Luminescent concentrator, photoelectric conversion device, and window material

Abstract

Provided is a luminescent concentrator capable of maintaining power generation efficiency by means of a simple configuration when increasing the surface area thereof. A luminescent concentrator 10 comprises: a first light concentrator 11 having a first light guide part 111 for receiving incident light L, and a first light-emitting part 112 for distributing a first light-emitting substance, which absorbs the incident light L received by the first light guide part 111 and emits light, in a surface direction along the first light guide part 111; a second light concentrator 12 having a second light-emitting part 121 for distributing a second light-emitting substance, which absorbs the first light L1 from the first light concentrator 11 and emits light, in a surface direction, and a second light guide part 122 for guiding second light L2 from the second light-emitting part 121 toward a photovoltaic element 20; and a light transmission section 13 for transmitting the first light L1 to the second light-emitting part 121. The first light concentrator 11 and the second light concentrator 12 have an overlapping structure while remaining separated from each other, and the second light-emitting part 121 is arranged more locally than is the first light emitting part 112, and corresponds to the region where the light transmission section 13 is positioned.

Description

Luminescent Light Concentrator, Photoelectric Conversion Device, and Window Material

[0001] The present disclosure relates to a luminescent light concentrator, a photoelectric conversion device, and a window material.

[0002] In recent years, technologies related to luminescence solar concentrator photovoltaics (LSC-PV) are known. For example, Patent Document 1 discloses a power generation module capable of suppressing a decrease in power generation efficiency due to an increase in size of the power generation device.

[0003] Japanese Unexamined Patent Publication No. 2018-170311

[0004] In LSC, a decrease in power generation efficiency caused by reabsorption of light by a luminescent material is an issue. For example, it is known that the phenomenon where light emitted first when the luminescent material distributed in the light guide portion of an LSC absorbs incident light such as sunlight, is reabsorbed by the luminescent material and causes re-emission is repeated several times. Losses accumulate during the repetition of such phenomena, creating a limit on the linear distance that light can travel in the planar direction of the LSC from the initial light emission point. As a result, when photovoltaic elements are arranged around the light guide portion of the LSC, even if the light guide portion of the LSC has a large area, although the total power generation increases, the light-receiving area contributing to actual power generation is limited to the peripheral portion excluding the central portion, and the power generation efficiency corresponding to the value obtained by dividing the power generation amount by the total area decreases.

[0005] In the conventional technology described in Patent Document 1, in order to solve such problems, studies have been conducted on a power generation module capable of suppressing a decrease in power generation efficiency due to an increase in size of the power generation device. However, the configuration of the power generation module for suppressing the decrease in power generation efficiency is complicated.

[0006] An object of the present disclosure is to provide a luminescent light concentrator, a photoelectric conversion device, and a window material that can maintain power generation efficiency when having a large area with a simple configuration.

[0007] Means for achieving the above object are as follows.

[0008] (1) A light-emitting type light concentrator that collects incident light and guides it to a photoelectric element, comprising: a first light concentrator having a first light guide that receives the incident light and a first light-emitting part that distributes a first light-emitting material that absorbs the incident light received by the first light guide in a planar direction along the first light guide; a second light concentrator having a second light-emitting part that absorbs a first light from the first light concentrator and distributes a second light-emitting material that absorbs a first light and emits light in a planar direction and a second light guide that guides the second light from the second light-emitting part toward the photoelectric element; and a light-transmitting part that transmits the first light to the second light-emitting part, wherein the first light concentrator and the second light concentrator have a superimposed structure spaced apart from each other, and the second light-emitting part is arranged more locally than the first light-emitting part, corresponding to the arrangement area of ​​the light-transmitting part.

[0009] (2) A light-emitting type concentrator as described in (1) above, wherein the first light-emitting part is enclosed within the first light guide part or is arranged in a film-like manner on the main surface of the first light guide part.

[0010] (3) A light-emitting type concentrator as described in (1) or (2) above, wherein the second light-emitting part is connected to the second end face in the direction of guiding the second light in the second light guide part, or is arranged in a film-like manner on the main surface of the second light guide part perpendicular to the second end face.

[0011] (4) A light-emitting type concentrator according to any one of (1) to (3) above, wherein the light transmission section includes a first optical member adjacent to the first end face in the direction of guiding the first light in the first light guide section, a space continuous with the first end face or a first low refractive index material, the first end face inclined toward the second light-emitting section, or a second optical member arranged in a film-like manner on the main surface of the first light guide section.

[0012] (5) A light-emitting type condenser as described in (4) above, wherein the first optical member includes a light scatterer, a mirror, or a prism.

[0013] (6) A light-emitting type concentrator as described in (4) or (5) above, wherein the second optical member includes a light scatterer.

[0014] (7) A light-emitting type concentrator according to any one of (1) to (6) above, wherein in the superposition structure, the first concentrator is located on the incident side of the incident light.

[0015] (8) A light-emitting type condenser as described in (7) above, comprising a pair of sets of the first condenser and the light transmission section, wherein the superposition structure includes a structure in which the second condenser is positioned spaced apart from each other between the pair of sets of the first condenser and the light transmission section.

[0016] (9) A light-emitting type concentrator according to any one of (1) to (6) above, wherein in the superposition structure, the second concentrator is located on the incident side of the incident light.

[0017] (10) A light-emitting type condenser as described in (9) above, comprising a pair of second condensers, the light transmission unit transmitting the first light to each of the pair of second light-emitting units, and the superposition structure including a structure in which the first condensers are positioned spaced apart from each other between the pair of second condensers.

[0018] (11) A light-emitting type concentrator according to any one of (1) to (10) above, wherein the combination of the light-transmitting part and the second light-emitting part is arranged to form letters, numbers, symbols, or figures when viewed from the overlapping direction of the superimposed structure.

[0019] (12) A light-emitting type concentrator according to any one of (1) to (11) above, wherein the first concentrator is divided into a smaller area than the second concentrator.

[0020] (13) A light-emitting type condenser according to any one of (1) to (12) above, further comprising at least one of: a second low refractive index material filled between the first condenser and the second condenser and having a lower refractive index than the material constituting each of the first and second condensers; and a spacer disposed between the first and second condensers to separate the first and second condensers and create an air gap.

[0021] (14) A photoelectric conversion device comprising a light-emitting type concentrator described in any one of (1) to (13) above, and the photoelectric power generation element disposed on the periphery of the light-emitting type concentrator.

[0022] (15) A window material equipped with the photoelectric conversion device described in (14) above.

[0023] According to this disclosure, it is possible to provide a light-emitting concentrator, a photoelectric converter, and a window material that can maintain power generation efficiency when the area is increased with a simple configuration.

[0024] This is a schematic diagram showing an example of the configuration of a light-emitting concentrator according to one embodiment of the present disclosure. This is a schematic diagram showing an example of a cross-section of a photoelectric converter having the light-emitting concentrator of Figure 1. This is a schematic diagram showing a part of the cross-section of the photoelectric converter of Figure 2. This is a graph diagram illustrating an example of the luminescence characteristics of a light-emitting material used in the light-emitting concentrator of Figure 1. This is a schematic diagram showing a first example of a connecting part for obtaining the superimposed structure of the light-emitting concentrator of Figure 1. This is a schematic diagram showing a second example of a connecting part for obtaining the superimposed structure of the light-emitting concentrator of Figure 1. This is a schematic diagram showing an example of a cross-section of a photoelectric converter having a light-emitting concentrator according to the first modified example. This is a schematic diagram showing an example of a cross-section of a photoelectric converter having a light-emitting concentrator according to the second modified example. This is a schematic diagram showing an example of a cross-section of a photoelectric converter having a light-emitting concentrator according to the third modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator according to the fourth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator according to the fifth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator according to the sixth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the seventh modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the eighth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the ninth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the tenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the eleventh modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the twelfth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the thirteenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the fourteenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the fifteenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the sixteenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the seventeenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the eighteenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting condenser according to the eighteenth modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator according to the 19th modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator according to the 20th modified example. This is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator according to the 21st modified example. This is a schematic diagram showing in cross-section how a window material having a photoelectric conversion device according to one embodiment of the present disclosure is assembled. This is a schematic diagram illustrating a part of the configuration of a light-emitting concentrator according to the 22nd modified example.This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 23). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 24). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 25). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 26). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 27). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 28). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 29). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 20). This is a schematic diagram illustrating a part of the configuration of a light-emitting condenser according to a modified example (No. 31).

[0025] In the following, one embodiment of this disclosure will be mainly described with reference to the attached drawings.

[0026] Figure 1 is a schematic diagram showing an example of the configuration of a light-emitting type concentrator 10 according to one embodiment of the present disclosure. In Figure 1, the entire light-emitting type concentrator 10 is schematically shown. In addition, a schematic enlarged view of a part of the light-emitting type concentrator 10 is also shown. Referring to Figure 1, the outline of the configuration of the light-emitting type concentrator 10 according to one embodiment of the present disclosure will be mainly described.

