Solar cell device
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- JAPAN DISPLAY INC
- Filing Date
- 2022-07-12
- Publication Date
- 2026-08-04
Smart Images
Figure 0007900043000001 
Figure 0007900043000002 
Figure 0007900043000003
Abstract
Description
Technical Field
[0001] Embodiments of the present invention relate to a solar cell device.
Background Art
[0002] For example, a liquid crystal polarization grating using a liquid crystal material has been proposed. The diffraction efficiency in a liquid crystal polarization grating depends on the incident angle. When such a liquid crystal polarization grating is applied to a solar cell device, the incident angle of sunlight changes depending on time and season, and the diffraction efficiency fluctuates. When a solar cell device is installed on a building or a moving object, it is desired to suppress fluctuations in power generation efficiency due to the diffraction efficiency.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] An object of an embodiment is to provide a solar cell device capable of suppressing fluctuations in power generation efficiency.
Means for Solving the Problems
[0005] According to one embodiment, a solar cell device includes The transparent substrate has a first main surface, a second main surface facing the first main surface, a first side surface, a second side surface intersecting the first side surface, a third side surface facing the second side surface, and a fourth side surface facing the first side surface. The transparent substrate is laminated on the second main surface side of the transparent substrate and has a first cholesteric liquid crystal. The liquid crystal layer is laminated on the first liquid crystal layer and has a second cholesteric liquid crystal. The solar cell has a first solar cell facing the first side surface, a second solar cell facing the second side surface, and a third solar cell facing the third side surface. The first liquid crystal layer has a first reflective surface inclined with respect to the second main surface, and the second liquid crystal layer has a second reflective surface inclined with respect to the second main surface. In a plan view, the angle between the normal of the first reflective surface and the normal of the second reflective surface is greater than 0° and less than 180°. [Brief explanation of the drawing]
[0006] [Figure 1] Figure 1 is a perspective view showing an example of a solar cell device 10. [Figure 2] Figure 2 is a cross-sectional view of the solar cell apparatus 10 shown in Figure 1 along line A and B. [Figure 3] Figure 3 is a cross-sectional view illustrating an example of cholesteric liquid crystal CL1 contained in liquid crystal layer 21 and cholesteric liquid crystal CL2 contained in liquid crystal layer 22. [Figure 4] Figure 4 shows an example of the orientation pattern of liquid crystal molecules LM11 and LM21 shown in Figure 3. [Figure 5] Figure 5 is a plan view showing the relationship between the light guide directions D1 and D2. [Figure 6] Figure 6 is another cross-sectional view of the solar cell apparatus 10 shown in Figure 1, along line A and B. [Figure 7] Figure 7 is another cross-sectional view of the solar cell apparatus 10 shown in Figure 1, along line A and B. [Figure 8] Figure 8 is another plan view of the solar cell device 10. [Figure 9] Figure 9 is another exploded perspective view of the solar cell device 10. [Figure 10]Figure 10 is a cross-sectional view of the solar cell apparatus 10 shown in Figure 9 along line A and B. [Figure 11] Figure 11 is a cross-sectional view of the solar cell device 10 shown in Figure 9 along the CD line. [Figure 12] Figure 12 shows an example of the orientation patterns of the liquid crystal molecules LM11 in liquid crystal layer 21 and LM41 in liquid crystal layer 24 shown in Figure 10, and the liquid crystal molecules LM21 in liquid crystal layer 22 and LM31 in liquid crystal layer 23 shown in Figure 11. [Figure 13] Figure 13 is a plan view showing the relationship between the light guide directions D1 to D4. [Figure 14] Figure 14 is another plan view showing the relationship between the light guide directions D1 to D4. [Figure 15] Figure 15 is another exploded perspective view of the solar cell device 10. [Figure 16] Figure 16 is a cross-sectional view of the solar cell device 10 shown in Figure 15 along line A and B. [Figure 17] Figure 17 is a cross-sectional view of the solar cell device 10 shown in Figure 15 along the CD line. [Figure 18] Figure 18 is a plan view showing the relationship between the light guide directions D1 to D4. [Figure 19] Figure 19 illustrates an alignment film 3 having irregularities that can be interposed between the transparent substrate 1 and the liquid crystal layer, and between the stacked liquid crystal layers. [Figure 20] Figure 20 illustrates a structure 4 having irregularities that may be interposed between the transparent substrate 1 and the liquid crystal layer, and between the stacked liquid crystal layers. [Modes for carrying out the invention]
[0007] Hereinafter, this embodiment will be described with reference to the drawings. Note that the disclosure is merely an example, and those that can be easily conceived by those skilled in the art for appropriate modifications while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual aspect, but this is merely an example and does not limit the interpretation of the present invention. Also, in this specification and each figure, components that exhibit the same or similar functions as those described above with respect to the previously shown figures may be assigned the same reference numerals, and detailed descriptions that are repeated may be omitted as appropriate.
[0008] In the drawings, for the purpose of facilitating understanding as necessary, the X-axis, Y-axis, and Z-axis that are orthogonal to each other are described. The direction along the Z-axis is referred to as the Z direction or the first direction A1, the direction along the Y-axis is referred to as the Y direction or the second direction A2, and the direction along the X-axis is referred to as the X direction or the third direction A3. The plane defined by the X-axis and the Y-axis is referred to as the X-Y plane, the plane defined by the X-axis and the Z-axis is referred to as the X-Z plane, and the plane defined by the Y-axis and the Z-axis is referred to as the Y-Z plane. Looking at the X-Y plane is referred to as a plan view.
[0009] FIG. 1 is a perspective view showing an example of the solar cell device 10.
[0010] The solar cell device 10 includes a liquid crystal optical element 100 and a solar cell PV1. The liquid crystal optical element 100 includes a transparent substrate 1, a liquid crystal layer 21, and a liquid crystal layer 22. Although not shown in FIG. 1, the liquid crystal optical element 100 may include alignment films interposed between the transparent substrate 1 and the liquid crystal layer 21, and between the liquid crystal layer 21 and the liquid crystal layer 22. Also, the liquid crystal optical element 100 may include structures interposed between the transparent substrate 1 and the liquid crystal layer 21, and between the liquid crystal layer 21 and the liquid crystal layer 22. Specific examples of these alignment films and structures will be described later.
[0011] The transparent substrate 1 is composed of, for example, a transparent glass plate or a transparent synthetic resin plate. The transparent substrate 1 may be composed of, for example, a flexible transparent synthetic resin plate. The transparent substrate 1 can take on any shape. For example, the transparent substrate 1 may be curved.
[0012] In this specification, "light" includes visible light and invisible light. For example, the lower limit wavelength of the visible light range is 360 nm or more and 400 nm or less, and the upper limit wavelength of the visible light range is 760 nm or more and 830 nm or less. Visible light includes a first component (blue component) in a first wavelength band (for example, 400 nm to 500 nm), a second component (green component) in a second wavelength band (for example, 500 nm to 600 nm), and a third component (red component) in a third wavelength band (for example, 600 nm to 700 nm). Invisible light includes ultraviolet rays in a wavelength band shorter than the first wavelength band and infrared rays in a wavelength band longer than the third wavelength band. In this specification, "transparent" preferably means colorless and transparent. However, "transparent" may be translucent or colored and transparent.
