Manufacturing method of colored solar cell

Abstract

To provide an improved method for laminating a polymer film containing an effect pigment to a solar cell or a solar cell module.SOLUTION: The present invention relates to a manufacturing method of a colored solar cell or a colored solar cell module including a colored polymer film containing an oriented effect pigment and to a colored solar cell or a colored solar cell module manufactured by this method.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a colored solar cell or colored solar cell module, which includes a colored polymer film containing effect pigments, and a colored solar cell or colored solar cell module manufactured by this method. [Background technology]

[0002] Solar cells have achieved great success in recent years, exceeding 600 GW of international grid-connected capacity in 2019, with the majority installed on a practical scale. All solar cells share the same basic function: a photoactive material absorbs light, generating excited electron-hole pairs. These electron-hole pairs are separated within the solar cell by regions with different electron-hole mobility, known as pn junctions. Because various light-absorbing materials can be used, the solar energy industry is known for a variety of solar cell technologies, including the following: 1) Crystalline silicon solar cells (monocrystalline c-Si and polycrystalline mc-Si) 2) Cadmium telluride solar cells (CdTe) 3) Copper-indium-gallium-diselenide (CIGS / CIS) 4) Amorphous silicon solar cells (a-Si) 5) III / V solar cells, for example, gallium arsenide (GaAs) solar cells, or multi-junction solar cells composed of stacks of Group III and Group V elements such as germanium / indium-(aluminum)-gallium arsenide or phosphide (In(Al)GaAs / P) 6) Dye-sensitized solar cells (DSSC) 7)Organic solar cells (OSC) 8) Perovskite solar cells (PSCs) 9) Quantum dot solar cells (QSC) 10) Other II / VI solar cells composed of Group II and Group VI elements such as zinc selenide (ZnSe) or iron sulfide (FeS) 11) Tandem solar cells

[0003] Nevertheless, using more surfaces of buildings and other objects (e.g., automobiles) increases the total surface area available for solar energy production. For this purpose, new technologies and methods for creating solar cells with attractive colors and improving efficiency at various absorption angles are of great interest to the solar energy business. WO2019 / 122079A1 discloses a method for coloring a solar cell module, which is formed from a single solar cell or multiple electrically interconnected solar cells, by incorporating an effect pigment into an application medium, such as a transparent lamination material, and then applying it to the solar cell module. WO2019 / 122079A1 further states that the effect pigment can provide sufficient color without significantly reducing the overall solar cell efficiency when printed on glass or Si or used on an EVA (ethylene vinyl acetate copolymer) film. Effect pigments reflect some of the visible sunlight but allow the light necessary to produce energy to pass through. However, because effect pigments are in the form of small plate-like structures, the more the pigment plates are oriented so that their edges face the visible side of the solar module, the less their reflected color is. Therefore, most effect pigments need to be oriented substantially parallel to the module surface, although some degree of irregular orientation can still be desirable to maintain the viewing angle relevant to the perceived color. Existing state-of-the-art technologies for manufacturing encapsulated solar cell modules generally involve assembling a stack of solar cells, each consisting of a windglass and busbars embedded in a backsheet or a sealing film laminated to the glass. The stack is then heated to, for example, 130°C to 160°C (depending on the type of encapsulant used) and compressed together by vacuum or other physical pressure. The components of the final encapsulated solar cell module are illustrated in Figure 1 and include a front sheet (11), a front sealing film (12), a pattern or array of solar cells with busbars (13), a rear sealing film (14), and a rear sheet (15). Arrows indicate the direction of incident light. However, when using a front sealing film (12) containing an effect pigment, it was observed that certain areas around a single cell and / or busbar appeared darker than other areas after lamination. While we do not wish to be bound by any particular theory, it is thought that pigments in the form of small plate-like particles tend to change their orientation from a desirable parallel orientation to the film surface to a more orthogonal orientation, resulting in reduced reflectivity. This disruption of pigment orientation can be explained by the outflow of molten polymer and / or shrinkage of the sealing film during the lamination process. As a result, a specific expansion pattern of cells and strings / bus bars remains visible in the colored solar cell module. This is a drawback and could limit the use of sealing films colored with effect pigments in certain areas, such as the facade of a building, or in other areas of a building that incorporate photovoltaic devices. [Overview of the Initiative]

[0004] Therefore, an object of the present invention is to provide an improved method for laminating a polymer film containing an effect pigment onto a solar cell or solar cell module, which does not have the drawbacks observed in prior art methods, enables the manufacture of a colored solar cell or colored solar cell module having improved reflective color, while avoiding unwanted reorientation of the effect pigment during the lamination process. Another object of the present invention is to provide an improved colored solar cell or colored solar cell module manufactured by this method. To our surprise, we found that at least one of these objectives can be achieved by providing solar cells in the manner disclosed and claimed below. In particular, and surprisingly, it was found that modifying the lamination process of the solar cell module to laminate a polymer film containing the effect pigment onto the front sheet during the pre-lamination step could reduce or even avoid unwanted reorientation of the effect pigment, thereby reducing the occurrence of unwanted dark patterns on the cells and strings / busbars in colored solar cells or solar cell modules. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 is a schematic diagram of the components of the final enclosed solar cell module. [Figure 2] Figure 2 is a schematic diagram of a solar cell module manufactured by a method according to a preferred embodiment of the present invention. [Figure 3] Figure 3 is a plan view of a solar cell module manufactured according to Stack 2 of Comparative Example 1. [Figure 4] Figure 4 is a plan view of a solar cell module manufactured according to stack 2 of Example 1. [Modes for carrying out the invention]

[0006] Therefore, this application relates to a method for manufacturing a colored solar cell or a colored solar cell module, which includes the following steps. a) Preferably, a polymer film containing at least one effect pigment is laminated onto a front sheet by applying heat and / or pressure, or by using an adhesive or bonding agent or layer, preferably in a vacuum press. b) Optionally, the front sheet having a laminated polymer film containing the effect pigment is cooled, preferably to room temperature. c) A stack containing the following layers is supplied onto a front sheet having a laminated polymer film containing an effect pigment, or a front sheet having a laminated polymer film containing an effect pigment is supplied onto a stack of layers C1 to C4. C1) Optionally, at least one front sealing film C2) At least one solar cell, or an array of solar cells electrically interconnected by conductive components, preferably by busbars. C3) Optional: at least one rear sealing film C4) Rear Seat d) Preferably, by applying heat and / or pressure, or by using an adhesive or bonding agent, preferably in a vacuum press, the stack of layers C1 to C4 is laminated onto a front sheet having a laminated polymer film containing the effect pigment.

