Solar cell device

Abstract

To provide a solar cell device that can reduce loss in guiding light.SOLUTION: According to an embodiment, a solar cell device comprises: a transparent substrate that has a first principal surface and a second principal surface opposite to the first principal surface; a liquid crystal layer that is arranged on the second principal surface of the transparent substrate, and has cholesteric liquid crystals including a plurality of liquid crystal molecules; and a plurality of solar batteries that are arranged on at least one of the first principal surface and the second principal surface of the transparent substrate, are respectively formed in a strip shape, and are arranged side by side at a predetermined interval.SELECTED DRAWING: Figure 1

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. In such a liquid crystal polarization grating, from the viewpoint of obtaining desired reflection performance, adjustment of various parameters such as the grating period T, 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 of the liquid crystal layer), and the thickness d of the liquid crystal layer is necessary.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the embodiment is to provide a solar cell device capable of suppressing loss when guiding light.

Means for Solving the Problems

[0005] According to one embodiment, a solar cell device includes a transparent substrate having a first main surface and a second main surface facing the first main surface, a liquid crystal layer disposed on the second main surface side of the transparent substrate and having a cholesteric liquid crystal containing a plurality of liquid crystal molecules, and a plurality of solar cells disposed on at least one of the first main surface side and the second main surface side of the transparent substrate, each formed in a strip shape and arranged at a predetermined interval.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is a perspective view showing an example of a solar cell device 10. [Figure 2] Figure 2 is a schematic cross-sectional view showing the liquid crystal optical element 100. [Figure 3] Figure 3 is a diagram illustrating an example of a cholesteric liquid crystal 31 contained in the liquid crystal layer 3. [Figure 4] Figure 4 is a schematic plan view showing the liquid crystal optical element 100. [Figure 5] Figure 5 is a diagram illustrating the spacing G of the solar cell PVs shown in Figure 1. [Figure 6] Figure 6 is a diagram illustrating the range of spacing G between solar cell photovoltaic displays (PVs) from another perspective. [Figure 7] Figure 7 is a perspective view showing another example of the solar cell device 10. [Figure 8] Figure 8 is a diagram illustrating the spacing G of the solar cell PVs shown in Figure 7. [Figure 9] Figure 9 is a perspective view showing another example of the solar cell device 10. [Figure 10] Figure 10 is a schematic cross-sectional view showing a modified example of the liquid crystal optical element 100. [Figure 11] Figure 11 shows an example of the orientation pattern of liquid crystal molecules contained in the liquid crystal layer 3 shown in Figure 10. [Figure 12] Figure 12 is a schematic cross-sectional view showing another modified example of the liquid crystal optical element 100. [Figure 13] Figure 13 shows an example of the orientation pattern of liquid crystal molecules contained in the liquid crystal layer 3 shown in Figure 12. [Figure 14] Figure 14 shows variations of the solar cell device 10. [Figure 15] Figure 15 shows variations of the solar cell device 10. [Figure 16] Figure 16 shows variations of the solar cell device 10. [Figure 17] Figure 17 shows variations of the solar cell device 10. [Figure 18] Figure 18 shows variations of the solar cell device 10. [Figure 19]FIG. 19 is a diagram showing variations of the liquid crystal optical element 100. [Figure 20] FIG. 20 is a diagram showing variations of the liquid crystal optical element 100. [Figure 21] FIG. 21 is a diagram showing variations of the liquid crystal optical element 100. [Figure 22] FIG. 22 is a diagram showing variations of the liquid crystal optical element 100. [Figure 23] FIG. 23 is a diagram showing an installation example of the liquid crystal optical element 100 on the solar cell PV. [Figure 24] FIG. 24 is a diagram showing another installation example of the liquid crystal optical element 100 on the solar cell PV.

Embodiments 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 for those that can be easily conceived by those skilled in the art with appropriate modifications while maintaining the gist of the invention, they are naturally included in the scope of the present invention. Also, 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. Further, in this specification and each figure, components that exhibit the same or similar functions as those described above with respect to the previously presented figures may be assigned the same reference numerals, and detailed descriptions that are repeated may be omitted as appropriate.

[0008] Note that in the drawings, for ease of understanding as necessary, the X-axis, Y-axis, and Z-axis that are perpendicular 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.

[0009] FIG. 1 is a perspective view showing an example of the solar cell device 10. The solar cell device 10 includes a liquid crystal optical element 100 and a plurality of solar cells PV. The liquid crystal optical element 100 includes a transparent substrate 1 and a liquid crystal layer 3. Although not shown in FIG. 1, the liquid crystal optical element 100 may include an alignment film interposed between the transparent substrate 1 and the liquid crystal layer 3. Further, the liquid crystal optical element 100 may include an adhesive layer between the liquid crystal layer 3 and the solar cell PV.

[0010] The transparent substrate 1 is formed of, for example, a transparent glass plate or a transparent synthetic resin plate. The transparent substrate 1 may be formed of, for example, a flexible transparent synthetic resin plate. The transparent substrate 1 can take any shape. For example, the transparent substrate 1 may be curved.

