EP4673980A1

EP4673980A1 - Method for producing a pv panel such as a pv integrated vehicle body panel with a moulded rear support structure and a directly coated moulded front cover structure

Info

Publication number: EP4673980A1
Application number: EP24708435.3A
Authority: EP
Inventors: Sebastian THENER; Dominik KÖHNLEIN; Eduardo Pastor Torcato Ribeiro; Harshan Kalenahalli RAMESHA
Original assignee: Sono Motors GmbH
Current assignee: Sono Motors GmbH
Priority date: 2023-03-02
Filing date: 2024-02-28
Publication date: 2026-01-07
Also published as: WO2024180145A1; DE102023105205A1

Abstract

A method for producing a photovoltaic panel (1), particularly a photovoltaic vehicle body panel, is presented. The method comprises: providing a photovoltaic (PV) label (3) comprising polymeric foils (5, 7, 9, 11) and a solar cell arrangement (9) interposed between the polymeric foils, preparing a rear support structure (17) by applying a first mouldable polymer (121) to a rear surface (4) of the PV label, including arranging the PV label in a first mould (103) forming a rear side cavity (119) adjacent to the rear surface of the PV label and applying the first mouldable polymer onto the rear surface of the PV label for filling the rear side cavity and solidifying the first polymer, and preparing a transparent front cover structure (23) covering a front surface (6) of the PV label, wherein the front cover structure is prepared by applying a transparent second mouldable polymer (133) to the front surface of the PV label, including arranging the PV label (3) together with the rear support structure in a second mould (123) forming a front side cavity (131) adjacent to the front surface of the photovoltaic label and applying the second mouldable polymer along the front surface of the photovoltaic label for filling the front side cavity of the second mould and solidifying the polymer. Using such direct coating technique for preparing the protective transparent front cover structure may significantly simplify the production method as compared to e.g conventional spray-coating.

Description

Sono Motors GmbH

Method for producing a PV panel such as a PV integrated vehicle body panel with a moulded rear support structure and a directly coated moulded front cover structure

FIELD OF THE INVENTION

The present invention relates to a method for producing a photovoltaic panel, particularly for producing a photovoltaic vehicle body panel, into which a solar cell arrangement is integrated. Furthermore, the present invention relates to the photovoltaic panel, particularly to the photovoltaic vehicle body panel which may optionally be produced with the method described herein.

TECHNICAL BACKGROUND

In the following, the term “photovoltaic” may be abbreviated by “PV”. PV cells may also be referred to as solar cells. Furthermore, while the term “vehicle body panel” or “solar body panel” may refer to a panel which may be included in a body of any kind of vehicles such as cars, trucks, busses, mobile homes, trains, ships, airplanes, etc., embodiments are described herein with reference to car body panels for simplicity of description.

Conventionally, most commercially available PV panels are typically produced by providing planar, rigid, wafer-based solar cells and then laminating these solar cells between a front side glass sheet and a rear side support structure such as another glass sheet or a metal sheet. Therein, the solar cells are interposed between thin lamination foils serving for both, tightly encapsulating the solar cells and mechanically interconnecting the stack including the front and rear side sheets with the interposed solar cell arrangement. Such PV panels are also referred to as PV modules and have typically a planar structure. These PV panels are well suited for installation on buildings or in solar farms. However, such planar PV panels are hardly suited for an integration into curved surfaces such as for example surfaces of body panels of a car or another vehicle.

Approaches have been presented in which PV cells are provided at a body of a car for generating electricity to be supplied to the car. Such electricity may be used for example for charging batteries of an electric car.

For example, it has been proposed e.g. in an earlier patent application WO 2019/020718 Al of the present applicant to provide solar cells in a body panel of a vehicle. Therein, a PV module shall be placed on top of such body panel or, preferably, the PV module shall be integrated into the body panel. Specifically, one or more solar cells may be arranged in an air tight and water tight manner in a recess provided in a carrier structure of a car body panel.

In an alternative approach for manufacturing PV modules, it has been proposed by the present applicant in an earlier patent application WO 2020/187792 Al to integrate a solar cell arrangement into a moulded layer formed by injection moulding. Therein, the solar cell arrangement is interposed between polymeric foils, thereby forming a so-called photovoltaic label which may be securely handled and in which the solar cells are for example protected against excessive mechanical stress during an injection moulding procedure.

