated. As a result, as shown in FIG. 5B, since the oxidation proceeds from the surface of the laminated film 26, a difference in the degree of oxidation occurred in the depth direction. In the laminated film 26 of FIG. 5B, the upper portion 28 is made of SiO ₂ . From this, it is considered that when the number of layers is relatively large, it is difficult to uniformly distribute the Ge quantum dots in a three-dimensional manner and it is impossible to arrange them at high density.

In the quantum dot structure 20 of the present embodiment, the matrix 22 is made of, for example, an oxide-based dielectric or organic substance having a band gap of 3 eV or more, and is made of, for example, SiOx (0 <x <2). By forming the matrix layer 22 with SiOx (0 <x <2) (inorganic material), reliability over time can be obtained.
The quantum dots 24 are made of, for example, Ge or SiGe mixed crystal.
For example, the interval between the quantum dots 24 and adjacent particles (quantum dots 24) is 10 nm or less. The quantum dots 24 preferably have a particle size variation σ _d of 1 <σ _d <d / 5 nm, more preferably 1 <σ _d <d / 10 nm. In addition, the particle diameter of the quantum dot 24 may differ in the range of variation.
The quantum dots 24 are in the form of particles and have a particle size of 3 nm to 20 nm, preferably 2 nm to 15 nm, and more preferably 2 nm to 5 nm.

  Further, in the quantum dot structure 20 of the present embodiment, the first amorphous layer has a composition composed of the first and second semiconductors or metal elements and oxygen, and the first amorphous layer has a composition with respect to oxygen. One having a high composition ratio of the first or second semiconductor or metal element can be used. Further, the stoichiometric dielectric material layer having a composition composed of the first semiconductor or the first metal element and oxygen can be used. The second amorphous layer can have a composition including the first semiconductor or the first metal element and oxygen, and the composition ratio of the first semiconductor or the first metal element is large. Heat treatment is performed on a laminate obtained by laminating them. At this time, a matrix is formed by the first semiconductor or the first metal element, and in this matrix, crystalline quantum dots (Ge quantum dots) made of the second semiconductor or the second metal element, or the first First, second and more types of semiconductor or metal element mixed crystal quantum dots (SiGe mixed crystal quantum dots) are uniformly distributed three-dimensionally.

In the present embodiment, when the electronegativity of the first semiconductor or the first metal element is A1, and the electronegativity of the second semiconductor or the second metal element is A2, A1> A2. preferable. When the melting point of the first semiconductor or the first metal element is M1, and the melting point of the second semiconductor or the second metal element is M2, it is preferable that M2 <M1.
In order to satisfy the above conditions, for example, the first semiconductor is Si, and the second semiconductor is Ge.

Next, a second embodiment will be described.
In the present embodiment, the same components as those of the quantum dot structure 20 of the first embodiment shown in FIGS. 1A to 1C are denoted by the same reference numerals, and detailed description thereof is omitted.
FIG. 6 (a) is a schematic cross-sectional view showing a laminate for producing the quantum dot structure of the second embodiment of the present invention, and FIG. 6 (b) is a second embodiment of the present invention. It is typical sectional drawing which shows the principal part of the quantum dot structure of a form.

  The quantum dot structure 20a shown in FIG. 6B is formed with quantum dots 24a to 24c having different sizes as compared with the quantum dot structure 20 of the first embodiment, and these quantum dots 24a. Since the multiple quantum well structure is configured by ˜24c, and the other configuration is the same as the quantum dot 20 of the first embodiment, detailed description thereof is omitted. In the quantum dot structure 20a of this embodiment, the quantum dots 24a at both ends in the thickness direction (vertical direction) of the quantum dot structure 20a are the largest, and the quantum dots 24b, The dot 24c and its size are reduced.

In the present embodiment, as long as quantum dots having different sizes are arranged, the arrangement of quantum dots having different sizes is not particularly limited. For example, as illustrated in FIG. 7A, the quantum dots at both ends in the thickness direction (vertical direction) of the quantum dot structure 20 are the smallest, and the size of the quantum dots increases toward the center of the quantum dot structure 20. May be larger.
Further, in the thickness direction (vertical direction) of the quantum dot structure 20, L1-L2-L1 and L1-L1 so that the quantum dot layer L2 having a large particle diameter is sandwiched between the quantum dot layers L1 having a small particle diameter. It may have a multiple quantum well structure by being periodically arranged such as -L2-L1.