[0013] The transparent substrate 1 is formed in a flat plate shape along the X-Y plane and has a main surface F1, a main surface F2, a side surface S1, a side surface S2, a side surface S3, and a side surface S4. The main surface F1 and the main surface F2 are planes substantially parallel to the X-Y plane and face each other in the first direction A1. The side surfaces S1 and S4 are planes substantially parallel to the X-Z plane and face each other in the second direction A2. The side surfaces S2 and S3 are planes substantially parallel to the Y-Z plane and face each other in the third direction A3. In the example shown in FIG. 1, the side surfaces S1 and S4 are the surfaces along the short sides of the transparent substrate 1, and the side surfaces S2 and S3 are the surfaces along the long sides of the transparent substrate 1. Note that the side surfaces S1 and S4 may be the surfaces along the long sides of the transparent substrate 1, and the side surfaces S2 and S3 may be the surfaces along the short sides of the transparent substrate 1.
[0014] The liquid crystal layer 21 is laminated on the side of the main surface F2 of the transparent substrate 1. The liquid crystal layer 22 is laminated on the liquid crystal layer 21. Details of these liquid crystal layers 21 and 22 will be described later.
[0015] The solar cell PV1 faces the side surface S1 of the transparent substrate 1 in the second direction A2. The solar cell PV1 is bonded to the side surface S1 by a transparent adhesive layer.
[0016] Examples of solar cells PV1 include silicon-based solar cells and organic thin-film solar cells. Silicon-based solar cells are formed using amorphous silicon, microcrystalline silicon, monocrystalline silicon, polycrystalline silicon, etc. Organic thin-film solar cells include organic semiconductor solar cells and perovskite solar cells, and may have light transmittance depending on the materials used.
[0017] Figure 2 is a cross-sectional view of the solar cell apparatus 10 shown in Figure 1 along line A and B.
[0018] The liquid crystal layer 21 has a cholesteric liquid crystal CL1 composed of multiple liquid crystal molecules, as shown schematically in an enlarged view. The cholesteric liquid crystal CL1 has a helical axis AX1 that is substantially parallel to the first direction A1, and also has a helical pitch P1 along the first direction A1. The liquid crystal layer 22 has a cholesteric liquid crystal CL2 composed of multiple liquid crystal molecules, as shown schematically in an enlarged view. The cholesteric liquid crystal CL2 has a helical axis AX2 that is substantially parallel to the first direction A1, and also has a helical pitch P2 along the first direction A1. The helical pitches P1 and P2 represent one period of the helix (the thickness along the first direction A1 required for the liquid crystal molecules to rotate 360 degrees).
[0019] Each of the liquid crystal layers 21 and 22 is configured to reflect circularly polarized light in a selected reflection band determined according to the helical pitch and refractive index anisotropy of the light LTi incident through the transparent substrate 1. In this specification, "reflection" in the liquid crystal layers 21 and 22 refers to reflection accompanied by diffraction within the liquid crystal layers 21 and 22.
[0020] The liquid crystal layer 21 has a reflective surface R1 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL1 within the selected reflection band. The liquid crystal layer 22 has a reflective surface R2 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL2 within the selected reflection band. In this specification, circularly polarized light may be strictly circularly polarized light or circularly polarized light that approximates elliptical polarization.
[0021] Details of the reflective surfaces R1 and R2 will be described later, but both reflective surfaces R1 and R2 are inclined with respect to the XY plane so as to face the solar cell PV1. However, reflective surface R1 is inclined in a different direction than reflective surface R2. In the YZ cross section, the normal N1 of reflective surface R1 is shown as a dotted arrow pointing from the liquid crystal layer 21 to the transparent substrate 1, and the normal N2 of reflective surface R2 is shown as a dotted arrow pointing from the liquid crystal layer 22 to the transparent substrate 1. Normal N1 is not parallel to normal N2.
[0022] In the example shown in Figure 2, the rotation direction of cholesteric liquid crystal CL1 is different from that of cholesteric liquid crystal CL2. Furthermore, the helical pitch P1 of cholesteric liquid crystal CL1 is equivalent to the helical pitch P2 of cholesteric liquid crystal CL2. Also, the refractive index anisotropy in liquid crystal layer 21 is equivalent to the refractive index anisotropy in liquid crystal layer 22.
[0023] In other words, the selective reflection band in liquid crystal layer 21 is equivalent to the selective reflection band in liquid crystal layer 22. Furthermore, the circularly polarized light reflected by reflective surface R1 is circularly polarized light in the opposite direction to that reflected by reflective surface R2.
[0024] Next, the optical function of the solar cell device 10 will be explained.
[0025] The illustrated example describes the case where each of the liquid crystal layers 21 and 22 reflects a portion of the light LTi incident from the side of the transparent substrate 1 back toward the transparent substrate 1.
[0026] The light LTi incident on the solar cell device 10 is, for example, sunlight and includes visible light, ultraviolet light, and infrared light. For the sake of ease of understanding, it is assumed that the light LTi is incident on the transparent substrate 1 at approximately perpendicular angles. The incident angle of the light LTi on the transparent substrate 1 is not particularly limited.
[0027] The light LTi enters the interior of the transparent substrate 1 from the main surface F1, exits from the main surface F2, and is incident on the liquid crystal layer 21. The liquid crystal layer 21 then reflects a portion of the light LTi towards the transparent substrate 1 at the reflective surface R1, while transmitting the remaining light. The reflected light LTr1 is, for example, circularly polarized light I1 in the infrared wavelength band.
[0028] Light LTt that has passed through the liquid crystal layer 21 is incident on the liquid crystal layer 22. The liquid crystal layer 22 then reflects a portion of the light LTt toward the transparent substrate 1 at the reflective surface R2, and transmits the remaining light. The reflected light LTr2 is, for example, circularly polarized light I2 in the infrared wavelength band. Circularly polarized light I2 is circularly polarized in the opposite direction to circularly polarized light I1. The light LTt that has passed through the liquid crystal layer 22 includes, for example, visible light and ultraviolet light.
[0029] The entry angles θi1 of light LTr1 reflected by the liquid crystal layer 21 into the transparent substrate 1, and the entry angles θi2 of light LTr2 reflected by the liquid crystal layer 22 into the transparent substrate 1, are set to satisfy the optical waveguide conditions in the transparent substrate 1. Here, the entry angles θi1 and θi2 are preferably angles greater than or equal to the critical angle θc at which total internal reflection occurs at the interface between the transparent substrate 1 and the air. The entry angles θi1 and θi2 are angles with respect to a perpendicular line perpendicular to the main surface F1 of the transparent substrate 1.
[0030] When the transparent substrate 1, liquid crystal layer 21, and liquid crystal layer 22 have equivalent refractive indices, this laminate can function as a single optical waveguide. In this case, the light LTr1 and LTr2 are guided toward side surface S1 while repeatedly reflecting at the interface between the transparent substrate 1 and the air, and at the interface between the liquid crystal layer 22 and the air. The light LTr1 and LTr2 emitted from side surface S1 are used for power generation in the solar cell PV1.
[0031] Figure 3 is a cross-sectional view illustrating an example of cholesteric liquid crystal CL1 contained in liquid crystal layer 21 and cholesteric liquid crystal CL2 contained in liquid crystal layer 22.
