Color adjustment board and solar cell module

Abstract

A color adjustment plate (11) is disposed on the light incident side of a solar cell module (1), and adjusts the color of the solar cell module (1). The color adjustment plate (11) comprises: a transparent substrate (12) including a rough surface having an irregular uneven shape; and an optical multilayer film (13) that is a laminate in which a high refractive index layer (131) and a low refractive index layer (132) having a lower refractive index than the high refractive index layer are alternately laminated, the optical multilayer film being formed on the rough surface of the transparent substrate (12). The uneven shape of the rough surface has a root-mean-square height Sq of 0.117 μm to 4.99 μm, and a minimum autocorrelation length Sal of 1.86 μm to 85.0 μm.

Description

Technical Field

[0001] The present invention relates to a color adjustment plate for adjusting the color of a solar cell module, and a solar cell module including the same.

Background Art

[0002] In recent years, solar cell modules have become widespread, and it has also become common to install solar cell modules on the roofs, walls, etc. of buildings and vehicles. Since the color of the surface of a solar cell module is generally black or dark blue, development of solar cell modules with improved design has been carried out from the viewpoints of improving design and harmonizing with the surrounding landscape (see, for example, Patent Document 1).

[0003] For example, Patent Document 1 describes a first structured surface formed on the surface on the sealing film side of glass laminated on the light receiving surface of a solar cell, and a glazing unit having a photonic structure thereon. In the glazing unit of Patent Document 1, the photonic structure reflects a first partial spectrum and transmits a second partial spectrum. The first partial spectrum reflected by the photonic structure corresponds to harmonics and is within the visible spectrum range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the glazing unit in Patent Document 1 uses harmonics for reflected light, which results in numerous side peaks (sub-reflection peaks) in addition to the main reflection peak, increasing the amount of reflected light and leading to greater optical loss due to reflection. Furthermore, the glazing unit in Patent Document 1 uses harmonic components in the visible light region, which increases the thickness of each film in the optical multilayer film forming the photonic structure, resulting in longer formation times for the optical multilayer film and reduced productivity.

[0006] The object of the present invention is to provide a color adjustment plate that can produce highly visible colors, has high design quality, and can suppress optical loss due to color production, and a solar cell module equipped therewith. [Means for solving the problem]

[0007] The present invention solves the above problem by the following means. (1) The present invention relates to a color adjustment plate that is placed on the light-receiving side in a solar cell module and adjusts the color of the solar cell module, comprising: a transparent substrate having a rough surface with an irregular uneven shape on one side; a laminate in which a high refractive index layer and a low refractive index layer with a lower refractive index are alternately laminated, and an optical multilayer film formed on the one side of the transparent substrate, wherein the uneven shape has a root mean square height Sq of 0.117 μm or more and 4.99 μm or less, and a minimum autocorrelation length Sal of 1.86 μm or more and 85.0 μm or less.

[0008] (2) In the optical multilayer film, when one high refractive index layer and one low refractive index layer are stacked, one unit is defined as one unit, and the ratio F1 is the ratio of the thickness of the high refractive index layer to the thickness of the unit, it is preferable that the ratio F1 is 0.025 or more and 0.1 or less.

[0009] (3) The solar cell module of the present invention comprises a color adjustment plate as described in (1) or (2) above, a solar cell element, a back protective plate that sandwiches the solar cell element together with the color adjustment plate, and a sealing layer provided between the color adjustment plate and the back protective plate to seal the solar cell element. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a color adjustment plate that can produce highly visible colors, has high design quality, and can suppress optical loss due to color expression, as well as a solar cell module equipped therewith. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows the layer configuration of the solar cell module according to this embodiment. [Figure 2] This is a diagram illustrating the optical multilayer film 13. [Figure 3] This table shows the grit size of the abrasive material used in the sandblasting method and the surface roughness of the first surface 121 of the transparent substrate 12 processed by this method. [Figure 4] This graph shows the reflection spectra of optical multilayer films 13 with different unit thicknesses L and ratios F1. [Figure 5] This graph shows the reflection spectra of optical multilayer films 13 with different unit thicknesses L and ratios F1. [Figure 6] This graph shows the reflection spectrum of a color adjustment plate equipped with an optical multilayer film 13 in which the thickness L and ratio F1 of one unit are adjusted so that the peak wavelength of the reflectance is within a predetermined wavelength range and the peak (maximum value) of the reflectance is different. [Figure 7] This table shows the relationship between the ratio F1, the grit size of the abrasive used to roughen the first surface 121, the L*, a*, b* values ​​in the L*a*b* color system, and the current loss ΔJsc in a solar cell module 1 to which the color adjustment plate 11 is applied. [Figure 8] This table shows the diffuse reflectance of 20 color adjustment plates 11 that were measured. [Figure 9]In the solar cell module 1 provided with the color adjustment plate 11, it is a graph showing the angular dependence of the color to be expressed. [Figure 10] It is a table summarizing the chromaticity, etc. of solar cell modules using three examples of color adjustment plates 11 presenting blue-violet, green, and brown colors.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. Note that each of the drawings shown below, including FIG. 1, is a schematically shown drawing, and the size and shape of each part are exaggerated as appropriate for easy understanding.

[0013] (Embodiment) FIG. 1 is a diagram showing the layer structure of the solar cell module of this embodiment. In FIG. 1, the upper side in the drawing is the light incident side (light receiving side) in the usage state, and the lower side in the drawing is the back side (rear side). The solar cell module 1 of this embodiment includes, in order from the light incident side, a color adjustment plate 11, a sealing material layer 14, a solar cell element 15, a sealing material layer 16, and a back protection plate 17.