[0027] The light-emitting concentrator 10 concentrates incident light and guides it to a photovoltaic element. In this disclosure, "incident light" includes, for example, sunlight incident on the light-receiving surface of the light-emitting concentrator 10. The light-receiving surface includes, for example, the first surface S11 of the first light-guiding portion 111 of the first concentrator 11. The photovoltaic element is not shown in Figure 1, but as will be described later, it is arranged on the periphery of the light-emitting concentrator 10. The light-emitting concentrator 10 constitutes a light-emitting solar concentrator (LSC) that concentrates light, such as sunlight, and guides it to a photovoltaic element. The light-emitting concentrator 10 has one side with a width d1. The width d1 is, for example, about 100 cm. The overall shape of the light-emitting concentrator 10 or the shape of the first concentrator 11 is not limited to a square as shown in Figure 1, but may be a rectangle, any other polygon, a circle, or any other shape.

[0028] Figure 2 is a schematic diagram showing an example of a cross-section of a photoelectric converter 1 having the light-emitting concentrator 10 shown in Figure 1. Figure 3 is a schematic diagram showing a part of the cross-section of the photoelectric converter 1 shown in Figure 2. An example of the configuration of a photoelectric converter 1 according to one embodiment of this disclosure will be described in detail, mainly with reference to Figures 2 and 3.

[0029] The photoelectric conversion device 1 includes a light-emitting type concentrator 10 shown in Figure 1 and a photoelectric power generation element 20 arranged on the periphery of the light-emitting type concentrator 10. The light-emitting type concentrator 10 has a first concentrator 11 and a second concentrator 12 having a spaced-apart superimposed structure. The light-emitting type concentrator 10 has a light transmission unit 13 that transmits first light L1 from the first concentrator 11 to the second concentrator 12 and optically couples the first concentrator 11 and the second concentrator 12. In the superimposed structure of the light-emitting type concentrator 10, the set of the first concentrator 11 and the light transmission unit 13 is arranged on the same side, and the set and the second concentrator 12 are configured to overlap facing each other in the overlapping direction D1. In the superimposed structure of the light-emitting type concentrator 10, for example, the first concentrator 11 is arranged on the incident side of the incident light L.

[0030] The first light condenser 11 has a first light guide 111 that receives incident light L. The first light condenser 11 has a first light-emitting section 112 that distributes a first light-emitting material, which absorbs the incident light L received by the first light guide 111 and emits light, in a planar direction along the first light guide 111. In this disclosure, "planar direction" includes, for example, two directions D2 and D3 that are perpendicular to the overlap direction D1. As the material of the first light guide 111, in addition to the first light-emitting material, a material similar to known materials used in conventional LSCs may be used. The main material of the first light guide 111 is a transparent material, and may include, for example, resin or glass. The main material of the first light guide 111 may be the same as that used in conventional LSCs.

[0031] As shown in Figure 1, in the first light condenser 11, multiple first light guides 111 are arranged along a planar direction perpendicular to the overlapping direction D1. Each first light guide 111 contains a first light-emitting section 112. The first light guide 111 is, for example, a transparent plate that uniformly contains the first light-emitting material of the first light-emitting section 112 throughout its entire interior. In the first light condenser 11, the multiple first light guides 111 are segmented, or partitioned. The segments of the first light guides 111 are arranged planarly in the planar direction. The first light condenser 11 is divided into a smaller area than the second light condenser 12. In addition to this physical segmentation, the segmentation may also be optical, as will be explained later.

[0032] The first light guide portion 111 has a first surface S11 that extends in the planar direction. The first surface S11 is included, for example, in the light-receiving surface of the incident light L. In the first light concentrator 11, a plurality of first light guide portions 111 are arranged in an array in the planar direction, so the overall light-receiving surface of the first light concentrator 11, which is composed of a plurality of first surfaces S11, has a large area. On the other hand, the first surface S11 of a single first light guide portion 111 that constitutes one segment has a significantly smaller area compared to the overall light-receiving surface area of ​​the first light concentrator 11.

[0033] The first light-emitting material of the first light-emitting section 112 enclosed within the first light-guiding section 111 includes a light-emitting material that absorbs light and emits light. The first light-emitting material, for example, absorbs incident light L and emits first light L1. The first light-emitting material may be the same as the light-emitting material used in conventional LSCs, and may include, for example, a known fluorescent material or phosphorescent material, or a material that performs upconversion emission. The first light-emitting material may include an organic molecular fluorescent dye, an inorganic material fluorescent material, a colloidal quantum dot phosphor, or semiconductor particles.

[0034] For example, the first luminescent material may be a colloidal quantum dot phosphor. The colloidal quantum dot phosphor may have a CdS / ZnS core-shell structure. Alternatively, the colloidal quantum dot phosphor may have a structure in which a ZnS shell is provided on an InP-based core. In the first luminescent material, the emission wavelength of the first light L1 may be controlled by controlling the particle size of various chemical species materials.

[0035] The second light condenser 12 has a second light-emitting section 121 that distributes a second light-emitting material in a planar direction, which absorbs the first light L1 from the first light condenser 11 and emits light. The second light condenser 12 has a second light guide section 122 that guides the second light L2 from the second light-emitting section 121 toward the photovoltaic element 20. As the material of the second light guide section 122, for example, a material similar to known materials used in conventional LSCs may be used. The main material of the second light guide section 122 is a transparent material, and may include, for example, resin or glass. Unlike the first light guide section 111 of the first light condenser 11, the second light guide section 122 does not contain any light-emitting material.

[0036] As shown in Figure 1, the second light condenser 12 extends along the planar direction, with the second light-emitting section 121 and the second light-guiding section 122 being arranged continuously with respect to each other in a planar direction perpendicular to the overlapping direction D1. The second light condenser 12 is a transparent plate in which the second light-emitting section 121 containing the second light-emitting material is locally arranged between a plurality of second light-guiding sections 122. The second light condenser 12 has a large area so as to overlap with the entire first light condenser 11. The main surface of the plate of the second light condenser 12, for example, the second surface S21, may be parallel to the main surface of the first light condenser 11, for example, the first surface S11.

[0037] In the second light concentrator 12, the second light guide section 122 is segmented into multiple sections by the second light-emitting section 121. The multiple sections in the second light guide section 122 are arranged planarly in the planar direction. The second light guide section 122 has a second surface S21 that extends in the planar direction. The area of ​​the second surface S21 in each section of the second light guide section 122 segmented by the second light-emitting section 121 is equivalent to the area of ​​the first surface S11 of a single first light guide section 111 that constitutes one segment in the first light concentrator 11. The second surface S21 is positioned in substantially the same position in the planar direction as the first surface S11.

[0038] In the second light concentrator 12, the region where the second light-emitting material exists is limited to the region where the second light-emitting section 121 is located. The second light-emitting section 121 is located more locally than the first light-emitting section 112, corresponding to the region where the light-transmitting section 13 is located. The second light-emitting section 121 is located near the light-transmitting section 13, which is located around the area of ​​the first light-guiding section 111. The second light-emitting material is contained only in the second light-emitting section 121 and not in the second light-guiding section 122 located elsewhere in the second light concentrator 12.

[0039] In the second light condenser 12, the second light-emitting section 121 is positioned substantially the same as the light-transmitting section 13 in the planar direction. The second light-emitting section 121 is connected to the second end face S22 in the direction that guides the second light L2 in the second light-guiding section 122. In this disclosure, "the direction that guides the second light L2 in the second light-guiding section 122" corresponds, for example, to the planar direction. As shown in Figures 2 and 3, the second light-emitting section 121 has the same width as the light-transmitting section 13, or a width slightly different from the light-transmitting section 13, along the planar direction. The second light-emitting section 121 may have a wider width than the light-transmitting section 13, or a narrower width than the light-transmitting section 13, along the planar direction.

[0040] In the second light concentrator 12, one section of the second light guide section 122, segmented by the second light-emitting section 121, is positioned in substantially the same location in the planar direction as one of the first light guide sections 111. As shown in Figures 2 and 3, one section of the second light guide section 122 has the same width as one of the first light guide sections 111, or a width slightly different from one of the first light guide sections 111, along the planar direction. One section of the second light guide section 122 may have a wider width than one of the first light guide sections 111, or a narrower width than one of the first light guide sections 111, along the planar direction.

[0041] The second light-emitting material of the second light-emitting unit 121, which is connected to the second light-guiding unit 122, includes a light-emitting material that absorbs light and emits light. The second light-emitting material, for example, absorbs the first light L1 from the first light-concentrator 11 and emits the second light L2. The second light-emitting material may include, for example, a known fluorescent material or phosphorescent material, or a material that performs upconversion emission. The second light-emitting material may include an organic molecular fluorescent dye, an inorganic material fluorescent material, a colloidal quantum dot phosphor, or semiconductor particles.

[0042] For example, the second luminescent material may be a colloidal quantum dot phosphor. The colloidal quantum dot phosphor may have a CdS / ZnS core-shell structure. Alternatively, the colloidal quantum dot phosphor may have a structure in which a ZnS shell is provided on an InP-based core. In the second luminescent material, the emission wavelength of the second light L2 may be controlled by controlling the particle size of various chemical species materials.