Next, the manufacturing method of the quantum dot structure 20a of this embodiment is demonstrated.
In this embodiment, the laminated body 10a shown in FIG. 6A is different from the laminated body 10 shown in FIG. 1A in place of the SiGeO layer 16 in the center, and the SiOx layer 18 (0 <X < 2) is different, and the other configuration is the same as that of the laminate 10 shown in FIG. 1A, and thus detailed description thereof is omitted.

In the present embodiment, SiGeO layer _{16 (Si x Ge y O (} 1-x-y) film), the periodic arrangement of the SiO ₂ layer 14, SiOx layer 18, as shown in FIG. 6 (a), Si _x By adopting a configuration in which a plurality of SiOx layers 18 are inserted between Ge _y O _(1-xy) layers, the SiGe particle diameter can be changed stepwise in accordance with the number of inserted SiOx layers 18. It becomes possible. For this reason, the quantum dot 24a-24c from which a magnitude | size can differ can be formed by implementing 900 degreeC and the heat processing for 1 minute with respect to the laminated body 10a, for example in the atmosphere which flowed nitrogen gas. .

Further, the wavelength conversion film (quantum dot structure) of the present invention shown in FIG. 7A and the wavelength conversion film (quantum dot structure) having the configuration shown in FIG. The luminescence intensity was measured. The results are shown in FIGS. 8 (a) and (b). FIG. 7B shows the quantum dots formed in the same size.
As shown in FIGS. 8A and 8B, in Ge and SiGe, in which particle synthesis is relatively difficult, the PL peak intensity was improved by about 100 times or more immediately after the heat treatment. Moreover, light-to-light conversion and photoelectric conversion are improved by periodically varying the particle size. Furthermore, a decrease in emission intensity was not confirmed in a one month storage test.
In addition, as the wavelength conversion film of this invention shown to Fig.7 (a), a thing with a particle size of 2-6 nm and a total of 57 layers which differ for every layer was produced. Layer structure _is SiO 2/8 (Ge quantum dot _{(QD) / SiO 2 / SiO} x1 / SiO 2 / SiO x2 / SiO x3 / SiO 2) / T4040 ( quartz glass substrate).
As the wavelength conversion film having the configuration shown in FIG. 7B, a film having a total particle size of 4 to 6 nm and 59 layers was prepared. Layer structure _is SiO 2/29 (Ge quantum dot _{(QD) / SiO 2) /} T4040 ( quartz glass substrate).
The film forming conditions of the wavelength conversion film of the present invention shown in FIG. 7A and the wavelength conversion film having the structure shown in FIG. 7B are as shown in Table 1 below.

  In the quantum dot structure 20a of the present embodiment, the reliability over time can be obtained by forming the matrix 22 from an inorganic material (SiOx (0 <x <2)). Further, by arranging the quantum dots at a high density, an effect such as reflection loss improvement can be obtained, and by defining the effective refractive index, an effect such as reflection loss improvement can be obtained. Also in the quantum dot structure 20a of this embodiment, it is preferable to have the above-mentioned passivation process similarly to the quantum dot structure 20 of 1st Embodiment.

The quantum dot structures 20 and 20a described above have a wavelength conversion function and can be used alone as a wavelength conversion film. Furthermore, the quantum dot structures 20 and 20a can all be used for, for example, a wavelength conversion element, a wavelength conversion device, and a solar cell.
The wavelength conversion element 40 shown in FIG. 9 is the wavelength conversion element 40 having the quantum dot structure 20 manufactured by the method for manufacturing the quantum dot structure 20 of the first embodiment. In addition, the wavelength conversion element 40 can also use the quantum dot structure 20a produced with the manufacturing method of the quantum dot structure 20a of 2nd Embodiment.
In the wavelength conversion element 40, the number of stacked quantum dots in the quantum dot structures 20 and 20a is not particularly limited.