[0014] The color adjustment plate 11 is a member including a transparent substrate 12 and an optical multilayer film 13. This color adjustment plate 11 is disposed on the light incident side of the solar cell element 15 of the solar cell module 1 with the optical multilayer film 13 side as the light incident side. This color adjustment plate 11 has a function of adjusting the color of the light incident surface of the solar cell module 1.

[0015] The transparent substrate 12 is a plate-shaped member made of glass with high light transmittance. The first surface 121 on the light incident side of the transparent substrate 12 has a rough surface shape with fine and irregular concavo-convex shapes. Also, in the thickness direction of the transparent substrate 12, the second surface 122 facing the first surface 121 does not have such concavo-convex shapes. Note that the second surface 122 is not limited to the above example, and may be a smooth surface or a rough surface having concavo-convex shapes like the first surface 121.

[0016] The first surface 121 of the transparent substrate 12 is roughened by sandblasting. Note that the first surface 121 of the transparent substrate 12 is not limited to this, and if a preferable surface roughness described later can be obtained, it may be formed by, for example, chemical etching or the like. In this embodiment, the first surface 121 is roughened by a sandblasting method in which particulate abrasive (Fujirandom A manufactured by Fuji Seisakusho Co., Ltd.) made of aluminum oxide is sprayed onto the first surface 121 of the transparent substrate 12.

[0017] FIG. 2 is a diagram for explaining the optical multilayer film 13. In FIG. 2, a flat optical multilayer film 13 is shown for easy understanding. In FIG. 2, the upper side in the drawing is the light-receiving side, and the lower side is the transparent substrate 12 side. As shown in FIG. 1, the optical multilayer film 13 is formed on the first surface 121 of the transparent substrate 12 so as to follow the uneven shape thereof.

[0018] Further, the optical multilayer film 13 is a laminate in which a plurality of high refractive index layers 131 and low refractive index layers 132 having a lower refractive index than this are alternately laminated in the thickness direction, that is, a so-called dielectric multilayer film. This optical multilayer film 13 exhibits a color corresponding to the wavelength range of the reflected light by reflecting a part of the light in a predetermined wavelength range. This optical multilayer film 13 is formed by forming a film on the first surface 121 of the transparent substrate 12 by a sputtering method. Note that the optical multilayer film 13 is not limited to this, and it may be formed using a reactive sputtering method, a vacuum evaporation method, a chemical vapor deposition method, a wet coating method, or the like.

[0019] The high refractive index layer 131 is formed using titanium oxide (TiO2), tantalum pentoxide (Ta2O5), alumina (Al2O3), silicon nitride (SiN X )), niobium pentoxide (Nb2O5). The low refractive index layer 132 is formed using silicon oxide (SiO2), magnesium fluoride (MgF), aluminum fluoride (AlF3), or the like. The high refractive index layer 131 preferably has a refractive index of about 1.8 to 2.8. The low refractive index layer 132 preferably has a refractive index of about 1.2 to 1.8.

[0020] In this embodiment, the high refractive index layer 131 is formed of titanium oxide (TiO2 refractive index 2.1), and the low refractive index layer 132 is formed of silicon oxide (SiO2 refractive index 1.5). The materials forming the high refractive index layer 131 and the low refractive index layer 132 may be appropriately selected depending on the color of the optical multilayer film 13, as long as they have a desirable refractive index. Furthermore, while Figure 2 shows an example where the layer closest to the transparent substrate 12 is a high refractive index layer 131, it is not limited to this and may be a low refractive index layer 132.

[0021] In this specification, a state in which one high refractive index layer 131 and one low refractive index layer 132 are stacked is defined as one unit. In this embodiment, the optical multilayer film 13 is stacked with five alternating layers of high refractive index layers 131 and low refractive index layers 132, i.e., five units are stacked. From the viewpoint of achieving good color development, it is preferable that the optical multilayer film 13 is stacked with three or more units. Furthermore, better color development can be achieved with a larger number of stacked units, but from the viewpoint of production costs, etc., it is preferable that the optical multilayer film 13 is stacked with three to five units.

[0022] The sealing layer 14 and sealing layer 16 are components that seal the solar cell element 15 placed between them. Suitable materials for the sealing layers 14 and 16 include, for example, transparent materials such as ethylene vinyl acetate (EVA), polyvinyl butyral (PVB), polyolefin resins, and ionomer resins. Various materials that have been conventionally used as sealing materials for solar cell modules can be used for the sealing layers 14 and 16. Alternatively, the sealing layers 14 and 16 may be sheet-like members formed using these materials. Furthermore, although this embodiment shows an example with two sealing layers 14 and 16, the sealing layer may be a single layer depending on the type of solar cell element 15 used in the solar cell module 1 and the structure of the solar cell module 1. The sealing layers 14 and 16 in this embodiment are formed from a polyolefin resin.

[0023] The solar cell element 15 is a photoelectric conversion element, and can be one that has been conventionally used as a solar cell element constituting a solar cell module. The solar cell element 15 may be, for example, a crystalline silicon solar cell element made using a single-crystal silicon substrate or a polycrystalline silicon substrate, a thin-film silicon solar cell element using amorphous silicon or microcrystalline silicon, a CIS solar cell element or CIGS solar cell element, a CdTe solar cell element, a perovskite solar cell element, etc. This solar cell element 15 is equipped with a reflection suppression layer (not shown) on its light-receiving side. The solar cell element 15 is also equipped with electrodes (not shown).