Another approach for a car body panel comprising an integrated solar cell arrangement has been proposed by the present applicant in earlier patent application WO 2022/122507 Al. A further approach for producing a PV panel has been presented in the applicant’s earlier patent application DE 10 2022 101 935 Al, wherein the technique of reaction injection moulding (RIM) is beneficially used for preparing, inter alia, PV-integrated vehicle body panels.

In each of these prior art approaches, the vehicle body panel including the solar cell arrangement may be regarded as a photovoltaic module having a planar or a non-planar shape. A body panel of a vehicle including an integrated PV module may be referred to herein as PV integrated vehicle body panel.

Possible features and characteristics of such approaches of vehicle body panels and approaches for fabricating a vehicle body panel including a PV module have been described by the applicant in the above mentioned patent applications as well as in several further prior patent applications such as WO 2021/260021 Al, WO 2021/260024 Al, DE 102022 108 014 Al as well as the EP applications with the application numbers EP 22 217 406, EP 22217402 and EP 22 217 403, the latter two applications relating to a use of a compression moulding technique. Features and characteristics of such approaches may also apply to the PV (vehicle body) panel and the production method described herein and the content of the earlier patent applications shall be incorporated in its entirety herein by reference.

SUMMARY OF THE INVENTION AND OF EMBODIMENTS

It may be an object to provide a method for producing a PV panel, particularly a PV vehicle body panel, in which a solar cell arrangement is integrated and which fulfils both, very high functional requirements as well as very high aesthetic requirements. Furthermore, it may be an object to provide a production method which enables a relatively simple fabrication procedure, high fabrication yield and/or low fabrication costs while providing a fabrication result as a highly functional, reliable and aesthetic PV-integrated (car body) panel. Furthermore, it may be an object to provide a PV panel, particularly a PV vehicle body panel, being highly functional and reliable as well as aesthetic and furthermore being producible in a reliable and cost efficient manner.

Such objects may be met with the subject-matter of the independent claims. Advantageous embodiments are defined in the dependent claims and described in the following specification and visualised in the associated figures.

According to a first aspect of the present invention, a method for producing a photovoltaic panel, particularly a photovoltaic vehicle body panel, is described. The method comprises at least the following steps, preferably in the indicated order: providing a photovoltaic label comprising polymeric foils and a solar cell arrangement interposed between the polymeric foils, preparing a rear support structure for supporting the photovoltaic label, wherein the rear support structure is prepared by applying a first mouldable polymer to a rear surface of the photovoltaic label, including arranging the photovoltaic label in a first mould forming a rear side cavity adjacent to the rear surface of the photovoltaic label and applying the first mouldable polymer onto the rear surface of the photovoltaic label for filling the rear side cavity of the first mould and solidifying the polymer, and preparing a transparent front cover structure covering a front surface of the photovoltaic label, wherein the front cover structure is prepared by applying a transparent second mouldable polymer to the front surface of the photovoltaic label, including arranging the photovoltaic label together with the rear support structure in a second mould forming a front side cavity adjacent to the front surface of the photovoltaic label and applying the second mouldable polymer along the front surface of the photovoltaic label for filling the front side cavity of the second mould and solidifying the polymer.

According to a second aspect of the invention, a PV panel, particularly a vehicle body panel, is described. The PV panel includes a PV label, a rear support structure and a transparent front cover structure. The PV label comprises polymeric foils and a solar cell arrangement interposed between the polymeric foils. The rear support structure supports the PV label, wherein the rear support structure comprises a first mouldable polymer adhering to a rear surface of the PV label. The transparent front cover structure covers a front surface of the photovoltaic label, wherein the front cover structure comprises a transparent second mouldable polymer adhering to the front surface of the photovoltaic label.

Briefly summarised and without limiting the scope of the invention, basic ideas underlying embodiments of the invention and associated possible advantages will be roughly described as follows:

As indicated above, various approaches for producing PV panels with a potentially curved surface have been suggested by the applicant. For a large volume fabrication of e.g. PV integrated car body panels, the approaches as described e.g. in WO 2020/187792 Al, in DE 10 2022 101 935 Al or in the EP applications with the application numbers EP 22217402 and EP 22 217403 are highly promising. Therein, a solar cell arrangement included in a PV label is provided at its rear surface with a support structure, wherein the support structure is prepared by moulding a polymer material using injection moulding techniques, reaction injection moulding techniques (RIM), compression moulding techniques or a combination thereof.