  The wavelength conversion element 40 absorbs the incident light L, and converts the wavelength of the absorbed light into light having energy lower than that of the absorbed light (hereinafter referred to as a wavelength conversion function). And a function of confining incident light L (hereinafter referred to as a light confinement function).

In the wavelength conversion element 40, the wavelength conversion function is specifically a down conversion function. This down-conversion function is exhibited by the effect of generating one or more photons per absorbed photon, called the multi-exciton effect. For example, as shown in FIG. 10, when a quantum well is formed by quantum dots, and a photon (photon) having energy equal to or higher than Eg _QD (band gap of the quantum dot) is incident on the quantum dot, a low energy level ( When electrons in E1) are excited to the upper energy level (E4) and then fall to the lower energy level (E3), photons with lower energy than the incident photons are emitted. Further, when an electron at a lower energy level (E2) is excited to an upper energy level (E3), a photon having a lower energy than the incident photon is emitted. Thus, wavelength conversion is performed by emitting two electrons having energy lower than that of a photon to one photon. When two electrons having energy lower than that of a photon are emitted for one photon, this is also referred to as light-light conversion. The wavelength conversion element 40 has a light-light conversion function.

About the wavelength conversion function of the wavelength conversion element 40, the wavelength range to convert and the wavelength after conversion are suitably selected with the use of the wavelength conversion element 40. FIG.
For example, when the wavelength conversion element 40 is disposed on the photoelectric conversion layer of a silicon solar cell having an Eg (band gap) of 1.2 eV, the wavelength of energy (2.4 eV or more) that is at least twice this 1.2 eV The region has a function of performing wavelength conversion to light having a wavelength of energy corresponding to the band gap.

As shown in FIG. 11, when the solar spectrum is compared with the spectral sensitivity curve of crystalline Si, the solar spectrum has a low intensity in the wavelength region of the band gap of crystalline Si. For this reason, photons of low energy, for example, light of 1.2 eV (wavelength of about 1100 nm) with respect to a wavelength region of energy (2.4 eV or more) twice or more of the band gap of crystalline Si in sunlight. By converting the wavelength, light effective for photoelectric conversion can be supplied to the photoelectric conversion layer made of crystalline Si. Thereby, the conversion efficiency of a solar cell can be made high.
This is because, as shown in FIG. 11, when the solar spectrum and the spectral sensitivity curve of crystalline Si are compared, the wavelength band of the crystalline Si bandgap is narrower than that of the solar spectrum, and the spectral sensitivity of relatively high energy light. Sunlight cannot be used effectively due to its low intensity. For this reason, sunlight can be used effectively for converting relatively high energy light into light suitable for the spectral sensitivity of crystalline Si. Further, when the wavelength region of energy (2.4 eV or more) twice as large as the band gap of crystalline Si is converted into light of 1.2 eV light (wavelength of about 1100 nm), two photons or more (2 .4 (eV) × 1 (photon) ≈1.2 (eV) × 2 (photon)), sunlight can be used more effectively, and the conversion efficiency of the solar cell can be improved. Can be high.

In the wavelength conversion element 40, the light confinement function is an antireflection function.
When the photoelectric conversion layer in which the wavelength conversion element 40 is disposed is crystalline Si, the refractive index n _PV is 3.6. The refractive index n _air of the air in which these are arranged is 1.0.
Here, when the wavelength conversion element 40 is considered as an antireflection film, for example, as shown in FIG. 12, a single layer film (reference A ₁ ) having a refractive index of 1.9 and a refractive index of 1.46 / 2. 35 two-layer film (reference A ₂ ) and three-layer film (reference A ₃ ) having a refractive index of 1.36 / 1.46 / 2.35 The reflectance can be reduced.
Thus, in order to exhibit the antireflection function in the wavelength conversion element 40, the effective refractive index n of the wavelength conversion element 40 is such that the refractive index n _PV of the photoelectric conversion layer (3.6 for crystalline silicon) and air If the refractive index can be set to a substantially intermediate refractive index, the antireflection function can be exhibited.
In the present embodiment, considering the use of the wavelength conversion element 40 (quantum dot structures 20, 20a) and the like, the effective refractive index n of the wavelength conversion element 40 (quantum dot structures 20, 20a) is, for example, a wavelength of 533 nm. In this case, 1.7 <n <3.0. The effective refractive index n is preferably 1.7 <n <2.5 at a wavelength of 533 nm.