[0043] The light transmission unit 13 transmits the first light L1 from the first light condenser 11 to the second light-emitting unit 121 of the second light condenser 12. The light transmission unit 13 changes the propagation direction of the first light L1 from the first light condenser 11 from a direction along the planar direction to a direction toward the second light-emitting unit 121, thereby guiding the first light L1 to the second light-emitting unit 121. As shown in Figure 1, the light transmission unit 13 is locally positioned between the multiple first light-guiding units 111, with the unit surrounded on its periphery in the planar direction by the multiple first light-guiding units 111. The light transmission unit 13 is positioned around the compartments of the first light-guiding units 111.

[0044] The light transmission section 13 includes a first optical member adjacent to a first end surface S12 in the direction in which the first light L1 is guided in the first light guide section 111. In the present disclosure, "the direction in which the first light L1 is guided in the first light guide section 111" corresponds to, for example, a planar direction. The "first optical member" includes an optical element such as a mirror or a prism. The first optical member is disposed around the first end surface S12 of the first light guide section 111 in the planar direction.

[0045] The light transmission section 13 includes, for example, a first mirror 131 and a second mirror 132 arranged along the planar direction shown in FIG. 3. The first mirror 131 faces the first end surface S12 of the first light guide section 111 disposed on one side in the planar direction, and is disposed so as to be inclined toward the second light emitting section 121 of the second condenser 12. The second mirror 132 faces the first end surface S12 of the first light guide section 111 disposed on the other side in the planar direction, and is disposed so as to be inclined toward the second light emitting section 121 of the second condenser 12. The first mirror 131 and the second mirror 132 are arranged in a V-shape along the planar direction.

[0046] The photovoltaic power generation element 20 includes, for example, a solar cell or the like that receives the second light L2 guided to the peripheral edge of the second condenser 12 of the light-emitting condenser 10 by the light-emitting condenser 10 and converts the second light L2 into electric power. The solar cell includes, for example, a silicon-based solar cell such as single-crystal silicon, polycrystalline silicon, or amorphous silicon, a compound-based solar cell such as CIGS or CdTe, an organic thin-film solar cell, a perovskite solar cell, or the like. The photovoltaic power generation element 20 may be disposed over the entire periphery in the planar direction of the light-emitting condenser 10 along each of the four end surfaces in the planar direction of the light-emitting condenser 10 shown in FIG. 1, or may be disposed on a part of the periphery in the planar direction of the light-emitting condenser 10.

[0047] As shown in FIG. 2, the light-emitting concentrator 10 has a width d3 on one side in the plane direction with respect to the center P in the plane direction. The width d1 shown in FIG. 1 corresponds to a value twice the width d3. The first light guide part 111 of the first concentrator 11 has a half-width of width d4 along the plane direction. The full width of the first light guide part 111 in the plane direction corresponds to a value twice the width d4. The pair of first light guide parts 111 arranged in the plane direction has an interval d5 along the plane direction. The width d2 shown in FIG. 1 corresponds to a value obtained by adding the interval d5 to twice the width d4, which is the full width of the first light guide part 111 in the plane direction.

[0048] As shown in FIG. 3, incident light L that enters the light-emitting concentrator 10 from the first concentrator 11 side enters the interior of the first light guide part 111 with the first surface S11 of the first light guide part 111 serving as a light-receiving surface. The incident light L that has entered the first light guide part 111 is absorbed by the first light-emitting substance of the first light-emitting part 112 distributed inside the first light guide part 111. The first light-emitting substance that has absorbed the incident light L emits first light L1. The first light guide part 111 is generally small, and has a full width of, for example, about 5 cm as described later. The value twice the width d4, which is the full width of the first light guide part 111 in the plane direction, is about 5 cm. In addition, the first light guide part 111 also has a thickness of several millimeters in the overlapping direction D1.

[0049] Therefore, most of the first light L1 obtained through light emission after the incident light L received by the first light guide part 111 is first absorbed by the first light-emitting substance is guided to the first end face S12 of the first light guide part 111. While most of the first light L1 is guided in the plane direction while repeating total internal reflection inside the first light guide part 111, it reaches the first end face S12 hardly undergoing reabsorption by the first light-emitting substance. It is assumed that reabsorption and re-emission occur with a certain low probability depending on the size of the first light guide part 111, but if the size of the first light guide part 111 is reduced as described above, the loss caused by reabsorption and re-emission will not become large.

[0050] Here, the loss based on reabsorption and re-emission of the first light L1 by the first light-emitting substance will be examined.

[0051] The incident light L incident on the first light guide 111 generally occurs in the thickness direction, that is, in the overlap direction D1 which is generally perpendicular to the main surface, so it needs to be absorbed well over a distance equal to the thickness of the first light guide 111. Optical density (OD) is generally known to represent the absorption rate (percentage). If the material science molar extinction coefficient of the first light-emitting material is ε (L / mol / cm), the concentration of the first light-emitting material is c (mol / L), and the thickness of the first light guide 111 is t (cm), then the OD with respect to the incident light L in the overlap direction D1 of the first light guide 111 is given by the following equation 1. Note that depending on the type of light-emitting material, it may be easier to handle the quantity in weight (grams) rather than moles (mol), in which case the unit should be changed as appropriate.

[0052] OD = ε × c × t (Equation 1) Here, we consider OD = 1 as the design value for the first light guide 111, with a transmittance of 10% (absorptance of 90%). The thickness is t = 0.3 cm. The concentration c is set to satisfy Equation 1 according to the molar absorption coefficient ε of the first light-emitting material distributed with respect to the first light guide 111.

[0053] Consider the reabsorption of light by the luminescent material when light travels, for example, in direction D2. The probability of this reabsorption must also take into account the spectral overlap between the absorption spectrum and the emission spectrum. Overlap Integration (OI), which represents the overlap between the absorption spectrum and the emission spectrum of the first luminescent material, expresses the probability of reabsorption with respect to the extinction coefficient of the first luminescent material. The value of OI can range from 0 (no reabsorption occurs at all) to 1 (reabsorption always occurs).

[0054] In the first light-emitting material, a typical example of OI is 0.074 (7.4%). For the sake of simplicity, let's consider the case where the first light L1 travels parallel to the planar direction inside the first light guide 111, as illustrated in Figure 2. Then, the first light L1 traveling to the right towards the first end face S12 inside the first light guide 111 will undergo reabsorption in the optical path inside the first light guide 111 according to the product of the molar absorption coefficient ε and OI. Compared to absorption in the overlapping direction D1, the probability of reabsorption corresponding to the absorption coefficient is reduced by OI.

[0055] Therefore, for example, the optical light guide distance at which the reabsorption OD = 1, where reabsorption is 90%, is t / OI, which is, for example, 0.3 / 0.074 = 4.05 cm. This indicates that, if the propagation of light is perfectly parallel to the plane direction, only 10% of the light emitted by the first light-emitting material can reach a point about 4 cm away in a straight line, and is exponentially reabsorbed by the first light-emitting material along the way. Suppose the probability that the first light L1 can reach a point 8 cm away in a straight line from the initial emission point is 0.1 × 0.1 = 0.01, or 1%. Almost all of the first light L1 undergoes reabsorption. Since the reabsorbed first light L1 does not completely disappear but produces re-emission, it is assumed that the percentage of light that can reach the point 8 cm away is greater than 1%, but not significantly greater than 1%. There are several possible reasons for this, as follows.

[0056] The first reason is that re-emission by the first light-emitting material results in losses based on the luminescence efficiency of the first light-emitting material itself, i.e., its internal quantum efficiency, and escape cone loss (ECL) due to the emission of light from the point light source. It is well known that ECL is not limited to re-emission by the first light-emitting material, but also occurs in the emission by the first light-emitting material that initially absorbed the incident light L. If the reabsorption and re-emission by the first light-emitting material does not end after just one instance but is repeated with a certain probability within the light guide inside the first light guide section 111, the amount of light emitted from the initial first light L1 decreases exponentially. Moreover, as explained in the second reason, the first light L1 repeats back and forth in the planar direction with a 50% probability, so it gradually attenuates.

[0057] The second reason is that, considering the direction in which the first light L1 travels due to reabsorption and re-emission by the first light-emitting material, the direction in which the first light L1 travels is, with a probability of 1 / 2, opposite to the direction in which the first light L1 travels before reabsorption, in the one-dimensional light-guiding direction in the planar direction inside the first light-guiding section 111. The re-emission by the first light-emitting material can also be considered as light emission from a point light source, and the direction in which the re-emissioned light travels is equally probable on both sides in the planar direction. With a probability of 1 / 2, the first light L1 tends to travel back and forth inside the first light-guiding section 111 and remain at the initial light emission point, and cannot easily move forward toward the first end face S12.