[0032] In Figure 3, the liquid crystal layers 21 and 22 are shown enlarged in the first direction A1. For simplification, one liquid crystal molecule LM1 is shown as the liquid crystal molecule LM1 constituting the cholesteric liquid crystal CL1, which is one of several liquid crystal molecules located in the same plane parallel to the XY plane. The orientation direction of the shown liquid crystal molecule LM1 corresponds to the average orientation direction of several liquid crystal molecules located in the same plane. Similarly, one liquid crystal molecule LM2 is shown as the liquid crystal molecule LM2 constituting the cholesteric liquid crystal CL2, which is one of several liquid crystal molecules located in the same plane parallel to the XY plane.
[0033] Focusing on the cholesteric liquid crystal CL1 enclosed by the dotted line, the cholesteric liquid crystal CL1 is composed of multiple liquid crystal molecules LM1 that are spirally stacked along the first direction A1 while rotating. The multiple liquid crystal molecules LM1 include liquid crystal molecules LM11 at one end of the cholesteric liquid crystal CL1 and liquid crystal molecules LM12 at the other end of the cholesteric liquid crystal CL1. Liquid crystal molecules LM11 are in close proximity to the transparent substrate 1. Liquid crystal molecules LM12 are in close proximity to the liquid crystal layer 22.
[0034] In the illustrated cross-sectional view, the orientation directions of adjacent cholesteric liquid crystal CL1 molecules are different from each other. That is, the orientation directions of adjacent liquid crystal molecules LM11 are different from each other. Similarly, the orientation directions of adjacent liquid crystal molecules LM12 are also different from each other. The orientation directions of multiple liquid crystal molecules LM11 change continuously, for example, from left to right in the figure. The orientation directions of multiple liquid crystal molecules LM12 also change continuously.
[0035] The reflective surface R1, shown by the dashed line in the figure, is inclined with respect to the principal plane F2, which is parallel to the XY plane. The angle between the reflective surface R1 and the XY plane is called the inclination angle θ1 of the reflective surface R1. The inclination angle θ1 is acute. The reflective surface R1 corresponds to a plane where the orientation directions of the liquid crystal molecules LM1 are aligned, or a plane where the spatial phases are aligned (equal phase plane).
[0036] Focusing on the cholesteric liquid crystal CL2 enclosed by the dotted line, the cholesteric liquid crystal CL2 is composed of multiple liquid crystal molecules LM2 that are spirally stacked along the first direction A1 while rotating. The multiple liquid crystal molecules LM2 have liquid crystal molecules LM21 at one end of the cholesteric liquid crystal CL2 and liquid crystal molecules LM22 at the other end of the cholesteric liquid crystal CL2. Liquid crystal molecules LM21 are close to the liquid crystal layer 21. Liquid crystal molecules LM22 are close to the interface between the liquid crystal layer 22 and the air layer.
[0037] In the illustrated cross-sectional view, the orientation directions of adjacent cholesteric liquid crystal CL2 molecules are different from each other. That is, the orientation directions of adjacent liquid crystal molecules LM21 are different from each other. Similarly, the orientation directions of adjacent liquid crystal molecules LM22 are also different from each other. The orientation directions of multiple liquid crystal molecules LM21 change continuously, for example, from left to right in the figure. The orientation directions of multiple liquid crystal molecules LM22 also change continuously.
[0038] The reflective surface R2, shown by the dashed line in the figure, is inclined with respect to the principal surface F2, which is parallel to the XY plane. The angle between the reflective surface R2 and the XY plane is called the inclination angle θ2 of the reflective surface R2. The inclination angle θ2 is acute. The reflective surface R2 corresponds to a surface where the orientation directions of the liquid crystal molecules LM2 are aligned, or a surface where the spatial phases are aligned (equal phase surface).
[0039] Each of these liquid crystal layers 21 and 22 is hardened with the orientation direction of the liquid crystal molecules fixed. In other words, the orientation direction of the liquid crystal molecules is not controlled in accordance with the electric field. For this reason, the liquid crystal optical element 100 does not have electrodes for forming an electric field in the liquid crystal layers 21 and 22.
[0040] Generally, in a liquid crystal layer having a cholesteric liquid crystal, the selective reflection band Δλ for light incident perpendicularly is given by the following equation (1), based on the helical pitch P of the cholesteric liquid crystal and the refractive index anisotropy Δn of the liquid crystal layer (the difference between the refractive index ne for extraordinary light and the refractive index no for ordinary light). Δλ = Δn * P …(1) The specific wavelength range for the selective reflection band Δλ is between (no*P) and (ne*P).
[0041] The central wavelength λm of the selective reflection band Δλ is given by equation (2) below, based on the helical pitch P of the cholesteric liquid crystal and the average refractive index nav (=(ne+no) / 2) of the liquid crystal layer. λm = nav * P …(2) In the examples shown in Figures 2 and 3, the liquid crystal layers 21 and 22 have equivalent selective reflection bands Δλ and equivalent central wavelengths λm.
[0042] The above example describes the case where infrared rays from sunlight are included in the selective reflection band, but this is not the only case. By adjusting the refractive index anisotropy Δn and the helical pitch P, a desired selective reflection band can be achieved.
[0043] Figure 4 shows an example of the orientation pattern of liquid crystal molecules LM11 and LM21 shown in Figure 3.
[0044] Arrow D1 shown in the liquid crystal layer 21 corresponds to the orthogonal projection of the normal vector N1 of the reflective surface R1 shown in Figure 2 onto the XY plane, and indicates the direction of light guidance of light LTr1 reflected by the reflective surface R1. Arrow D2 shown in the liquid crystal layer 22 corresponds to the orthogonal projection of the normal vector N2 of the reflective surface R2 shown in Figure 2 onto the XY plane, and indicates the direction of light guidance of light LTr2 reflected by the reflective surface R2. Light guidance direction D1 is in a different direction from light guidance direction D2. In addition, light guidance directions D1 and D2 intersect with the X axis and Y axis, respectively.
[0045] In the liquid crystal layer 21, the orientation directions of each liquid crystal molecule LM11 aligned in the light-guiding direction D1 are different from each other. In the illustrated example, focusing on multiple liquid crystal molecules LM11 aligned along the light-guiding direction D1, the orientation direction of each liquid crystal molecule LM11 changes by a constant angle counterclockwise along the arrow indicating the light-guiding direction D1. Here, the amount of change in the orientation direction of adjacent liquid crystal molecules LM11 is constant along the light-guiding direction D1, but it may gradually increase or gradually decrease. On the other hand, in the liquid crystal layer 21, the orientation directions of each liquid crystal molecule LM11, which are aligned along a direction perpendicular to the light guide direction D1, are approximately the same.
[0046] In the liquid crystal layer 22, the orientation directions of each liquid crystal molecule LM21 aligned in the light guide direction D2 are different from each other. In the illustrated example, focusing on multiple liquid crystal molecules LM21 aligned along the light guide direction D2, the orientation direction of each liquid crystal molecule LM21 changes by a constant angle clockwise along the arrow indicating the light guide direction D2. Here, the amount of change in the orientation direction of adjacent liquid crystal molecules LM21 is constant along the light guide direction D2, but it may gradually increase or gradually decrease. On the other hand, in the liquid crystal layer 22, the orientation directions of each liquid crystal molecule LM21, which are aligned along a direction perpendicular to the light guide direction D2, are approximately the same.
[0047] In this context, the orientation direction of liquid crystal molecules LM11 and LM21 corresponds to the long axis direction of liquid crystal molecules LM11 and LM21 in the XY plane.