It has been found that such approaches of preparing a PV panel by moulding the solar cell arrangement into a support structure prepared by some moulding techniques appears to allow rapid and/or cost efficient production of large numbers of PV panels. In such approaches, the rear side of the PV label is well supported and protected by the moulded support structure. However, it has been observed that the front side surface of the PV label is generally pressure sensitive, temperature-sensitive, UV sensitive and/or may be scratched easily and therefore needs some additional protection. Conventionally, such protection is typically provided by applying an additional layer using e.g. coating techniques such as spray coating or using painting techniques. However, applying such additional protective layer by spray-coating or painting generally requires additional efforts such as additional processing steps as well as additional processing equipment, thereby inducing, inter aha, additional costs, increased scrap rates and/or additional logistics requirements.

In order to overcome such deficiencies, it is suggested herein to prepare not only the rear support structure for the PV label using moulding techniques but also to prepare an additional cover structure at the front surface of the PV label using moulding techniques. Such approach may also be referred to as direct coating or direct moulded coating.

Compared to the conventional approach of protecting the PV label’s front surface using spraycoating or painting for generating a protective layer, such approach of using moulding techniques for generating the protective layer may provide multiple advantages. For example, as moulding techniques are used for generating both, the rear support structure as well as the front cover structure, a single moulding apparatus may potentially be used for performing both moulding steps. Furthermore, instead of generating the rear support structure using moulding techniques and generating a front protection layer using e.g. spray-coating, i.e. using different techniques, both processes may be combined and may both use moulding techniques, thereby enabling an elimination of process steps, a reduction of logistics efforts, a reduction of energy consumption, a reduction of a risk of damages (e.g. scratches) being induced e.g. during transportation between different processing stages, a reduction of investment costs, etc. Furthermore, as the moulding procedures for preparing the rear support structure as well as the front cover structure may be included in a closed process, highest reproducibility is enabled as well as orange peel or frame effects may be prevented. Additionally, the proposed approach may be beneficial with regards to health and environment as it may be completely solvent-free, may not require any overspray and/or may enable reduced energy consumption. Furthermore, the front cover structure prepared by moulding techniques may have improved characteristics as compared to e.g. spray-coated or painted layers. For example, such moulded cover structure may have improved protection characteristics such as increased scratch resistance and/or superior abrasion resistance.

Furthermore, such moulded front cover structure may provide for an excellent brilliance and/or depth effect. Particularly, the moulded front cover structure may be easily prepared such as to have beneficial characteristics such as an attractive visual appearance e.g. with a matt surface finish and/or a smooth surface structure (i.e. e.g. without waviness). It may even be possible to provide the moulded front cover structure with optical characteristics, such as light-trapping characteristics, which enable an improved efficiency of the solar cell arrangement comprised in the underlying PV label. Last but not least, the moulded front cover structure may show a self- healing effect in which e.g. superficial scratches may automatically disappear, i.e. “heal”, within relatively short times at room temperature or slightly increased temperatures.

In the following, possible features of embodiments of the invention and associated possible advantages will be described in more detail.

The approach proposed herein is particularly suitable for a PV-integrated (car body) panel comprising multiple PV cells which are prepared based on brittle semiconductor wafers. The PV cells may be for example solar cells being fabricated based on crystalline silicon wafers. Such wafer-based Si-PV cells may generally have e.g. a high efficiency of more than 15% (i.e. e.g. between 17% and 26%) and a high reliability. Furthermore, well established industrial processes exist for their fabrication. Such PV cells typically have lateral dimensions of between 50x50 mm² and 300x300 mm², mostly between 150x150 mm² and 200x200 mm², with a square shape, a rectangular shape, a round shape, a semi-round shape or any other shape. Furthermore, such PV cells generally have a thickness of more than 50 pm, typically between 100 pm and 300 pm.

Having such thickness, the PV cells are relatively rigid, i.e. they may generally not be bent into small bending radii of e.g. less than their lateral dimensions. Generally, it may be assumed that, depending on a cell size, bending radii of less than 80 cm, less than 90 cm or less than 100 cm should be avoided.