In order to exhibit the wavelength conversion function and the light confinement function as described above in the wavelength conversion element 40, the quantum dot structures 20, 20a have the following configurations.
In the quantum dot structures 20 and 20a, the matrix 22 is made of a non-transparent cured resin material or inorganic material having a band gap of 3 eV or more.
For example, a photocurable resin or a thermosetting resin is used as the cured resin material of the matrix 22 and is not particularly limited as long as it transmits light. As a photocurable resin or a thermosetting resin, for example, an acrylic resin, an epoxy resin, a silicone resin, an ethylene vinyl acetate (EVA) resin, or the like can be used.
Examples of the silicone resin include commercially available silicone resins for LEDs. As the ethylene vinyl acetate (EVA) resin, for example, Solar EVA (trademark) manufactured by Mitsui Chemicals Fabro Co., Ltd. can be used. Furthermore, an ionomer resin or the like can be used.

The epoxy resin has a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, a naphthalene type epoxy resin or a hydrogenated product thereof, an epoxy resin having a dicyclopentadiene skeleton, and a triglycidyl isocyanurate skeleton. Examples thereof include an epoxy resin, an epoxy resin having a cardo skeleton, and an epoxy resin having a polysiloxane structure.
As the acrylic resin, (meth) acrylate having two or more functional groups can be used. A water-dispersed acrylic resin can be used as the acrylic resin. This water-dispersed acrylic resin is an acrylic monomer, oligomer or polymer dispersed in a dispersion medium containing water as the main component. In a dilute state like an aqueous dispersion, the crosslinking reaction hardly proceeds, but the water is evaporated. If this is done, the crosslinking reaction will proceed and solidify at room temperature, or it will have a functional group capable of self-crosslinking, and it will be crosslinked and solidified only by heating without the use of additives such as catalysts, polymerization initiators, and reaction accelerators. Acrylic resin.

  When the matrix 22 is made of an inorganic material, for example, SiOx (0 <x <2) is used.

  Each quantum dot of the quantum dot structures 20 and 20a is made of a wavelength conversion composition that converts the wavelength into light having energy lower than that of light absorbed in a specific wavelength region of absorbed light. Each quantum dot bears the wavelength conversion function of the wavelength conversion element 40. Each quantum dot is arranged such that the distance between adjacent quantum dots is equal to or smaller than the particle size of the quantum dots in at least one of the in-plane direction of the matrix 22 and the thickness direction of the matrix 22.

In the wavelength conversion element 40, the quantum dot is configured with a band gap larger than the band gap of the photoelectric conversion layer of the photoelectric conversion device in which the wavelength conversion element 40 is provided.
For example, the quantum dot has a function of performing wavelength conversion to light of Eg of the photoelectric conversion layer with respect to a wavelength region having energy twice or more Eg of the photoelectric conversion layer in which the wavelength conversion element 40 is provided. For this reason, as a material constituting the quantum dots, energy levels more than twice Eg of the photoelectric conversion layer are absorbed, and energy levels for light absorption exist in more than twice the photoelectric conversion band caps. Material is selected.

  For this reason, a material that emits light with energy higher than Eg of the photoelectric conversion layer is selected for the quantum dot, the ground level of the quantum dot exists above Eg of the photoelectric conversion layer, and the energy level is discretized. In addition, an energy level more than twice the Eg of the photoelectric conversion layer exists.

  In addition, in order to convert the light into usable light in the photoelectric conversion layer, it is necessary to arrange the quantum dots so as to form an inversion distribution state in which the existence probability of excited photons excited from the ground level is increased. is there. Therefore, the quantum dots are arranged periodically as described above. In this case, the periodic interval of the quantum dots is 10 nm or less, preferably 2 nm to 5 nm. This results in an array of quantum dots in which excited photons can exist. Further, in order to cause localization of energy, a specific periodic array is formed by quantum dots having different particle diameters.