[0048] Figure 5 is a plan view showing the relationship between the light guide directions D1 and D2.
[0049] As described above, when viewing the arrow indicating the normal N1 of the reflective surface R1 shown in Figure 2 from a plan view, the normal N1 coincides with the light guide direction D1 in the XY plane. Similarly, when viewing the arrow indicating the normal N2 of the reflective surface R2 shown in Figure 2 from a plan view, the normal N2 coincides with the light guide direction D2 in the XY plane. Because the reflective surface R1 is inclined in a different direction than the reflective surface R2, the light guide direction D1 does not coincide with the light guide direction D2. In the XY plane, the angle α between the light guide direction D1 (or normal N1) and the light guide direction D2 (or normal N2) is greater than 0° and less than 180°.
[0050] The arrow indicating the light guide direction D1 points towards sides S1 and S2. In other words, the light reflected by the reflective surface R1 is guided toward sides S1 and S2. The arrow indicating the light guide direction D2 points towards sides S1 and S3. In other words, the light reflected by the reflective surface R2 is guided toward sides S1 and S3.
[0051] In a solar cell apparatus 10 in which solar cells PV1 are arranged along a side surface S1, it is desirable that the angle α is greater than 0° and less than or equal to 90°. Furthermore, it is desirable that the light guide directions D1 and D2 be symmetric with respect to the normal NS1 of the side surface S1.
[0052] In such a solar cell device 10, the liquid crystal optical element 100 is equipped with multiple liquid crystal layers with different light-guiding directions. Therefore, compared to the case where the light-guiding direction is limited to one direction, fluctuations in diffraction efficiency are reduced when the angle of incidence of sunlight changes with time or season. Furthermore, even if the angle of incidence of sunlight changes, the wavelength band used for power generation (e.g., infrared) of sunlight can be stably guided to the solar cell PV1, and fluctuations in the power generation efficiency of the solar cell PV1 can be suppressed.
[0053] Furthermore, in the example shown in Figure 2, right-handed and left-handed circularly polarized light in the wavelength range used for power generation is reflected by the liquid crystal layers 21 and 22, respectively, and guided to the solar cell PV1. This improves the efficiency of light utilization. On the other hand, the selective reflection bands in the liquid crystal layers 21 and 22 contain almost no visible light wavelengths. Therefore, unwanted coloration of the light transmitted through the liquid crystal optical element 100 is suppressed.
[0054] Next, other configuration examples of the solar cell device 10 will be described.
[0055] Figure 6 is another cross-sectional view of the solar cell device 10 shown in Figure 1 along line A and B. The configuration example shown in Figure 6 differs from the configuration example shown in Figure 2 in the configuration of liquid crystal layers 21 and 22. Specifically, the helical pitch P1 of the cholesteric liquid crystal CL1 is different from the helical pitch P2 of the cholesteric liquid crystal CL2. However, the rotation direction of the cholesteric liquid crystal CL1 is different from that of the cholesteric liquid crystal CL2, and the refractive index anisotropy in liquid crystal layer 21 is the same as that in liquid crystal layer 22, as in the configuration example shown in Figure 2.
[0056] In other words, in the configuration example shown in Figure 6, the center wavelength of the first selective reflection band in the liquid crystal layer 21 is different from the center wavelength of the second selective reflection band in the liquid crystal layer 22, and furthermore, the circularly polarized light reflected by the reflective surface R1 is circularly polarized light in the opposite direction to the circularly polarized light reflected by the reflective surface R2. However, the first selective reflection band may not overlap with the second selective reflection band, or it may overlap with a part of the second selective reflection band.
[0057] More specifically, the liquid crystal layer 21 reflects some of the light LTi, specifically light LTr1, toward the transparent substrate 1 at the reflective surface R1, while transmitting the remaining light. The liquid crystal layer 22 reflects some of the light LTi, specifically light LTr2, toward the transparent substrate 1 at the reflective surface R2, while transmitting the remaining light. The central wavelength λ1 of light LTr1 is different from the central wavelength λ2 of light LTr2.
[0058] With this configuration example, the wavelength range used for power generation can be broadened.
[0059] Figure 7 is another cross-sectional view of the solar cell device 10 shown in Figure 1 along line A and B. The configuration example shown in Figure 7 differs from the configuration example shown in Figure 2 in the configuration of liquid crystal layers 21 and 22. Specifically, the helical pitch P1 of the cholesteric liquid crystal CL1 is different from the helical pitch P2 of the cholesteric liquid crystal CL2, and the rotation direction of the cholesteric liquid crystal CL1 is the same as that of the cholesteric liquid crystal CL2. The refractive index anisotropy in liquid crystal layer 21 is the same as that in the configuration example shown in Figure 2.
[0060] In other words, in the configuration example shown in Figure 7, the center wavelength of the first selective reflection band in the liquid crystal layer 21 is different from the center wavelength of the second selective reflection band in the liquid crystal layer 22, and furthermore, the circularly polarized light reflected by the reflective surface R1 is circularly polarized light that rotates in the same direction as the circularly polarized light reflected by the reflective surface R2. However, the first selective reflection band may not overlap with the second selective reflection band, or it may overlap with a part of the second selective reflection band.
[0061] In this configuration example, as in the configuration example shown in Figure 6, the wavelength band used for power generation can be broadened.
[0062] Figure 8 is another plan view of the solar cell device 10. The configuration example shown in Figure 8 differs from the configuration examples shown in Figure 5, etc., in that the solar cell device 10 further includes solar cells PV2 and PV3.
[0063] Solar cell PV1 faces side surface S1, as in the example configuration described above. Solar cell PV2 faces side surface S2 and is bonded to side surface S2 via a transparent adhesive layer. Solar cell PV3 faces side surface S3 and is bonded to side surface S3 via a transparent adhesive layer. Solar cells PV2 and PV3 may be of the same type as solar cell PV1 described above, or they may be of a different type.
[0064] The liquid crystal optical element 100 may include a liquid crystal layer 21 and a liquid crystal layer 22 as described with reference to Figure 2, or a liquid crystal layer 21 and a liquid crystal layer 22 as described with reference to Figure 6, or a liquid crystal layer 21 and a liquid crystal layer 22 as described with reference to Figure 7.
[0065] In the XY plane, the angle α between the light guide direction D1 (or normal N1) and the light guide direction D2 (or normal N2) is greater than 0° and less than 180°. Furthermore, in a solar cell device 10 in which multiple solar cells PV1 to PV3 are arranged, it is desirable that the angle α is greater than 90° and 180° or less.
[0066] In the above description, the solar cell device 10 comprises two liquid crystal layers 21 and 22, but it is not limited to this. The solar cell device 10 may comprise three or more liquid crystal layers. Each of the multiple liquid crystal layers contains cholesteric liquid crystal, and the rotation direction, helical pitch, and refractive index anisotropy of the cholesteric liquid crystal can be freely selected as appropriate according to the desired characteristics.
[0067] Figure 9 is another exploded perspective view of the solar cell device 10. The configuration example shown in Figure 9 differs from the configuration example shown in Figure 1, etc., in that the solar cell device 10 further includes liquid crystal layers 23 and 24 and solar cells PV2 to PV4.