[0011] In this specification, "light" includes visible light and invisible light. For example, the lower limit wavelength of the visible light region is 360 nm or more and 400 nm or less, and the upper limit wavelength of the visible light region 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" is preferably colorless and transparent. However, "transparent" may be translucent or colored and transparent.

[0012] The transparent substrate 1 is formed in a flat plate shape along the X-Y plane and has a first main surface F1 and a second main surface F2. The first main surface F1 and the second main surface F2 are surfaces substantially parallel to the X-Y plane and face each other in a first direction A1.

[0013] The liquid crystal layer 3 is disposed on the side of the second main surface F2 of the transparent substrate 1. Details of the liquid crystal layer 3 will be described later.

[0014] Multiple solar cell PVs are arranged on at least one side of the transparent substrate 1, either the side of the first main surface F1 or the side of the transparent substrate 1, either of the first main surface F2 or the second main surface F2. Each of the multiple solar cell PVs is formed in a strip shape and arranged at predetermined intervals. In the illustrated example, each solar cell PV extends in a third direction A3 and is arranged along the second direction A2 at a constant interval G. That is, the second direction A2 corresponds to the short side direction of the solar cell PV, and the third direction A3 corresponds to the long side direction of the solar cell PV. In this example, the width W along the short side direction of the solar cell PV is equal to or less than the interval G.

[0015] The illustrated example corresponds to a case where multiple solar cell PVs are arranged on the second main surface F2 side of the transparent substrate 1. Each solar cell PV is positioned in contact with the liquid crystal layer 3. In other words, the solar cell PVs face the transparent substrate 1 with the liquid crystal layer 3 in between. As a method for providing the solar cell PVs on the liquid crystal optical element 100, separately manufactured solar cell PVs may be bonded to the liquid crystal layer 3, or the solar cell PVs may be directly formed on the liquid crystal layer 3 by applying a material to the surface of the liquid crystal layer 3.

[0016] Examples of photovoltaic (PV) solar cells 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 exhibit light transmittance depending on the materials used.

[0017] Figure 2 is a schematic cross-sectional view of the liquid crystal optical element 100. Note that the solar cell PV shown in Figure 1 has been omitted.

[0018] The liquid crystal layer 3 has a cholesteric liquid crystal 31, as shown schematically in an enlarged view. The cholesteric liquid crystal 31 has a helical axis AX that is substantially parallel to the first direction A1, and also has a helical pitch P along the first direction A1. The helical pitch P represents one period of the helix (the layer thickness along the helical axis AX required for the liquid crystal molecules to rotate 360 ​​degrees).

[0019] Such a liquid crystal layer 3 reflects circularly polarized light in a selective reflection band determined according to the helical pitch P and refractive index anisotropy Δn from the light LTi incident through the transparent substrate 1. In this specification, "reflection" in the liquid crystal layer 3 is accompanied by diffraction within the liquid crystal layer 3.

[0020] In the liquid crystal layer 3, the cholesteric liquid crystal 31 has a reflective surface 32 that reflects circularly polarized light corresponding to the rotation direction of the cholesteric liquid crystal 31 within the selected reflection band. In this specification, the circularly polarized light may be strictly circularly polarized light or circularly polarized light that approximates elliptical polarization.

[0021] Next, the optical function of the liquid crystal optical element 100 will be explained.

[0022] The illustrated example describes the case where the liquid crystal layer 3 reflects at least a portion of the light LTi incident from the side of the transparent substrate 1 back towards the transparent substrate 1.

[0023] The light LTi incident on the liquid crystal optical element 100 includes, for example, visible light, ultraviolet light, and infrared light. For the sake of clarity, we will assume that the optical LTi is incident on the transparent substrate 1 approximately perpendicularly. The incident angle of the optical LTi on the transparent substrate 1 is not particularly limited.

[0024] Light LTi enters the interior of the transparent substrate 1 from the first main surface F1, exits from the second main surface F2, and enters the liquid crystal layer 3. The liquid crystal layer 3 then reflects a portion of the light LTi towards the transparent substrate 1 at the reflective surface 32, while transmitting the remaining light. The reflected light LTr is circularly polarized light with wavelength λ. For example, wavelength λ is in the infrared wavelength band. The light LTr that has passed through the liquid crystal layer 3 includes, for example, visible light V.

[0025] The angle θa at which the light LTr reflected by the liquid crystal layer 3 enters the transparent substrate 1 is set to satisfy the optical waveguide conditions in the transparent substrate 1. Here, the angle θa corresponds to an angle greater than or equal to the critical angle at which total internal reflection occurs at the interface between the transparent substrate 1 and the air. The angle θa represents the angle with respect to a perpendicular line perpendicular to the first main surface F1 of the transparent substrate 1.

[0026] If the transparent substrate 1 and the liquid crystal layer 3 have equivalent refractive indices, these laminates can function as a single optical waveguide. In this case, the optical light LTr is guided by repeated reflections at the interface between the transparent substrate 1 and the air, and at the interface between the liquid crystal layer 3 and the air.

