WO2013027509A1

WO2013027509A1 - Wavelength conversion film and photoelectric conversion device

Info

Publication number: WO2013027509A1
Application number: PCT/JP2012/067936
Authority: WO
Inventors: 蔵町　照彦; 笠松　直史
Original assignee: 富士フイルム株式会社
Priority date: 2011-08-25
Filing date: 2012-07-13
Publication date: 2013-02-28
Also published as: JP2013045948A

Abstract

Provided is a wavelength conversion film, in which a first quantum dot and a second quantum dot in a matrix layer have a first base energy level which is excited by projecting a multiplexed light upon the first quantum dot which is greater than a second base energy level which is excited by projecting the multiplexed light upon the second quantum dot. The matrix layer is configured of either a dielectric body or an organic material in which the band gap is greater than the first base energy level. When the first quantum dot is joined to the second quantum dot, the energy band structure forms a type II. The matrix layer in the periphery of each quantum dot forms a selective tunnel barrier, forms a mini band wherein an energy transition rate at a higher energy level than an energy level difference at which an optically stimulated luminescent material within the matrix layer transitions in light emission increases, and energy transitions and up-converts within the optically stimulated luminescence material.

Description

Wavelength conversion film and photoelectric conversion device

The present invention relates to a wavelength conversion film and a photoelectric conversion device having an up-conversion function, and particularly to a wavelength conversion film and a photoelectric conversion device having two types of quantum dots and a stimulable light emitting material.

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 a PN junction solar cell and a PIN junction solar cell, light with 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. There is a problem of doing. In addition, since it is necessary to join semiconductors with good crystal quality and different hand gaps while maintaining good crystal quality, it is necessary to select materials with materials with almost the same crystal lattice length. Selection is narrow and difficult to create.

For this reason, in a single-junction solar cell such as a crystalline Si solar cell, a rare earth fine particle or a rare earth complex such as tempered glass or EVA, for example, Yb ³⁺ -Ln ³⁺ (Ln ³⁺ = Tb ³⁺ , Ce ³⁺ ) down-conversion films that change the wavelength of sunlight into a wavelength distribution suitable for the spectral sensitivity characteristics of single-junction solar by adding co-doped glass) are known. A method for improving photovoltaic power generation efficiency has been proposed (Patent Document 1, Non-Patent Document 1, etc.).

Patent Document 1 discloses a photovoltaic device that includes a photovoltaic layer that generates an electromotive force by light, and is provided with a wavelength conversion layer made of a wavelength conversion composition on the light incident surface side of the photovoltaic layer. ing.
The wavelength conversion layer converts sunlight in the ultraviolet region into the visible light region. The wavelength conversion layer includes a photocurable resin, oxide fine particles dispersed in the photocurable resin, and oxide fine particles. And a wavelength conversion material dispersed in the substrate. The wavelength converting substance is not particularly limited as long as it can convert light in a wavelength region that cannot be absorbed by a photovoltaic device such as ultraviolet or near infrared into light in a wavelength region that can be absorbed and generated by the photovoltaic device. Although it is not disclosed, it is disclosed that rare earth element-containing substances, transition metal-containing substances, semiconductor fine particles, silicon nanocrystals, organic dyes and the like can be mentioned. These may be used alone or in combination, and it is disclosed that the rare earth elements are preferably europium (Eu), erbium (Er), dysprodium (Dy), and neodymium (Nd).
Patent Document 1 also discloses a wavelength conversion layer that converts sunlight in the infrared region into a visible light region.

Non-Patent Document 1 discloses that a down conversion film is provided on the surface of the Si solar cell, and an up conversion film is provided on the back surface of the Si solar cell.

In addition, a combination of quantum dots and rare earth ions or metal ions or a combination of two types of semiconductor materials to absorb long wavelength photons and emit short wavelength photons, which cannot normally occur from the viewpoint of energy conservation law In addition, an upconversion film and an element have been proposed for forming an MQW structure (Patent Documents 2 and 3).
In addition to this, Patent Document 1 discloses that power generation efficiency by sunlight is improved by using a wavelength conversion layer (up-conversion film).

Patent Document 2 discloses a photostimulable light-emitting device having a semiconductor quantum dot and a base material including the semiconductor quantum dot, and this quantum dot has a group IV, a group III-V, a group II-VI, It is made of a semiconductor including semiconductor quantum dots such as group I-VII, ion crystals such as rare earth ions and metal ions, glass, or a polymer material.

Patent Document 3 discloses an up-conversion element that uses quantum dots to absorb particularly long-wavelength light and generate short-wavelength light. In Patent Document 3, an n-type semiconductor (for example, n-type GaAs) layer is formed with a base layer in which quantum dots are formed, and a p-side transparent electrode or a semi-transparent electrode is formed on this layer. A conversion element is disclosed. As a combination of quantum dots / _{_{maternal, GaAs / AlAs, InP / Ga}} X In 1-X P, InAs / GaAs is disclosed.

JP 2010-219551 A Japanese Patent Laid-Open No. 2000-21987 JP 2001-196627 A

Since the wavelength conversion layer (up-conversion film) uses light that could not be absorbed in the band gap of the single junction solar cell, it is desired to form a quantum dot with a relatively low band gap of 1.0 eV or less. .
However, in the system in which the rare earth oxide quantum dots are discretely arranged and the energy transfer rate is suppressed as disclosed in Non-Patent Document 2, the expression of the upconversion function is being put into practical use as a single particle. The up-conversion function is more efficient due to the loss of thermal energy due to phonon oscillation or recombination loss when excitons move between particles because the energy transfer speed between particles is not as discrete as a single particle. Not expressed.

As disclosed in the above-mentioned Patent Document 2, in a stimulable light-emitting device in which a semiconductor quantum dot and an ion crystal such as a rare earth ion and a metal ion are simply contained in glass or a polymer material, an ion crystal such as a rare earth ion and a metal ion is used. Has a low absorption cross section, so the excitation probability is low, and the light energy conversion efficiency is poor. For this reason, it is preferable that the photon energy is preferentially absorbed by the semiconductor quantum dots, energy is transferred to rare earth ions or metal ions, and light is emitted to release the energy.
In addition, in order to absorb and emit light having a long wavelength that is smaller than the ΔEC of the rare earth ion or metal ion (difference in energy level of the photostimulable luminescent material), the semiconductor quantum dots can be used to emit many long wavelength photons. After stepwise absorption and higher energy than ΔEC, it is necessary to transition to rare earth ions or metal ions.
Furthermore, since the probability of energy transition to the low energy side is usually high, energy transition to the low energy side is necessary to efficiently absorb photons with long wavelengths in multiple stages and upconvert to higher energy than ΔEC. It is necessary to have a band structure and a material configuration in which the energy transition probability increases to the higher energy side than the probability.
For this reason, although a quantum well structure as disclosed in Patent Document 3 has been studied, recombination and interfacial recombination easily occur in a quantum well portion having a small energy gap, and it is difficult to up-convert.