[0068] Liquid crystal layer 21 is laminated on the transparent substrate 1. Liquid crystal layer 22 is laminated on liquid crystal layer 21. Liquid crystal layer 23 is laminated on liquid crystal layer 22. Liquid crystal layer 24 is laminated on liquid crystal layer 23. Both of these liquid crystal layers 23 and 24 have cholesteric liquid crystals, which will be described later.
[0069] Solar cell PV1 faces side surface S1 and is bonded to side surface S1 via a transparent adhesive layer. Solar cell PV2 faces side surface S2 and is bonded to side surface S2 via a transparent adhesive layer. Solar cell PV3 faces side surface S3 and is bonded to side surface S3 via a transparent adhesive layer. Solar cell PV4 faces side surface S4 and is bonded to side surface S4 via a transparent adhesive layer. These solar cells PV2 to PV4 may be of the same type as solar cell PV1 described above, or they may be of a different type than solar cell PV1.
[0070] Figure 10 is a cross-sectional view of the solar cell apparatus 10 shown in Figure 9 along line A and B. Figure 11 is a cross-sectional view of the solar cell device 10 shown in Figure 9 along the CD line.
[0071] The liquid crystal layer 21 has a cholesteric liquid crystal CL1 composed of multiple liquid crystal molecules, as shown schematically in an enlarged view. The cholesteric liquid crystal CL1 has a helical axis AX1 that is substantially parallel to the first direction A1, and also has a helical pitch P1 along the first direction A1. The liquid crystal layer 22 has a cholesteric liquid crystal CL2 composed of multiple liquid crystal molecules, as shown schematically in an enlarged view. The cholesteric liquid crystal CL2 has a helical axis AX2 that is substantially parallel to the first direction A1, and also has a helical pitch P2 along the first direction A1.
[0072] The liquid crystal layer 23 has a cholesteric liquid crystal CL3 composed of multiple liquid crystal molecules, as shown schematically in an enlarged view. The cholesteric liquid crystal CL3 has a helical axis AX3 that is substantially parallel to the first direction A1, and also has a helical pitch P3 along the first direction A1. The liquid crystal layer 24 has a cholesteric liquid crystal CL4 composed of multiple liquid crystal molecules, as shown schematically in an enlarged view. The cholesteric liquid crystal CL4 has a helical axis AX4 substantially parallel to the first direction A1, and also has a helical pitch P4 along the first direction A1.
[0073] The liquid crystal layer 21 has a reflective surface R1 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL1 within the selected reflection band. The liquid crystal layer 22 has a reflective surface R2 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL2 within the selected reflection band. The liquid crystal layer 23 has a reflective surface R3 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL3 within the selected reflection band. The liquid crystal layer 24 has a reflective surface R4 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL4 within the selected reflection band.
[0074] In the example shown in Figure 10, the reflective surface R1 is tilted with respect to the XY plane so as to face the solar cell PV1. Similarly, the reflective surface R4 is tilted with respect to the XY plane so as to face the solar cell PV4. In the YZ cross section, the normal N1 of the reflective surface R1 is shown as a dotted arrow pointing from the liquid crystal layer 21 to the transparent substrate 1, and the normal N4 of the reflective surface R4 is shown as a dotted arrow pointing from the liquid crystal layer 22 to the transparent substrate 1. Normal N1 is not parallel to normal N4.
[0075] In the illustrated example, the rotation direction of cholesteric liquid crystal CL1 is different from that of cholesteric liquid crystal CL4. Also, the helical pitch P1 of cholesteric liquid crystal CL1 is equivalent to the helical pitch P4 of cholesteric liquid crystal CL4.
[0076] In other words, the selective reflection band in liquid crystal layer 21 is equivalent to the selective reflection band in liquid crystal layer 24. Furthermore, the circularly polarized light reflected by reflective surface R1 is circularly polarized light in the opposite direction to that reflected by reflective surface R4.
[0077] In the example shown in Figure 11, the reflective surface R2 is tilted with respect to the XY plane so as to face the solar cell PV2. Similarly, the reflective surface R3 is tilted with respect to the XY plane so as to face the solar cell PV3. In the XZ cross section, the normal N2 of the reflective surface R2 is shown as a dotted arrow pointing from the liquid crystal layer 22 to the transparent substrate 1, and the normal N3 of the reflective surface R3 is shown as a dotted arrow pointing from the liquid crystal layer 23 to the transparent substrate 1. Normal N2 is not parallel to normal N3.
[0078] In the illustrated example, the rotation direction of cholesteric liquid crystal CL2 is different from that of cholesteric liquid crystal CL3. Furthermore, the helical pitch P2 of cholesteric liquid crystal CL2 is equivalent to the helical pitch P3 of cholesteric liquid crystal CL3. Note that the rotation direction of cholesteric liquid crystal CL2 is the same as that of cholesteric liquid crystal CL1. Also, the helical pitch P2 is different from the helical pitch P1.
[0079] In other words, the selective reflection band in liquid crystal layer 22 is equivalent to the selective reflection band in liquid crystal layer 23. Furthermore, the circularly polarized light reflected by reflective surface R2 is circularly polarized light in the opposite direction to that reflected by reflective surface R3. Also, the selective reflection band in liquid crystal layer 22 is different from the selective reflection band in liquid crystal layer 21.
[0080] In the examples shown in Figures 10 and 11, the configuration of the liquid crystal layers 21 to 24 is not limited to the examples described above. For example, the helical pitch P1 may be different from that of the helical pitch P4, the helical pitch P2 may be different from that of the helical pitch P3, the rotation direction of the cholesteric liquid crystal CL1 may be different from that of the cholesteric liquid crystal CL2, and the rotation direction of the cholesteric liquid crystal CL3 may be different from that of the cholesteric liquid crystal CL4.
[0081] As shown in Figure 10, the liquid crystal layer 21 reflects some of the light LTi, LTr1, toward the transparent substrate 1 at the reflective surface R1, and transmits the remaining light. The liquid crystal layer 24 reflects some of the light LTi, LTr4, toward the transparent substrate 1 at the reflective surface R4, and transmits the remaining light. Light LTr1 is left-handed circularly polarized light λ1L with a central wavelength λ1, and is guided toward solar cell PV1 for use in generating electricity. Light LTr4 is right-handed circularly polarized light λ1R with a central wavelength λ1, and is guided toward solar cell PV4 for use in generating electricity.
[0082] As shown in Figure 11, the liquid crystal layer 22 reflects some of the light LTi, specifically light LTr2, toward the transparent substrate 1 at the reflective surface R2, while transmitting the remaining light. The liquid crystal layer 23 reflects some of the light LTi, specifically light LTr3, toward the transparent substrate 1 at the reflective surface R3, while transmitting the remaining light. Light LTr2 is left-handed circularly polarized light λ2L with a central wavelength λ2, guided toward solar cell PV2, and used for power generation by solar cell PV2. Light LTr3 is right-handed circularly polarized light λ2R with a central wavelength λ2, guided toward solar cell PV3, and used for power generation by solar cell PV3. However, the central wavelength λ2 is different from the central wavelength λ1.
[0083] Figure 12 shows an example of the orientation patterns of the liquid crystal molecules LM11 in liquid crystal layer 21 and LM41 in liquid crystal layer 24 shown in Figure 10, and the liquid crystal molecules LM21 in liquid crystal layer 22 and LM31 in liquid crystal layer 23 shown in Figure 11.