  In addition, in order to convert the light into usable light in the photoelectric conversion layer, it is also possible to change the arrangement of the matrix 22 in the horizontal direction (the direction parallel to the surface of the matrix 22 orthogonal to the thickness direction) of the matrix 22. It is possible to selectively cause the localization of energy. In this case, even if the quantum dots have an array different from the above-described periodic array, by having a particle density bias in a three-dimensional space, a spatial energy bias can be formed and an inverted distribution state can be formed. Is possible. Also in this case, as described above, the particle size variation σd of the quantum dots is different within the range of 1 <σd <d / 5 nm, and preferably 1 <σd <d / 10 nm.

Furthermore, in order to convert into light that can be used in the photoelectric conversion layer, when the wavelength conversion element 40 has a multilayer structure, the stacking direction of the quantum dots and the arrangement in the direction orthogonal to the stacking direction are similar, that is, When quantum dots are three-dimensionally arranged at equal intervals in the wavelength conversion element 40 as in the above-described periodic arrangement, photons are generated by localizing energy due to deviation in the particle size of the quantum dots. It can also be realized by changing the existence probability of. Even in this case, there is a variation in the particle size of the quantum dots, and the variation in the particle size σ _d of the quantum dots is 1 <σ _d <d / 5 nm, preferably 1 <σ _d <d / 10 nm. Is varied within the range of the aforementioned variation.

As described above, in order to obtain the antireflection function, the effective refractive index n of the wavelength conversion element 40 needs to be 2.4, which is an intermediate value between the photoelectric conversion layer and air, for example. Therefore, the refractive index when the matrix 22 is made of SiO ₂ and the quantum dots are made of Si was examined by simulation calculation. As a result, as shown in FIG. 13A, the refractive index increases as the content of quantum dots increases.
Furthermore, the relationship between the quantum dot spacing and the refractive index was investigated by simulation calculation. As a result, as shown in FIG. 13B, in order to increase the refractive index, it is necessary to narrow the interval between the quantum dots.
As shown in FIGS. 13A and 13B, for example, in order to set the effective refractive index n of the wavelength conversion element 40 to 2.4, the interval between the quantum dots is narrow and arranged in the matrix 22 with high density. There is a need to.

Next, a wavelength conversion element 40 on the Si substrate, was determined reflectivity for those forming the SiO ₂ film on the wavelength conversion element 40. The wavelength conversion element 40 is one in which Si quantum dots are provided on the SiO ₂ matrix 22 (Si quantum dots / SiO 2 _Mat ), and the quantum dots have a uniform particle size. At this time, the refractive index of the wavelength conversion element 40 is 1.80.
In this case, as shown in FIG. 14, the reflectance can be about 10%. In addition, the reflectance was measured using the spectral reflection measuring device (Hitachi U4000).

Further, by making the particle size of the quantum dots non-uniform, the filling rate was increased and the refractive index of the wavelength conversion element 40 was increased to 2.35. In this case, the wavelength conversion element 40 is an element in which Si quantum dots are provided on the SiO ₂ matrix 22 (Si quantum dots / SiO 2 _Mat ). The result is shown in FIG. In addition, the reflectance was measured using the spectral reflection measuring device (Hitachi U4000).
As shown in FIG. 15, the reflectance can be further reduced as compared with FIG. Thus, by increasing the filling rate of the quantum dots, the refractive index is increased, and as a result, the reflectance can be decreased. For this reason, the utilization efficiency of the light L incident on the wavelength conversion element 40 can be increased.

The wavelength conversion element 40 of this embodiment can be used for a solar cell as described later, for example. The wavelength conversion element 40 can be used as an infrared light source, for example, because it can convert the wavelength of 533 nm light to 1100 nm wavelength light. In this case, by appropriately selecting the arrangement and composition of the quantum dots, the light emission intensity of the wavelength-converted light can be increased, that is, the infrared light emission intensity can be increased.
In addition, by changing the band gap of the quantum dots as appropriate, for example, by changing the band gap to 3.5 eV (wavelength 350 nm), the wavelength can be converted into light having an energy of 1.75 eV (wavelength 800 nm). Is also available.