Each PV cell comprises electric contacts. The electric contacts of neighbouring PV cells may be interconnected via electrical connections such that these PV cells may be electrically connected in series, in parallel or in any combination of series and parallel connections. The electrical connections may be provided by one or more electrically conducting ribbons and/or one or more copper solderings between two adjacent photovoltaic cells, preferably between each two adjacent photovoltaic cells of a respective string. A plurality of interconnected PV cells forms part of a solar cell arrangement, sometimes also referred to as solar cell string. The solar cell arrangement may further comprise additional components such as external contacts via which the solar cell arrangement may be connected to an external electric circuit, such external contacts sometimes being referred to as forming part of a junction box or connection box. Furthermore, the solar cell arrangement may comprise for example bypass diodes or other electric components.

Additionally, one or more release loops for releasing mechanical tensions may be included in the solar cell arrangement.

The solar cell arrangement is generally comprised in an encapsulation into which the solar cells, the electrical interconnections and possibly other components are embedded. Typically, the encapsulation comprises or consists of a thermoplastic polymer such as EVA (Ethylene Vinyl Acetate) or POE (Polyolefin Elastomer). The encapsulation may be composed of a front side polymeric lamination foil or sheet and a rear side polymeric lamination foil or sheet enclosing the plurality of solar cells from opposite sides. The lamination foils may also be referred to as encapsulation foils. In a lamination procedure, such front and rear side encapsulation foils may then be heated beyond a glassifying temperature of the polymeric material while being pressed against each other. Accordingly, the sticky viscous or even partially molten polymer material of both encapsulation foils may combine in regions where the foils contact each other and/or may glue to solar cells interposed between the encapsulation foils. Accordingly, upon cooling down and solidifying the polymer material, the solar cells and the polymer material of the lamination foils may form an encapsulation.

As the solar cell arrangement in its encapsulation is generally very fragile, the solar cell arrangement including the solar cells, the electric connections and the encapsulation is reinforced by one or more stabilisation foils for forming a PV label. Preferably, a front side polymeric stabilisation foil and a rear side polymeric stabilisation foil may enclose the interposed solar cell arrangement and may form a substrate and a superstate, respectively, prior to reinforcing the PV label by moulding the support structure. In specific embodiments, the PV label may not necessarily comprise the rear side polymeric stabilisation foil. The one or more polymeric stabilisation foils may have a thickness of typically between 250pm and 3500pm. Each of the foils may adjoin and/or cover a part or an entirety of one of opposing surfaces of all of the PV cells. The polymeric stabilisation foils may be made with various polymeric materials such as, polycarbonate (PC), polyethylenterephthalat (PET), polyamide (PA), polyetheretherketone (PEEK), Acrylonitrile butadiene styrene (ABS), Polymethyl methacrylate) (PMMA), Polyvinylchlorid (PVC) or a mix of them. At least the front side stabilisation foil as well as the front side lamination foil shall consist of an optically translucent or transparent material. Particularly, a material forming the stabilisation foil may be a thermoplastic material, i.e. a material which becomes plastic or viscous upon being heated to elevated temperatures. The front and rear side polymeric stabilisation foils may enclose the interposed solar cell arrangement and, upon being joined with each other, encapsulate the solar cell arrangement. Optionally, glass fiber reinforced or carbon fiber reinforced plastics may be included between the polymeric foils.

Particularly, the front side stabilisation polymeric foil, the rear side stabilisation polymeric foil, the lamination foils and the PV cells may be joined together by an application of heat and/or a lamination process. In other words, after having arranged e.g. the rear side polymeric stabilisation foil, the solar cell arrangement with its encapsulation and finally the front side polymeric stabilisation foil on top of each other in a lose manner, these stacked layers may be interconnected by mechanically joining with each other. Such joining may be induced for example by applying sufficient heat to the stack such that the polymeric material of the polymeric foils becomes viscous and/or sticky. Accordingly, upon such temporary application of heat, the polymeric stabilisation foils may mechanically interconnect with each other and/or with the interposed solar cell arrangement.