[0084] The arrow D1 shown in the liquid crystal layer 21 corresponds to the orthogonal projection of the normal N1 of the reflective surface R1 shown in Figure 10 onto the XY plane, and indicates the direction of light guidance of the light LTr1 reflected by the reflective surface R1. The arrow D2 shown in the liquid crystal layer 22 corresponds to the orthogonal projection of the normal N2 of the reflective surface R2 shown in Figure 11 onto the XY plane, and indicates the direction of light guidance of the light LTr2 reflected by the reflective surface R2. The arrow D3 shown in the liquid crystal layer 23 corresponds to the orthogonal projection of the normal N3 of the reflective surface R3 shown in Figure 11 onto the XY plane, and indicates the direction of light guidance of the light LTr3 reflected by the reflective surface R3. The arrow D4 shown in the liquid crystal layer 24 corresponds to the orthogonal projection of the normal N4 of the reflective surface R4 shown in Figure 10 onto the XY plane, and indicates the direction of light guidance of the light LTr4 reflected by the reflective surface R4.
[0085] Light guide directions D1, D2, D3, and D4 are all different directions from each other.
[0086] In the liquid crystal layer 21, the orientation directions of each liquid crystal molecule LM11 aligned in the light-guiding direction D1 are different from each other. In the illustrated example, focusing on multiple liquid crystal molecules LM11 aligned along the light-guiding direction D1, the orientation direction of each liquid crystal molecule LM11 changes by a constant angle counterclockwise along the arrow indicating the light-guiding direction D1. Furthermore, in the liquid crystal layer 21, the orientation directions of each liquid crystal molecule LM11 aligned in a direction perpendicular to the light-guiding direction D1 are approximately the same.
[0087] In the liquid crystal layer 22, the orientation directions of each liquid crystal molecule LM21 aligned in the light-guiding direction D2 are different from each other. In the illustrated example, focusing on multiple liquid crystal molecules LM21 aligned along the light-guiding direction D2, the orientation direction of each liquid crystal molecule LM21 changes by a constant angle counterclockwise along the arrow indicating the light-guiding direction D2. Furthermore, in the liquid crystal layer 22, the orientation directions of each liquid crystal molecule LM21 aligned in a direction perpendicular to the light-guiding direction D2 are approximately the same.
[0088] In the liquid crystal layer 23, the orientation directions of each liquid crystal molecule LM31 aligned in the light-guiding direction D3 are different from each other. In the illustrated example, focusing on multiple liquid crystal molecules LM31 aligned along the light-guiding direction D3, the orientation direction of each liquid crystal molecule LM31 changes by a constant angle counterclockwise along the arrow indicating the light-guiding direction D3. Furthermore, in the liquid crystal layer 23, the orientation directions of each liquid crystal molecule LM31 aligned in a direction perpendicular to the light-guiding direction D3 are approximately the same.
[0089] In the liquid crystal layer 24, the orientation directions of each liquid crystal molecule LM41 aligned in the light-guiding direction D4 are different from each other. In the illustrated example, focusing on multiple liquid crystal molecules LM41 aligned along the light-guiding direction D4, the orientation direction of each liquid crystal molecule LM41 changes by a constant angle counterclockwise along the arrow indicating the light-guiding direction D4. Furthermore, in the liquid crystal layer 24, the orientation directions of each liquid crystal molecule LM41 aligned in a direction perpendicular to the light-guiding direction D4 are approximately the same.
[0090] Figure 13 is a plan view showing the relationship between the light guide directions D1 to D4.
[0091] The arrow indicating the normal vector N1 of reflective surface R1 coincides with the arrow indicating the light guide direction D1 in the XY plane. The arrow indicating the normal vector N2 of reflective surface R2 coincides with the arrow indicating the light guide direction D2 in the XY plane. The arrow indicating the normal vector N3 of reflective surface R3 coincides with the arrow indicating the light guide direction D3 in the XY plane. The arrow indicating the normal vector N4 of reflective surface R4 coincides with the arrow indicating the light guide direction D4 in the XY plane.
[0092] Reflecting surfaces R1, R2, R3, and R4 are inclined in different directions from each other. Therefore, the light guide directions D1, D2, D3, and D4 are in different directions from each other.
[0093] In the XY plane, the angle between the light guide direction D1 (or normal N1) and the light guide direction D2 (or normal N2) is greater than 0° and less than 180°. The angle between the light guide direction D3 (or normal N3) and the light guide direction D4 (or normal N4) is also greater than 0° and less than 180°. In the illustrated example, the angles between the light guide direction D1 and D2, the angles between the light guide direction D2 and D4, the angles between the light guide direction D3 and D4, and the angles between the light guide direction D1 and D3 are all 90°.
[0094] The arrow indicating the light guide direction D1 points towards the side surface S1. In other words, the light reflected by the reflective surface R1 is guided towards the side surface S1 (or solar cell PV1). The arrow indicating the light guide direction D2 points towards the side surface S2. In other words, the light reflected by the reflective surface R2 is guided towards the side surface S2 (or the solar cell PV2). The arrow indicating the light guide direction D3 points towards the side surface S3. In other words, the light reflected by the reflective surface R3 is guided towards the side surface S3 (or the solar cell PV3). The arrow indicating the light guide direction D4 points towards the side surface S4. In other words, the light reflected by the reflective surface R4 is guided towards the side surface S4 (or the solar cell PV4).
[0095] In this solar cell device 10, solar cells PV1 to PV4 are arranged to surround a liquid crystal optical element 100, and the liquid crystal optical element 100 has multiple liquid crystal layers that guide sunlight toward each of the solar cells PV1 to PV4. Therefore, when the angle of incidence of sunlight changes with time or season, fluctuations in diffraction efficiency are reduced. Furthermore, even if the angle of incidence of sunlight changes, the wavelength band used for power generation (e.g., infrared) of sunlight can be stably guided to the solar cell PV1, and fluctuations in the power generation efficiency of the solar cell PV1 can be suppressed.
[0096] Furthermore, the wavelength range used for power generation can be broadened, and right-handed and left-handed circularly polarized light is guided to solar cells PV1 to PV4. As a result, the efficiency of light utilization is improved. On the other hand, the selective reflection band in the liquid crystal layers 21 to 24 contains almost no visible light wavelengths. Therefore, unwanted coloration of the light transmitted through the liquid crystal optical element 100 is suppressed.
[0097] Such configurations are particularly suitable for solar cell devices mounted on mobile vehicles.
[0098] Figure 14 is another plan view showing the relationship between the light guide directions D1 to D4.
[0099] The configuration example shown in Figure 14 differs from the configuration example shown in Figure 13 in that the light guide directions D1 to D4 are each rotated by 45° in the XY plane.
[0100] The arrow indicating the light guide direction D1 points towards sides S1 and S3. In other words, the light reflected by the reflective surface R1 is guided toward sides S1 and S3. The arrow indicating the light guide direction D2 points towards sides S1 and S2. In other words, the light reflected by the reflective surface R2 is guided toward sides S1 and S2. The arrow indicating the light guide direction D3 points towards sides S3 and S4. In other words, the light reflected by the reflective surface R3 is guided toward sides S3 and S4. The arrow indicating the light guide direction D4 points towards sides S2 and S4. In other words, the light reflected by the reflective surface R4 is guided toward sides S2 and S4.
[0101] Even in this configuration example, the same effects as the configuration example described with reference to Figure 13 can be obtained.