[0027] Figure 3 is a diagram illustrating an example of a cholesteric liquid crystal 31 contained in the liquid crystal layer 3. In Figure 3, the liquid crystal layer 3 is 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 31, among multiple 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 multiple liquid crystal molecules located in the same plane.

[0028] Focusing on one cholesteric liquid crystal 31 enclosed by a dotted line, the cholesteric liquid crystal 31 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 on one end of the cholesteric liquid crystal 31 and liquid crystal molecules LM12 on the other end of the cholesteric liquid crystal 31. The liquid crystal molecules LM11 are in close proximity to the transparent substrate 1.

[0029] In the liquid crystal layer 3, the orientation directions of adjacent cholesteric liquid crystals 31 along the second direction A2 are different from each other. Furthermore, the spatial phases of adjacent cholesteric liquid crystals 31 along the second direction A2 are different from each other. The orientation directions of adjacent liquid crystal molecules LM11 along the second direction A2 are different from each other. The orientation directions of multiple liquid crystal molecules LM11 change continuously along the second direction A2. The orientation directions of adjacent liquid crystal molecules LM12 along the second direction A2 are also different from each other. The orientation directions of multiple liquid crystal molecules LM12 also change continuously along the second direction A2.

[0030] The reflective surface 32 of the liquid crystal layer 3, shown by the dashed line in the figure, is inclined with respect to the XY plane. The angle between the reflective surface 32 and the XY plane is called the inclination angle θ of the reflective surface 32. The inclination angle θ is acute. The reflective surface 32 corresponds to a surface where the orientation directions of the liquid crystal molecules LM1 are aligned, or a surface where the spatial phases are aligned (equal phase surface).

[0031] In this type of liquid crystal layer 3, the orientation direction of the liquid crystal molecules LM1 is fixed during curing. In other words, the orientation direction of the liquid crystal molecules LM1 is not controlled in response to the electric field. For this reason, the liquid crystal optical element 100 does not have electrodes to form an electric field in the liquid crystal layer 3.

[0032] 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).

[0033] Figure 4 is a schematic plan view showing the liquid crystal optical element 100. Figure 4 shows an example of the spatial phase of the cholesteric liquid crystal 31. The spatial phase shown here represents the orientation direction of the liquid crystal molecules LM11 located near the transparent substrate 1, among the liquid crystal molecules LM1 contained in the cholesteric liquid crystal 31.

[0034] For each of the cholesteric liquid crystals 31 aligned along the second direction A2, the orientation direction of the liquid crystal molecules LM11 is different from that of the others. In other words, the spatial phase of the cholesteric liquid crystals 31 differs along the second direction A2. Here, the second direction A2 corresponds to the short side direction of the solar cell PV, as explained with reference to Figure 1.

[0035] On the other hand, for each of the cholesteric liquid crystals 31 aligned along the third direction A3, the orientation direction of the liquid crystal molecules LM11 is approximately the same. In other words, the spatial phases of the cholesteric liquid crystals 31 are approximately the same in the third direction A3. Here, the third direction A3 corresponds to the direction of the long side of the solar cell PV, as explained with reference to Figure 1.

[0036] In particular, focusing on the cholesteric liquid crystals 31 aligned in the second direction A2, the orientation direction of each liquid crystal molecule LM11 differs by a certain angle. That is, the orientation direction of multiple liquid crystal molecules LM11 aligned along the second direction A2 changes linearly. Therefore, the spatial phase of the cholesteric liquid crystals 31 aligned along the second direction A2 changes linearly along the second direction A2. As a result, a reflective surface 32 tilted with respect to the XY plane is formed, as shown in the liquid crystal layer 3 in Figure 3. "Linear change" here means, for example, that the amount of change in the orientation direction of the liquid crystal molecules LM11 can be expressed as a linear function. Note that the orientation direction of the liquid crystal molecules LM11 here corresponds to the long axis direction of the liquid crystal molecules LM11 in the XY plane.

[0037] Here, within a single plane, the period T is defined as the distance between two liquid crystal molecules LM11 when their orientation direction changes by 180 degrees along the second direction A2. In Figure 4, DP indicates the rotational direction of the liquid crystal molecules LM11. The tilt angle θ of the reflective surface 32 shown in Figure 3 is appropriately set by the period T and the helical pitch P.

[0038] Here, assuming that the solar cell PV is arranged on the second main surface F2 side of the transparent substrate 1, a preferred range for the spacing G of the solar cell PV will be explained with reference to Figure 5.

[0039] Here, the light LTi is assumed to be incident along the normal N of the transparent substrate 1, and the light transmitted through the liquid crystal optical element 100 is not shown or explained. The diffraction angle α of the light LTr reflected by the reflective surface 32 of the liquid crystal layer 3 is expressed by equation (1) in the figure, based on the wavelength λ of the light LTr and the period T of the cholesteric liquid crystal 31.