[0024] In this embodiment, an example in which a crystalline silicon solar cell element is used as the solar cell element 15 will be described. Also, Figure 1 shows a simplified configuration of the solar cell module 1, and shows an example in which one solar cell element 15 is provided between the encapsulating material layers 14 and 16. However, when a crystalline silicon solar cell is used as the solar cell element 15, as in this embodiment, multiple solar cell elements 15 are arranged between the encapsulating material layers 14 and 16 at predetermined intervals in the left-right direction within the screen.

[0025] The back protective plate 17 is a plate-shaped member positioned on the furthest back side of the solar cell module 1. The back protective plate 17 is preferably made of a material with high weather resistance and water vapor barrier properties. In this embodiment, the back protective plate 17 is made of a glass plate-shaped member. Therefore, the solar cell module 1 in this embodiment is a so-called double-sided glass substrate type solar cell module. The back protective plate 17 is not limited to those described above; it may also be made of a resin plate such as polycarbonate resin, acrylic resin, or polyethylene terephthalate (PET), and it does not need to be light-transmitting; it may also be made of a metal plate such as aluminum. Furthermore, the back protective plate 17 may be in the form of a film or a sheet.

[0026] The color adjustment plate 11 will be described in more detail. The transparent substrate 12 in this embodiment is made of optical glass, and the first surface 121 is processed by sandblasting. The first surface 121 of the transparent substrate 12 was sandblasted using abrasives of different grit sizes, and its surface roughness was measured. The abrasive used for sandblasting was aluminum oxide particles (Fuji Random A, manufactured by Fuji Seisakusho).

[0027] Figure 3 is a table showing the grit sizes of the abrasives used in the sandblasting method and the surface roughness of the first surface 121 of the transparent substrate 12 processed by this method. In sandblasting, the average particle size of abrasives decreases as the grit number increases. For example, a grit #220 abrasive has an average particle size (nominal value) of 50 μm, a grit #2000 abrasive has an average particle size (nominal value) of 6.7 μm, and a grit #4000 abrasive has an average particle size (nominal value) of 3 μm. The surface roughness of the first surface 121 was measured using a confocal laser microscope (Keyence VK-X3000) in accordance with ISO 25178, by determining the root mean square height Sq [μm], arithmetic mean height Sa [μm], and minimum autocorrelation length Sal [μm].

[0028] As shown in the table in Figure 3, the value of the root mean square height Sq increases as the grit size of the abrasive decreases (as the average particle size of the abrasive increases). Also, the value of the minimum autocorrelation length Sal increases as the grit size of the abrasive decreases (as the average particle size of the abrasive increases), indicating a large uneven structure in the in-plane direction.

[0029] In this embodiment, the uneven shape of the first surface 121 is more preferable if the root mean square height Sq is 0.177 μm or more and 4.99 μm or less, and the minimum autocorrelation length Sal is 1.86 μm or more and 85.0 μm or less, from the viewpoint of improving the expression of highly visible colors, reducing optical loss due to the expression of color on the surface of the solar cell module, providing an anti-glare effect that suppresses reflection from the solar cell module to the surrounding environment, and suppressing the change in color depending on the angle at which the color adjustment plate 11 is observed, i.e., the angle dependence of the color.

[0030] Furthermore, as shown in Figure 2, in the optical multilayer film 13, when the thickness of the high refractive index layer 131 is L1 and the thickness of the low refractive index layer 132 is L2, the thickness L of one unit is L = L1 + L2. If the ratio of the thickness of the high refractive index layer 131 to the thickness L of this one unit is F1, then F1 = L1 / L. In this embodiment, it is preferable that the ratio F1 of the optical multilayer film 13 is 0.025 or more and 0.1 or less, from the viewpoint of improving the ability to produce highly visible colors and reducing optical loss due to the color expression on the surface of the solar cell module. Depending on the color that the color adjustment plate 11 is to produce, the optimal value of the ratio F1 will differ within the above range. The reasons for this will be explained below.

[0031] Figures 4 and 5 are graphs showing the reflection spectra of optical multilayer films 13 with different unit thicknesses L and ratios F1. Figures 4 and 5 were obtained through simulation. Various optical simulation software can be used as simulation tools, such as RSoft's DiffractMod or OptiLayer's optical thin film design software (OptiLayer). Figure 4 shows the reflection spectra of six optical multilayer films 13 with a constant thickness L per nit and varying ratio F1, while Figure 5 shows the reflection spectra of four optical multilayer films 13 with a constant thickness L per unit and varying ratio F1. In the graphs shown in Figures 4 and 5, the vertical axis represents total light reflectance [%], and the horizontal axis represents wavelength [nm].

[0032] The conditions for the optical multilayer film 13 in the simulation are as follows: The optical multilayer film 13 consists of a high refractive index layer 131 made of titanium oxide (TiO2) and a low refractive index layer 132 made of silicon oxide (SiO2), with 5 units stacked. The optical multilayer film 13 is assumed to be formed on a smooth surface. The six examples of optical multilayer films 13 shown in Figure 4 have a constant unit thickness L of 130 nm and ratios F1 of 0.1, 0.2, 0.3, 0.5, 0.7, and 0.9. The four examples of optical multilayer films 13 shown in Figure 5 have a constant ratio F1 of 0.2 and unit thicknesses L of 130 nm, 150 nm, 170 nm, and 210 nm.