[0058] The third reason is that the proportion of light emission from the first light L1 traveling parallel to the surface direction inside the first light guide 111 is small, and most of the light emission from the first light-emitting material is from the first light L1 traveling through the first light guide 111 by total internal reflection. In light guidance by total internal reflection inside the first light guide 111, the first light L1 travels in a zigzag pattern between the first surface S11 of the first light guide 111 and the first back surface facing the first surface S11, as illustrated in Figure 3. Therefore, the straight-line distance at which 90% of the reabsorption of the first light L1 by the first light-emitting material occurs is the distance obtained by multiplying the optical distance of the zigzag by the cosine of the angle of total internal reflection. For example, if the angle of total internal reflection is 45°, it is reduced to about 2.8 cm. The angle of total internal reflection can take a range from the critical angle (the angle determined by the refractive index of the light guide and the refractive index of air, etc., in contact with the main surface of the light guide) to less than 90°.

[0059] As described above, it is understood that the straight-line distance that the first light L1 obtained by the initial emission from the first light-emitting material can travel before it first receives reabsorption and re-emission in the planar direction of the first light guide 111 is limited. If the concentration of the first light-emitting material necessary to absorb a certain proportion of incident light L, such as sunlight, in the thickness direction of the first light guide 111 and cause emission is obtained, even if the probability of reabsorption of the first light L1 by the first light-emitting material is only a few percent, the longer the straight-line light-guiding distance to the first end face S12, the higher the probability of reabsorption may become. If the width of the first light guide 111 is made large, for example, to a practical size of 1 meter, the straight-line light-guiding distance to the first end face S12 is long, so reabsorption and re-emission by the first light-emitting material will inevitably occur several times, and the emission (including re-emission) caused by the initial incident light L will almost never reach the first end face S12.

[0060] In one embodiment of the light-emitting concentrator 10, as described later, the overall width of the first light guide portion 111 is not increased, thereby reducing losses due to reabsorption and re-emission of the first light L1 by the first light-emitting material. The first light L1 guided to the first end face S12 of the first light guide portion 111 is emitted from the first end face S12. The first light L1 emitted from the first end face S12 of the first light guide portion 111 is guided by the light transmission portion 13 to the second light-emitting portion 121 of the second concentrator 12.

[0061] The first light L1 incident on the second light-emitting section 121 of the second light-concentrator 12 is absorbed by the second light-emitting material. The second light-emitting material that absorbed the first light L1 emits the second light L2. These processes are the same as the process of the initial light emission that occurs when the incident light L in the first light-concentrator 11 is absorbed by the first light-emitting material. The second light L2 obtained by the emission of light from the second light-emitting material is guided through the inside of the second light-guiding section 122, undergoing total internal reflection, to the second end face S22, which is located on the outermost side of the second light-concentrator 12. For much of the light-guiding process in the second light-concentrator 12, the second light L2 passes through the second light-guiding section 122 where the second light-emitting material is not present.

[0062] The initial light emission from the second light-emitting part 121 in the central part of the second light-concentrator 12 results in a long linear distance for the second light L2 to reach the second end face S22, which is the outermost part of the second light-concentrator 12. However, the total linear distance over which the second light L2 passes through the second light-emitting part 121 where the second light-emitting material is present is much shorter than the linear distance for which the second light L2 reaches the second end face S22, which is the outermost part of the second light-concentrator 12. Therefore, the probability of reabsorption of the second light L2, generated by the incidence of the first light L1 into the central part of the second light-concentrator 12, before reaching the second end face S22 is not large. In conventional large-area LSCs of the 1m x 1m class, the light emitted from sunlight incident in the central part hardly reaches the periphery of the LSC and does not contribute to power generation. In contrast, the light-emitting type concentrator 10 according to one embodiment can guide most of the light emitted by the incident light L to the second end face S22, which is located on the outermost side of the light-emitting type concentrator 10, even if the incident light L is incident on the central part of the first concentrator 11, even if it is a large area of ​​1 m x 1 m.

[0063] Figure 4 is a graph illustrating an example of the luminescence characteristics of the light-emitting material used in the light-emitting concentrator 10 of Figure 1. Figure 4 shows the light absorption spectrum and emission spectrum for the first light-emitting material and the second light-emitting material, respectively. Examples of combinations of the first and second light-emitting materials having emission spectra as shown in Figure 4 can be illustrated.

[0064] The first light-emitting material preferably has an absorption wavelength range that is as broad as possible, spanning from the ultraviolet region to the visible region to the near-infrared region (the longest wavelength range in which the photoelectric element can generate electricity), and preferably has a wavelength range of emission that is as narrow as possible, which is the same as the requirements for light-emitting materials required for conventional LSCs. The second light-emitting material is selected as two types of light-emitting materials, such that the wavelength range of emission of the first light-emitting material and the wavelength range of absorption of the second light-emitting material overlap, enabling emission of light from the second light-emitting material based on the first light L1. The second light-emitting material may be appropriately selected so that the wavelength range of emission matches the longest possible wavelength range in the wavelength range in which the photoelectric element 20 has photosensitive capabilities. The second light-emitting material also preferably has a wavelength range of emission that is as narrow as possible. The above preferred requirements are for using the widest possible wavelength range of sunlight for photoelectric power generation, thereby increasing the total amount of power generated, i.e., the power generation efficiency (energy conversion efficiency) as much as possible. For example, if the photoelectric element 20 is a silicon solar cell, the second light-emitting material may have a central emission wavelength of 1000 nm. In this case, the first light-emitting material may have a central wavelength of 900 nm for emission. Needless to say, it is preferable that the first and second light-emitting materials have as high an emission efficiency as possible.

[0065] For example, colloidal quantum dot phosphors allow for changes in emission wavelength by altering the particle size, resulting in a narrow wavelength range. Colloidal quantum dot phosphors are suitable for obtaining the necessary emission characteristics for the first and second emission materials used in an emission-type light concentrator 10 according to one embodiment. Even if the material composition of the first and second emission materials is the same, they can be realized as different types of emission materials by changing the particle size.

[0066] Regarding the amount (concentration) of the first and second light-emitting materials used, that is, the setting of OD, the OD of the first light-emitting material at the first light-guiding section 111 may be, for example, OD = 1 (absorption rate 90%) or OD = 1.3 (absorption rate 95%) in the overlapping direction D1. If the photoelectric conversion device 1 is used as a window material for lighting, OD may be 0.3 (absorption rate 50%). The second light-emitting section 121 of the second light-concentrator 12 needs to reliably absorb the first light L1 from the first light-concentrator 11, and the OD of the second light-emitting material at the overlapping direction D1 may be, for example, OD = 1 (absorption rate 90%) or OD = 1.3 (absorption rate 95%).

[0067] Figure 5 is a schematic diagram showing a first example of a connecting portion 14 for obtaining the superimposed structure of the light-emitting type concentrator 10 of Figure 1. Figure 6 is a schematic diagram showing a second example of a connecting portion 14 for obtaining the superimposed structure of the light-emitting type concentrator 10 of Figure 1. Referring to Figures 5 and 6, an example of the configuration of the connecting portion 14 for obtaining the superimposed structure of the light-emitting type concentrator 10 of Figure 1 will be mainly described. The light-emitting type concentrator 10 further has at least one of the spacer 141 and the second low refractive index material 142 as a connecting portion 14 for supporting and integrating the first concentrator 11 with respect to the second concentrator 12. In addition, the connecting portion 14 (at least one of the spacer 141 and the second low refractive index material 142) works to ensure that the light emission in the first concentrator 11 and the second concentrator 12 is efficiently totally reflected.

[0068] For example, as shown in Figure 5, the connecting portion 14 is positioned between the first light condenser 11 and the second light condenser 12 and may include a spacer 141 that separates the first light condenser 11 and the second light condenser 12 from each other to form an air gap G. The connecting portion 14 is positioned to achieve total internal reflection in the first light guide portion 111 and the second light guide portion 122. In the light-emitting type light condenser 10 according to one embodiment, a superimposed structure is obtained by stacking a plurality of plates including the first light condenser 11 and the second light condenser 12, and in order to achieve total internal reflection, it is necessary to position an air gap G along the overlapping direction D1 between the first light condenser 11 and the second light condenser 12.

[0069] At this time, it is necessary to ensure that total internal reflection is effectively generated in each of the plates of the first light condenser 11 and the second light condenser 12. Therefore, the spacers 141 of the connecting portion 14 are arranged so that the contact area with each of the first light condenser 11 and the second light condenser 12 is kept to a minimum. In addition, the spacers 141 are arranged so that the number of spacers 141 per unit area is kept to a minimum. In Figure 5, a spacer 141 with a rectangular cross-sectional shape is shown as an example, but it is not limited to this. The spacers 141 may also be spherical microparticles.

[0070] The material of the spacer 141 is preferably such that it has a refractive index smaller than that of the first light guide portion 111 and the second light guide portion 122, but it may also have a refractive index of about the same. In addition, the material of the spacer 141 may be such that no light scattering occurs. The material of the spacer 141 may also be colorless and transparent. As a result, compared to the case in which the spacer 141 has a large refractive index, the spacer 141 can reduce the adverse effects of disrupting total internal reflection at the contact points with the first light guide portion 111 and the second light guide portion 122, thereby reducing the efficiency of light guidance, and can reduce the amount of light emitted that deviates from total internal reflection.