[0040] When light LTr reflected by the reflective surface 32 is reflected at the first interface between the transparent substrate 1 and the air, and then further reflected at the second interface between the liquid crystal layer 3 and the air, the distance from the reflection position at the reflective surface 32 to the reflection position at the second interface is expressed as the total reflection distance L. The total reflection distance L is expressed by equation (2) in the figure, based on the total thickness d of the transparent substrate 1 and the liquid crystal layer 3, and the diffraction angle α.

[0041] As shown in equation (3) in the figure, it is desirable that the spacing G between the solar cell PVs be smaller than the total reflection distance L. This reduces the light guide distance of the light LTr that is guided from the reflective surface 32 to the solar cell PV, or the number of reflections within the liquid crystal optical element 100. As a result, problems such as scattering of light LTr due to foreign matter or minute cracks adhering to the transparent substrate 1 and liquid crystal layer 3, or leakage of light LTr to the outside of the liquid crystal optical element 100 are suppressed. Consequently, losses when guiding light from the liquid crystal optical element 100 to the solar cell PV are suppressed, and the decrease in power generation efficiency is suppressed.

[0042] Furthermore, if the solar cell PV is opaque, from the viewpoint of improving the transmittance of the liquid crystal optical element 100, it is desirable for the width W of the solar cell PV to be small, and for the spacing G to be small.

[0043] Photovoltaic (PV) solar cells generate electricity by receiving, for example, invisible light, especially infrared light. For this reason, it is desirable to set the spacing G by setting the wavelength λ of the optical LTr to 700 nm.

[0044] Figure 6 is a diagram illustrating the range of spacing G between solar cell photovoltaic displays (PVs) from another perspective. The example shown in Figure 5 assumed that light LTi of wavelength λ is reflected at the reflective surface 32 in only one direction (the direction to the right in the figure), but the example shown in Figure 6 assumes that in addition to being reflected at the reflective surface 32 in one direction (the direction to the right in the figure), a portion of the light LTi is diffracted in another direction (the direction to the left in the figure).

[0045] For example, when light LTd diffracted by the reflective surface 32 is reflected at the first interface between the transparent substrate 1 and the air, and then further reflected at the second interface between the liquid crystal layer 3 and the air, the distance from the diffraction position at the reflective surface 32 to the reflection position at the second interface is approximately equal to the total reflection distance L explained with reference to Figure 5. The total reflection distance L is expressed by equation (2) in the figure, based on the total thickness d of the transparent substrate 1 and the liquid crystal layer 3, and the diffraction angle α. As shown in equation (4) in the figure, it is desirable that the spacing G between solar cell PVs is less than twice the total reflected distance L.

[0046] Figure 7 is a perspective view showing another example of the solar cell device 10. The example shown in Figure 7 differs from the example shown in Figure 1 in that multiple solar cell PVs are arranged on the side of the first main surface F1 of the transparent substrate 1. Each solar cell PV is positioned in contact with the transparent substrate 1. As a method for providing the solar cell PVs on the liquid crystal optical element 100, separately manufactured solar cell PVs may be bonded to the liquid crystal layer 3, or the solar cell PVs may be directly formed on the liquid crystal layer 3 by applying a material to the surface of the liquid crystal layer 3.

[0047] Multiple solar cell photovoltaic (PV) cells are formed in a strip shape and arranged at predetermined intervals. In the illustrated example, each solar cell PV extends in the third direction A3 and is arranged along the second direction A2 at a constant interval G. In other words, the second direction A2 corresponds to the short side direction of the solar cell PV, and the third direction A3 corresponds to the long side direction of the solar cell PV.

[0048] Here, assuming that the solar cell PV is arranged on the first main surface F1 side of the transparent substrate 1, a preferred range for the spacing G of the solar cell PV will be explained with reference to Figure 8.

[0049] Here, the light LTi is assumed to be incident along the normal N of the transparent substrate 1, and the light transmitted through the liquid crystal optical element 100 is not shown or explained. The diffraction angle α of the light LTr reflected by the reflective surface 32 of the liquid crystal layer 3 is expressed by equation (1) as explained with reference to Figure 5. The total reflection distance L is expressed by equation (2) as explained with reference to Figure 5.

[0050] In this case, as shown in equation (5) in the figure, it is desirable that the spacing G between the solar cell PVs be less than half of the total reflection distance L. This reduces the light guide distance of the light LTr that is guided from the reflective surface 32 to the solar cell PV, or the number of reflections within the liquid crystal optical element 100. As a result, similar to the example above, the loss when guiding light from the liquid crystal optical element 100 to the solar cell PV is suppressed, and the decrease in power generation efficiency is suppressed.

[0051] Figure 9 is a perspective view showing another example of the solar cell device 10. The example shown in Figure 9 differs from the example shown in Figure 1 in that multiple solar cell PVs are arranged on the side of the first main surface F1 and the side of the second main surface F2 of the transparent substrate 1, respectively.

[0052] On the first main surface F1, each solar cell PV is positioned in contact with the transparent substrate 1. On the second main surface F2, each solar cell PV is positioned in contact with the liquid crystal layer 3, and faces the transparent substrate 1 across the liquid crystal layer 3.