[0033] As shown in Figure 4, when the thickness L of one unit is fixed and the ratio F1 is changed, as the ratio F1 increases, the peak wavelength of the reflectance shifts to the longer wavelength side, and the peak also becomes smaller. Furthermore, the peak (maximum value) of the reflectance is largest when the ratio F1 is between 0.2 and 0.5, but when the ratio F1 is large, i.e., when the ratio F1 is 0.7 or 0.9, the side peaks also become very large. On the other hand, when the ratio F1 is small, i.e., when the ratio F1 is 0.1, the side peaks are suppressed. On the other hand, as shown in Figure 5, when the ratio F1 is fixed and the thickness L of one unit is changed, increasing the thickness L of one unit causes only the peak wavelength of the reflectance to shift to the longer wavelength side, while the waveform of the reflection spectrum remains approximately constant.

[0034] Figure 6 is a graph showing the reflection spectrum of a color adjustment plate equipped with an optical multilayer film 13 in which the thickness L and ratio F1 of one unit are adjusted so that the peak wavelength of the reflectance is within a predetermined wavelength range and the peak (maximum value) of the reflectance is different. The graph in Figure 6 shows the reflection spectra of three color-adjustable plates, measured using a spectrophotometer (Lambda 950, PerkinElmer) equipped with an integrating sphere. In the graph in Figure 6, the vertical axis represents total light reflectance [%], and the horizontal axis represents wavelength [nm].

[0035] In the three color adjustment plates used in this measurement, the transparent substrate was made of optical glass, and in all cases, the first surface on which the optical multilayer film 13 is formed was not subjected to sandblasting, resulting in the optical multilayer film 13 being formed on a smooth surface. Furthermore, in all of the color adjustment plates used in this measurement, the high refractive index layer 131 was titanium oxide (TiO2), the low refractive index layer 132 was silicon oxide (SiO2), and the optical multilayer film 13 was made of five stacked units. The color adjustment plates used for the measurements consisted of three examples: one with a thickness L=150nm and a ratio F1=0.2 per unit of the optical multilayer film 13; one with a thickness L=160nm and a ratio F1=0.1 per unit; and one with a thickness L=180nm and a ratio F1=0.025 per unit.

[0036] As shown in Figure 6, the three color-adjusted plates have a reflection peak (maximum value) in the wavelength range of 500-550 nm, but the height of that reflectance peak, i.e., the maximum reflectance, differs. Therefore, the three color-adjusted plates exhibit similar hues but have different brightness (lightness). As shown in Figure 6, increasing the thickness L of one unit and decreasing the ratio F1 suppressed the reflectance peak and reduced the brightness (lightness) of the color exhibited by the color adjustment plate. Conversely, decreasing the thickness L of one unit and increasing the ratio F1 increased the reflectance peak and increased the brightness (lightness) of the color adjustment plate.

[0037] As described above, by adjusting the thickness L of one unit and the ratio F1, the optical multilayer film 13 can adjust the wavelength of the main reflectance peak of the optical multilayer film 13, the width of that peak, and its reflectance (intensity), thereby reducing the reflectance of side peaks. However, by adjusting only the ratio F1 and the thickness L of one unit, even if the color of the optical multilayer film 13 can be controlled, the optical loss caused by that color cannot be sufficiently controlled, and the amount of light received by the solar cell element 15 decreases. Furthermore, in the case of a flat optical multilayer film formed on a smooth first surface without an uneven shape, the optical interference conditions are angle-dependent, so the color easily changes depending on the observation angle. In addition, such a flat optical multilayer film does not have an anti-glare effect, which presents the problem of reflection from the solar cell module to the surrounding environment.

[0038] The inventors of this application have found a suitable range for the surface roughness of the first surface 121 (particularly the root mean square height Sq and the minimum autocorrelation length Sal), thereby realizing a color adjustment plate 11 that achieves both good color development and reduced optical loss, and further possesses an anti-glare effect and exhibits minimal color change depending on the observation angle, as well as a solar cell module 1 equipped therewith. Furthermore, by finding a suitable range for the ratio F1 of the optical multilayer film 13 in this color adjustment plate 11 and combining it with the surface roughness of the first surface 121 described above, the inventors have realized a color adjustment plate 11 and a solar cell module 1 equipped therewith that further enhance these effects.

[0039] (Regarding color development and current loss ΔJsc) Here, multiple color-adjusted plates 11 were fabricated that exhibited the same hue (green) but differed in surface roughness of the first surface 121 of the transparent substrate 12, the thickness L of one unit of the optical multilayer film 13, and the ratio F1. Each was then applied to the solar cell module 1, and its chromaticity, current loss ΔJsc, etc., were measured. Figure 7 is a table showing the ratio F1, the grit size of the abrasive used to roughen the first surface 121, the L*, a*, and b* values ​​in the L*a*b* color system, and the current loss ΔJsc in a solar cell module 1 to which the color adjustment plate 11 is applied.