[0007] In the above and below, the term "front side" of a solar cell or solar cell module means the side that receives radiation or faces incident light, and the term "rear side" or "back side" of a solar cell or solar cell module means the side opposite to the side that receives radiation or the side opposite to the incident light. The term "front glass / sheet" or "front sealing film" means glass, sheet, or sealing film provided on the front side of a solar cell or solar cell module, and the terms "rear glass / sheet" and "rear sealing film" mean glass, sheet, or sealing film provided on the rear side of a solar cell or solar cell module. In the above and below, unless otherwise specified, the term “solar cell” shall be interpreted to include both single solar cells and solar cell modules, as well as the aforementioned arrays, strings, or patterns. Similarly, unless otherwise specified, the term “solar cell module” shall be interpreted to include single solar cells.

[0008] The present invention provides a highly efficient method for coloring state-of-the-art solar cells, and furthermore, solar cell modules formed of multiple electrically interconnected solar cells, which have excellent adaptability and provide a method for obtaining a wide range of colors with low or negligible losses and a high level of long-term stability. Furthermore, the present invention provides a solution for achieving high color uniformity, which allows for darkening of the busbars and the inside of the solar cell module so that a single solar cell is invisible, while simultaneously achieving low or negligible losses. In particular, and surprisingly, it was found that by modifying the manufacturing method of the solar cell to laminate a polymer film containing the effect pigment onto the front sheet of the solar cell in a pre-lamination step (also referred to as "step a)" above and below), it is possible to reduce or even avoid the occurrence of unwanted dark patterns in the cells and strings / busbars of colored solar cells or solar cell modules. Since the effect pigment is pre-fixed to the front sheet together with the polymer film, and the pre-lamination step itself does not cause any or only minor disruption to the orientation of the effect pigment, it is thought that it is possible to reduce or even avoid disruption to the orientation of the effect pigment during the final lamination formation of the solar cell.

[0009] The effect pigment according to the present invention has also been found to be ideal for providing sufficient color without significantly reducing the overall solar cell efficiency, especially when used in EVA film (ethylene vinyl acetate film). Long-term testing showed a high level of stability. Direct contact between the effect pigment-containing film and the solar cell is the most harsh location in the configuration of a solar module, so it is assumed that there will be no adverse effects anywhere in the solar module stack. Effect pigments reflect a portion of the incident visible light but allow the light necessary to pass through to produce energy through the photovoltaic process. The effect pigments can be oriented to change the angle of maximum efficiency, thereby controlling color and efficiency. A polymer film containing an effect pigment can be easily applied to the latest solar cells, which makes its application more efficient. Both the pre-lamination step and the process step of applying a front sheet having a laminated polymer film containing an effect pigment to a solar cell module can be easily incorporated into existing state-of-the-art methods to construct an encapsulated solar cell module.

[0010] By using the present invention, the appearance of solar cells can be adapted to special requirements. The appearance of objects containing solar cells, such as buildings, devices and automobiles, can be improved, and the transparency and reflectivity of solar cells can be controlled. Furthermore, by using a dark backsheet and darkening the busbars and connections, the visibility of the cells and bright-colored busbars can be avoided. Also, the present invention can be used to provide solar cells of wonderful colors for obtaining special effects and designs. For example, depending on the effect pigment used, a texture such as a sparkle effect can be imparted to the panel.

[0011] Another advantage of the present invention is that by changing the appearance to a conventional appearance that people are accustomed to, the solar cell can be integrally incorporated into any surface. The coloring of the solar cell can be carried out over a variety of colors and is not limited to a hard substrate such as glass or a single solar cell technology. Furthermore, complex solutions such as additional layers in the laminate stack are not required. The effect pigment layer makes the appearance on the front side of the solar cell various colors, such as red, blue, purple, green. In addition to the thickness of the polymer film and the type of polymer used therein, the concentration of the effect pigment or combinations thereof may be changed to obtain the desired color effect. In particular, the method according to the present invention can be used to integrate solar cells into various surfaces such as buildings (fronts and roofs), handholds, portable and stationary devices, self-propelled vehicles (cars, motorcycles, scooters, trucks, and similar vehicles), or other high-visibility surfaces that require seamless integration of solar cells without altering their optical appearance, or other solar installations where the typical technical appearance of solar cells changes to a typical appearance that people are accustomed to, and long-term stability is required. Furthermore, these improvements can be achieved without significantly losing solar cell efficiency.

[0012] Colored solar cells can be used on typical colored surfaces such as buildings, communication and transport objects, for example, automobiles, trains, trucks, trailers, manual devices, ships, price tags, plastics, wearable goods and household items or similar. Furthermore, in contrast to currently available technologies, which have a major drawback affecting solar cell performance and where the efficiency of solar cells can drop from an initial performance of >15% to less than 10% under real-world conditions, the efficiency of colored solar cells is not significantly affected, and therefore the cost of solar energy does not increase dramatically. Surprisingly, by appropriately selecting the concentration of the effect pigment, it is possible to uniformly color solar cells while minimizing the impact on battery efficiency. Even more surprisingly, conventional effect pigments, such as pearlescent pigments, interference pigments, and / or multilayer pigments, were found to exhibit the desired effect. Because the operating principle of these effect pigments is based on selective reflection in specific wavelength regions, the color effect can be selectively tuned, and the resulting efficiency can be correlated with the light transmission area. Generally, the desired color effect is already achieved with low reflection at specific wavelengths. Performance can also be improved at specific wavelengths of 700-1100 nm, which is important for quantum efficiency, as detected by some flakes. The long-term stability of the entire system against heat, ultraviolet light, humidity, and temperature changes was also actively tested.