[0071] The spacer 141 preferably has adhesive or tackiness on its own. Alternatively, an arbitrary transparent adhesive or tackiness bond (not shown in Figure 5) can be used to bond the first light guide portion 111 and the spacer 141 with the minimum thickness, and the spacer 141 and the second light guide portion 122 in the same manner, thereby obtaining the superimposed structure of the first light condenser 11 and the second light condenser 12.

[0072] For example, as shown in Figure 6, the connecting portion 14 may be filled between the first light condenser 11 and the second light condenser 12 and may contain a second low refractive index material 142 having a lower refractive index than the materials constituting the first light condenser 11 and the second light condenser 12, respectively. The second low refractive index material 142 may be, for example, a fluororesin or a resin in which hollow silica nanoparticles are dispersed at a high concentration, and may include thermoplastic or monomer-polymerized resins. The refractive index of the second low refractive index material 142 may be, for example, about 1.2.

[0073] By filling, i.e., joining, the space between the first light condenser 11 and the second light condenser 12 with a second low refractive index material 142 instead of an air gap G, light guidance by total internal reflection is achieved in each of the first light guide section 111 and the second light guide section 122. The second low refractive index material 142 may be used between the first light condenser 11 and the second light condenser 12 in a minimum thickness as any transparent adhesive that itself has bonding, adhesive, or tackiness. Alternatively, by joining the first light guide section 111 and the second low refractive index material 142 in a minimum thickness using a bonding agent (any transparent material with adhesive or tackiness) not shown in Figure 6, and similarly joining the second low refractive index material 142 and the second light guide section 122, a superimposed structure of the first light condenser 11 and the second light condenser 12 can be obtained.

[0074] According to the light-emitting concentrator 10 and photoelectric converter 1 of the above embodiment, it is possible to maintain power generation efficiency when the area is increased with a simple configuration. In the light-emitting concentrator 10, the first concentrator 11 and the second concentrator 12 have a superimposed structure spaced apart from each other, and the second light-emitting part 121 is positioned more locally than the first light-emitting part 112, corresponding to the arrangement area of ​​the light-transmitting part 13.

[0075] As a result, unlike the conventional technology described in Patent Document 1, which has a complex structure in which a photoelectric element is provided in each section of the LSC to suppress a decrease in power generation efficiency, the photoelectric conversion device 1 can be configured simply. The photoelectric concentrator 10 does not require a photoelectric element to be provided in each section of the LSC, and the photoelectric elements 20 can be arranged on the periphery of the photoelectric concentrator 10. Therefore, the number of photoelectric elements 20 used in the photoelectric conversion device 1 can be reduced.

[0076] Even when the light-emitting concentrator 10 has a large area of, for example, 1 m x 1 m, it is possible to use the incident light L received in the center of the first concentrator 11 for power generation in the photoelectric element 20 without wasting any of it. The light-emitting concentrator 10 converts the first light L1 emitted by the first light-emitting material based on the incident light L received in the center of the large area into second light L2 which is absorbed and emitted by the second light-emitting material, and then guides the second light L2 to the second end face S22 of the second light guide 122. In this case, the presence of the second light guide 122 makes it possible to keep the probability of reabsorption by the second light-emitting material low without making it high.

[0077] For example, in a conventional LSC composed of a square, it is thought that as the size increases, the total amount of electricity generated increases in proportion to the length of the perimeter (the total amount of electricity generated increases in proportion to the length of one side), and the average power generation efficiency over the entire area decreases inversely in proportion to the length of one side. Power generation efficiency can be estimated by the light guide distance of the light-emitting material layer through which the light emitted inside the LSC passes. Below, in a light-emitting type concentrator 10 according to one embodiment, the light guide distance in the straight line of the light emitted, that is, the light guide distance in the straight line including the light-emitting material (first light-emitting material and second light-emitting material) between the light emitted at the center of the light-emitting type concentrator 10 and its end face is calculated, and the power generation efficiency is estimated.

[0078] Here, the estimate is made using the following dimensions. For example, the width d1 shown in Figure 1 is 96.6 cm. The width d2 is 5.1 cm. The width d3 shown in Figure 2 is 48.3 cm. The width d4 is 2.4 cm. The spacing d5 is 0.3 cm.

[0079] As shown in Figure 2, the first light L1, caused by the initial emission of incident light L incident on the center P of the light-receiving surface of the first light concentrator 11, travels a width d4, which is half the length of the first light guide 111, and exits from the first light guide 111. The first light L1, incident on the second light-emitting part 121 of the second light concentrator 12 by the light transmission part 13, is absorbed by the second light-emitting part 121. The second light-emitting part 121 emits second light L2 through emission. The second light L2 passes through multiple sections and multiple second light-emitting parts 121 in the second light guide 122, but is not reabsorbed in the second light guide 122. The distance that light based on emission from the light-emitting material passes through the light-emitting material can be calculated as follows.

[0080] For example, the distance that the first light L1 generated at the center P travels through the light-emitting material to reach the second end face S22 of the second light concentrator 12 is d4 + d5 × 9 = 2.4 + 2.7 = 5.1 cm. This is approximately the same distance as that of a conventional 10 cm square LSC. The power generation efficiency is estimated in the light-emitting type concentrator 10 according to one embodiment as shown in Equation 2.

[0081] The power generation efficiency of the light-emitting concentrator 10 = (power generation efficiency of a conventional 10 cm square LSC) × (transmission efficiency in the light transmission section 13) × (luminous efficiency of the initial emission in the second light-emitting section 121) = 10% × 0.8 × 0.8 ≈ 6% (Equation 2) Here, it is assumed that the only difference between the first light-emitting material and the second light-emitting material is the absorption wavelength range and the emission wavelength, and that their luminous efficiencies are equivalent. Here, as a premise, it is assumed that a conventional 10 cm square LSC has a power generation efficiency of 10%.

[0082] In the light-emitting concentrator 10, it is necessary to consider the transmission efficiency in the light transmission section 13 and the luminous efficiency resulting from the inevitable conversion of light emission due to absorption and emission by the second light-emitting section 121 having a second light-emitting material. Both were assumed to be 0.8. For the former, if the light transmission section 13 is, for example, a mirror made of a thin metal film, a reflectance value of more than 0.93 can be expected. Considering the magnitude of the reflectance of light in the light transmission section 13 and the probability that the reflected first light L1 is incident on the second light-emitting material, the transmission efficiency in the light transmission section 13 was assumed to be 0.8.

[0083] In addition, the light-emitting concentrator 10 involves a process in which the first light L1 emitted by the first light-emitting material is absorbed by the second light-emitting material, and the second light L2 is emitted. Therefore, this can be said to be the luminous efficiency of the initial emission in the second light-emitting section 121, and this efficiency was also estimated as "luminous efficiency of the initial emission in the second light-emitting section 121 = 0.8". It is presumed that even in a conventional 10 cm square LSC, there is a certain probability of reabsorption and re-emission, and this is already taken into account in its power generation efficiency (10%). Therefore, when considering the absorption and emission efficiency attributable to the second light-emitting section 121 of the light-emitting concentrator 10, it is sufficient to consider only the efficiency of the initial emission that occurs when the first light L1 is absorbed by the second light-emitting material (the wavelength conversion of light occurs only once, which is more than in the conventional case).

[0084] In addition, in the light-emitting type concentrator 10, for the first light guide portion 111 facing the photoelectric element 20 among the multiple first light guide portions 111, the first light L1 emitted from the first end face S12 may directly enter the photoelectric element 20 without passing through the second concentrator 12. In conventional LSCs, the contribution to power generation by the surrounding frame-shaped photoelectric elements is large. In the above estimate, the light-emitting type concentrator 10 is configured so that the first light L1 emitted by the multiple first concentrators 11 arranged in a frame shape around its periphery can directly enter the photoelectric element 20 without passing through the second concentrator 12. In such a process, the absence of transmission loss by the light transmission portion 13 and the absence of loss during conversion to the second light L2 are not taken into consideration, so it is possible that the above estimate is a slight underestimation.

[0085] In conventional LSCs, the power generation efficiency is thought to be inversely proportional to the length of one side. If a conventional 10cm square LSC has a power generation efficiency of 10%, then a conventional 1m square LSC would have an average power generation efficiency of about 1% across the entire surface. On the other hand, according to the light-emitting concentrator 10 of one embodiment, even though it has a large area of ​​approximately 1m square with sides of 96.6cm, a power generation efficiency of 6%, which is six times higher than conventional models, can be expected. The above estimate is merely an example, and by appropriately setting the form and size of each component, it is possible to ensure power generation efficiency even in large areas.

[0086] It will be obvious to those skilled in the art that this disclosure can be implemented in other predetermined forms other than the embodiments described above without deviating from its spirit or essential features. Therefore, the prior description is illustrative and not limiting. The scope of the disclosure is defined not by the prior description but by the added claims. Any modifications within their equivalent scope are included therein.