[0040] In the solar cell module 1 used in this measurement, the solar cell elements 15 sealed in the encapsulating layers 14 and 16 are experimental heterojunction crystalline silicon solar cell elements. Three color adjustment plates 11 were prepared with ratios F1 of 0.2, 0.1, and 0.025. Each of these color adjustment plates 11 comprises a transparent substrate 12 made of optical glass and an optical multilayer film 13 consisting of five units of high refractive index layers 131 and low refractive index layers 132. The optical multilayer film 13 consists of titanium oxide (TiO2) for the high refractive index layer 131 and silicon oxide (SiO2) for the low refractive index layer 132. The thickness L of each unit of the optical multilayer film 13 is adjusted within the range of 150-180 nm according to F1 to ensure consistent hue (green) of the resulting color. Color adjustment plates without the optical multilayer film 13 were also prepared.

[0041] For roughening the first surface 121 of the transparent substrate 12, five examples of abrasive grits were prepared: #220, #1000, #2000, #3000 (only for ratio F1=0.025), and #4000. Note that "Planar" as shown in Figure 7, which will be described later, indicates the state in which the surface has not been roughened, that is, the first surface 121 of the transparent substrate 12 is a smooth surface.

[0042] In the L*a*b* color system, L* represents lightness (brightness), and a* and b* represent chromaticity (hue and saturation). The L*, a*, and b* values ​​were measured by placing the center of the surface of each solar cell module 1 in the measurement window of the integrating sphere of a spectrophotometer (Konica Minolta Japan CM-36dG). The measurement mode was SCI (including specular reflection), the reflection measurement conditions were di:8°, de:8° (diffuse illumination, 8° direction reception), the field of view was 8°, the light source was a D65 light source, and the UV condition was 100% Full. The measurements were performed in accordance with JIS Z 8722 condition c, CIE No.15 (2004), ISO 7724 / 1, DIN 5033 Teil7, and ASTM E1164.

[0043] Current loss ΔJsc is the rate of decrease in the short-circuit current value of the solar cell module 1 in the state in which the solar cell element 15 is sealed between the back protective plate 17 and the color adjustment plate 11 by sealing material layers 14 and 16, compared to the short-circuit current value of the solar cell module 1 in the state in which only the solar cell element 15 is used in each measurement example. The smaller the value of current loss ΔJsc, the better the solar cell module is in terms of efficiently converting incident light into current. For the solar cell module 1, it is preferable that this current loss ΔJsc is small, and in particular, it is desirable that the current loss ΔJsc is less than 5.0%.

[0044] The current loss ΔJsc was measured and calculated using a Class AAA solar simulator (Wacom WXS-50S-L2) as the light source for irradiating the solar cell module with light, and a source measure unit (Keithley Instruments SMU2400).

[0045] As shown in Figure 7, the larger the ratio F1 of the color adjustment plate 11, the more vivid the apparent color (green) and the higher the brightness (L*). Furthermore, when the ratio F1 of the color adjustment plate 11 was small, a lower grit abrasive was used to roughen the first surface 121 of the transparent substrate 12, that is, a higher surface roughness of the first surface 121 of the transparent substrate 12 resulted in a clearer visible color and a brighter green color.

[0046] On the other hand, solar cell modules in which the color adjustment plate 11 does not have an optical multilayer film 13 (shown as "without optical multilayer film" in the table in Figure 7) exhibited a black color, similar to conventional solar cell modules, due to the surface shape of the silicon and an unillustrated reflection suppression layer provided on the solar cell element 15. Furthermore, in solar cell modules where the first surface 121 of the transparent substrate 12 is a smooth surface ("Planar" as shown in the table in Figure 7), a larger ratio F1 resulted in clearer color development and a brighter green color.

[0047] Next, we will examine the relationship between the brightness (luminosity) of the color exhibited by the color adjustment plate 11 and the optical loss (current loss ΔJsc). The fact that the color adjustment plate 11 exhibits a high brightness color means that it has a high light reflectivity, which means that the amount of light incident on the solar cell element 15 is small and the optical loss is large. Therefore, a solar cell module equipped with a color adjustment plate 11 that exhibits a high brightness color will have a large optical loss due to the color adjustment plate 11 and a large current loss ΔJsc. As can be seen from the table in Figure 7, there is a trade-off relationship between the brightness L* of the exhibited color and the current loss ΔJsc. In general, it is difficult to reduce current loss (optical loss) while exhibiting vivid colors in a solar cell module 1.

[0048] As shown in the table in Figure 7, by roughening the first surface 121 on which the optical multilayer film 13 of the transparent substrate 12 is formed with an abrasive of grit #220 to #3000, and setting the root mean square height Sq of the uneven shape of the first surface 121 to 0.071 μm to 4.99 μm and the minimum autocorrelation length Sal to 0.688 μm to 85.0 μm, a color adjustment plate 11 and solar cell module 1 can be realized that exhibit good color development while suppressing optical loss.

[0049] Furthermore, by setting the surface roughness of the first surface 121 within the above range, and further setting the ratio F1 to 0.025 or more and 0.1 or less, good color development can be achieved while suppressing optical loss. In particular, in the case of a color adjustment plate 11 that exhibits green color, as shown in Figure 7, by setting the ratio F1 = 0.025, it is possible to achieve both good color development and a reduction in optical loss, and a color adjustment plate 11 and solar cell module 1 with a current loss ΔJsc of 5% or less can be realized.

[0050] Furthermore, we will also examine the anti-glare effect of this color adjustment plate 11. If the anti-glare effect of the color adjustment plate 11 is small, specular reflection from the surface of the solar cell module 1 increases, and depending on the angle of incidence of sunlight and the angle from which the solar cell module 1 is observed, the specular reflection may be strongly observed. Such specular reflection from the surface of the solar cell module 1 is also called glare and has an undesirable effect on the surrounding environment.