Next, a photoelectric conversion apparatus using the wavelength conversion element 40 of this embodiment will be described.
Note that the photoelectric conversion device using the wavelength conversion element 40 also functions as a light-to-light conversion device.
FIG. 16 is a schematic cross-sectional view showing a photoelectric conversion device having a wavelength conversion element according to an embodiment of the present invention.
In the photoelectric conversion device 50 illustrated in FIG. 16, the photoelectric conversion element 60 is provided on the surface 42 a of the substrate 42. The photoelectric conversion element 60 is formed by laminating an electrode layer 62, a P-type semiconductor layer (photoelectric conversion layer) 64, an N-type semiconductor layer 66, and a transparent electrode layer 68 from the substrate 42 side.
The P-type semiconductor layer 64 is made of, for example, polycrystalline silicon or single crystal silicon.

In the present embodiment, the wavelength conversion element 40 is provided on the surface 60 a of the photoelectric conversion element 60 (the surface of the transparent electrode layer 68).
In this case, the wavelength conversion element 40 is 1.2 eV corresponding to a half band gap of Si with respect to a wavelength region of energy more than twice the band gap of 1.2 eV of Si constituting the P-type semiconductor layer 64. The wavelength conversion function for converting the wavelength of light into light having a wavelength of 533 nm (wavelength 533 nm) is obtained. Further, the effective refractive index of the wavelength conversion element 40 is set to an intermediate refractive index between the refractive index of Si and the refractive index of air.
As a result, reflected light is reduced, and light in a specific wavelength region that does not contribute to photoelectric conversion is wavelength-converted, and the amount of light having a wavelength that can be used for photoelectric conversion increases, so the conversion efficiency of the photoelectric conversion element 60 is improved. In addition, the power generation efficiency of the entire photoelectric conversion device 50 can be improved.

Here, when polycrystalline silicon is used for the P-type semiconductor layer (photoelectric conversion layer) 64 of the photoelectric conversion element 60, the reflectance is not uniform because various plane orientations appear. For this reason, even if an antireflection film effective in a certain plane orientation is formed, the entire photoelectric conversion layer is not effective. However, the wavelength conversion element 40 can improve the transmission characteristics in a specific wavelength region and keep reflection loss low. Also from this point, the power generation efficiency of the entire photoelectric conversion device 50 can be improved.
Moreover, when providing the wavelength conversion element 40, it should just be arrange | positioned on the surface 60a of the photoelectric conversion element 60, and an etching etc. are unnecessary. For this reason, the photoelectric conversion device is not damaged by etching or the like. Thereby, generation | occurrence | production of a manufacturing defect can be suppressed.

  In the present invention, the photoelectric conversion layer is not limited to those using silicon, but a CIGS photoelectric conversion layer, a CIS photoelectric conversion layer, a CdTe photoelectric conversion layer, a dye-sensitized photoelectric conversion layer, Or it may be an organic photoelectric conversion layer.

  As the substrate 42, a substrate having relatively heat resistance is used. Examples of the substrate 42 include glass substrates such as blue plate glass, heat resistant glass, quartz substrates, stainless steel substrates, metal multilayer substrates in which stainless steel and different metals are laminated, aluminum substrates, or oxidation treatment, for example, anodic oxidation treatment on the surface. By applying this, an aluminum substrate with an oxide film whose surface insulation is improved can be used.

Next, another photoelectric conversion device using the quantum dot structures 20 and 20a will be described. In addition, although the quantum dot structure 20 is demonstrated to an example, it cannot be overemphasized that the other quantum dot structure 20a may be sufficient.
Another photoelectric conversion device 70 (solar cell) of this embodiment shown in FIG. 17 includes a substrate 42, an electrode layer 72, a P-type semiconductor layer 74, a photoelectric conversion layer 76, an N-type semiconductor layer 78, and a transparent It has an electrode layer 80 and is called a substrate type.
In the photoelectric conversion device 70, a stacked structure of an electrode layer 72 / P-type semiconductor layer 74 / photoelectric conversion layer 76 / N-type semiconductor layer 78 / transparent electrode layer 80 is formed on the surface 42 a of the substrate 42. That is, in the photoelectric conversion device 70, the N-type semiconductor layer 78 is provided on one side of the light absorption layer 76, and the P-type semiconductor layer 74 is provided on the other side. The P-type semiconductor layer 74 is provided with an electrode layer 72 on the side opposite to the light absorption layer 76. The N-type semiconductor layer 78 is provided with a transparent electrode layer 80 on the side opposite to the light absorption layer 76. The photoelectric conversion layer 76 is configured by the quantum dot structure 20. The matrix of the photoelectric conversion layer 76 is a matrix 22 of quantum dot structures, and is composed of SiOx (0 <x <2).