[0053] Multiple solar cell PVs are formed in a strip shape and arranged at predetermined intervals. In the illustrated example, each solar cell PV extends in the third direction A3. Multiple solar cell PVs located on the side of the first main surface F1 are arranged along the second direction A2 at a constant interval G1. Multiple solar cell PVs located on the side of the second main surface F2 are arranged along the second direction A2 at a constant interval G2. It is desirable that the interval G1 be set based on equation (5) explained with reference to Figure 8. It is also desirable that the interval G2 be set based on equation (3) explained with reference to Figure 5 or equation (4) explained with reference to Figure 6. For this reason, the interval G1 is smaller than the interval G2 (G1 <G2)。

[0054] Next, a modified example of the liquid crystal optical element 100 will be described.

[0055] Figure 10 is a schematic cross-sectional view showing a modified example of the liquid crystal optical element 100. The solar cell PV is shown by a dotted line in the figure. The liquid crystal layer 3 has a first layer 3A and a second layer 3B. The first layer 3A is located between the transparent substrate 1 and the second layer 3B. Although not shown, the liquid crystal optical element 100 may include an alignment film interposed between the transparent substrate 1 and the liquid crystal layer 3.

[0056] The first layer 3A and the second layer 3B each have cholesteric liquid crystals 31A and 31B, respectively, as shown schematically in an enlarged view. The cholesteric liquid crystal 31A has a helical axis AXA substantially parallel to the first direction A1, and a helical pitch PA along the first direction A1. The cholesteric liquid crystal 31B has a helical axis AXB substantially parallel to the first direction A1, and a helical pitch PB along the first direction A1. The helical axis AXA is parallel to the helical axis AXB. The helical pitch PA is the same as the helical pitch PB, but may be different from the helical pitch PB. The rotation direction of the cholesteric liquid crystal 31A is opposite to the rotation direction of the cholesteric liquid crystal 31B.

[0057] The tilt direction of the reflective surface 32A of the first layer 3A is different from the tilt direction of the reflective surface 32B of the second layer 3B. Reflective surface 32A is tilted to reflect the incident light LTi toward the right side of the figure. Reflective surface 32B is tilted to reflect the incident light LTi toward the left side of the figure.

[0058] The diffraction angle αA of light LTrA reflected from the reflective surface 32A is the same as the diffraction angle αB of light LTrB reflected from the reflective surface 32B, but may be different from the diffraction angle αB. If the diffraction angle αA is the same as the diffraction angle αB, the total reflection distance LA of light LTrA is the same as the total reflection distance LB of light LTrB.

[0059] In such modified cases, it is desirable that the spacing G between the solar PVs be smaller than the sum of the total reflection distances LA and LB.

[0060] Figure 11 shows an example of the orientation pattern of liquid crystal molecules contained in the liquid crystal layer 3 shown in Figure 10. Figure 11 shows the orientation pattern of liquid crystal molecules LMA, which are arranged in a plane parallel to the XY plane, among the liquid crystal molecules contained in the first layer 3A, and the orientation pattern of liquid crystal molecules LMB, which are arranged in a plane parallel to the XY plane, among the liquid crystal molecules contained in the second layer 3B.

[0061] In the first layer 3A, the orientation directions of each liquid crystal molecule LMA aligned in the second direction A2 are different from each other. For example, focusing on the five liquid crystal molecules LMA aligned along the A-A' line, the orientation direction of each liquid crystal molecule LMA changes by a constant angle clockwise along the second direction A2 (from left to right in the figure). Note that the orientation directions of each liquid crystal molecule LMA aligned in the third direction A3 are approximately the same.

[0062] In the second layer 3B, the orientation directions of each liquid crystal molecule LMB aligned in the second direction A2 are different from each other. For example, focusing on the five liquid crystal molecule LMBs aligned along the B-B' line, the orientation direction of each liquid crystal molecule LMB changes by a constant angle clockwise along the second direction A2 (from left to right in the figure). Note that the orientation directions of each liquid crystal molecule LMB aligned in the third direction A3 are approximately the same.

[0063] An example of a manufacturing method for such a liquid crystal layer 3 is briefly described below. First, an alignment film is formed on the transparent substrate 1, and then the alignment film is subjected to an alignment treatment. After that, a first liquid crystal material for forming the cholesteric liquid crystal 31A is applied to the alignment film, and then the first liquid crystal material is cured. This forms a first layer 3A having the cholesteric liquid crystal 31A. Subsequently, a second liquid crystal material for forming cholesteric liquid crystal 31B is applied onto the first layer 3A. The second liquid crystal material contains a different chiral agent than the first liquid crystal material. Then, the second liquid crystal material is cured. This forms the second layer 3B having cholesteric liquid crystal 31B. The liquid crystal molecules LMA of the second layer 3B formed in this way inherit the orientation pattern of the liquid crystal molecules LMB of the first layer 3A. As a result, the orientation pattern shown in Figure 11 is formed. However, the rotation direction of the cholesteric liquid crystal 31A is opposite to the rotation direction of the cholesteric liquid crystal 31B. Therefore, as shown in Figure 10, the inclination direction of the reflective surface 32A formed on the first layer 3A is different from the inclination direction of the reflective surface 32 formed on the second layer 3B.