[0051] Therefore, from the viewpoint of suppressing glare from the solar cell module 1, it is preferable that the color adjustment plate 11 has an anti-glare effect. As an indicator of this anti-glare effect, the diffuse reflectance of each color adjustment plate 11 was measured. A higher diffuse reflectance results in a lower specular reflectance. Therefore, a higher diffuse reflectance indicates a larger proportion of diffusely reflected light and a higher anti-glare effect. From the viewpoint of exhibiting a high anti-glare effect, it is preferable that the diffuse reflectance be 80% or higher.

[0052] The color adjustment plates 11 used for measuring diffuse reflectance consisted of 21 examples, all of which shared the characteristic of comprising a transparent substrate 12 made of optical glass and an optical multilayer film 13 formed by laminating five units of a high refractive index layer 131 made of titanium oxide (TiO2) and a low refractive index layer 132 made of silicon oxide (SiO2). However, the 21 color adjustment plates 11 used for measuring diffuse reflectance differed in the roughness of the uneven shape of the first surface 121, the presence or absence of the optical multilayer film 13, the value of the ratio F1, etc. The surface roughness of the first surface 121 of the transparent substrate 12 consisted of six examples: one in which the grit of the abrasive used for roughening by sandblasting was #220, #1000, #2000, #3000 (only for ratio F1=0.025), and #4000, and another in which the first surface 121 was a smooth surface (Planar). Regarding the optical multilayer film 13, there are a total of four examples: one without the optical multilayer film 13, and two with the optical multilayer film 13 and ratios F1 of 0.025, 0.1, and 0.2.

[0053] Figure 8 is a table showing the diffuse reflectance of 20 color adjustment plates 11 that were measured. The diffuse reflectance [%] of each color adjustment plate 11 is the ratio of the L* value measured using the SCE (specular reflection removal) method to the L* value measured using the SCI (specular reflection included) method with a spectrophotometer (Konica Minolta Japan CM-36dG). The reflectance measurement conditions were di:8°, de:8° (diffuse illumination, light reception in the 8° direction), field of view was 8°, and the light source was a D65 light source.

[0054] As shown in the table in Figure 8, the diffuse reflectance of the color adjustment plate 11 (Planar) in which the first surface 121 of the transparent substrate 12 was not roughened was low, which is undesirable. Furthermore, the diffuse reflectance of the color adjustment plate 11 in which the first surface 121 was roughened with an abrasive of grit #4000 was low compared to when abrasives of other grits were used, resulting in a low and insufficient anti-glare effect. Also, as the grit value decreased, the unevenness of the surface became coarser, resulting in a higher diffuse reflectance.

[0055] Therefore, from the viewpoint of enhancing the anti-glare effect of the color adjustment plate 11, it is preferable that the first surface 121 has an uneven surface shape with a size greater than or equal to the surface roughness obtained when the surface is roughened using an abrasive with a grit of #220 or more and #2000 or less; that is, the root mean square height Sq of the uneven surface shape of the first surface 121 is 0.117 μm or more and 4.99 μm or less, and the minimum autocorrelation length Sal is 1.86 μm or more and 85.0 μm or less.

[0056] (Angle dependence of color) Next, multiple color-adjustment plates with different surface roughnesses of the first surface 121 were prepared, and the angle dependence of the color, which changes depending on the direction in which the color-adjustment plate is observed, was measured. Figure 9 is a graph showing the angle dependence of the color produced in a solar cell module 1 equipped with a color adjustment plate 11. In the graph shown in Figure 9, the vertical axis is the color difference ΔE, which is calculated according to the CIE DE2000 method. The horizontal axis is the angle [deg], which is the angle made with respect to the normal direction of the surface of the solar cell module 1.

[0057] The color difference ΔE was measured using a spectrochromatometer (GC-5000, manufactured by Nippon Denshoku Industries Co., Ltd.). The illumination light used during measurement was a D65 light source with a color temperature of 6500°C, with an angle of 45 degrees corresponding to the specular reflection position. A white diffuser plate was used as the reference reflector. The color difference ΔE was measured from an angle of 35 degrees to -40 degrees. Note that in the direction of specular reflection (angle of 45 degrees), the measured value was saturated by the specular reflection component in some samples. Therefore, the color observed at a reflection angle of 35 degrees, which is slightly smaller than specular reflection, was used as the reference color, and the change in color relative to this reference color was defined as the color difference ΔE.

[0058] The graph in Figure 9 shows the color difference ΔE at different observation angles for six color adjustment plates 11: one where the grit of the abrasive used to roughen the first surface 121 of the transparent substrate 12 was #220, #1000, #2000, #3000, and #4000, and another where the first surface 121 was a smooth surface (Planar). In all seven of these color adjustment plates 11, five units of optical multilayer film 13 are stacked, with the high refractive index layer being titanium oxide (TiO2) and the low refractive index layer being silicon oxide (SiO2). In all seven of these color adjustment plates 11, the thickness of one unit L = 160-180 nm, the ratio F1 = 0.025, and the color is greenish.

[0059] Generally, color differences are distinguished by the magnitude of the color difference ΔE. The Class D tolerance for color difference ΔE is 13 to 25, and beyond this range, the color is perceived as a different color. Therefore, in the graph shown in Figure 9, the larger the angular range where the color difference ΔE is 25 or less (ΔE ≤ 25), the smaller the angular dependence of the resulting color.