[0013] Next, the method according to the present invention will be described in more detail. Preferred solar cells or solar cell modules obtained by the method according to the present invention include the following: - Two outer seats, also referred to above and below, made of glass or a plastic film such as TPT (Tedlar®-Polyester-Tedlar®, Tedlar® is a PVF (polyvinyl fluoride) film commercially available from DuPont), which are also referred to above and below as the front and rear seats. - For example, two transparent layers of polymer materials, one of which contains at least one effect pigment, including but not limited to polyethylene copolymers such as polyolefins, particularly EVA (ethylene vinyl acetate), EBA (ethylene butyl acrylate), EMA (ethylene methyl acrylate), EEA (ethylene ethyl acrylate), POE (polyolefin elastomer), BPO (polymer of ethylene and methyl acrylate or polypropylene commercially available from Borealis under the name Quentys®), and PVB or TPU (thermoplastic polyurethane). - A solar cell or a string or array of electrically interconnected solar cells.

[0014] These components are stacked in the following order: windshield / front polymer film containing effect pigment / preferably a second polymer film without effect pigment / solar cell / rear polymer film without effect pigment / rear glass or TPT.

[0015] Instead of laminating the above stack in a single step as proposed in the prior art, the method according to the present invention involves laminating a polymer (EVA) film containing an effect pigment onto the front sheet in a pre-lamination step (step a). The pre-lamination step a can be carried out using standard methods, for example, by exposing the two layers to heat and pressure, or by applying vacuum and / or other physical pressure for a specific duration in a lamination machine. Alternatively and / or additionally, lamination can be achieved or supported by using at least one adhesive and / or bonding agent or layer. The adhesive / bonding agent may be reactive or non-reactive, and may contain or consist of natural or synthetic products. Suitable and preferred examples, depending on the desired application, include, but are not limited to, polyurethane (PUR), thermoplastic polyurethane (TPU), rubber, acrylic, and silicone adhesives.

[0016] If heat is applied after the pre-lamination step a) for lamination, the front sheet having the laminated polymer film containing the effect pigment is cooled in step b), and very preferably to room temperature. The polymer film containing the effect pigment is permanently fixed to the glass and cannot be peeled off by hand. The pigment is uniformly distributed on the surface.

[0017] In the next step c), the remaining stack of the optional front sealant, solar cell, optional rear sealant, and rear sheet is placed on top of the pre-laminated bilayer of the windshield and polymer film containing the effect pigment, or alternatively, the pre-laminated bilayer is placed on top of the remaining stack. Preferably, the pre-laminated bilayer is placed so that the polymer film containing the effect pigment faces the solar cell.

[0018] Next, the final layer formation of the stack is carried out in step d), preferably under the same conditions as those in the pre-lamination step. In the pre-lamination step a) and the final lamination step d), the appropriate heat, pressure, and duration applied depend on the type of sheet and film used and can be easily selected by those skilled in the art. When windshield sheets and EVA polymer films are used, the heating temperature is preferably in the range of 130°C to 160°C, very preferably 135°C, and the duration is preferably 20 to 30 minutes. Preferably, a vacuum press is used. Preferably, a pressure of 400 to 900 mbar is applied.

[0019] After the final lamination step d), the laminated stack is preferably allowed to cool again to room temperature. Excess material from the sealing film and rear sheet (if a plastic rear sheet is used) can be trimmed, and the junction box can be installed for the electrical connections of the solar modules. Finally, the laminated stack can be assembled. Preferably, the resulting laminate is completely sealed and, in ideal cases, can protect the solar cells for at least 25 years.

[0020] A solar cell module manufactured by a method according to a preferred embodiment of the present invention is illustrated in Figure 2 and comprises a front sheet (21), which is preferably a glass sheet; a polymer film (22), which is preferably an EVA film and contains an effect pigment; a front sealing film (23), which is preferably an EVA film and does not contain an effect pigment or other colorant; a solar cell array (24) having busbars; a rear sealing film (25), which is preferably an EVA film; and a rear sheet (26), which is preferably a TPT film or a glass sheet. The arrows indicate the direction of incident light. In a preferred embodiment, at least one further sealing film (not shown in Figure 2) is placed between the polymer film (22) containing the effect pigment and the solar cell (24), and / or between the solar cell (24) and the rear sheet (26). The further sealing film does not contain the effect pigment. In another preferred embodiment, the solar cell module does not include a front sealing film (23). In another preferred embodiment, the polymer film (22) containing the effect pigment functions as a sealing film. In another preferred embodiment, a protective foil or outer foil (not shown in Figure 2) is applied over the completed solar cell or solar cell module.

[0021] Components located on the front side of the solar cell module, such as the front sheet (21), polymer film (22), and front sealing film (23), are substantially transparent to incident light passing through the solar cell or solar cell array (24). The front sheet (21) and the rear sheet (26) are preferably selected from glass sheets. In another preferred embodiment, the front sheet (21) and / or the rear sheet (26), more preferably the rear sheet (26), are polymer sheets, preferably TPT sheets. More preferred polymers for use as or within a rear sheet can be classified into double fluoropolymers, single fluoropolymers, and non-fluoropolymers, as well as various structures within each category. Generally, double fluoropolymer rear sheets consist mainly of an outer layer of Tedlar® polyvinyl fluoride (PVF) film or Kynar® polyvinylidene fluoride (PVDF) film and a core layer of polyethylene terephthalate (PET). Generally, single fluoropolymer rear sheets consist of an air-side Tedlar or Kynar® and an inner PET and primer or EVA layer. Generally, non-fluoropolymer rear sheets consist of two PET and one primer or EVA layer.

[0022] Furthermore, the solar cell array (24) shown exemplified in Figure 2 may be replaced with a single solar cell. Solar cells (24) can be selected from all kinds of solar cell technologies, such as amorphous, monocrystalline and polycrystalline silicon solar cells, CIGS, CdTe, III / V solar cells, II / VI solar cells, perovskite solar cells, organic solar cells, quantum dot solar cells and dye-sensitized solar cells, as well as solar cell modules made from a single cell. Crystalline solar cells include cell structures such as Al-BSF, PERC, PERL, PERT, HIT, IBC, and double-sided or other cell types based on crystalline silicon substrates.