[0064] Figure 12 is a schematic cross-sectional view showing another modification of the liquid crystal optical element 100. The solar cell PV is shown by a dotted line in the figure. The modified example shown in Figure 12 differs from the modified example shown in Figure 10 in that both the reflective surface 32A and the reflective surface 32B are tilted so as to reflect the incident light LTi toward the right side of the figure.

[0065] The first layer 3A of the liquid crystal layer 3 is located between the transparent substrate 1 and the second layer 3B and has a cholesteric liquid crystal 31A. The cholesteric liquid crystal 31A has a helical axis AXA that is substantially parallel to the first direction A1, and also has a helical pitch PA along the first direction A1. The second layer 3B of the liquid crystal layer 3 has a cholesteric liquid crystal 31B. The cholesteric liquid crystal 31B has a helical axis AXB that is substantially parallel to the first direction A1, and a helical pitch PB along the first direction A1. The helical axis AXA is parallel to the helical axis AXB. The helical pitch PA is the same as the helical pitch PB, but may be different from the helical pitch PB. The rotation direction of the cholesteric liquid crystal 31A is opposite to the rotation direction of the cholesteric liquid crystal 31B.

[0066] In such modified examples, it is desirable that the spacing G between the solar cell PVs be smaller than the total reflected distance LA of light LTrA, and also smaller than the total reflected distance LB of light LTrB.

[0067] Figure 13 shows an example of the orientation pattern of liquid crystal molecules contained in the liquid crystal layer 3 shown in Figure 12. Figure 13 shows the orientation pattern of liquid crystal molecules LMA, which are arranged in a plane parallel to the XY plane, among the liquid crystal molecules contained in the first layer 3A, and the orientation pattern of liquid crystal molecules LMB, which are arranged in a plane parallel to the XY plane, among the liquid crystal molecules contained in the second layer 3B.

[0068] In the first layer 3A, the orientation directions of each liquid crystal molecule LMA aligned in the second direction A2 are different from each other. For example, focusing on the five liquid crystal molecules LMA aligned along the A-A' line, the orientation direction of each liquid crystal molecule LMA changes by a constant angle clockwise along the second direction A2 (from left to right in the figure). Note that the orientation directions of each liquid crystal molecule LMA aligned in the third direction A3 are approximately the same.

[0069] In the second layer 3B, the orientation directions of each liquid crystal molecule LMB aligned in the second direction A2 are different from each other. For example, focusing on the five liquid crystal molecule LMBs aligned along the B-B' line, the orientation direction of each liquid crystal molecule LMB changes by a constant angle counterclockwise along the second direction A2 (from left to right in the figure). Note that the orientation directions of each liquid crystal molecule LMB aligned in the third direction A3 are approximately the same.

[0070] An example of a manufacturing method for such a liquid crystal layer 3 is briefly described below. First, an alignment film is formed on the transparent substrate 1, and then the alignment film is subjected to an alignment treatment. After that, a first liquid crystal material for forming the cholesteric liquid crystal 31A is applied to the alignment film, and then the first liquid crystal material is cured. This forms a first layer 3A having the cholesteric liquid crystal 31A. On the other hand, an alignment film is formed on a separately prepared support, and then the alignment film is subjected to an alignment treatment. After that, a second liquid crystal material for forming the cholesteric liquid crystal 31B is applied to the alignment film, and then the second liquid crystal material is cured. This forms a second layer 3B having the cholesteric liquid crystal 31B. Subsequently, only the second layer 3B is peeled off from the support, and the second layer 3B is bonded to the first layer 3A. Thus, the liquid crystal molecules LMA in the second layer 3B, which are formed separately from the first layer 3A, can have a different orientation pattern from the liquid crystal molecules LMB in the first layer 3A. As a result, the orientation pattern shown in Figure 13 is formed.

[0071] In the modified example described with reference to Figures 10 to 13, the liquid crystal layer 3 has a first layer 3A and a second layer 3B. When the helical pitch PA of the cholesteric liquid crystal 31A is the same as the helical pitch PB of the cholesteric liquid crystal 31B, and the rotation direction of the cholesteric liquid crystal 31A is opposite to that of the cholesteric liquid crystal 31B, the reflectivity of light LTr of the same wavelength λ among the light LTi incident on the liquid crystal optical element 100 is improved. For example, when the rotation direction of the cholesteric liquid crystal 31A is clockwise and the rotation direction of the cholesteric liquid crystal 31B is counterclockwise, the reflective surface 32A of the cholesteric liquid crystal 31A reflects clockwise circularly polarized light of wavelength λ, and the reflective surface 32B of the cholesteric liquid crystal 31B reflects counterclockwise circularly polarized light of wavelength λ. Therefore, compared to the example described with reference to Figure 2, the reflectivity of the liquid crystal layer 3 is improved, and the power generation efficiency of the solar cell PV is also improved.