[0102] Figure 15 is another exploded perspective view of the solar cell device 10. The configuration example shown in Figure 15 differs from the configuration example shown in Figure 1, etc., in that the solar cell device 10 further includes liquid crystal layers 23 and 24, solar cells PV2 and PV3, and a protective substrate 5.
[0103] Liquid crystal layer 21 is laminated on the transparent substrate 1. Liquid crystal layer 22 is laminated on liquid crystal layer 21. Liquid crystal layer 23 is located on the opposite side of the transparent substrate 1 from liquid crystal layer 21. Liquid crystal layer 24 is laminated on liquid crystal layer 23. These liquid crystal layers 21 to 24 all have cholesteric liquid crystals CL1 to CL4, similar to the configuration example shown in Figure 10, etc.
[0104] The protective substrate 5 is a transparent substrate, made of glass or synthetic resin. The protective substrate 5 faces the liquid crystal layer 23 in the first direction A1. That is, the liquid crystal layers 23 and 24 are positioned between the transparent substrate 1 and the protective substrate 5. The liquid crystal layers 23 and 24 face the side into which sunlight is incident. The protective substrate 5 protects these liquid crystal layers 23 and 24. Such a transparent protective substrate 5 functions as a light guide plate that propagates light reflected from each reflective surface, similar to the transparent substrate 1.
[0105] The protective substrate 5 has sides S5, S6, S7, and S8. Sides S5 and S8 are planes substantially parallel to the XZ plane and face each other in the second direction A2. Sides S6 and S7 are planes substantially parallel to the YZ plane and face each other in the third direction A3.
[0106] In the example shown in Figure 15, side surface S5 overlaps with side surface S1 in the first direction A1. Side surface S6 overlaps with side surface S2 in the first direction A1. Side surface S7 overlaps with side surface S3 in the first direction A1. Side surface S8 overlaps with side surface S4 in the first direction A1.
[0107] Solar cell PV1 faces sides S1 and S5 and is bonded to sides S1 and S5 via a transparent adhesive layer. Solar cell PV2 faces sides S2 and S6 and is bonded to sides S2 and S6 via a transparent adhesive layer. Solar cell PV3 faces sides S3 and S7 and is bonded to sides S3 and S7 via a transparent adhesive layer. Solar cells PV2 and PV3 may be of the same type as solar cell PV1 described above, or they may be of a different type.
[0108] Figure 16 is a cross-sectional view of the solar cell device 10 shown in Figure 15 along line A and B. Figure 17 is a cross-sectional view of the solar cell device 10 shown in Figure 15 along the CD line.
[0109] The liquid crystal layer 21 is positioned in contact with the main surface F2. The liquid crystal layer 22 is laminated on the liquid crystal layer 21. The liquid crystal layer 24 is positioned in contact with the main surface F1. The liquid crystal layer 23 is laminated on the liquid crystal layer 24. The protective substrate 5 is positioned in contact with the liquid crystal layer 23.
[0110] The liquid crystal layer 21 has a reflective surface R1 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL1 within the selected reflection band. The liquid crystal layer 22 has a reflective surface R2 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL2 within the selected reflection band. The liquid crystal layer 23 has a reflective surface R3 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL3 within the selected reflection band. The liquid crystal layer 24 has a reflective surface R4 that reflects circularly polarized light corresponding to the rotational direction of the cholesteric liquid crystal CL4 within the selected reflection band.
[0111] For example, each of the reflective surfaces R1 and R3 is tilted with respect to the XY plane so as to face solar cells PV1 and PV2. Each of the reflective surfaces R2 and R4 is tilted with respect to the XY plane so as to face solar cells PV1 and PV3.
[0112] Liquid crystal layer 21 reflects a portion of the light LTi, light LTr1, toward the transparent substrate 1 at its reflective surface R1, while transmitting the remaining light. Liquid crystal layer 22 reflects a portion of the light LTi, light LTr2, toward the transparent substrate 1 at its reflective surface R2, while transmitting the remaining light. Liquid crystal layer 23 reflects a portion of the light LTi, light LTr3, toward the protective substrate 5 at its reflective surface R3, while transmitting the remaining light. Liquid crystal layer 24 reflects a portion of the light LTi, light LTr4, toward the protective substrate 5 at its reflective surface R4, while transmitting the remaining light.
[0113] Optical light LTr1, optical light LTr2, optical light LTr3, and optical light LTr4 are guided toward each side surface S1 to S3 while repeatedly reflecting at the interface between the protective substrate 5 and the air, and at the interface between the liquid crystal layer 22 and the air.
[0114] Light LTr1 is left-handed circularly polarized light λ1L with a central wavelength λ1, which is guided toward solar cells PV1 and PV2 and used for power generation by solar cells PV1 and PV2. Light LTr2 is left-handed circularly polarized light λ2L with a central wavelength λ2, which is guided toward solar cells PV1 and PV3 and used for power generation by solar cells PV1 and PV3.
[0115] Light LTr3 is a right-handed circularly polarized light λ2R with a central wavelength λ2, which is guided toward solar cells PV1 and PV2 and used for power generation by solar cells PV1 and PV2. Light LTr4 is a right-handed circularly polarized light λ1R with a central wavelength λ1, which is guided toward solar cells PV1 and PV3 and used for power generation by solar cells PV1 and PV3. However, the central wavelength λ2 is different from the central wavelength λ1.
[0116] Figure 18 is a plan view showing the relationship between the light guide directions D1 to D4.
[0117] The arrow indicating the normal vector N1 of reflective surface R1 in Figure 16 coincides with the arrow indicating the light guide direction D1 in the XY plane. The arrow indicating the normal vector N2 of reflective surface R2 coincides with the arrow indicating the light guide direction D2 in the XY plane. The arrow indicating the normal vector N3 of reflective surface R3 coincides with the arrow indicating the light guide direction D3 in the XY plane. The arrow indicating the normal vector N4 of reflective surface R4 coincides with the arrow indicating the light guide direction D4 in the XY plane.
[0118] In one example, reflective surfaces R1 and R2 are inclined in different directions, but reflective surfaces R1 and R3 are parallel to each other, and reflective surfaces R2 and R4 are parallel to each other. Therefore, light guide directions D1 and D3 are parallel to each other, and light guide directions D2 and D4 are parallel to each other.
[0119] In the XY plane, the angle α between the light guide direction D1 (or normal N1) and the light guide direction D2 (or normal N2) is greater than 0° and less than 180°. The angle between the light guide direction D3 (or normal N3) and the light guide direction D4 (or normal N4) is also greater than 0° and less than 180°.
[0120] The arrows indicating light guidance directions D1 and D3 point toward sides S1 and S2. In other words, the light reflected by reflective surfaces R1 and R3 is guided toward sides S1 and S2 (or solar cells PV1 and PV2).
[0121] The arrows indicating light guidance directions D2 and D4 point toward sides S1 and S3. In other words, the light reflected by reflective surfaces R2 and R4 is guided toward sides S1 and S3 (or solar cells PV1 and PV3). With such a solar cell device 10, as in the above-described configuration example, fluctuations in diffraction efficiency can be reduced, and fluctuations in power generation efficiency can be suppressed.
[0122] Furthermore, while liquid crystal layers 21 and 22 are arranged on the back side of the transparent substrate 1, liquid crystal layers 23 and 24 are also arranged on the front side (the side where sunlight enters) of the transparent substrate 1. The liquid crystal layers 23 and 24 are covered by the protective substrate 5. Thus, the liquid crystal layers 23 and 24 are protected.