[0023] The rear sheet (26) is preferably black or dark in color, and / or a black or dark sheet, such as a rear sealing film or additional sealing film, is placed on the rear side of the solar cell or solar cell module, i.e., between the solar cell (24) and the rear sheet (26), and the dark color is preferably a dark blue, which is the same color as the solar cell.

[0024] In the solar cell (24), the conductive components preferably include metallic conductive components, and examples of metallic conductive components include, but are not limited to, the following components. i) H-grids, also known as busbars, which consist of the main vertical connecting components. ii) Horizontal current collection components, also known as fingers. iii) Connecting components and solder between batteries

[0025] In a preferred embodiment of the present invention, in order to achieve a completely uniform appearance of the solar cell (24), the metallic conductive components, including but not limited to the aforementioned components i) to iii), are preferably colored black or a dark color such as dark solar blue before the application of the polymer film (22) containing the effect pigment. In another preferred embodiment of the present invention, a dark, preferably black or dark blue, grid is incorporated into at least one layer of the solar cell, and the grid covers bright areas such as the space between a single solar cell and conductive components including busbars, conduction paths, and solder joints. In another preferred embodiment of the present invention, a black or dark blue rear layer is applied behind the solar cells to conceal the space between the single solar cells. The black or dark blue rear layer may be printed or applied as foil. Suitable and preferred methods for darkening metal components that appear white in addition to the solar cell (24) using an H-grid front pattern include covering the metal strips with black polymer foil or applying black paint to the metal components. In the case of printed silver H-grids, the silver can be directly blackened by forming a thin layer of silver sulfide (e.g., by treatment using H2S) or by copper plating and oxidation. In the case of plated metal grids, the top layer of the metal stack can be directly plated using a highly absorbent metal oxide or sulfide such as CuO or Ag2S, or a similar dark metal oxide or another. In the case of using new metal processing methods (such as smart wire technology), black wires, or wires having a microstructure that reduces reflectivity to form a dark appearance of the metal grid, can also be used in this invention. Using a black or dark solar blue rear sheet as the background of the module allows for a very uniform appearance of the entire module, even from close range.

[0026] The polymer and sealing film are preferably selected from organic polymers. Examples of organic polymers include, but are not limited to, polyolefins such as polyethylene copolymers like EVA (ethylene vinyl acetate), EBA (ethylene butyl acrylate), EMA (ethylene methyl acrylate), EEA (ethylene ethyl acrylate), POE (polyolefin elastomer), and BPO; as well as polyester, polyamide, polyurethane, polyvinyl butyral PVB, polycarbonate, polyvinyl chloride, polyvinyl acetate, polyacrylate, polyol, polyisocyanate, or polyamine; and the aforementioned copolymers, resins, mixtures, or multilayers, such as polycarbonate-containing urethane resin, vinyl chloride-vinyl acetate-containing urethane resin, acrylic resin, polyurethane acrylate resin, polyester resin, or TPU (thermoplastic polyurethane). The front, rear, and further sealing films preferably contain, and very preferably consist of, TPU or polyolefin, where the polyolefin includes, but is not limited to, EVA, EBA, EMA, EEA, POE, or BOP.

[0027] The polymer film (22) containing the effect pigment is placed on the radiation-receiving side, i.e., within the visible portion of the solar cell or solar cell module according to the present invention. It may be placed on the inside of the front sheet (21), i.e., on the side facing the solar cell or solar cell array, as shown in Figure 2, or it may be placed on the outside of the front sheet (21), i.e., on the side facing the incident light. The polymer film (22) containing the effect pigment can be applied locally and flexibly to any surface. Therefore, it can be applied to the outer surface of a finished solar cell or solar cell module, to a protective substrate (glass or plastic) covering the solar cell or solar cell module, or directly to the photoactive material / solar cell. Advantageously, the polymer film (22) containing the effect pigment can also be used as an anti-reflective film.

[0028] The effect pigment used in the polymer film (22) according to the present invention is preferably transparent or at least translucent. The effect pigment useful in the present invention is preferably green. However, other colors such as blue, gray, white, blue-violet, red, orange, and black are also suitable. Other colors or mixtures thereof can be used to produce specific colors and tones. The effect pigment can also produce metallic effects, including but not limited to silver, platinum, gold, copper, and various other metals. Various color mixtures can also be used to create printed images / pictures.

[0029] The effect pigment and / or polymer film (22) containing the effect pigment has a total transmittance of preferably at least 30%, more preferably at least 60%, and most preferably 80% for radiation associated with a particular solar cell or solar cell module, preferably in the range of 260 to 1200 nm, more preferably in the range of 400 to 800 nm. The effect pigment and / or polymer film (22) containing the effect pigment has a selective maximum reflectance of preferably 1 to 40%, more preferably 1 to 30%, and most preferably 1 to 20% in the visible region of the solar spectrum, more preferably in the range of 400 to 800 nm. For example, a localized reflectance peak in the range of 450 to 550 nm having a selected maximum reflectance such that the total reflectance in the following range is 5% is sufficient to obtain a strong green impression of a solar cell that is otherwise optically blue. Preferably, the effect pigment and / or polymer film (22) containing the effect pigment has a total reflectance of <40%, more preferably <30%, very preferably <20%, and most preferably <10% for radiation associated with a particular solar cell or solar cell module, preferably in the range of 260 to 1200 nm, more preferably in the range of 400 to 800 nm. More preferably, the effect pigment and / or the polymer film (22) containing the effect pigment has a reflectance of <30%, very preferably <20%, and most preferably <10% for radiation in the range of 800 to 1000 nm. The polymer film (22) containing the effect pigment exhibits high transmittance (at least 30%, preferably >80%) not only to specific colors but also to radiation associated with specific solar cells, preferably in the range of 260 to 1200 nm, and exhibits a total reflectance of preferably about 5 to 40%, preferably less than 10%, in the range of 260 to 1200 nm.