  As the substrate 42, a substrate having relatively heat resistance is used. Examples of the substrate 42 include glass substrates such as blue plate glass, heat resistant glass, quartz substrates, stainless steel substrates, metal multilayer substrates in which stainless steel and different metals are laminated, aluminum substrates, or oxidation treatment, for example, anodic oxidation treatment on the surface. An aluminum substrate or the like with an oxide film whose surface insulation is improved by applying is used.

The electrode layer 72 is provided on the surface 42 a of the substrate 42, and takes out the current obtained from the photoelectric conversion layer 76 together with the transparent electrode layer 80. As the electrode layer 72, for example, Mo, Cu, Cu / Cr / Mo, Cu / Cr / Ti, Cu / Cr / Cu, Ni / Cr / Au, or the like is used.
When the electrode layer 72 is in contact with the N-type semiconductor layer, Nb-doped Mo, Ti / Au, or the like is used as the electrode layer 72, for example.

The P-type semiconductor layer 74 is provided on the electrode layer 72 and is provided in contact with the photoelectric conversion layer 76. The P-type semiconductor layer 74 is made of, for example, a layer that is equal to or larger than the band gap of SiOx (0 <x <2) that constitutes a matrix (a matrix 22 of quantum dot structures) of a photoelectric conversion layer 76 described later. . Note that CuAlS ₂ , CuGaS, B-doped SiC, or the like can also be used for the P-type semiconductor layer 74.

  The N-type semiconductor layer 78 has the same composition as the matrix of the photoelectric conversion layer 76 (the matrix 22 of the quantum dot structure). That is, it is composed of SiOx (0 <x <2).

The transparent electrode layer 80 takes out the current obtained in the photoelectric conversion layer 76 to the outside together with the electrode layer 72, and is provided on the entire surface of the N-type semiconductor layer 78. The transparent electrode layer 80 may be provided on a part of the N-type semiconductor layer 78. In the photoelectric conversion device 70, sunlight L enters from the transparent electrode layer 80 side.
The transparent electrode layer 80 is made of an N-type conductive material. The transparent electrode layer _{80, Ga 2 O 3, SnO} 2 system (ATO, FTO), ZnO-based _{(AZO, GZO), In 2} O 3 system (ITO), Zn (O, S) CdO or these materials, Two or three kinds of alloys can be used. Furthermore, as the transparent electrode layer 80, MgIn ₂ O ₄ , GaInO ₃ , CdSb ₃ O _6, or the like can be used.

In the present embodiment, the film thickness of the P-type semiconductor layer 74 and the N-type semiconductor layer 78 is, for example, 50 to 300 nm, and preferably 100 nm.
In the present embodiment, the electron mobility of the P-type semiconductor layer 74, N-type semiconductor layer 78 is, for example, 0.01~100cm ² / Vsec, preferably 1 to 100 cm ² / Vsec.

  The photoelectric conversion layer 76 is composed of the quantum dot structure 20 as described above, and a plurality of quantum dots 24 are provided in the matrix 22 as shown in FIG. In the photoelectric conversion layer 76, a PNN layered structure having 20 to 50 periods is formed by pairing the layer made of the quantum dots 24 and the matrix 22 with each other. The quantum dot 24 is made of, for example, Ge or SiGe.

Further, in the photoelectric conversion layer 76, the quantum dots 24 are three-dimensionally sufficiently distributed and regularly spaced so that a plurality of wave functions overlap between adjacent quantum dots 24 to form a miniband. Has been placed.
Specifically, the quantum dots 24 are arranged with an interval t of 10 nm or less, preferably 2 to 6 nm.
The quantum dots 24 have, for example, an average particle diameter of 2 to 12 nm, preferably 2 to 6 nm. Further, the quantum dots 24 preferably have a variation in particle diameter of ± 20% or less.