An object of the present invention is to provide a wavelength conversion film and a photoelectric conversion device having an up-conversion function that eliminates the problems based on the above-described conventional technology and has excellent conversion efficiency.

In order to achieve the above object, the present invention provides a matrix layer, a first quantum dot provided in the matrix layer, a second quantum dot provided in the matrix layer, and a matrix layer. The first quantum dot and the second quantum dot have a first ground energy level excited when the first quantum dot is irradiated with multiple light, The matrix layer is made of a dielectric or organic material that is larger than the second ground energy level excited when the multiple quantum dots are irradiated with multiple light, and whose band gap is larger than the first ground energy level. When the first quantum dot and the second quantum dot are joined, the energy band structure is type II, and the matrix layer around each quantum dot is a band cap of the matrix layer. A combination of the distance between each quantum dot and the thickness of the matrix layer forms a selective tunnel barrier, and the energy transition probability at an energy level higher than the energy level difference ΔEC at which the light-emitting transition of the stimulable luminescent material is high is high. The wavelength conversion film is characterized in that an up-conversion is performed by forming a miniband and transferring energy to a stimulable light emitting material provided in a matrix layer.

In the type II energy band structure, when the minimum energy level difference between the conduction band miniband and the valence band miniband is ΔEAB, ΔEAB ≧ ΔEC and long wavelength light absorbed by at least the second quantum dot However, it is preferable to generate light having a short wavelength from the photostimulable luminescent material in the matrix layer.
The first quantum dot and the second quantum dot have a diameter of 2 to 20 nm, and the first quantum dot and the second quantum dot are layered at a predetermined distance in the thickness direction of the matrix layer, respectively. It is preferable that they are alternately arranged.

Moreover, it is preferable that the photostimulable luminescent material is disposed at approximately the middle between the first quantum dots and the second quantum dots that are adjacent at least in the thickness direction of the matrix layer.
Furthermore, it is preferable that the first quantum dot and the second quantum dot are made of an indirect transition semiconductor.
Furthermore, the matrix layer is preferably made of an inorganic material or organic material having a band gap of 3 eV or more, and the stimulable light emitting material is preferably made of rare earth ions or metal ions.
When the effective refractive index of the wavelength conversion film is n, the effective refractive index n is preferably 1.8 ≦ n ≦ 4.
The first quantum dot is made of Si _x Ge _(1-x) (X> 0.7), and the second quantum dot is made of Si _x Ge _(1-x) (X <0.7). It is preferable that the rare earth ions are Yb ³⁺ ions, Er ³⁺ ions, or Tm ³⁺ ions, and the metal ions are Mn ions.
The matrix layer is preferably made of SiO ₂ , SiN _X or SiC.

Moreover, the said wavelength conversion film is arrange | positioned on the opposite side to the light incident side of a photoelectric converting layer, The photoelectric conversion apparatus characterized by the above-mentioned is provided.
The wavelength conversion film preferably has an optical confinement function that transmits long wavelength light and reflects short wavelength light.
The first layer made of a dielectric or organic material and the second layer made of the wavelength conversion film have a laminated structure, and each of the first layer and the second layer has a thickness. A photoelectric conversion device having an optical wavelength order, 0.3 <| nb−na |, where na is the effective refractive index of the first layer and nb is the refractive index of the second layer. Is to provide.

According to the present invention, an up-conversion function with excellent conversion efficiency can be obtained.

(A) And (b) is typical sectional drawing which shows the manufacturing method of the wavelength conversion film of embodiment of this invention in order of a process. It is a schematic diagram which shows the energy band structure of the wavelength conversion film of embodiment of this invention. It is a graph which shows the light emission intensity of the wavelength conversion film of embodiment of this invention, and the light emission intensity of the conventional wavelength conversion film. 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 and the refractive index of the quantum dots of the Si in the matrix layer of SiO _2, (b) is a distance between the quantum dots of Si in the matrix layer of SiO ₂ It is a graph which shows the relationship with a refractive index. Is a graph showing the SiO ₂ film / Wavelength conversion film (Si quantum dots _{/ SiO} 2Mat) _/ Si substrate reflectivity, a wavelength conversion film having a refractive index of 1.80. Is a graph showing the SiO ₂ film / Wavelength conversion film (Si quantum dots _{/ SiO} 2Mat) _/ Si substrate reflectivity, a wavelength conversion film having a refractive index of 2.35. It is typical sectional drawing which shows the photoelectric conversion apparatus of embodiment of this invention. (A) is a typical sectional view showing a photoelectric conversion device of other embodiments of the present invention, and (b) is a typical perspective view showing an important section of other composition of a wavelength conversion layer. It is typical sectional drawing which shows the conventional wavelength conversion film. It is a schematic diagram which shows the energy band structure of the conventional wavelength conversion film. It is a schematic diagram which shows the energy band structure of the other conventional wavelength conversion film.

Hereinafter, a wavelength conversion film and a photoelectric conversion device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1A and FIG. 1B are schematic cross-sectional views showing a method of manufacturing a wavelength conversion film according to an embodiment of the present invention in the order of steps. FIG. 2 is a schematic diagram showing an energy band structure of the wavelength conversion film according to the embodiment of the invention.

As shown in FIG. 1B, the wavelength conversion film 10 of the present embodiment includes a first quantum dot 16, a second quantum dot 18, and a stimulable light emitting material 20 in a matrix layer 14. Yes. The wavelength conversion film 10 is formed on the substrate 12, for example.
In the wavelength conversion film 10, the first quantum dots 16 and the second quantum dots 18 each have a predetermined interval in the thickness direction H of the matrix layer 14 so as to form a miniband in which a plurality of wave functions overlap. The first quantum dots 16 and the second quantum dots 18 form a multiple quantum well structure.
As will be described in detail later, the first quantum dot 16 and the second quantum dot 18 form a miniband in which a plurality of wave functions are overlapped except for a part on the conduction band side. However, the present invention is not limited to the conductor side, and a miniband in which a plurality of wave functions are overlapped may be formed except for a part on the valence band side.