[0030] The internal and external quantum efficiencies of the solar cell and solar cell module according to the present invention are preferably ≥60% (≥0.6), preferably ≥70% (≥0.7), and preferably ≥80% (≥0.8) in the wavelength range of 260 to 1200 nm. Quantum efficiency indicates the amount of photons used for power generation. External quantum efficiency (EQE) correlates with the amount of photons absorbed by the solar cell and efficiently converted into electricity, indicating the wavelength-selective relationship of the total amount of photons illuminating the solar cell. Internal quantum efficiency (IQE) indicates the relationship of the amount of photons that reach the solar cell and are converted into electricity. In the present invention, the difference between internal and external quantum efficiency can be explained as follows. EQE = IQE - Reflected photons from sealing film containing effect pigments Therefore, high levels of both IQE and EQE indicate a limited effect of the effect pigment on solar cell performance. Relative current loss [A / m²] of the effect pigment and / or polymer film (22) containing the effect pigment. 2 The efficiency reduction of the effect pigment and / or polymer film (22) containing the effect pigment [W / m 2 This is less than 40%, preferably less than 30%, and most preferably less than 20%.

[0031] The effects of pigments and layers on c-Si solar cells can be evaluated by reflectance data. Reflectance data is used to evaluate the maximum power absorption / maximum photocurrent generation of the treated cell. Measurement and calculation of reflectance and transmittance are carried out by general methods known to those skilled in the art, and as further described in the experimental section. The standard using TPU-based encapsulants exhibits a typical 90% EQE across a wide wavelength range, the effect pigment mixture according to the present invention, which results in the white / gray appearance of solar cells, shows a decrease of approximately 7%, and the green effect pigment according to the present invention, based on coated glass flakes, shows an average decrease of less than 5% and even an increase in quantum efficiency in the IR region.

[0032] The effect pigment preferably comprises a flake-like substrate including at least one coating containing a metal oxide, a metal oxide hydrate, or a mixture thereof. Preferably, the effect pigment consists of a transparent or translucent and colorless flake-like substrate covered with at least one layer of transparent or translucent and colorless material. The use of pearlescent pigments, interference pigments, and / or multilayer pigments is preferred. The long-term stability of the effect pigment can preferably be improved by using a post-coating of an organic coating and / or an inorganic coating as the final layer of the effect pigment, as described in WO2011 / 095326A1 and below. Suitable substrates for effect pigments are, for example, all known coated or uncoated flake substrates, preferably transparent or translucent, and preferably colorless flakes. Suitable examples include phyllosilicates, particularly synthetic or natural mica, glass flakes, SiO2 flakes, Al2O3 flakes, TiO2 flakes, liquid crystal polymers (LCPs), holographic pigments, BiOCl flakes, or mixtures of the above flakes. Aluminum flakes with dielectric coatings can also be used in accordance with the present invention at low concentrations to obtain very high opacity of the active photovoltaic layer. Glass flakes can be made from all types of glass known to those skilled in the art, such as A glass, E glass, C glass, ECR glass, recycled glass, window glass, borosilicate glass, Duran® glass, laboratory glass, or optical glass. The refractive index of the glass flakes is preferably 1.45 to 1.80, and particularly 1.50 to 1.70. Particularly preferred glass flakes are made from A glass, C glass, E glass, ECR glass, quartz glass, or borosilicate glass. Coated or uncoated flakes of synthetic or natural mica, SiO2 flakes, Al2O3 flakes, and glass flakes, particularly C glass, ECR glass, or calcium aluminum borosilicate glass flakes, are preferred. Effect pigments based on calcium aluminum borosilicate glass are particularly preferred. In a modified version of the present invention, Al2O3 flakes are preferred.

[0033] The substrate generally has a thickness of 0.01 to 5 μm, particularly 0.05 to 4.5 μm, and especially preferably 0.1 to 1 μm. The length or width is typically 1 to 500 μm, preferably 1 to 200 μm, and especially 5 to 125 μm. These generally have an aspect ratio (ratio of average diameter to average particle thickness) of 2:1 to 25,000:1, preferably 3:1 to 1,000:1, and especially 6:1 to 250:1. The additional coating is generally in the range of only a few hundred nanometers and therefore does not significantly affect the thickness, length, or width (particle size) of the effect pigment; therefore, in principle, the dimensions of the flake substrate also apply to the coated effect pigment used according to the present invention. The particle size and particle size distribution of the effect pigment and its substrate can be measured by various methods commonly used in this art. However, the use of laser diffraction in standard methods using equipment such as the Malvern Mastersizer 2000, Beckman Coulter, and Microtrac is preferred. Furthermore, other techniques such as scanning electron microscope (SEM) imaging can be used.

[0034] In a preferred embodiment, the substrate is covered with at least one transparent or translucent layer comprising a metal oxide, a metal oxide hydrate, a metal hydroxide, a metal suboxide, a metal fluoride, a metal nitride, a metal oxynitride, or a mixture thereof. Preferably, the substrate is partially or entirely covered with these layers. Furthermore, a multilayer structure including high refractive index layers and low refractive index layers is also possible, preferably with the high refractive index layers and low refractive index layers alternating. A layer package including a high refractive index layer (refractive index ≥ 2.0) and a low refractive index layer (refractive index < 1.8) is particularly preferred, and at least one layer package may be applied to the substrate. Here, in order to include the substrate in the multilayer structure, the order of the high refractive index layers and low refractive index layers can be matched to the substrate. Metal oxides, metal oxide hydrates, or mixtures thereof are particularly preferred, preferably Ti, Sn, Si, Al, Zr, and Zn, and especially Ti, Sn, and Si. The oxides and / or oxide hydrates may be present in a single layer or in separate layers. In particular, rutile or anatase type, preferably rutile type titanium dioxide, is used. A tin dioxide layer is preferably applied beneath the titanium dioxide layer for the conversion of titanium dioxide to the rutile type. A preferred multilayer coating comprises alternating high refractive index layers and low refractive index layers, preferably, for example, TiO2-SiO2-TiO2. The layer of metal oxide, hydroxide, and / or oxide hydrate is preferably applied by a known wet chemical method, in which a wet chemical coating method developed for the production of effect pigments, which results in a coating of the substrate, can be used. After the wet chemical application, the coating product is subsequently separated, washed, dried, and preferably calcined. The thickness of these individual layers is typically 10 to 1000 nm, preferably 15 to 800 nm, particularly 20 to 600 nm, and especially 20 to 200 nm.