  Thus, by configuring and arranging the quantum dots 24, the tunnel probability between the quantum wells configured by the quantum dots 24 is increased, the wave nature is increased, the loss due to carrier transport is improved, and the electron quantum Movement between the wells, that is, between the quantum dots 24 can be accelerated.

  In the photoelectric conversion layer 76, the matrix 22 including the quantum dots 24 is made of, for example, SiOx (0 <x <2). The matrix 22 has a thickness of, for example, 200 to 800 nm, and preferably 400 nm.

  The present invention is basically configured as described above. As mentioned above, although the manufacturing method, wavelength conversion element, and photoelectric conversion apparatus of the quantum dot structure of this invention were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, it is various. Of course, improvements or changes may be made.

10, 10a Laminated body 12 Substrate 14 SiO ₂ layer 16 SiGeO layer 18 SiOx layer 20, 20a Quantum dot structure 22 Matrix (matrix layer)
24 Quantum dot 40 Wavelength conversion element 50, 70 Photoelectric conversion device 60 Photoelectric conversion element

Claims (10)

The first and second semiconductors or metal elements have a composition comprising oxygen and oxygen, and the composition ratio of the first and second semiconductors or metal elements is large with respect to the oxygen. A first amorphous layer, a stoichiometric dielectric material layer having a composition comprising the first semiconductor or the first metal element and oxygen, the first semiconductor or the first metal element and oxygen. And a second amorphous layer having a composition ratio of the first semiconductor or the first metal element with a high composition ratio, and obtaining a laminate,
The stacked body is heat-treated, a matrix is formed of the first semiconductor or the first metal element, and crystalline quantum dots made of the second semiconductor or the second metal element are formed in the matrix Or a step of forming quantum dots of mixed crystals of the first and second semiconductors or metal elements, and a method of manufacturing a quantum dot structure.   The stacked body includes a first amorphous layer adjacent to the first amorphous layer or the second amorphous layer, the stoichiometric dielectric material layer being formed, and the first amorphous layer being adjacent to the first amorphous layer. The method for producing a quantum dot structure according to claim 1, wherein at least one second amorphous layer is present between the layers.   In the heat treatment step of the stacked body, the second semiconductor or the second metal element of the first amorphous layer forms a quantum dot in the first amorphous layer and the second amorphous layer. Quantum dots that diffuse into the layer and oxidize the first semiconductor or the first metal element contained in the second amorphous layer and that have the second semiconductor or the second metal element as a main component The manufacturing method of the quantum dot structure of Claim 1 or 2 which forms.   The A1> A2 when the electronegativity of the first semiconductor or the first metal element is A1 and the electronegativity of the second semiconductor or the second metal element is A2. 4. The method for producing a quantum dot structure according to any one of 3 above.   5. If M 1 is the melting point of the first semiconductor or the first metal element and M 2 is the melting point of the second semiconductor or the second metal element, M 1> M 2. The manufacturing method of the quantum dot structure as described in a term. The method for manufacturing a quantum dot structure according to claim 1, wherein the first amorphous layer is formed of a Si _x Ge _y O _(1-xy) layer. The method of manufacturing a quantum dot structure according to claim 1, wherein the stoichiometric dielectric material layer is made of a SiO ₂ layer, and the second amorphous layer is made of a SiO _x layer. . The method of manufacturing a quantum dot structure according to claim 7, wherein the SiO _x layer is formed by reactive sputtering of Si. A quantum dot structure manufactured by the method for manufacturing a quantum dot structure according to any one of claims 1 to 8,
The quantum dot is made of a wavelength conversion composition that converts the wavelength of light into energy having a lower energy than the absorbed light with respect to a specific wavelength region of the absorbed light, and the quantum dot has an interval between adjacent particles. A wavelength conversion element, wherein the wavelength conversion element is arranged to be equal to or smaller than a particle size of a quantum dot. The wavelength conversion element according to claim 9 is disposed on the incident light side of the photoelectric conversion layer,
The photoelectric conversion device, wherein the wavelength conversion element has an effective refractive index that is an intermediate refractive index between the refractive index of the photoelectric conversion layer and the refractive index of air.