[0087] For example, the shape, pattern, size, arrangement, orientation, type, and number of each component described above are not limited to those shown in the above description and drawings. The shape, pattern, size, arrangement, orientation, type, and number of each component may be configured arbitrarily as long as they can realize their function. Each component of the illustrated light-emitting concentrator 10 and photoelectric converter 1 is a functional concept. The specific form of each component is not limited to those shown. For example, the following modifications of the light-emitting concentrator 10 are also possible.

[0088] In the above embodiment, the first light guide portion 111 was described as uniformly containing the first light-emitting material of the first light-emitting portion 112 throughout its entire interior, but it is not limited to this. The first light guide portion 111 may contain the first light-emitting material of the first light-emitting portion 112 uniformly in the planar direction within the interior of the first light guide portion 111, while having a concentration distribution in the thickness direction and not being uniformly distributed.

[0089] In addition to the configuration of the above embodiment, the light-emitting concentrator 10 may have an anti-reflective coating placed on the main surface of the first light guide portion 111, including the first surface S11 of the first light guide portion 111. This allows the light-emitting concentrator 10 to reduce the loss due to reflection at the interface of the first light guide portion 111 that occurs before the incident light L enters the first concentrator 11. The explanation of the placement and operation of the anti-reflective coating also applies to all of the following modifications.

[0090] In the above embodiment, the photoelectric element 20 is installed on the end face of the light-emitting concentrator 10, but is not limited to this. The photoelectric element 20 may be installed in a frame-like manner around the main surface of the second concentrator 12, for example, as shown in Figure 17, which will be described later.

[0091] Figure 7 is a schematic diagram showing an example of a cross-section of a photoelectric converter 1 having a light-emitting type concentrator 10 according to the first modified example. In the above embodiment, the superposition structure of the light-emitting type concentrator 10 is a two-layer structure including one first concentrator 11 and one second concentrator 12, but is not limited to this. The superposition structure of the light-emitting type concentrator 10 may have three or more layers.

[0092] For example, the light-emitting type concentrator 10 may have a pair of sets of a first concentrator 11 and a light transmission unit 13. In this case, the superposition structure of the light-emitting type concentrator 10 may include a structure in which the second concentrator 12 is positioned spaced apart from each other between the pair of sets of the first concentrator 11 and the light transmission unit 13. The light-emitting type concentrator 10 may have a superposition structure in which the first concentrator 11 is in two layers and the second concentrator 12 is positioned between them.

[0093] In the overlapping direction D1, the total optical density of the two layers of the first light condenser 11 is the same as in the above embodiment where the first light condenser 11 is a single layer. For example, if the thickness of the two layers of the first light condenser 11 in the overlapping direction D1 is the same, the optical density of each layer of the first light condenser 11 will be half that of the above embodiment.

[0094] The first modified light-emitting type concentrator 10 has first concentrators 11 arranged on both sides of the overlap direction D1, thereby improving the degree of freedom of orientation in the overlap direction D1. For example, the light-emitting type concentrator 10 can function similarly even when the state shown in Figure 7 is inverted vertically, when incident light L is incident on the light-emitting type concentrator 10 from the upper side of Figure 7. Alternatively, the light-emitting type concentrator 10 can receive incident light L over a wide area by using a pair of first concentrators 11 on each side of the overlap direction D1. Alternatively, even if the pair of first concentrators 11 have different structures, the light-emitting type concentrator 10 can more effectively receive incident light L by arranging the first concentrator 11 with the larger size of the first light-emitting part 112 on the incident side of the incident light L.

[0095] Figure 8 is a schematic diagram showing an example of a cross-section of a photoelectric converter 1 having a light-emitting type concentrator 10 according to a second modified example. In the above embodiment, it was explained that in the superposition structure of the light-emitting type concentrator 10, the first concentrator 11 is arranged on the incident side of the incident light L, but this is not limited to this. As shown in Figure 8, in the superposition structure of the light-emitting type concentrator 10, the second concentrator 12 may be arranged on the incident side of the incident light L.

[0096] The light-emitting type concentrator 10 according to the second modification can receive incident light L without loss even in the portion of the light-receiving surface corresponding to the area of ​​the light-transmitting portion 13. Even if the light-transmitting portion 13 is an optical element such as a mirror and does not allow light to pass in the direction normal to the light-receiving surface, i.e., the overlapping direction D1, the incident light L is absorbed by the second light-emitting material of the second light-emitting portion 121 in the portion corresponding to the area of ​​the light-transmitting portion 13. As a result, the light-emitting type concentrator 10 can directly generate second light L2 based on the incident light L and guide it to the second end face S22. Therefore, the light-emitting type concentrator 10 can also improve the power generation efficiency of the photoelectric converter 1.

[0097] The light-emitting type concentrator 10 may have an anti-reflective coating placed on the main surface of the second light guide portion 122, including the second surface S21 of the second light guide portion 122 and the second back surface facing the second surface S21. This allows the light-emitting type concentrator 10 to reduce the loss due to reflection at the interface of the second light guide portion 122 of the second light concentrator 12 that occurs before the incident light L enters the first light concentrator 11.

[0098] Figure 9 is a schematic diagram showing an example of a cross-section of a photoelectric converter 1 having a light-emitting concentrator 10 according to the third modified example. In the second modified example described above, the superposition structure of the light-emitting concentrator 10 is a two-layer structure including one first concentrator 11 and one second concentrator 12, but is not limited to this. The superposition structure of the light-emitting concentrator 10 may have three or more layers.

[0099] For example, the light-emitting condenser 10 may have a pair of second condensers 12. In this case, the light transmission unit 13 may transmit the first light L1 to each of the pair of second light-emitting units 121. The superposition structure of the light-emitting condenser 10 may include a structure in which the first condenser 11 is positioned spaced apart from each other between the pair of second condensers 12. The light-emitting condenser 10 may have a superposition structure in which the second condensers 12 are in two layers and the first condenser 11 is positioned between them.

[0100] The third modified light-emitting type concentrator 10 can improve the efficiency of transmitting the first light L1 to the second concentrator 12 by the light transmission unit 13. The light transmission unit 13 only needs to guide the first light L1 to the pair of second concentrators 12 in either of the overlapping directions D1. Therefore, the light-emitting type concentrator 10 can also improve the structural freedom for realizing the function of the light transmission unit 13 and reduce the light transmission loss by the light transmission unit 13. For example, even if the pair of second concentrators 12 have different structures, the light-emitting type concentrator 10 can more effectively receive the incident light L if the second concentrator 12 with the larger size of the second light-emitting unit 121 is placed on the incident side of the incident light L.

[0101] In the above embodiment, the light transmission unit 13 was described as including a first optical element such as a mirror or a prism, but it is not limited thereto. The light transmission unit 13 may have any other configuration as long as it has the function of guiding the first light L1 generated in the first light guide unit 111 to the second light emission unit 121. Below, other examples of the light transmission unit 13 will be mainly described with reference to Figures 10A to 14.

[0102] Figure 10A is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the fourth modified example. The first optical member of the light transmission section 13 is not limited to optical elements such as mirrors or prisms, and may also include a light scatterer 133. The light scatterer 133 may be, for example, a transparent resin in which fine particles with different refractive indices are dispersed.

[0103] Figure 10B is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the fifth modified example. In the above embodiment, the light transmission section 13 was described as including a first optical member adjacent to the first end face S12 in the direction of guiding the first light L1 in the first light guide section 111, but is not limited thereto. The light transmission section 13 may also include the first end face S12 itself which is inclined toward the second light-emitting section 121. For example, the tip of the first light guide section 111 may be tapered by the inclination of the first end face S12 of the light transmission section 13.

[0104] Figure 10C is a schematic diagram illustrating a part of the cross-section of the light-emitting concentrator 10 according to the sixth modified example. In the fifth modified example, the tip of the first light guide portion 111 was described as being tapered by the inclination of the first end face S12 of the light transmission portion 13, but it is not limited to this. The tip of the first light guide portion 111 may be configured in a zigzag shape by the inclination of the first end face S12 of the light transmission portion 13 by the repeated inclination while reciprocating along the surface direction.

[0105] Figure 10D is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the seventh modified example. In the above embodiment, the first optical member of the light transmission section 13 was described as having a first mirror 131 and a second mirror 132, but is not limited thereto. The first optical member may also include a single double-sided mirror 134.

[0106] Figure 10E is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the eighth modified example. In the above embodiment, the light transmission section 13 was described as including a first optical member adjacent to the first end face S12 in the direction in which the first light L1 is guided in the first light guide section 111, but is not limited thereto. The light transmission section 13 may include a space 135 or a first low refractive index material continuous with the first end face S12 in the direction in which the first light L1 is guided in the first light guide section 111. In Figure 10E, a space 135 is shown as an example of the light transmission section 13.