[0123] The above describes several configuration examples, but these configuration examples can be combined as appropriate.
[0124] Next, the alignment film 3 that can be interposed between the transparent substrate 1 and the liquid crystal layer, and between the stacked liquid crystal layers, will be explained with reference to Figure 19.
[0125] This section describes the alignment film 3 interposed between the transparent substrate 1 and the liquid crystal layer 21, and the alignment film 3 interposed between the liquid crystal layer 21 and the liquid crystal layer 22. The alignment film 3 is formed of, for example, polyimide. The alignment film 3 is subjected to a predetermined alignment treatment. In one example, the alignment treatment is photo-alignment treatment by two-beam interference exposure using a first circularly polarized ray and a second circularly polarized ray that rotates in the opposite direction to the first circularly polarized ray. The wavelengths of the first and second circularly polarized rays are, for example, ultraviolet light, but are not limited to this.
[0126] By exposing the alignment film 3 to interference patterns of first and second circular polarizations, a spatially varying polarization pattern is recorded as the orientation processing direction. This imparts an orientation restricting force to the alignment film 3 along the orientation processing direction.
[0127] Subsequently, by coating the alignment film 3 with a liquid crystal material, the liquid crystal molecules contained in the liquid crystal material are aligned in a predetermined direction by the alignment-regulating force of the alignment film 3, forming an alignment pattern as shown in Figure 4, etc.
[0128] Such an orientation film 3 can be applied to each of the above-described configuration examples.
[0129] Next, a structure 4 having irregularities that can be interposed between the transparent substrate 1 and the liquid crystal layer, and between the stacked liquid crystal layers, will be described with reference to Figure 20.
[0130] This section describes the structures 4 interposed between the transparent substrate 1 and the liquid crystal layer 21, and the structures 4 interposed between the liquid crystal layer 21 and the liquid crystal layer 22. The structures 4 are formed from, for example, an organic material. Nanoimprint lithography is applied as one example of a method for forming the structures 4 with irregularities. In one example, an organic material is applied to the transparent substrate 1, a mold is pressed onto it, and the organic material is cured by heating or light irradiation. As a result, the minute irregularity pattern formed on the mold is transferred to the organic material, and the structures 4 are formed.
[0131] Subsequently, by applying a liquid crystal material onto the structure 4, the liquid crystal molecules contained in the liquid crystal material align along the uneven pattern of the structure 4, forming an orientation pattern as shown in Figure 4, etc.
[0132] Such a structure 4 can be applied to each of the configuration examples described above.
[0133] In addition to using the alignment film 3 and structure 4 described here, other methods may include transferring a separately formed liquid crystal layer onto the transparent substrate 1 or onto a previously formed liquid crystal layer.
[0134] In this embodiment, for example, the main surface F1 of the transparent substrate 1 corresponds to the first main surface, the main surface F2 corresponds to the second main surface, the side surface S1 corresponds to the first side surface, the side surface S2 corresponds to the second side surface, the side surface S3 corresponds to the third side surface, and the side surface S4 corresponds to the fourth side surface. Furthermore, liquid crystal layer 21 corresponds to the first liquid crystal layer, liquid crystal layer 22 corresponds to the second liquid crystal layer, liquid crystal layer 23 corresponds to the third liquid crystal layer, liquid crystal layer 24 corresponds to the fourth liquid crystal layer, cholesteric liquid crystal CL1 corresponds to the first cholesteric liquid crystal, cholesteric liquid crystal CL2 corresponds to the second cholesteric liquid crystal, cholesteric liquid crystal CL3 corresponds to the third cholesteric liquid crystal, cholesteric liquid crystal CL4 corresponds to the fourth cholesteric liquid crystal, reflective surface R1 corresponds to the first reflective surface, reflective surface R2 corresponds to the second reflective surface, reflective surface R3 corresponds to the third reflective surface, and reflective surface R4 corresponds to the fourth reflective surface. Furthermore, solar cell PV1 corresponds to the first solar cell, solar cell PV2 corresponds to the second solar cell, solar cell PV3 corresponds to the third solar cell, and solar cell PV4 corresponds to the fourth solar cell. Furthermore, side S5 of the protective substrate 5 corresponds to the fifth side, side S6 corresponds to the sixth side, side S7 corresponds to the seventh side, and side S8 corresponds to the eighth side.
[0135] As described above, this embodiment provides a solar cell device that can suppress fluctuations in power generation efficiency.
[0136] Although several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]
[0137] 10…Solar cell device PV1~PV4…Solar cell 100...Liquid crystal optical elements 1...Transparent substrate F1~F2...Main surface S1~S4...Side surface 21-24…Liquid crystal layer CL1-CL4…Cholesteric liquid crystal P1-P4…Spiral pitch R1~R4...Reflecting surface N1~N4...Normal line D1~D4...Light guide direction 3…Alignment film 4…Structure 5…Protective board S5~S8…Side
Claims
1. A transparent substrate having a first main surface, a second main surface opposite the first main surface, a first side surface, a second side surface intersecting the first side surface, a third side surface opposite the second side surface, and a fourth side surface opposite the first side surface. A first liquid crystal layer having a first cholesteric liquid crystal is laminated on the second main surface side of the transparent substrate, A second liquid crystal layer is laminated on the first liquid crystal layer and has a second cholesteric liquid crystal, A first solar cell facing the first side surface, A second solar cell facing the second side surface, A third solar cell facing the third side, A third liquid crystal layer having a third cholesteric liquid crystal is laminated on the first main surface side of the transparent substrate, A transparent protective substrate facing the third liquid crystal layer, Equipped with, The first liquid crystal layer has a first reflective surface that is inclined with respect to the second main surface, The second liquid crystal layer has a second reflective surface that is inclined with respect to the second main surface, In a plan view, the angle between the normal of the first reflective surface and the normal of the second reflective surface is greater than 0° and less than 180°. The protective substrate has a fifth side surface superimposed on the first side surface, a sixth side surface superimposed on the second side surface, and a seventh side surface superimposed on the third side surface. The first solar cell faces the fifth side, The second solar cell faces the sixth side, The third solar cell is a solar cell device facing the seventh side surface.
2. The rotation direction of the first cholesteric liquid crystal is different from the rotation direction of the second cholesteric liquid crystal. The solar cell apparatus according to claim 1, wherein the helical pitch of the first cholesteric liquid crystal is equivalent to the helical pitch of the second cholesteric liquid crystal.
3. The rotation direction of the first cholesteric liquid crystal is different from the rotation direction of the second cholesteric liquid crystal. The solar cell apparatus according to claim 1, wherein the helical pitch of the first cholesteric liquid crystal is different from the helical pitch of the second cholesteric liquid crystal.
4. The rotation direction of the first cholesteric liquid crystal is the same as the rotation direction of the second cholesteric liquid crystal. The solar cell apparatus according to claim 1, wherein the helical pitch of the first cholesteric liquid crystal is different from the helical pitch of the second cholesteric liquid crystal.
5. Furthermore, the solar cell apparatus according to claim 1, comprising an alignment film interposed between the first liquid crystal layer and the second liquid crystal layer.
6. Furthermore, the solar cell apparatus according to claim 1, comprising a structure having irregularities interposed between the first liquid crystal layer and the second liquid crystal layer.