The first quantum dot 16 and the second quantum dot 18 each have a diameter d of 2 to 20 nm, preferably 2 nm to 15 nm, more preferably 2 nm to 5 nm. The first quantum dot 16 and the second quantum dot 18 preferably have a particle size (diameter d) variation σ _d (standard deviation) of 1 <σ _d <d / 5 nm, more preferably 1 <σ _d <d / 10 nm. In addition, the particle diameter (diameter d) of the 1st quantum dot 16 and the 2nd quantum dot 18 may differ in the range of variation.
The first quantum dots 16 and the second quantum dots 18 each have an interval between adjacent particles of 20 nm or less. Further, in the first quantum dots 16 and the second quantum dots 18, the interval in the thickness direction H is also preferably 20 nm or less.

The first quantum dot 16 and the second quantum dot 18 are made of, for example, an indirect transition semiconductor. As this indirect transition semiconductor, for example, SiQD (quantum dot), Si _x Ge _(1-x) QD (quantum dot) (X> 0.7) is used for the first quantum dot 16, and the second quantum dot 16 is used. As the dots 18, GeQD (quantum dots), Si _x Ge _(1-x) QD (quantum dots) (X <0.7) are used.

As will be described in detail later, the first quantum dot 16 and the second quantum dot 18 form a miniband in which a plurality of wave functions overlap.
Here, the mini-band is an energy level formed by overlapping the level formed by each quantum dot (quantum well) with an adjacent quantum dot (quantum well).
Further, the first ground energy level excited when the first quantum dot 16 is irradiated with multiple light (sunlight (AM1.5)) is applied to the second quantum dot 18 with multiple light (sunlight (sunlight ( Greater than the second ground energy level excited when irradiated with AM 1.5)). As will be described in detail later, for example, in FIG. 2, the first base energy level is level SB1, and the second base energy level is level SB2 (base band).

Between the first quantum dots 16 and the second quantum dots 18 that are adjacent in the thickness direction H, for example, the photostimulable luminescent material 20 is arranged at a substantially intermediate position in the thickness direction H, and the matrix layer 14 Of 20 wt% (mass%) or less. The arrangement of the photostimulable luminescent material 20 is not limited to a substantially intermediate position in the thickness direction H.
The photostimulable luminescent material 20 is made of, for example, Yb ₂ O ₃ . The photostimulable luminescent material 20 is made of, for example, rare earth ions or metal ions. The rare earth ions are, for example, Yb ³⁺ ions, Er ³⁺ ions, or Tm ³⁺ ions, and the metal ions are, for example, Mn ions, and two or more types of photostimulable luminescent materials may be combined.

The matrix layer 14 is made of a dielectric or organic material having a band gap (Eg _mat ) larger than a first ground energy level (for example, the level SB2 shown in FIG. 2). The matrix layer 14 becomes a tunneling barrier (tunnel barrier) between the first quantum dots 16 and the second quantum dots 18 that are adjacent in the thickness direction H, and between the second quantum dots 18, that is, between the matrix layers 14. In the width direction w perpendicular to the thickness direction H, the second quantum dot 18 becomes a barrier.
In the present embodiment, the matrix layer 14 around each quantum dot of the first quantum dot 16 and the second quantum dot 18 includes the band cap (Eg _mat ) of the matrix layer 14, the distance between the quantum dots, and the matrix layer. In combination with the thickness 14, a selective tunnel barrier is formed so as to serve as a barrier for the second quantum dots 18 in the width direction w orthogonal to the thickness direction H of the matrix layer 14.
The matrix layer 14 is made of an inorganic material or an organic material having a band gap of 3 eV or more, and is made of, for example, SiO ₂ , SiN _X or SiC.

Next, a method for manufacturing the wavelength conversion film 10 will be described.
First, on the substrate 12, the SiO ₂ layer 32, the SiO ₂ / Yb ₂ O ₃ layer 34, the SiO ₂ layer 32, the Si / SiO ₂ layer 36, the SiO ₂ layer 32, the SiO ₂ / Yb ₂ O ₃ layer 34, the SiO 2 ₂ layer 32, SiGeO layer 38, SiO ₂ layer 32, SiO ₂ / Yb ₂ O ₃ layer 34, SiO ₂ layer 32, Si / SiO ₂ layer 36, SiO ₂ layer 32, SiO ₂ / Yb ₂ O ₃ layer 34, The layered product 30 is obtained by forming the SiO ₂ layer 32, the SiGeO layer 38, the SiO ₂ layer 32, the SiO ₂ / Yb ₂ O ₃ layer 34, and the SiO ₂ layer 32 in this order.
The thicknesses of the SiO ₂ layer 32, the SiO ₂ / Yb ₂ O ₃ layer 34, the Si / SiO ₂ layer 36, and the SiGeO layer 38 are, for example, 3 to 6 nm.

Next, the laminated body 30 is annealed, for example, at about 900 ° C. for 10 minutes in a nitrogen atmosphere. Accordingly, the first quantum dot 16 made of Si _x Ge _(1-x) QD (X> 0.7) and the second quantum dot made of Si _x Ge _(1-x) QD (X <0.7) are obtained. A stimulable light emitting material 20 composed of dots 18 and Yb ³⁺ is formed, and the wavelength conversion film 10 shown in FIG. 1B is formed.
In the wavelength conversion film 10, in order to prevent the occurrence of defects in the interface between the first quantum dots 16 and the matrix layer 14, the interface between the second quantum dots 18 and the matrix layer 14, and the matrix layer 14, It is preferable to have a passivation process such as hydrogen termination in the manufacturing process.
For example, when performing hydrogen termination in plasma hydrogen treatment, the treatment conditions are, for example, H ₂ flow rate 300 l / min, vacuum degree 0.9 Torr, microwave 2.5 KW, substrate temperature 300 ° C., treatment time 30 minutes. is there.