Thus, the front and rear side polymeric stabilisation foils and the solar cell arrangement are joined in a lamination procedure. The lamination procedure may be integral with the lamination procedure used for forming the encapsulation embedding the PV cells, i.e. both the front and rear side polymeric stabilisation foils as well as the front and rear side polymeric encapsulation foils may be glassified or partially molten within a single lamination step. Alternatively, two separate lamination steps may be performed, i.e., first, the solar cell arrangement is laminated with the encapsulation foils enclosing the PV cells and, then, the PV label is laminated with the stabilisation foils enclosing the solar cell arrangement in between. As a result of such lamination procedure, the front and rear side polymeric foils and, optionally, also the PV cells are integrally joined with each other in a positive substance jointing. However, the lamination procedure may alternatively or additionally include other measures for joining the polymeric foils such as for example applying a glue or adherent at an interface between the polymeric foils and/or at an interface between one of the polymeric foils and the solar cell arrangement.

The entire PV label may have a thickness in a range of between 0.5 mm to 10 mm, typically between 0.5 mm to 5 mm or between 1 mm and 3 mm. Lateral dimensions of the PV label may range from about 0.1 m to 2 m, typically from 0.2 m to 1 m. The PV label may be flexible and bendable and may be formed into an arbitrary contour being adapted to a shape of the intended car body panel. Therein, the solar cells comprised in the car body panel cover a substantial portion, i.e. for example more than 30%, preferably more than 50% or even more than 70%, of an outer surface of the car body panel.

The PV label is generally flexible, bendable and/or, at least in some applications, not sufficiently self-supporting. Accordingly, for forming a self-supporting PV panel, the PV label generally has to be reinforced by a support structure. Such support structure typically has a higher mechanical stability than the PV label. Such higher mechanical stability may result, inter-alia, from larger geometrical dimensions such as a larger thickness compared to the thickness of the PV label and/or higher stiffness due to material properties of the polymer used. The support structure and the PV label are generally mechanically interconnected such that forces acting onto the PV label may be transmitted to the support structure and vice versa.

According to the approach described herein, the support structure shall be prepared with a first mouldable polymer. The first mouldable polymer may be thermoplastic or thermosetting. Specifically, the support structure is prepared by applying the first mouldable polymer to a rear surface of the PV label, i.e. to a surface which is directed in the opposite direction compared to the light-sensitive surfaces of the solar cells comprised in the PV label. For such purpose, the PV label is first arranged in or at a first mould. Such first mould may be part of a moulding apparatus comprising for example at least two moulds in the form of moulding halves which may be displaced relative to each other and which are configured such as to generate a cavity between each other. Particularly, such cavity shall be formed adjacent to the rear surface of the PV label and should extend along major portions of the PV label. Accordingly, for forming the rear support structure, the first mouldable polymer is applied to the rear surface of the PV label and spread along this rear surface such as to finally fill the rear side cavity formed between an inside surface of the first mould, on the one side, and the rear surface of the PV label, on the other side.

In such procedure, the rear support structure may be formed using one of various moulding techniques including injection moulding, reaction injection moulding (RIM) or injection compression moulding (I CM). Possible details of approaches using such moulding techniques are described in the applicant’s prior applications, particularly in WO 2020/187792 Al, in DE 10 2022 101 935 Al or in the EP applications with the application numbers EP 22 217 402 and EP 22 217403. In principle, the rear support structure may be made from any one of various polymeric materials or a combination of such materials. However, it has been found that, for the PV panel discussed herein, it may be advantageous to prepare the rear support structure with a thermoplastic polymer material. Particularly, polycarbonate (PC), acrylonitrile butadiene styrene (ABS) or a combination of both materials have been found to provide superior characteristics for preparing the rear support structure.

The PV label together with the rear support structure may already form an operative and self- supporting PV panel. However, in such PV panel, one of the polymeric foils of the PV label forming its outermost front side layer, i.e. in most cases the front side polymeric stabilisation foil, would be exposed and its would therefore be subject to environmental stresses such as mechanical attacks (e.g. scratching), chemical attacks, thermal stress, etc. As such outermost polymeric foil is generally not sufficiently resistant to such stresses, it has been found that the PV label should be covered at its front side with a protective structure.

Conventionally, such protective front cover structure may be formed by a cover layer which may be applied using coating techniques in which coating material is applied in a liquid form and which form a thin layer of coating material after solidification, such layer generally having a uniform thickness. For example, such layer may be spray-coated or painted on top of the PV label’s front surface.