[0107] For example, the first light L1 emitted from the first end face S12 includes not only light parallel to the surface of the first light condenser 11, but also light traveling out of that surface. Therefore, even without providing a reflective structure in the light transmission section 13, much of the first light L1 emitted from the first end face S12 of the first light condenser 11 will travel to the second light condenser 12. The first light L1 emitted in parallel will enter the adjacent first light guide section 111, but will contribute to reabsorption and re-emission by the first light-emitting material in the first light guide section 111, and although the amount will decrease, it can also return to the light transmission section 13.

[0108] The first low refractive index material may be the same material as the second low refractive index material 142 described above, or it may be a different material. The first low refractive index material may be a transparent material. The first low refractive index material may fill the entire space 135 instead of the space 135.

[0109] Figure 10F is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the ninth modified example. In the above embodiment, the first optical member of the light transmission section 13 was described as having a first mirror 131 and a second mirror 132, but is not limited thereto. The first optical member may also include a mirror 136 adjacent to the lower end of the first end face S12 in the direction that guides the first light L1 in the first light guide section 111.

[0110] Figure 10G is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 10th modified example. In the above embodiment, the light transmission section 13 was described as including a first optical member adjacent to the first end face S12 in the direction that guides the first light L1 in the first light guide section 111, but is not limited thereto. The light transmission section 13 may also include the first end face S12 itself that is inclined toward the second light-emitting section 121. For example, the tip of the first light guide section 111 may be tapered by the inclination of the first end face S12 of the light transmission section 13. When the light-emitting concentrator 10 has a pair of second concentrators 12, each first end face S12 may be inclined such that the tip of the first light guide section 111 located on one side in the planar direction and the tip of the first light guide section 111 located on the other side in the planar direction face each other.

[0111] Figure 11 is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 11th modified example. The light-emitting concentrator 10 according to the 11th modified example may have a light transmission section 13 formed by combining the light transmission section 13 in the 10th modified example and the light transmission section 13 in the 7th modified example, with a pair of first end faces S12 that are inclined opposite each other and a double-sided mirror 134 as the light transmission section 13. In this case, the double-sided mirror 134 may be, for example, aluminum foil. The double-sided mirror 134 may be spaced apart from the first end face S12 of the first light guide section 111, as shown in Figure 11, or it may be joined to the first end face S12.

[0112] Figure 12 is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 12th modified example. In the light-emitting concentrator 10 according to the 12th modified example, the light scatterer 133 of the 4th modified example shown in Figure 10A may be arranged throughout the space between the pair of first light guides 111 so as to contact or join with the first end face S12 of the first light guide 111. The light scatterer 133 may be in contact with the first end face S12 as an optically separate component from the first light guide 111, or it may be integrated with the first end face S12 as an optically identical component to the first light guide 111.

[0113] Figure 13 is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 13th modified example. The light-emitting concentrator 10 according to the 13th modified example may be configured to have a light scatterer 133 positioned between a pair of first end faces S12 that are inclined opposite each other, compared to the configuration of the 12th modified example.

[0114] Figure 14 is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 14th modified example. In the above embodiment, the light transmission section 13 was described as including a first optical member adjacent to the first end face S12 in the direction of guiding the first light L1 in the first light guide section 111, but is not limited thereto. The light transmission section 13 may also include a second optical member arranged in a film-like manner on the main surface of the first light guide section 111. The second optical member may include a light scatterer 133.

[0115] In this case, the first light concentrator 11 may be configured as a continuous plate with a large area that is not physically segmented, instead of the configuration in the above embodiment in which a plurality of first light guides 111 are segmented. The light scatterer 133 as the second optical member of the light transmission unit 13 may be arranged in a film-like manner on at least one of the main surfaces of the first light guide unit 111, including the first surface S11 and the first back surface S13 facing the first surface S11. In Figure 14, as an example, a configuration is shown in which the light scatterer 133 is arranged in a film-like manner on the first surface S11 of the first light guide unit 111. The light scatterer 133 may disrupt the total internal reflection in the portion of the first light guide unit 111 where the light scatterer 133 is arranged, scatter the first light L1, and guide it out of the first light guide unit 111 to the second light emitting unit 121. The first light guide section 111 of the first light concentrator 11 can be said to be optically segmented into multiple sections by the light scatterer 133.

[0116] In the above embodiment, the first light-emitting section 112 was described as being enclosed within the first light-guiding section 111, but this is not the only possible configuration. The first light-emitting section 112 may be arranged in a film-like manner on the main surface of the first light-guiding section 111. The first light-emitting material does not need to be uniform in the thickness direction of the first light-concentrator 11. The first light-emitting section 112 may be configured in any way that allows the required OD to be maintained in the thickness direction, i.e., the overlap direction D1.

[0117] The first light-emitting section 112 may be configured as a coating film of a first light-emitting substance located on the main surface of the colorless and transparent first light-guiding section 111. As the coating film, a colorless and transparent resin, for example, a resin having the same refractive index as the first light-guiding section 111, may be dissolved in a solvent, and the first light-emitting substance may be dissolved or dispersed in it. The first light-emitting section 112 may be configured by coating the main surface of the first light-guiding section 111 with this coating and allowing the solvent to evaporate. Alternatively, for example, the first light-emitting section 112 may be configured by similarly coating a coating in which the first light-emitting substance is dissolved or dispersed in a polymerizable monomer solution having the same refractive index as the first light-guiding section 111 after curing, and then polymerizing and curing it with light or heat.

[0118] In the following sections, other examples of the first light-emitting unit 112 will be mainly described with reference to Figures 15A to 15E.

[0119] Figure 15A is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 15th modified example. The first light-emitting part 112 may be arranged in a film-like manner on the first surface S11 of the first light-guiding part 111, for example. In the overlapping direction D1, the optical density of the first light-emitting part 112 may be the same as that of the first light-emitting part 112 when it was enclosed in the first light-guiding part 111 in the above embodiment.

[0120] Figure 15B is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 16th modified example. The first light-emitting portion 112 may be arranged in a film-like manner on the first surface S11 and the first back surface S13 of the first light-guiding portion 111, for example. In the overlapping direction D1, the optical density of the pair of first light-emitting portions 112 may be the same as that of the first light-emitting portion 112 when it was enclosed in the first light-guiding portion 111 in the above embodiment.

[0121] Figure 15C is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 17th modified example. The first light-emitting part 112 may be sandwiched in an overlapping direction D1 by a pair of first light-guiding parts 111, for example. In the overlapping direction D1, the optical density of the first light-emitting part 112 may be the same as that of the first light-emitting part 112 when it was enclosed in the first light-guiding part 111 in the above embodiment.

[0122] Figure 15D is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 18th modified example. The first light-emitting portion 112 may be arranged in a film-like manner on, for example, the first surface S11 and the first back surface S13 of the first light-guiding portion 111. In this case, the first light-emitting portions 112 may be arranged alternately along the surface direction. In the overlapping direction D1, the optical density of each of the pair of first light-emitting portions 112 may be the same as that of the first light-emitting portion 112 when it was enclosed in the first light-guiding portion 111 in the above embodiment.

[0123] Figure 15E is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 19th modified example. The first light-emitting portion 112 may be arranged in a film-like manner on the first surface S11 and the first back surface S13 of the first light-guiding portion 111, for example. In this case, the first light-emitting portion 112 may be arranged more finely and alternately along the surface direction. In the overlapping direction D1, the optical density of the first light-emitting portion 112 may be the same as that of the first light-emitting portion 112 when it was enclosed in the first light-guiding portion 111 in the above embodiment.

[0124] In the 18th and 19th modified examples shown in Figures 15D and 15E, respectively, a transparent resin having the same refractive index as the first light guide 111 may be coated onto the main surface of the first light guide 111 in the portion where the first light-emitting portion 112 is not located. In this case, the thickness of the transparent resin may be the same as the thickness of the first light-emitting portion 112, or it may be greater than the thickness of the first light-emitting portion 112 so as to cover the entire first light-emitting portion 112 located on the main surface.

[0125] In the above embodiment, the second light-emitting section 121 was described as being connected to the second end face S22 in the direction that guides the second light L2 in the second light guide section 122, but this is not the only possible configuration. The second light-emitting section 121 may be arranged in a film-like manner on the main surface of the second light guide section 122 that is perpendicular to the second end face S22. The same description as above for the first light-emitting section 112 applies to the second light-emitting section 121 as well. Below, other examples of the second light-emitting section 121 will be mainly described with reference to Figures 16A and 16B.

[0126] Figure 16A is a schematic diagram illustrating a part of the cross-section of a light-emitting concentrator 10 according to the 20th modified example. The second light-emitting part 121 may be arranged in a film-like manner on at least one of the main surfaces of the second light-guiding part 122, including the second surface S21 and the second back surface S23. For example, the second light-emitting part 121 may be arranged in a film-like manner on the second surface S21 of the second light-guiding part 122, or it may be arranged in a film-like manner on each of the second surface S21 and the second back surface S23.