[0035] To enhance stability against light, temperature, water, and weather, effect pigments may undergo post-coating or post-treatment. The post-coating may be an organic and / or inorganic coating as the final layer. The post-coating preferably comprises at least one metal oxide layer of the elements Al, Si, Zr, Ce, or mixtures or mixed phases thereof. Furthermore, organic or organic / inorganic post-coatings are possible. Silanes and / or organically functionalized silanes can also be used alone or in combination with metal oxides. Suitable post-coating or post-treatment methods include, for example, those described in DE2215191, DE-A3151354, DE-A3235017 or DE-A3334598, EP0090259, EP0634459, WO99 / 57204, WO96 / 32446, WO99 / 57204, US5,759,255, US5,571,851, WO01 / 92425, WO2011 / 095326 or other methods known to those skilled in the art. Effect pigments usable in the present invention include, for example, commercially available interference pigments or pearlescent pigments offered under trade names such as Iriodin®, Pyrisma®, Xirallic®, Miraval®, Colorstream®, RonaStar®, Biflair®, and Lumina Royal®. Other commercially available effect pigments may also be used. In particular, pigments from Colorstream®, Xirallic®, Miraval®, and Ronastar® may be used.

[0036] In many cases, special effects can be obtained by using at least two different effect pigments, so the polymer film (22) may contain a mixture of different effect pigments. In this case, the effect pigments can be mixed in any proportion, but the total content of all effect pigments in the polymer film (22) should not exceed 60% by mass. The concentration of the effect pigment in the polymer film (22) is preferably in the range of 0.1 to 40% by mass, preferably 0.1 to 20% by mass. More preferably, the concentration of the effect pigment in the polymer film (22) is in the range of 0.1 to 15% by mass, particularly in the range of 0.2 to 10% by mass, and most preferably in the range of 0.2 to 8% by mass. Unless otherwise specified, the mass percent of the effect pigment in the above and below is based on the total mass of the solid part of the sealing film. The amount of the effect pigment, m, in the polymer film (22) 2 Gram per is defined by the thickness of the film. For example, a 20-μm-thick film containing 1% of the effect pigment in a component based on the binder medium corresponds to about 0.4 g of the effect pigment per m, while a 100-μm-thick film containing 12% of the effect pigment corresponds to about 18 g of the effect pigment per m. Therefore, the general range of the effect pigment per m of the treated solar surface is from 0.1 g / m for a thin film (1 μm) and low concentration to 75 g / m for a thick film (200 μm) and high concentration. 2 A film containing 1% of the effect pigment in a component based on the binder medium corresponds to about 0.4 g of the effect pigment per m, while a 100-μm-thick film containing 12% of the effect pigment corresponds to about 18 g of the effect pigment per m. Therefore, the general range of the effect pigment per m of the treated solar surface is from 0.1 g / m for a thin film (1 μm) and low concentration to 75 g / m for a thick film (200 μm) and high concentration. 2 A film containing 1% of the effect pigment in a component based on the binder medium corresponds to about 0.4 g of the effect pigment per m, while a 100-μm-thick film containing 12% of the effect pigment corresponds to about 18 g of the effect pigment per m. Therefore, the general range of the effect pigment per m of the treated solar surface is from 0.1 g / m for a thin film (1 μm) and low concentration to 75 g / m for a thick film (200 μm) and high concentration. 2 The general range of the effect pigment per m of the treated solar surface is from 0.1 g / m for a thin film (1 μm) and low concentration to 75 g / m for a thick film (200 μm) and high concentration. 2 from 0.1 g / m for a thin film (1 μm) and low concentration to 75 g / m for a thick film (200 μm) and high concentration. 2 The preferred amount is in the range of 0.2 to 30 g / m, preferably 1 to 15 g / m, particularly preferably 1 to 6 g / m. 2 The preferred amount is in the range of 0.2 to 30 g / m, preferably 1 to 15 g / m, particularly preferably 1 to 6 g / m. 2 The preferred amount is in the range of 0.2 to 30 g / m, preferably 1 to 15 g / m, particularly preferably 1 to 6 g / m. 2 The preferred amount is in the range of 0.2 to 30 g / m, preferably 1 to 15 g / m, particularly preferably 1 to 6 g / m.

[0037] The effect pigment can be introduced into the polymer film (22) by, for example, an extrusion method known to those skilled in the art. In extrusion molding, the thermoplastic plastic is melted into a viscous mass in the screw and then pressed through a nozzle to form a shape. The types of possible shapes are enormous. Films, foils, and plates are extruded through a flat nozzle. Nozzles with larger openings are used for solid rods, tubes, or flat profiles. Sheet / film extrusion is used to extrude plastic sheets or films that are too thick to blow out. Two types of dies are available: T-type and coat hanger. The purpose of these dies is to change and guide the flow of the polymer molten material from a uniform circular product from the extruder to a thin, planar flow. Both types of dies ensure a constant and uniform flow across the entire cross-sectional area of ​​the die. Cooling is generally achieved by pulling through a series of cooling rolls (calender or "chill" rolls). In sheet extrusion, these rolls not only provide the necessary cooling but also determine the thickness and surface properties of the sheet. Often, co-extrusion is used to apply at least one layer on top of the substrate to obtain specific properties such as improved mechanical properties, UV absorption, texture, oxygen permeability resistance, or energy reflectivity. Masterbatches or compounds are typically used to color molten masses using effect pigments. For satisfactory results in plastic extrusion molding using effect pigments, it is necessary to maintain an unbiased ratio between mixing energy and pigments that are as undamaged as possible. Excessive shearing or improper threading or filtering of the mixing section will destroy the effect pigments and dramatically reduce the pearlescent effect. Pigment orientation is crucial for a uniform effect. This must be ensured through corresponding engineering techniques and mechanical design.