The SiO ₂ layer 32 is formed, for example, by oxidizing Si by reactive sputtering. The film formation conditions for the SiO ₂ layer 32 include, for example, an ultimate vacuum of 3.0 × 10 ⁻⁴ Pa or less, a substrate temperature of room temperature (RT), Si as a target, an input power of 100 W, and a film formation pressure. Is 0.35 Pa, the Ar gas flow rate is 15 sccm, the O ₂ gas flow rate is 0.35 sccm, and the film formation time is 2 minutes.

The SiO ₂ / Yb ₂ O ₃ layer 34 is sputtered, for example, with a pellet (1 mm square piece) having a surface area ratio of Yb ₂ O ₃ : SiO ₂ = 1: 1000 on the SiO ₂ target surface. It is formed by. The film formation conditions of the SiO ₂ / Yb ₂ O ₃ layer 34 include, for example, an ultimate vacuum of 3.0 × 10 ⁻⁴ Pa or less, a substrate temperature of room temperature (RT), and a surface area ratio on the surface of the SiO ₂ target. Is a pellet (1 mm square piece) with Yb ₂ O ₃ : SiO ₂ = 1: 1000, input power is 100 W, deposition pressure is 0.35 Pa, Ar gas flow rate is 15 sccm, O ₂ gas flow rate is 0 sccm, The membrane time is 2 minutes.

SiO ₂ layer 32 on the SiO ₂ / _Yb 2 _{O 3} layer 34, for example, is formed by sputtering SiO _2. The film formation conditions for the SiO ₂ layer 32 on the SiO ₂ / Yb ₂ O ₃ layer 34 are, for example, that the ultimate vacuum is 3.0 × 10 ⁻⁴ Pa or less, the substrate temperature is room temperature (RT), and the target is SiO 2 ₂ , the input power is 100 W, the deposition pressure is 0.35 Pa, the Ar gas flow rate is 15 sccm, the O ₂ gas flow rate is 1 sccm, and the deposition time is 2 minutes.

The Si / SiO ₂ layer 36 is formed, for example, by co-sputtering Si and SiO ₂ . The film forming conditions for the Si / SiO ₂ layer 36 include, for example, an ultimate vacuum of 3.0 × 10 ⁻⁴ Pa or less, a substrate temperature of room temperature (RT), Si, SiO ₂ as a target, and input power. 100 W for Si, 200 W for SiO ₂ , a film formation pressure of 0.35 Pa, an Ar gas flow rate of 15 sccm, an O ₂ gas flow rate of 0 sccm, and a film formation time of 4 minutes.

The SiGeO layer 38 is formed by, for example, co-reactive sputtering of Si and Ge. The film formation conditions for the SiGeO layer 38 include, for example, an ultimate vacuum of 3.0 × 10 ⁻⁴ Pa or less, a substrate temperature of room temperature (RT), Ge and Si as targets, and an input power of 50 W for Ge. For Si, the deposition pressure is 0.3 W, the Ar gas flow rate is 15 sccm, the O ₂ gas flow rate is 0.5 sccm, and the deposition time is 20 seconds.

Further, the SiO ₂ layer _32, SiO 2 / _Yb 2 _{O 3} layer 34 and _SiO 2 / _Yb 2 _{O 3} layer 34 on the SiO ₂ layer 32 of, for example, while sputtering the SiO _{_2,} SiO 2 / _Yb 2 _{O 3} When the layer 34 is formed, it can be formed by sputtering Yb ₂ O ₃ .

In the wavelength conversion film 10 of the present embodiment, when the first quantum dots 16 and the second quantum dots 18 are joined, the energy band structure close to the type II type (type II structure) as shown in FIG. It becomes. The first quantum dots 16 form quantum wells 22a, 23a, 22b, and 23b, and the second quantum dots 18 form quantum wells 24a, 25a, 24b, 25b, 24c, and 25c.
The quantum wells 24a, 22a, 24b, 22b, and 24c each have a level SB1, and the quantum wells 24a, 24b, and 24c further have a level SB2 (base level).
The quantum wells 25a, 23a, 25b, 23b, and 25c have a level SB3 and a level SB4, respectively.

As shown in FIG. 2, on the valence band side, the quantum wells 24a, 22a, 24b, 22b, 24c have overlapping levels SB1, and a miniband is formed.
On the conductor side, quantum wells 25a, 23a, 25b, 23b, and 25c have overlapping levels SB3 and SB4, and a miniband is formed.
Note that the level SB1, the level SB3, and the level SB4 indicate miniband levels.

On the other hand, on the valence band side, the quantum well 22a between the quantum well 24a and the quantum well 24b does not have a level overlapping with the level SB2 (base level) of the quantum wells 24a and 24b. The quantum well 22b between the quantum well 24b and the quantum well 24c does not have a level overlapping with the level SB2 (base level) of the quantum wells 24b and 24c.
Here, the level SB2 is a base band of the second quantum dot 18 (Ge quantum dot (quantum well)). In the present embodiment, the entire band structure has a type II structure, as described above. In addition, since the adjacent first quantum dots 16 (Si quantum dots (quantum wells)) do not have overlapping levels, a miniband cannot be formed.
Thus, in the level SB2 (base level) of the quantum wells 24a and 24b and the quantum wells 24b and 24c, there is a region D in which no miniband is formed. In this region D, the matrix layer 14 becomes a tunneling barrier. By providing the region D, the movement of holes h in the thickness direction H of the quantum well is suppressed. Note that the region D where the miniband is not formed is not limited to being provided in the valence band, and may be formed on the conduction band side. When it is provided on the conduction band side, the movement of the electrons e instead of the holes h is suppressed.

In FIG. 2, Eg _mat represents the band gap of the matrix layer 14, Eg _Si represents the band gap of the first quantum dot 16, and Eg _Ge represents the band gap of the second quantum dot 18. Each band gap has a relationship of Eg _mat > Eg _Si > Eg _Ge .
As shown in FIG. 2, in this embodiment, the difference in energy level at which the photostimulable luminescent material 20 undergoes emission transition is ΔEC, and the conduction band miniband excited between two-photon absorption and the valence band miniband is excited. Let the minimum energy level difference be ΔEAB.
In this case, ΔEAB ≧ ΔEC. In the wavelength conversion film 10, the long wavelength incident light L is absorbed by the second quantum dots 18, and the short wavelength light Ls is emitted from the photostimulable luminescent material 20 in the matrix layer 14.
Here, ΔEAB is the minimum energy level difference between the conduction band miniband and the valence band miniband, and is between level SB1 and level SB3. When there is no level SB1, ΔEAB is between level SB1 and level SB4.