[0072] Furthermore, the liquid crystal layer 3 may be a laminate of three or more layers. Also, the liquid crystal layer 3 may include layers with different helical pitches.

[0073] The modified examples described with reference to Figures 10 to 13 are applicable not only when multiple solar cell PVs are arranged on the side of the second main surface F2, but also when multiple solar cell PVs are arranged on the side of the first main surface F1, or when multiple solar cell PVs are arranged on both the first main surface F1 and the second main surface F2.

[0074] Next, variations of the solar cell device 10 will be explained with reference to Figures 14 to 18.

[0075] In the example shown in Figure 14, the solar cell device 10 includes protective substrates 21 and 22 in addition to the liquid crystal optical element 100 and the solar cell PV. Protective substrate 21 is located between the liquid crystal optical element 100 and protective substrate 22. Both protective substrates 21 and 22 are transparent substrates, and are made of glass or synthetic resin. The liquid crystal layer 3 of the liquid crystal optical element 100 faces the side into which light LTi is incident. Multiple solar cell PVs are located between the transparent substrate 1 and the protective substrate 21, and also between the protective substrate 21 and protective substrate 22. This protects the solar cell PV. In addition, light that could not be used for power generation by the solar cell PV between the transparent substrate 1 and the protective substrate 21 can be used for power generation by the solar cell PV between the protective substrate 21 and the protective substrate 22.

[0076] In the example shown in Figure 15, the components of the solar cell device 10 are the same as those in the example shown in Figure 14, but the transparent substrate 1 of the liquid crystal optical element 100 faces the side into which light LTi is incident. Multiple solar cell PVs are located between the liquid crystal layer 3 and the protective substrate 21, as well as between the protective substrate 21 and the protective substrate 22. Even in this example, the same effect as in the example shown in Figure 14 can be obtained.

[0077] In the example shown in Figure 16, the components of the solar cell device 10 are the same as those in the example shown in Figure 14, except that the protective substrate 21 faces the side into which the light LTi is incident. The protective substrate 22 is located between the protective substrate 21 and the liquid crystal optical element 100. Multiple solar cell PVs are located between the protective substrate 21 and the protective substrate 22, as well as between the protective substrate 22 and the transparent substrate 1. Even in this example, the same effect as in the example shown in Figure 14 can be obtained.

[0078] In the example shown in Figure 17, the solar cell device 10 comprises two liquid crystal optical elements 100A and 100B, and a protective substrate 21. Liquid crystal optical element 100A is located between the protective substrate 21 and liquid crystal optical element 100B. Liquid crystal optical elements 100A and 100B have the same configuration and each comprises a transparent substrate 1 and a liquid crystal layer 3. The protective substrate 21 faces the side into which light LTi is incident. Multiple solar cell PVs are located between the protective substrate 21 and the transparent substrate 1 of liquid crystal optical element 100A, and also between the liquid crystal layer 3 of liquid crystal optical element 100A and the transparent substrate 1 of liquid crystal optical element 100B. Even in this example, the same effect as in the example shown in Figure 14 can be obtained.

[0079] In the example shown in Figure 18, the solar cell device 10 comprises a liquid crystal optical element 100, solar cell PVs, a protective substrate 21, and a protective substrate 22. The protective substrate 21 faces the side into which light LTi is incident. The protective substrate 22 is located between the protective substrate 21 and the liquid crystal optical element 100. Multiple solar cell PVs are located between the protective substrate 21 and the protective substrate 22, as well as between the protective substrate 22 and the transparent substrate 1. In the liquid crystal optical element 100, the liquid crystal layer 3 is formed on the support 30, and the support 30 is bonded to the transparent substrate 1. Even in this example, the same effect as in the example shown in Figure 14 can be obtained.

[0080] The liquid crystal layer 3 may be arranged on the main surfaces of the protective substrates 21 and 22, not limited to the examples shown in Figures 14 to 18.

[0081] Next, variations of the liquid crystal optical element 100 will be explained with reference to Figures 19 to 22.

[0082] In the example shown in Figure 19, the transparent substrate 1 includes locally arranged scatterers 41. The scatterers 41 scatter light of wavelength λ used for power generation in the solar cell PV. For example, the scatterers 41 can be those that transmit visible light and scatter infrared light. The solar cell PV faces the scatterer 41 in the first direction A1. In the illustrated example, the solar cell PV is positioned on the side of the second main surface F2 of the transparent substrate 1 and faces the scatterer 41 across the liquid crystal layer 3. Alternatively, the solar cell PV may be positioned on the side of the first main surface F1. In this example, the light LTi incident on the liquid crystal optical element 100 is repeatedly reflected and scattered by the scatterer 41. The solar cell PV receives a portion of the light scattered by the scatterer 41 and generates electricity.

[0083] In the example shown in Figure 20, the liquid crystal optical element 100 further includes a reflector 42. The reflector 42 faces the scatterer 41 in the first direction A1. The scatterer 41 is located between the solar cell PV and the reflector 42. In the illustrated example, the reflector 42 is positioned on the first main surface F1. In this example, the light scattered by the scatterer 41 is reflected by the reflector 42 towards the solar cell PV. As a result, the power generation efficiency is improved compared to the example shown in Figure 19.