[0038] In a preferred embodiment of the present invention, a masterbatch containing a desired amount, for example 20% by mass, of an effect pigment in a polymer material is added to the polymer film extrusion process. This can be done, for example, by preparing a premixture of colored masterbatch pellets using EVA pellets, or by other known methods. Due to the shear forces acting on the effect pigment during the melt extrusion process, the effect pigment is oriented substantially parallel to the surface of the sealing film.

[0039] In another preferred embodiment, the polymer film comprising at least one effect pigment is a co-extruded film of two or more layers of the same or different polymer material, wherein one layer, preferably the layer facing the front sheet, comprises at least one effect pigment. When such a two-layer film is used, the front sealing film (23) can be omitted, and is preferably omitted.

[0040] EVA, used as a encapsulant for lamination of PV modules, is a thermosetting polymer with components particularly adapted to exposure to photo-oxidative stress. Typical EVA components generally include, in addition to the polymer resin, crosslinking agents, adhesion promoters, UV absorbers, UV stabilizers, and antioxidants. The crosslinking agent is a radical initiator, usually a peroxide, which decomposes thermally during lamination, forming free radicals that generate radicals in the polymer's main chain. The formed radicals then form covalent bonds between polymer chains.

[0041] The layer thickness of the polymer film (22) containing the effect pigment before the pre-lamination step is preferably in the range of 5 μm to 1000 μm, more preferably 20 μm to 800 μm, and even more preferably 100 μm to 400 μm. The thickness of the film after the pre-lamination step typically decreases depending on the lamination conditions. [Examples]

[0042] The following examples are intended to illustrate the present invention without limiting it.

[0043] Example 1 Preparation of sealing film using effect pigments 1g / m 2 A sealing EVA film containing the effect pigment Iriodin® 7235 Ultra Rutile Green Pearl and other additives is manufactured as follows: By manufacturing separate masterbatches containing different additives, we avoid unnecessary flexibility in formulation. An EVA masterbatch containing 10% Iriodin® 7235 Ultra Rutile Green Pearl is manufactured as granules using a standard extrusion method. 2.5% of this masterbatch is used to manufacture EVA encapsulating film. A second EVA masterbatch containing 5% triallyl isocyanurate (TAIC crosslinking agent), 2.5% 3-methacryloxypropyltrimethoxysilane (VMMS, silane glass coupling agent), 3% Tinuvin 770 (HALS, UV stabilizer), and 7% Cyasorb UV 531 (UV absorber) is produced as fine granules by a standard extrusion method. Ten percent of this masterbatch is used to produce EVA encapsulating film. A third masterbatch of EVA containing 10% tert-butylperoxy 2-ethylhexyl carbonate (Luperox® TBEC, peroxide crosslinking agent) is produced as fine granules using a standard extrusion method. Since the extrusion temperature is kept low, no crosslinking reaction occurs at this stage (<120°C). Various masterbatches (2.5% pigment masterbatch, 10% additive masterbatch, and 10% peroxide masterbatch) are added and mixed with colorless EVA granules, then fed into a hopper toward a heated nozzle on a state-of-the-art film extrusion line. EVA film is produced to a thickness of 0.40 mm. Since the extrusion temperature is kept low, no crosslinking reaction occurs at this stage (<120°C).

[0044] Preparation of sealing film without effect pigments The film is manufactured using a similar method, but without using a masterbatch containing effect pigments.

[0045] a) Prelamination An EVA film containing the effect pigment Iriodin® Ultra Rutile Green Pearl is placed on a windshield sheet with a thickness of 4000 μm and lateral dimensions of 40 × 40 cm, which is conventionally used in solar modules. The EVA film is then laminated onto the glass sheet in a vacuum press at 145°C with a lamination pressure profile of 400 mbar for 20 seconds / 700 mbar for 20 seconds / 900 mbar for 650 seconds. During lamination, the EVA film is covered with a Teflon® textile film and a glass plate on top to prevent adhesion to the film surface and to ensure flat pressing and uniform temperature distribution.

[0046] b) cooling After pre-lamination step a), the windshield sheet having a laminated EVA film containing the effect pigment is cooled to room temperature.

[0047] c+d) Module stacking The following stack was assembled using the windshield sheets manufactured in steps a) and b) with the laminated EVA film containing the effect pigment on the inside. 1. Pre-laminated windshield using EVA film containing green effect pigment / colorless EVA film / solar cell with busbar / colorless EVA film / black EVA film / glass 2. Pre-laminated windshield using EVA film containing green effect pigment / colorless EVA film / solar cell with busbar / colorless EVA film / black TPT film / colorless EVA film / glass 3. Pre-laminated windshield using EVA film containing green effect pigment / colorless EVA film / solar cell with busbars / black EVA film / glass 4. Pre-laminated windshield using EVA film containing green effect pigment / colorless EVA film / solar cell with busbar / colorless EVA film / black TPT film

[0048] Stacks 1-4 are placed in a standard lamellar laminator that uses pins and thin-film pressure adjustable by controlling the vacuum level of the upper chamber, which can heat the upper lamella and hot plate. Stacks 1-4 are arranged in a laminator, and the stacks are processed at 145°C with the following lamination pressure profiles: 400 mbar for 20 seconds / 700 mbar for 20 seconds / 900 mbar for 650 seconds. After lamination, the module is cooled to room temperature. Visual inspection indicates that there are no patterns that would occur after lamination.