In the wavelength conversion film 10, adjacent to each other on the valence band side, for example, between the quantum wells 24 a and 24 b of the second quantum dot 18 sandwiching the first quantum dot 16 and between the quantum wells 24 b and 24 c. By providing the region D in which no miniband is formed between the second quantum dots 18, for example, there is no level overlapping with the level SB2 (base level) of the quantum wells 24a and 24b, so that the level of the quantum well 24a The holes (holes) h in SB2 are difficult to move to the quantum well 24b. In this way, energy transfer to the upper level is suppressed by suppressing charge transport in the thickness direction H (hole h on the valence band side, movement of electron e on the conduction band side). , That is, the probability of up-conversion, selectively extract excitation energy, and suppress non-radiative recombination during charge transport.

In the wavelength conversion film 10, for example, holes (holes) h in the quantum well 24a of the second quantum dot 18 in the level SB1 absorb the incident incident light L, and the level SB2 one level higher. It rises to (base level), further absorbs incident light L, and rises to level SB3 of quantum well 25a. In this way, the level is raised by two levels. The level SB3 raised by two levels is the same as the level of the photostimulable light emitting material 20 (Yb ₂ O ₃ (Yb ³⁺ )) in the matrix layer 14. Then, the electrons e are transported (transitioned) to the stimulable light emitting material 20 (Yb ₂ O ₃ (Yb ³⁺ )), and the stimulable light emitting material 20 (Yb on the valence band side from the level corresponding to the level SB3). ₂ O ₃ (Yb ³⁺ )) level (corresponding to level SB1). At this time, the short wavelength light Ls having a shorter wavelength than the absorbed incident light L is emitted from the stimulable light emitting material 20 in the matrix layer 14. That is, high energy light is generated from the photostimulable luminescent material 20 in the matrix layer 14. The wavelength conversion film 10 is up-converted in this way.

Further, for example, holes (holes) h in the quantum well 24b of the second quantum dot 18 in the level SB2 (base level) absorb the incident incident light L, and the quantum well 25a one level higher. To the level SB3, and further absorbs the incident incident light L and rises to the level SB4 of the quantum well 25a. In this way, the level increases by two levels. In this case, the level SB4 in two steps and the level of the stimulable light emitting material 20 (Yb ₂ O ₃ (Yb ³⁺ )) are the same. Then, electrons e are transported in the stimulable luminescent material _{_{^{20 (Yb 2 O 3 (Yb}}} 3+)), level SB4 valence from the level corresponding to the electron band side of the stimulable luminescent material 20 _(Yb 2 _{O 3} (Yb ³⁺ )) level (corresponding to level SB2). At this time, the short wavelength light Ls having a shorter wavelength than the absorbed incident light L is emitted from the photostimulable light emitting material 20 in the matrix layer 14. That is, high energy light is generated from the photostimulable luminescent material 20 in the matrix layer 14. The wavelength conversion film 10 is up-converted in this way. The wavelength conversion film 10 is up-converted in this way.

Further, for example, the level SB1, holes in the quantum well 22b (holes) h will absorb the incident light L incident, beyond the band gap Eg _Si, up to level SB3 of the quantum well 23b. In this case, the level SB3 and the level of the photostimulable luminescent material 20 (Yb ₂ O ₃ (Yb ³⁺ )) are the same. Then, electrons e are transported in the stimulable luminescent material _{_{^{20 (Yb 2 O 3 (Yb}}} 3+)), level SB3 valence from the level corresponding to the electron band side of the stimulable luminescent material 20 _(Yb 2 _{O 3} (Yb ³⁺ )) level (corresponding to level SB1). At this time, shorter wavelength light Ls than the absorbed incident light L is emitted from the stimulable light emitting material 20 in the matrix layer 14. That is, high energy light is generated from the photostimulable luminescent material 20 in the matrix layer 14. The wavelength conversion film 10 is up-converted in this way.

The emission intensity of the wavelength conversion film 10 of the present invention and the conventional wavelength conversion film was examined using light having a wavelength of 1300 nm as excitation light. As a result, as shown in FIG. 3, the wavelength conversion film 10 of the present embodiment was able to wavelength-convert light having a wavelength of 1300 nm to light having a wavelength of about 1010 nm, for example. Furthermore, the wavelength conversion film 10 of the present invention can obtain a sufficiently large emission intensity as compared with the conventional wavelength conversion film, and has an up-conversion function with excellent conversion efficiency. In FIG. 3, symbol α indicates the wavelength conversion film 10 of the present invention, and symbol β indicates a conventional wavelength conversion film.

A conventional wavelength conversion film is shown in FIG. In this conventional wavelength conversion film 100, a plurality of Ge quantum dots 104 are provided in a matrix at a predetermined interval in the thickness direction H of the matrix layer 102 in a matrix layer 102 formed on the substrate 12. Is. Yb ₂ O ₃ particles 106 are provided in layers between the layers of the Ge quantum dots 104 and are doped with rare earths.
The energy band structure of the conventional wavelength conversion film 100 has the structure shown in FIG. As shown in FIG. 12, the energy level excited by two-photon absorption or more is equal to the emission transition level energy of the doped rare earth. In this excited energy level, since the transition probability of rare earth is high, it makes a selective transition and tends to make an up-conversion transition. However, conventionally, light emission or non-light emission recombination may occur before two-photon absorption, and the transition probability needs to be improved.

On the other hand, in the wavelength conversion film 10 of the present embodiment, by adopting the above-described configuration, the transition probability of up-conversion can be increased, and long wavelength light is converted into short wavelength light, that is, low energy light. Can be converted into high energy light with higher efficiency than in the past.
Here, in another conventional energy band structure in which the quantum well 112 is formed by Ge quantum dots (not shown) in the Si matrix layer 110 shown in FIG. 13, the light emission path (including non-radiative recombination). Has the problem that the establishment of up-conversion that requires two or more transitions is low by absorbing photons p, which is equal to or more than the excitation path. In addition, although electrons (not shown) are excited by two-photon absorption or more, non-radiative recombination (reference numeral 114) occurs due to defects in the matrix layer 110 between the quantum wells 112. Furthermore, interface recombination (reference numeral 116) also occurs. As shown in FIG. 13, it is necessary to improve the transition probability even in other conventional energy band structures.