[0084] In the example shown in Figure 21, the liquid crystal optical element 100 further includes a scatterer 43. The scatterer 43 is locally arranged on the second main surface F2 and covered by the liquid crystal layer 3. The solar cell PV faces the scatterer 43 in the first direction A1 via the liquid crystal layer 3. Even in this example, the PV solar cell generates electricity by receiving a portion of the light scattered by the scatterer 41.

[0085] In the example shown in Figure 22, the liquid crystal optical element 100 further comprises a transparent member 44 and a reflective film 45. The transparent member 44 has a flat surface 441 that is in contact with the first main surface F1 and a convex curved surface 442 that is opposite to the flat surface 441. It is desirable that such a transparent member 44 has a refractive index equivalent to that of the transparent substrate 1. The reflective film 45 covers the curved surface 442. The solar cell PV faces the transparent member 44 in the first direction A1. In the illustrated example, the solar cell PV is positioned on the second main surface F2 side of the transparent substrate 1 and faces the transparent member 44 with the transparent substrate 1 and liquid crystal layer 3 in between. In this example, the light LTi incident on the liquid crystal optical element 100 is repeatedly reflected before being guided to the transparent member 44 and reflected by the reflective film 45. The solar cell PV receives the light reflected by the reflective film 45 and generates electricity.

[0086] Next, we will explain how to install the solar cell PV onto the liquid crystal optical element 100.

[0087] Figure 23 shows an example of the installation of a solar cell PV onto a liquid crystal optical element 100. In the illustrated example, the solar cell PV is, for example, a silicon-based solar cell and is formed separately from the liquid crystal optical element 100. Such a solar cell PV is bonded to the liquid crystal optical element 100 via a transparent adhesive 50. In the illustrated example, the solar cell PV is bonded to the liquid crystal layer 3 by the adhesive 50. Alternatively, the solar cell PV may be bonded to the first main surface F1 of the transparent substrate 1 with the adhesive.

[0088] Figure 24 shows another example of the installation of a solar cell PV onto a liquid crystal optical element 100. In the illustrated example, the solar cell PV is, for example, an organic thin-film solar cell, formed by coating a material onto the liquid crystal optical element 100. In the illustrated example, the solar cell PV is formed directly on the surface of the liquid crystal layer 3. Alternatively, the solar cell PV may be formed directly on the first main surface F1 of the transparent substrate 1.

[0089] As described above, according to this embodiment, it is possible to provide a solar cell device that can suppress losses when guiding light.

[0090] 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]

[0091] 10…Solar cell device PV…Solar cell 100...Liquid crystal optical elements 1…Transparent substrate F1…First main surface F2…Second main surface 3...Liquid crystal layer 31...Cholesteric liquid crystal 32...Reflective surface 21, 22… Protective substrate 41...Scatterer 42...Reflector 43...Scatterer 44...Transparent component 45...Reflective film 50…Adhesive

Claims

1. A transparent substrate having a first main surface and a second main surface opposite to the first main surface, Displaced on the second main surface side of the transparent substrate, a liquid crystal layer having a cholesteric liquid crystal containing a plurality of liquid crystal molecules, A plurality of solar cells are arranged on at least one of the first main surface side and the second main surface side of the transparent substrate, each formed in a strip shape and arranged at predetermined intervals, Equipped with, The plurality of solar cells are arranged on the first main surface side and the second main surface side of the transparent substrate, respectively. A solar cell device in which the spacing between the plurality of solar cells arranged on the first main surface side is smaller than the spacing between the plurality of solar cells arranged on the second main surface side.

2. The orientation directions of the liquid crystal molecules arranged along the short side of the solar cell are different from each other. The solar cell apparatus according to claim 1, wherein the orientation directions of the liquid crystal molecules arranged along the long side direction of the solar cell are substantially the same.

3. Furthermore, it is equipped with a transparent protective substrate, The solar cell apparatus according to claim 1, wherein the plurality of solar cells are located between the transparent substrate and the protective substrate.

4. The transparent substrate includes locally arranged scattering bodies, The solar cell apparatus according to claim 1, wherein the solar cell is facing the scattering body.

5. Furthermore, the system includes a reflector facing the scattering body, The solar cell apparatus according to claim 4, wherein the scattering body is located between the solar cell and the reflector.

6. Furthermore, the transparent substrate is provided with a scattering body locally arranged on the second main surface, The solar cell apparatus according to claim 1, wherein the solar cell is facing the scattering body.

7. Furthermore, a transparent member having a plane in contact with the first main surface of the transparent substrate and a curved surface opposite to the plane, The transparent member comprises a reflective film covering the curved surface, The solar cell apparatus according to claim 1, wherein the solar cell is located on the second main surface side of the transparent substrate and faces the transparent member.

8. The solar cell apparatus according to claim 1, wherein the solar cell is a silicon-based solar cell.

9. The solar cell apparatus according to claim 1, wherein the solar cell is an organic thin-film solar cell.

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