[0060] In the graph shown in Figure 9, the color adjustment plate 11, where the first surface 121 is a smooth surface (Planar), had an angular range of only about 10 degrees where ΔE ≤ 25, indicating a high degree of angular dependence. However, by roughening the first surface 121, the angular range where ΔE ≤ 25 expanded to over 20 degrees. Furthermore, in cases where the surface roughness of the first surface 121 is high, such as in the color adjustment plate 11 where the first surface 121 was roughened using abrasive materials of grit #220 and #1000, the angular range where ΔE ≤ 25 expanded even further to over 70 degrees, resulting in even less angular dependence.

[0061] Therefore, when the color adjustment plate 11 has small angle dependence of color, it is preferable to use an abrasive with a grit of #220 or more and #4000 or less to roughen the first surface 121, that is, to set the root mean square height Sq of the uneven shape of the first surface 121 to 0.046 μm or more and 4.99 μm or less, and the minimum autocorrelation length Sal to 0.337 μm or more and 85.0 μm or less.

[0062] As described above, from the viewpoint of reducing the optical loss (current loss) of the solar cell module 1 as much as possible, it is preferable that the surface roughness of the uneven shape of the first surface 121 of the color adjustment plate 11 is small. It is preferable that the first surface 121 be roughened with an abrasive of grit #220 to #3000. Furthermore, from the viewpoint of suppressing glare from the solar cell module 1 (enhancing the anti-glare effect), it is preferable that the surface roughness of the uneven shape of the first surface 121 of the color adjustment plate 11 is large. It is preferable that the first surface 121 be roughened with an abrasive material with a grit of #220 or higher and a grit of #2000 or lower. Furthermore, from the viewpoint of mitigating the angle dependence of the color of the color adjustment plate 11, it is preferable that the first surface 121 of the color adjustment plate 11 is rough, and that the surface roughness of its uneven shape is large. It is preferable that the first surface 121 be roughened with an abrasive material with a grit of #220 or more and #4000 or less.

[0063] From the above results, in order to provide a color adjustment plate 11 that reduces optical loss, exhibits good color development with high visibility, and suppresses angle dependence of color, it is preferable that the first surface 121 is roughened with an abrasive of grit #220 to #2000, the root mean square height Sq of the uneven shape of the first surface 121 is 0.117 μm to 4.99 μm, and the minimum autocorrelation length Sal is 1.86 μm to 85.0 μm.

[0064] The color adjustment plate 11 and solar cell module 1 of this embodiment are provided with a transparent substrate 12 in which the first surface 121 is roughened with an abrasive of grit #220 to #2000, the root mean square height Sq of the uneven shape of the first surface 121 is 0.117 μm to 4.99 μm, and the minimum autocorrelation length Sal is 1.86 μm to 85.0 μm, and an optical multilayer film 13 is formed on this roughened first surface 121. As a result, it is possible to produce a highly visible and good color, improve the design, have an anti-glare effect, and reduce optical loss to improve power generation efficiency.

[0065] Furthermore, in this embodiment, the color adjustment plate 11 and solar cell module 1 have a multilayer optical film 13 in which one high refractive index layer 131 and one low refractive index layer 132 are stacked as one unit. The ratio F1 of the thickness L1 of the high refractive index layer 131 to the thickness L of this unit is 0.025 or more and 0.1 or less. In particular, in the form exhibiting green color, the ratio F1 = 0.025, so that it is possible to reduce optical loss while producing a good color with high visibility. In addition, since the ratio of the thickness of the high refractive index layer 131 can be reduced, the overall film thickness of the multilayer optical film 13 can also be reduced, improving the productivity of the color adjustment plate 11 and solar cell module.

[0066] From the above, according to this embodiment, by adjusting the surface roughness (root mean square height Sq, minimum autocorrelation length Sal) of the uneven shape of the first surface 121 on which the optical multilayer film 13 is formed, and further adjusting the thickness L and ratio F1 of one unit of the optical multilayer film 13, it is possible to realize a color adjustment plate 11 and a solar cell module 1 that have low optical loss (current loss ΔJsc) and good color development and anti-glare effect.

[0067] In the above-described embodiment, the color adjustment plate 11 and solar cell module 1 were explained using an example where they exhibit a green color. However, for other colors as well, by satisfying the above conditions, the color adjustment plate 11 and solar cell module can be made to have low current loss and clear color development.

[0068] Figure 10 is a table summarizing the chromaticity of solar cell modules using three examples of color adjustment plates 11 exhibiting blue-violet, green, and brown colors. These three color adjustment plates 11 have their color development adjusted based on the technical concept of this embodiment, as described above, and the color adjustment plates 11 and solar cell modules 1 have substantially the same configuration. Furthermore, in the table shown in Figure 10, Jsc represents the short-circuit current [mA / cm²]. 2 ] is where Voc is the open-circuit voltage [V], FF is the curve factor, η is the conversion efficiency [%], and ΔJsc is the current loss [%] as described above.

[0069] Each of the blue-violet, green, and brown color adjustment plates 11 has its first surface 121 roughened by sandblasting with a #2000 grit abrasive. The root mean square height Sq of the uneven surface of the first surface 121 is 0.117 μm, and the minimum autocorrelation length Sal is 1.86 μm. The green color adjustment plate 11 has a ratio F1 = 0.025, while the blue-violet and brown color adjustment plates have a ratio F = 0.05. By appropriately selecting the thickness L of one unit and the materials of each layer of the optical multilayer film 13, the peak wavelength of the reflected light is adjusted to achieve the desired color.