Regarding the wavelength conversion function of the wavelength conversion film 10, the wavelength range to be up-converted and the wavelength after conversion are appropriately selected depending on the application of the wavelength conversion film 10.
For example, when the wavelength conversion film 10 is disposed on a 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 twice or more of 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. 4, when the solar spectrum is compared with the spectral sensitivity curve of crystalline Si, the solar spectrum has a low intensity in the wavelength range of the band gap of crystalline Si. For this reason, among sunlight, a photon having a high energy, for example, light of 1.0 eV (wavelength of about 1.0 eV) with respect to a wavelength region (long wavelength light region) smaller than the band gap energy (1.2 eV) of crystalline Si. By converting the wavelength to 1300 nm, light effective for photoelectric conversion can be supplied to the photoelectric conversion layer made of crystalline Si. Thereby, the conversion efficiency of a photoelectric conversion apparatus (solar cell) can be made high.

The wavelength conversion film 10 may have a function of confining incident light (hereinafter referred to as a light confinement function), for example, an antireflection function. In this case, when the photoelectric conversion layer on which the wavelength conversion film 10 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 film 10 is considered as an antireflection film, for example, as shown in FIG. 5, a single layer film (reference symbol 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 film 10, the effective refractive index n of the wavelength conversion film 10 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 film 10 and the like, the effective refractive index n of the wavelength conversion film 10 is set to 1.8 ≦ n ≦ 4.0 at a wavelength of 533 nm, for example. The effective refractive index n is preferably 1.8 ≦ n ≦ 2.5 at a wavelength of 533 nm.

In addition, in order to convert light into light that can be used in the photoelectric conversion layer, it is necessary to arrange quantum dots so as to form an inversion distribution state in which the existence probability of photons in the excited state is high with respect to the ground state. . 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. As a result, an array of quantum dots capable of transferring energy of excited photons is obtained. Further, in order to cause the localization of energy, the specific periodic interval of the quantum dots has a variation in the particle diameter of the quantum dots.

Further, in order to convert light into light that can be used in the photoelectric conversion layer, in the wavelength conversion film 10, the arrangement of the matrix layer 14 in the thickness direction H and the width direction w is made different to cause localization of energy. Can be realized. In this case, the existence probability of photons can be changed by having the quantum dots have an arrangement different from the above-described periodic arrangement and having a deviation in particle density in a three-dimensional quantum size space of 20 nm square or less. Also in this case, as described above, the variation in the particle size of the quantum dots σ _d (standard deviation) is different within the range of 1 <σ _d <d / 5 nm, preferably 1 <σ _d <d / 10 nm. It is.

Furthermore, in order to convert into light that can be used in the photoelectric conversion layer, when the wavelength conversion film 10 has a multilayer structure, when the stacking direction of the quantum dots and the arrangement in the direction orthogonal to the stacking direction are similar, that is, In the case where the quantum dots are three-dimensionally arranged at regular intervals in the wavelength conversion film 10 as in the above-described periodic arrangement, energy localization is caused by the deviation in the particle size of the quantum dots, and the photons It can also be realized by changing the existence probability. Even in this case, the particle diameters of the quantum dots vary, and the dispersion of the quantum dot particle diameters σ _d (standard deviation) is 1 <σ _d <d / 5 nm, preferably 1 <σ _d <d / 10 nm. Yes, the quantum dots are varied within the above-mentioned variation range.

As described above, in order to obtain the antireflection function, the effective refractive index n of the wavelength conversion film 10 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 layer 14 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. 6A, 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. 6B, in order to increase the refractive index, it is necessary to narrow the interval between the quantum dots.
As shown in FIGS. 6A and 6B, for example, in order to set the effective refractive index n of the wavelength conversion film 10 to 2.4, the interval between the quantum dots is narrow and the matrix layer 14 has a high density. Need to be placed.

Next, a wavelength conversion film 10 on the Si substrate, was determined reflectivity for those forming the SiO ₂ film on the wavelength conversion film 10. The wavelength conversion film 10 is a SiO ₂ matrix layer 14 provided with Si quantum dots (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 film 10 is 1.80.
In this case, as shown in FIG. 7, 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 film 10 was increased to 2.35. In this case, the wavelength conversion film 10 is formed by providing Si quantum dots on the SiO ₂ matrix layer 14 (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. 8, the reflectance can be further lowered as compared with FIG. As described above, 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 incident light L incident on the wavelength conversion film 10 can be increased.

Next, a photoelectric conversion device having the wavelength conversion film 10 of this embodiment will be described.
FIG. 9 is a schematic cross-sectional view illustrating the photoelectric conversion device according to the embodiment of the present invention.
In the photoelectric conversion device 40 shown in FIG. 9, a reflective layer 44 is formed on a base material 42, and a wavelength conversion layer 46 is provided on the reflective layer 44. The wavelength conversion layer 46 has the same configuration as the wavelength conversion film 10 described above. A first transparent electrode layer 48 is provided on the wavelength conversion layer 46.
A photoelectric conversion layer 50 is provided on the first transparent electrode layer 48, and a second transparent electrode layer 52 is provided on the photoelectric conversion layer 50.

Further, a light confinement layer 54 is provided on the second transparent electrode layer 52.
In the photoelectric conversion device 40 of the present embodiment, among the incident light L incident from the surface 54a side of the light confinement layer 54, the photoelectric conversion layer 50 passes through without being used for photoelectric conversion, for example, infrared rays and Near-infrared long wavelength light Lu is reflected by the reflection layer 44 and is incident on the wavelength conversion layer 46. In this wavelength conversion layer 46, long wavelength light Lu that has not been used, for example, light having a wavelength of 1300 nm, is converted into short wavelength light Ls that can be used for photoelectric conversion by the photoelectric conversion layer 50, for example, about 1000 nm, by the up-conversion function. To do. Thereby, the incident light L can be used effectively, and the utilization efficiency of the incident light L in the photoelectric conversion layer 50 can be increased.

The base material 42 is made of a relatively heat-resistant support substrate material when a direct thermal process is performed. For example, surface insulation can be improved by applying oxidation treatment (for example, anodizing treatment) to heat-resistant glass, quartz substrate, stainless steel substrate, metal multilayer substrate laminated with dissimilar metals with stainless steel, or aluminum substrate. An aluminum substrate with an oxide film is used.