[0127] Figure 16B is a schematic diagram illustrating a part of the cross-section of the light-emitting concentrator 10 according to the 21st modified example. In the 20th modified example shown in Figure 16A, a transparent resin 123 having the same refractive index as the second light-guiding portion 122 may be coated on the second surface S21 of the second light-guiding portion 122 in the portion where the second light-emitting portion 121 is not arranged. In this case, the thickness of the transparent resin 123 may be the same as the thickness of the second light-emitting portion 121, or it may be greater than the thickness of the second light-emitting portion 121 so as to cover the entire second light-emitting portion 121 located on the main surface.

[0128] Figure 17 is a schematic cross-sectional view showing the assembly of a window material W having a photoelectric conversion device 1 according to one embodiment of the present disclosure. The window material W functions, for example, by using a window glass installed in an existing sash W1 as a second light guide 122. For example, the window material W is assembled in the following steps. Note that the configuration of the light-emitting concentrator 10 shown in Figure 17 is an example of when it is installed in an existing window, and if a new window is to be installed, the configuration of the above embodiment or other modified configurations may be used.

[0129] The first light condenser 11 and light transmission unit 13 are attached to the second light guide unit 122, which is a window glass, by applying adhesive or bonding properties to the second light-emitting unit 121, which is arranged via a colorless, transparent, rigid, low-refractive-index material M to the first light condenser 11 and light transmission unit 13. At this time, the first light condenser 11 and light transmission unit 13 are also attached to the second light guide unit 122, which is a window glass, by adhesive W2 arranged via the low-refractive-index material M at both ends of the first light condenser 11 in the planar direction. Multiple photovoltaic elements 20 coated with adhesive W2 are attached to the second light guide unit 122 at both ends in the planar direction. Light scatterers W3 coated with adhesive W2 are attached to the second light guide unit 122 at both ends in the planar direction. At this time, the light scatterers W3 are arranged to face the photovoltaic elements 20.

[0130] A window material W having a photoelectric conversion device 1 according to one embodiment is assembled through the process described above. In the window material W, the photoelectric element 20 is not placed on the end face of the window glass, but is attached to the frame-like portion around the window glass, which serves as the second light guide portion 122. This eliminates the need to modify the sash W1. When the photoelectric element 20 is optically bonded to the second light guide portion 122 by an adhesive W2 having a refractive index equivalent to that of glass, the second light L2 that has been guided through the inside of the second light guide portion 122 by total internal reflection is incident on the surface of the photoelectric element 20 and contributes to power generation.

[0131] In addition, a light scatterer W3 positioned opposite the photoelectric element 20 may disrupt the total internal reflection in the corresponding portion of the second light guide 122, scattering the second light L2 and causing it to exit the second light guide 122 and be guided to the photoelectric element 20. The window material W having the above structure makes it possible to retrofit the photoelectric conversion device 1 according to one embodiment to an existing window glass. Even when retrofitted, the window material W can generate electricity with relatively high power generation efficiency.

[0132] In the above embodiment, the light-emitting concentrator 10 is configured such that the combination of the light transmission unit 13 and the second light-emitting unit 121 forms a rectangle when viewed from the overlapping direction D1 of the superimposed structure, as shown in Figure 1, for example, but is not limited to this. The combination of the light transmission unit 13 and the second light-emitting unit 121 may be arranged to form letters, numbers, symbols, or figures when viewed from the overlapping direction D1 of the superimposed structure. In this case, the first light guide unit 111 may be, for example, a transparent plate containing a first light-emitting unit 112 having a first light-emitting material, which has a cut in it, and the cut is filled with a resin monomer coating containing a light-scattering material as the light transmission unit 13 and cured as a transparent plate.

[0133] Figure 18A is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 22nd modified example. Figure 18B is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 23rd modified example. As shown in Figures 18A and 18B, the combination of the light transmission unit 13 and the second light-emitting unit 121 may be arranged to form a hexagon when viewed from the overlapping direction D1 of the superimposed structure.

[0134] Figure 19A is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 24th modified example. Figure 19B is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 25th modified example. Figure 19C is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 26th modified example. Figure 19D is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 27th modified example. Figure 19E is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 28th modified example. Figure 19F is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 29th modified example. As shown in Figures 19A to 19F, the combination of the light transmission unit 13 and the second light-emitting unit 121 may be arranged to form a regular or irregular figure when viewed from the overlapping direction D1 of the superimposed structure.

[0135] Figure 20A is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 30th modified example. Figure 20B is a schematic diagram illustrating a part of the configuration of the light-emitting concentrator 10 according to the 31st modified example. When viewed from the overlapping direction D1 of the superimposed structure, the combination of the light transmission unit 13 and the second light-emitting unit 121 may be arranged to form characters or symbols. The photoelectric conversion device 1 including the light-emitting concentrator 10 can represent characters or symbols, or patterns or pictures (illustrations), and may serve purposes other than power generation, such as a function to display something, i.e., a signboard.

[0136] 1 Photoelectric conversion device 10 Light-emitting concentrator 11 First concentrator 111 First light guide 112 First light-emitting part 12 Second concentrator 121 Second light-emitting part 122 Second light guide 123 Transparent resin 13 Light transmission part 131 First mirror 132 Second mirror 133 Light scatterer 134 Double-sided mirror 135 Space 136 Mirror 14 Connecting part 141 Spacer 142 Second low refractive index material 20 Photoelectric element D1 Overlap direction D2 Direction (surface direction) D3 Direction (surface direction) d1 Width d2 Width d3 Width d4 Width d5 ​​Spacing G Air gap L Incident light L1 First light L2 Second light M Material P Center S11 First surface S12 First end surface S13 First back surface S21 Second front surface S22 Second end surface S23 Second back surface W Window material W1 Sash W2 Adhesive W3 Light scatterer

Claims

1. A light-emitting type light concentrator for concentrating incident light and guiding it to a photoelectric element, comprising: a first light concentrator having a first light guide for receiving the incident light and a first light-emitting part that distributes a first light-emitting material that absorbs the incident light received by the first light guide in a planar direction along the first light guide; a second light concentrator having a second light-emitting part that distributes a second light-emitting material that absorbs first light from the first light concentrator in a planar direction and a second light guide for guiding second light from the second light-emitting part toward the photoelectric element; and a light-transmitting part that transmits the first light to the second light-emitting part, wherein the first light concentrator and the second light concentrator have a superimposed structure spaced apart from each other, and the second light-emitting part is arranged more locally than the first light-emitting part, corresponding to the arrangement area of ​​the light-transmitting part.

2. A light-emitting type concentrator according to claim 1, wherein the first light-emitting portion is enclosed within the first light-guiding portion or is arranged in a film-like manner on the main surface of the first light-guiding portion.

3. A light-emitting type concentrator according to claim 1, wherein the second light-emitting portion is connected to a second end face in the second light-guiding portion in the direction of guiding the second light, or is arranged in a film-like manner on the main surface of the second light-guiding portion perpendicular to the second end face.

4. A light-emitting type concentrator according to any one of claims 1 to 3, wherein the light transmission section includes a first optical member adjacent to a first end face in the direction of guiding the first light in the first light guide section, a space continuous with the first end face or a first low refractive index material, the first end face inclined toward the second light-emitting section, or a second optical member arranged in a film-like manner on the main surface of the first light guide section.

5. A light-emitting type concentrator according to claim 4, wherein the first optical member includes a light scatterer, a mirror, or a prism.

6. A light-emitting type concentrator according to claim 4, wherein the second optical member includes a light scatterer.

7. A light-emitting type concentrator according to any one of claims 1 to 3, wherein in the superimposed structure, the first concentrator is located on the incident side of the incident light.

8. A light-emitting type condenser according to claim 7, comprising a pair of the first condenser and the light transmission section, wherein the superposition structure includes a structure in which the second condenser is positioned spaced apart from each other between the pair of the first condenser and the light transmission section.

9. A light-emitting type concentrator according to any one of claims 1 to 3, wherein in the superimposed structure, the second concentrator is located on the incident side of the incident light.

10. A light-emitting type condenser according to claim 9, comprising a pair of second condensers, wherein the light transmission unit transmits the first light to each of the pair of second light-emitting units, and the superposition structure includes a structure in which the first condensers are positioned spaced apart from each other between the pair of second condensers.

11. A light-emitting type concentrator according to any one of claims 1 to 3, wherein the combination of the light-transmitting part and the second light-emitting part is arranged to form letters, numbers, symbols, or figures when viewed from the overlapping direction of the superimposed structure.

12. A light-emitting type concentrator according to any one of claims 1 to 3, wherein the first concentrator is divided into a smaller area than the second concentrator.

13. A light-emitting type condenser according to any one of claims 1 to 3, further comprising: a second low refractive index material filled between the first condenser and the second condenser and having a lower refractive index than the materials constituting the first condenser and the second condenser; and a spacer disposed between the first condenser and the second condenser to separate the first condenser and the second condenser and to create an air gap.

14. A photoelectric conversion device comprising a light-emitting concentrator according to any one of claims 1 to 3, and the photoelectric element disposed on the periphery of the light-emitting concentrator.

15. A window material comprising the photoelectric conversion device described in claim 14.

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