[0049] Comparative Example 1 1 g / m² manufactured as described in Example 1 2 The following stack was assembled using an encapsulated EVA film containing the effect pigment Iriodin® 7235 Ultra Rutile Green Pearl, and a separate windshield sheet. 1. Windshield / EVA film containing green effect pigment / colorless EVA film / solar cell with busbar / colorless EVA film / black EVA film / glass 2. Windshield / EVA film containing green effect pigment / colorless EVA film / solar cell with busbar / colorless EVA film / black TPT film / colorless EVA film / glass 3. Windshield / EVA film containing green effect pigment / Colorless EVA film / Solar cell with busbar / Black EVA film / Glass 4. Windshield / EVA film containing green effect pigment / colorless EVA film / solar cell with busbars / colorless EVA film / black TPT film

[0050] Stacks 1-4 are placed in a standard lamellar laminator that uses pins and thin-film pressure adjustable by controlling the vacuum level of the upper chamber, which can heat the upper lamella and hot plate. Stacks 1-4 are arranged in a laminator, and the stacks are processed at 145°C with the following lamination pressure profiles: 400 mbar for 20 seconds / 700 mbar for 20 seconds / 900 mbar for 650 seconds. After lamination, the module is cooled to room temperature.

[0051] result Figure 3 shows a solar cell module manufactured according to Stack 2 of Comparative Example 1. Figure 4 shows a solar cell module manufactured according to stack 2 of Example 1. Modules manufactured by the method based on Comparative Example 1 without pre-lamination step a) showed a clearly visible pattern (Figure 3), while modules manufactured by the method based on Example 1 with pre-lamination step a) did not show this pattern (Figure 4). For solar modules manufactured according to the method of Example 1, including the prelamination step, the climate chamber damp heat 1000 test (described at http: / / sinovoltaics.com / learning-center / testing / damp-heat-test / ) shows no impact on long-term stability. These results demonstrate that the method according to the present invention enables highly efficient coloring of a solar cell module formed from multiple electrically interconnected solar cells with a high level of long-term stability, while simultaneously reducing the occurrence of unwanted dark patterns in the cells and busbars.

Claims

1. 1. A method for producing a colored solar cell or a colored solar cell module, comprising the steps of: a) A polymer film containing at least one effect pigment is laminated to a front sheet. b) Optionally, cooling the front sheet having the polymer film containing the effect pigments laminated thereto. c) providing a stack comprising the following layers on top of the front sheet having the polymer film comprising the effect pigment laminated thereto, or providing the front sheet having the polymer film comprising the effect pigment laminated thereto on top of the stack of layers C1 to C4: C1) Optionally, at least one front sealing film C2) At least one solar cell or an array of solar cells electrically interconnected by conductive parts, preferably by bus bars. C3) Optionally, at least one rear sealing film C4) Rear seat d) Laminating said stack of layers C1-C4 to said front sheet having laminated thereto said polymer film containing said effect pigments.

2. 2. The method of claim 1, wherein the stack in step c) comprises a front sealing film between the polymer film containing the effect pigment and the solar cell or solar cell array, the front sealing film being free of effect pigments.

3. 2. The method of claim 1, wherein the rear sheet is black or dark in color and / or the stack in step c) comprises an additional sheet or sealing film disposed between the solar cell or solar cell array and the rear sheet, the additional sheet or sealing film being black or dark in color.

4. 2. The method according to claim 1, wherein the conductive parts interconnecting the solar cells are pigmented black or a dark color prior to application of the polymer film containing the effect pigment.

5. 10. The method of claim 1, wherein a dark grid is incorporated into the solar cell or solar cell array, the grid covering light areas including, but not limited to, the space between the solar cell and the conductive component.

6. 2. The method according to claim 1, wherein the polymer film comprising the effect pigment, the front seal film and the rear seal film are selected from polyolefin films, preferably polyethylene copolymer films selected from EVA, EBA, EMA, EEA, POE and BPO films, or PVB or TPU films, very preferably EVA films.

7. The method of claim 1 , wherein the front sheet and / or the rear sheet is a glass sheet.

8. The method of claim 1 , wherein the front sheet and / or the rear sheet is a polymer sheet.

9. 2. The method of claim 1, wherein the solar cell or the solar cell module is selected from an amorphous silicon solar cell, a monocrystalline silicon solar cell, a polycrystalline silicon solar cell, a CIGS solar cell, a CdTe solar cell, a III / V solar cell, a II / VI solar cell, a perovskite solar cell, a quantum dot solar cell, an organic solar cell, and a dye-sensitized solar cell.

10. 2. The method according to claim 1, wherein the laminating steps a) and d) are carried out by applying heat and / or pressure or by using adhesives or bonding agents or layers, preferably in a vacuum press.

11. The method of claim 1, wherein the heating temperature in the laminating steps a) and d) is in the range of 130°C to 160°C.

12. 2. The method according to claim 1, wherein the effect pigment and / or the polymer film comprising the effect pigment has a selective reflection maximum in the visible region of the solar spectrum.

13. The method according to claim 1, wherein the effect pigment and / or the polymer film comprising the effect pigment has a total transmittance of at least 60% for radiation in the range of 260 to 1200 nm.

14. 2. The method of claim 1, wherein the effect pigment and / or the polymer film comprising the effect pigment has a total reflectance of <40% for radiation in the range of 260-1200 nm.

15. The method of claim 1 , wherein the effect pigment is selected from pearlescent pigments, interference pigments and multi-layer pigments.

16. The effect pigments are made of synthetic or natural mica, flake glass substrates, flake SiO 2 Substrate or flake-like Al 2 O 3 The method of claim 1 which is based on a substrate.

17. 17. The method of claim 16, wherein the flaky substrate is coated with at least one layer of metal oxides and / or metal oxide hydrates of Ti, Sn, Si, Al, Zr and Zn.

18. The method of claim 1, wherein the amount of the effect pigment in the polymer film is in the range of 0.2 to 40% by weight.

19. The method of claim 1, wherein the thickness of the polymer film containing the effect pigments is in the range of 5 to 1000 μm.

20. 2. The method of claim 1, wherein the polymer film containing the effect pigment is produced by melt extrusion of an organic polymeric material, the effect pigment being added to the polymer melt prior to extrusion.

21. 21. The method of claim 20, wherein the polymer film comprising the effect pigment is a coextruded film of at least two layers, one of the at least two layers comprising the effect pigment.

22. A colored solar cell or a colored solar cell module produced by the method according to any one of claims 1 to 21.

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