In a method that can be formed by a low-temperature process, an organic support substrate material or the like can be used. Specifically, saturated polyester / polyethylene terephthalate (PET) resin substrate, polyethylene naphthalate (PEN) resin substrate, cross-linked fumaric acid diester resin substrate, polycarbonate (PC) resin substrate, polyethersulfone (PES) resin substrate , Polysulfone (PSF, PSU) resin substrate, polyarylate (PAR) resin substrate, cyclic polyolefin (COP, COC) resin substrate, cellulose resin substrate, polyimide (PI) resin substrate, polyamideimide (PAI) resin substrate, maleimide -Olefin resin substrate, polyamide (PA) resin substrate, acrylic resin substrate, fluorine resin substrate, epoxy resin substrate, silicone resin film substrate, polybenzazole resin substrate, substrate liquid crystal polymer with episulfide compound (L P) Substrate, cyanate resin substrate, aromatic ether resin substrate, composite plastic material with silicon oxide particles, composite plastic material with metal nanoparticles, inorganic oxide nanoparticles, inorganic nitride nanoparticles, metal / Composite plastic materials with inorganic nanofibers & microfibers, carbon fibers, composite plastic materials with carbon nanotubes, glass ferkes, glass fibers, composite plastic materials with glass beads, particles with clay mineral and mica derived crystal structure Composite plastic material, laminated plastic material having at least one bonding interface between thin glass and the above-mentioned single organic material, inorganic layer (for example, SiO ₂ , Al ₂ O ₃ , SiOxNy) and the above organic layer alternately By laminating, it has at least one bonding interface. It can be used composite materials having that barrier performance.

The reflective layer 44 reflects the light that has passed through the photoelectric conversion layer 50, the first transparent electrode layer 48, and the wavelength conversion layer 46, and re-enters the wavelength conversion layer 46. The photoelectric conversion layer 50 uses photoelectric conversion. It did not, for example, reflect infrared and near infrared.
The reflection layer 44 is made of, for example, an Al film having a thickness of 500 nm. This Al film is formed by vapor deposition, for example. The reflective layer 44 can also be made of Au, Ag, and a dielectric laminated film.

The first transparent electrode layer 48 is composed of a P-type transparent electrode layer. As this first transparent electrode layer 48 (P-type transparent electrode layer), for example, a composition such as CuAlO ₂ , CuGaO ₂ , CuInO _2, etc .: when expressed as ABO ₂ , A is Cu, Ag, and B is Al , Ga, In, Sb, Bi. In addition, an alloy represented by ABO ₂ , a solid solution material thereof, and a Delaphosite type microcrystalline body, and two or three kinds of alloys of these materials are used. For the first transparent electrode layer 48, CuAlS ₂ , CuGaS, B-doped SiC, or the like can be used.

The second transparent electrode layer 52 is composed of an N-type transparent electrode layer. As the second transparent electrode layer (N-type transparent electrode layer), for example, Ga ₂ O ₃ , SnO ₂ (ATO, FTO), which is equal to or larger than the band gap of IGZO, a-IGZO (amorphous IGZO) ZnO-based (AZO, GZO), In ₂ O ₃ -based (ITO,), Zn (O, S) CdO, or two or three alloys of these materials can be used. Furthermore, as the second transparent electrode layer 52, MgIn ₂ O ₄ , GaInO ₃ , CdSb ₃ O _6, or the like can be used.

The photoelectric conversion layer 50 is made of, for example, polycrystalline silicon or single crystal silicon. Moreover, as the photoelectric conversion layer 50, a CIGS type photoelectric conversion layer, a CIS type photoelectric conversion layer, a CdTe type photoelectric conversion layer, a dye-sensitized photoelectric conversion layer, or an organic type photoelectric conversion layer can also be used.

The light confinement layer 54 has a light confinement function, for example, an antireflection function. As the light confinement layer 54, a known antireflection film can be used.

Next, another photoelectric conversion device of this embodiment will be described.
FIG. 10A is a schematic cross-sectional view illustrating a photoelectric conversion device according to another embodiment of the present invention, and FIG. 10B is a schematic perspective view illustrating a main part of another configuration of the wavelength conversion layer. .
The photoelectric conversion device 40a illustrated in FIG. 10A is different from the photoelectric conversion device 40 illustrated in FIG. 9 in the configuration of the wavelength conversion layer 56, and other configurations are the same as the photoelectric conversion device 40 illustrated in FIG. Since the configuration is similar, detailed description thereof is omitted.

The wavelength conversion layer 56 of the photoelectric conversion device 40a illustrated in FIG. 10A has a stacked structure in which a wavelength conversion unit 58a (second layer) and a resin unit 58b (first layer) are stacked. is there.
The wavelength conversion portion 58a (second layer) and the resin portion 58b (first layer) each have an optical wavelength order (several hundred nm).
The wavelength conversion layer 56 prevents the long wavelength light Lu that is not used for photoelectric conversion by the photoelectric conversion layer 50 that has passed through the photoelectric conversion layer 50 and the first transparent electrode layer 48 from being emitted from the surface 56 a of the wavelength conversion layer 56. It is to make. That is, the wavelength conversion layer 56 confines the long-wavelength light Lu that is not used for photoelectric conversion in the photoelectric conversion layer 50.
As a configuration for confining the long-wavelength light Lu, for example, the configuration of the antireflection film as shown in FIG. 5 described above can be used.
In the wavelength conversion layer 56, the wavelength conversion part 58a can be set as the same structure as the said wavelength conversion film 10, for example. For this reason, detailed description of the wavelength conversion unit 58a is omitted.

The resin portion 58b is made of a dielectric material or an organic material, and is not particularly limited as long as, for example, a photocurable resin and a thermosetting resin are used and transmit light.
As the photocurable resin and the 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 even 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 using additives such as catalysts, polymerization initiators or reaction accelerators. Acrylic resin.

In the photoelectric conversion device 40a, the long-wavelength light Lu that has passed through the photoelectric conversion layer 50 and is not used for photoelectric conversion by the photoelectric conversion layer 50 is not emitted from the surface 56a of the wavelength conversion layer 56, and thus photoelectric conversion is performed. It is not incident on the layer 50 again. In addition, since the long wavelength light Lu is not emitted from the surface 56a of the wavelength conversion layer 56 without generating heat, the photoelectric conversion layer 50 is not adversely affected. Thus, in the photoelectric conversion device 40a, the re-incidence of the long wavelength light Lu that is not used for photoelectric conversion in the photoelectric conversion layer 50 can be suppressed, and the adverse effect of the long wavelength light Lu that is not used for photoelectric conversion can be suppressed.