[0070] As shown in Figure 10, the color adjustment plates 11 exhibiting the three colors all have a low current loss ΔJsc of less than 5.0% and a power generation efficiency η exceeding 21%, making them excellent as solar cell modules 1. Furthermore, each color has sufficient chromaticity and brightness to exhibit its respective color. Based on the above, by setting the surface roughness of the first surface 121 on which the optical multilayer film 13 is formed to satisfy the above-mentioned preferred range, and further by adjusting the thickness L and ratio F1 of one unit of the optical multilayer film 13, it is possible to achieve low current loss, high power generation efficiency, and good color development in various colors.

[0071] (Transformed form) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, all of which fall within the scope of the present invention. (1) The solar cell module 1 may be configured in which a color adjustment plate 11, a solar cell element 15, a sealing material layer 16, and a back protective plate 17 are stacked in that order from the light incident side. In this case, the surface of the solar cell element 15 facing the transparent substrate 12 is not covered by the sealing material layer, and the electrodes and lead wires of the solar cell element 15 are arranged on the back side (back protective plate 17 side) of the solar cell element 15. In this case, the solar cell element 15 can be a thin-film solar cell element that uses the color adjustment plate 11 itself as a substrate and can be directly fabricated on the back surface thereof. For example, CdTe solar cell elements, some thin-film silicon solar cell elements, and perovskite solar cell elements are preferred. Alternatively, the solar cell element 15 may be integrally formed on the surface side of the back protective plate 17, and a sealing material layer and a color adjustment plate 11 may be laminated on the surface side thereof. In this case, the solar cell element 15 can be a thin-film solar cell element formed on an opaque substrate, and for example, CIS solar cells, some thin-film silicon solar cell elements, perovskite solar cell elements, etc., can be used.

[0072] (2) In the description, the color adjustment plate 11 was explained as being positioned as the light-receiving substrate among the two substrates that sandwich the solar cell element in a solar cell module. However, it is not limited to this, and for example, the two substrates may be formed from a resin film or the like, and the plate may be positioned on the light-receiving side of the light-receiving substrate.

[0073] (3) Although an example has been shown in which the optical multilayer film 13 is provided on the light-receiving side of the transparent substrate 12, it is not limited to this and may be provided on the back side of the transparent substrate 12, that is, on the side of the sealing material layer 14. In this case, the second surface 122 is a rough surface and has a fine and irregular uneven shape. Even in this form, as long as the root mean square height Sq and the minimum autocorrelation length Sal of the uneven shape satisfy the numerical range shown in the above embodiment, a good color adjustment plate 11 and solar cell module 1 can be made that have good color development and low current loss. In this form, since the refractive index around the optical multilayer film 13 is different from that of the above embodiment, the thickness L of one unit, the ratio F1, the material of the layer of the optical multilayer film closest to the transparent substrate 12, etc., may be adjusted as appropriate.

[0074] (4) The transparent substrate 12 may be made of a resin with high light transmittance, such as polycarbonate resin, acrylic resin, or polyethylene terephthalate (PET), if it is possible to set the root mean square height Sq and minimum autocorrelation length Sal of the uneven shape of the first surface 121 to a preferred numerical range.

[0075] (5) A protective sheet made of resin or glass with high light transmittance may be provided on the light-receiving side of the color adjustment plate 11 to protect the color adjustment plate 11. Alternatively, a protective layer made of resin with high light transmittance may be formed on the light-receiving side of the optical multilayer film 13.

[0076] The embodiments and variations of this invention can be used in combination as appropriate, but a detailed explanation is omitted. Furthermore, the present invention is not limited to the embodiments described above. [Explanation of symbols]

[0077] 1. Solar cell module 11 Color adjustment board 12 Transparent substrate 121 First side 13 Optical multilayer film 131 High refractive index layer 132 Low refractive index layer 14 Encapsulant layer 15 Solar cell elements 16 Encapsulant layer 17. Back protective plate

Claims

1. A color adjustment plate, which is positioned on the light-receiving side of a solar cell module and adjusts the color of the solar cell module, A transparent substrate having a rough surface with an irregular uneven shape on one side, A laminate in which a high refractive index layer and a low refractive index layer with a lower refractive index are alternately stacked, and an optical multilayer film is formed on one surface of the transparent substrate, Equipped with, The aforementioned uneven shape has a root mean square height Sq of 0.117 μm or more and 4.99 μm or less, and a minimum autocorrelation length Sal of 1.86 μm or more and 85.0 μm or less. In the optical multilayer film, a state in which one high refractive index layer and one low refractive index layer are stacked is defined as one unit, and the optical multilayer film is formed by stacking a plurality of such units, and when the ratio F1 is the ratio of the thickness of the high refractive index layer to the thickness of one unit, In all of the units forming the optical multilayer film, the ratio F1 is 0.025 or more and 0.1 or less. Color adjustment board.

2. The thickness of all the units forming the optical multilayer film is the same, The color adjustment plate according to claim 1.

3. The optical multilayer film is stacked in 3 to 5 units, The color adjustment plate according to claim 1.

4. A color adjustment plate according to any one of claims 1 to 3, Solar cell element and A back protective plate that sandwiches the solar cell element together with the color adjustment plate, A sealing layer is provided between the color adjustment plate and the back protective plate, which seals the solar cell element, A solar cell module equipped with the following features.

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