In addition, the structure of the wavelength conversion part 58a of the wavelength conversion layer 56 of the photoelectric conversion apparatus 40a is not limited to the said wavelength conversion film 10, For example, using the wavelength conversion part 60 shown in FIG.10 (b) is used. it can.
In the wavelength conversion unit 60, a plurality of quantum dots 64 are periodically arranged on a matrix layer 62. In this case, for example, as shown in FIGS. 6A and 6B, the refractive index of the wavelength conversion unit 60 is adjusted using the relationship between the content of the quantum dots and the refractive index, and combined with the resin unit 58b. For example, the long wavelength light Lu may be confined in the wavelength conversion layer 56.

In the photoelectric conversion device 40a, when the effective refractive index of the resin portion 58b (first layer) is na and the refractive index of the wavelength conversion portion 58a (second layer) is nb, 0.3 <| nb It is preferable that −na |. In this case, the refractive index nb of the wavelength conversion unit 58a (second layer) is, for example, 1.8 ≦ n ≦ 4.0 at a wavelength of 533 nm, which is preferably the same as the effective refractive index n of the wavelength conversion film 10. Is 1.8 ≦ n ≦ 2.5 at a wavelength of 533 nm.
The larger the refractive index difference between the effective refractive index na of the resin portion 58b (first layer) and the refractive index nb of the wavelength converting portion 58a (second layer), the smaller the number of layers for obtaining the same reflection. it can. However, increasing the refractive index difference narrows the material selection range. In order to obtain a predetermined reflectance when the number of wavelength conversion layers 56 is about 10 for example, the difference in refractive index is about 0.3. For this reason, the refractive index difference between the effective refractive index na of the resin portion 58b (first layer) and the refractive index nb of the wavelength conversion portion 58a (second layer) is 0.3 <| nb−na |. Is preferred.

The present invention is basically configured as described above. As described above, the wavelength conversion film and the photoelectric conversion device of the present invention have been described in detail. Of course.

DESCRIPTION OF SYMBOLS 10 Wavelength conversion film 12 Substrate 14, 62 Matrix layer 16 1st quantum dot 18 2nd quantum dot 20 Stimulable luminescent material 22a, 22b, 23a, 23b, 24a, 24b, 25a, 25b Quantum well 30 Laminate body 32 SiO ₂ layer 34 SiO ₂ / Yb ₂ O ₃ layer 36 Si / SiO ₂ layer 38 SiGeO layer 40 photoelectric conversion device 42 base material 44 reflective layer 46, 56 wavelength conversion layer 48 first transparent electrode layer 50 photoelectric conversion layer 52 first 2 transparent electrode layers 54 light confinement layer 58a, 60 wavelength conversion unit 64 quantum dots

Claims

A matrix layer;
A first quantum dot provided in the matrix layer;
A second quantum dot provided in the matrix layer;
A stimulable luminescent material provided in the matrix layer,
The first quantum dot and the second quantum dot have a first ground energy level excited when the first quantum dot is irradiated with multiple light, and the second quantum dot has multiple light. Greater than the second ground energy level excited when irradiated with
The matrix layer is made of a dielectric or organic material having a band gap larger than the first ground energy level,
When the first quantum dot and the second quantum dot are joined, the energy band structure is type II,
The matrix layer around each quantum dot forms a selective tunnel barrier by a combination of the band cap of the matrix layer, the distance between each quantum dot, and the thickness of the matrix layer, and the photostimulable luminescent material By forming a mini-band that has a higher energy transition probability at an energy level higher than the energy level difference ΔEC of the light emission transition of the light source, and making the energy transition to the photostimulable luminescent material provided in the matrix layer A wavelength conversion film characterized by being converted.
In the energy band structure, when the minimum energy level difference between the conduction band miniband and the valence band miniband is ΔEAB, ΔEAB ≧ ΔEC,
The wavelength conversion film according to claim 1, wherein at least the long-wavelength light absorbed by the second quantum dots generates short-wavelength light from the photostimulable luminescent material in the matrix layer.
The first quantum dot and the second quantum dot have a diameter of 2 to 20 nm,
3. The wavelength conversion film according to claim 1, wherein the first quantum dots and the second quantum dots are alternately arranged in layers at a predetermined distance in the thickness direction of the matrix layer.
4. The stimulable luminescent material is disposed at approximately the middle between the first quantum dots and the second quantum dots that are adjacent at least in the thickness direction of the matrix layer. The wavelength conversion film described in 1.
5. The wavelength conversion film according to claim 1, wherein the first quantum dot and the second quantum dot are made of an indirect transition semiconductor.
6. The wavelength conversion film according to claim 1, wherein the matrix layer is made of an inorganic material or an organic material having a band gap of 3 eV or more, and the stimulable light emitting material is made of rare earth ions or metal ions.
7. The wavelength conversion film according to claim 1, wherein the effective refractive index n is 1.8 ≦ n ≦ 4, where n is an effective refractive index of the wavelength conversion film.
The first quantum dot is made of Si x Ge (1-x) (X> 0.7), and the second quantum dot is made of Si x Ge (1-x) (X <0.7). The wavelength conversion film according to claim 6, wherein the rare earth ions are Yb 3+ ions, Er 3+ ions, or Tm 3+ ions, and the metal ions are Mn ions.
The wavelength conversion film according to any one of claims 1 to 8, wherein the matrix layer is made of SiO 2 , SiN X, or SiC.
10. A photoelectric conversion device, wherein the wavelength conversion film according to claim 1 is disposed on a side opposite to a light incident side of the photoelectric conversion layer.
The photoelectric conversion device according to claim 10, wherein the wavelength conversion film has a light confinement function of transmitting long wavelength light and reflecting short wavelength light.
A first layer made of a dielectric material or an organic material and a second layer made of the wavelength conversion film according to any one of claims 1 to 9, wherein the first layer has a laminated structure. And each of the second layers has an optical wavelength order of thickness,
A photoelectric conversion device, wherein 0.3 <| nb−na |, where the effective refractive index of the first layer is na and the refractive index of the second layer is nb.