However, such spray-coating or painting requires additional efforts, particularly additional processing steps and/or additional machinery. For example, the semifinished PV panel with the rear support structure being applied to the PV label has to be transported to another processing stage where it is then coated with the cover layer on top of its front surface using a separate spray-coating machine or painting machine. Furthermore, as such spray-coated or painted cover layer is typically very thin and is applied with a coating material being in its liquid state, the cover layer generally may not provide superior mechanical protection and/or generally conforms with the underlying front surface of the PV label. Accordingly, on the one hand, characteristics of an outside surface of the cover layer may not be set independently from characteristics of the underlying front surface of the PV label. Particularly, any unwanted uneven surface or waviness of the PV label, which may occur due to tolerances in a procedure for producing the PV label, is generally also transferred to the front surface of the thin coating. On the other hand, the outer surface of such coating is generally microscopically smooth and therefore provides a glossy appearance, which might not be wanted for certain applications. As a beneficial alternative to conventional coating techniques, it is proposed herein to prepare the protective front cover structure using a technique which is also referred to as direct coating or inmould coating. Therein, similar to the preparation of the rear support structure, a structure consisting of polymer material is generated at the front side of the PV label using a specific second mould. This second mould has a geometry differing from the one of the first mould. Particularly, the second mould has a geometry such that a cavity is formed adjacent to the front surface of the PV label upon the PV label together with its previously prepared support structure being arranged in the second mould. Such cavity is therefore referred to herein as front side cavity. Such front side cavity may then be filled with the second mouldable polymer. Accordingly, this polymer is applied and distributed along the front surface of the PV label and, upon subsequent solidification, forms the front cover structure. An inner volume of the second mould is larger than the inner volume of the first mould, as it comprises the volume of the front side cavity in addition to the volume required for accommodating the PV label together with the rear support structure.

Contrary to conventional coatings, the moulded front cover structure generally does not need to have a thin uniform layer structure with its outer surface conforming with the front surface of the underlying PV label. Instead, characteristics such as its thickness, its thickness distribution along its lateral extension and/or its surface are defined for such moulded front cover structure mainly by characteristics of the second mould used for defining the front side cavity.

Accordingly, as explained in further detail below, the moulded front cover structure may have a thickness being substantially larger than the one of conventional coatings, the thickness may vary along the lateral extension of the front cover structure and/or the surface of the front cover structure may be prepared with a specific texture, thereby enabling valuable advantages especially for the present application in which the front cover structure covers solar cells in the PV label.

According to an embodiment, the front cover structure is prepared using a reaction injection moulding procedure in which the transparent second mouldable polymer is a thermosetting polymer and the procedure includes at least one of the following characteristics:

- mixing at least two chemical components for preparing the thermosetting polymer, wherein the two chemical components are mixed immediately before injecting the thermosetting polymer into the second mould;

- injecting the thermosetting polymer into the mould with a pressure of between 30 bar and 100 bar, preferably between 50 bar and 80 bar;

- injecting the second mouldable polymer into the mould with the thermosetting polymer having a temperature of between 20°C and 100 °C, preferably between 50°C and 80°C.

In other words, the front cover structure is prepared preferably by using a reaction injection moulding (RIM) procedure including arranging the photovoltaic label in the second mould, injecting the thermosetting polymer into the second mould and removing the front cover structure formed upon solidifying the thermosetting polymer together with the photovoltaic label and the rear support structure from the mould.

Reaction injection moulding (RIM) is a technique which is well established for producing for example large parts using low-cost tooling. Therein, a mould having a cavity is provided. The shape of the cavity corresponds to the shape of an intended moulded product. Similarly as in conventional injection moulding, a polymer being in a liquefied state is injected into the mould and is then solidified within the mould. However, in contrast to conventional injection moulding where a thermoplastic polymer is heated for being temporarily liquefied and then solidifies within the mould by cooling down, a thermosetting polymer is injected into the cavity of the mould. As such thermosetting polymer may generally have a substantially lower viscosity as compared to typical viscosities of a liquefied thermoplastic polymer, the thermosetting polymer may be injected in a RIM technology at substantially lower pressures as compared to pressures used in conventional injection moulding.

RIM is conventionally used for preparing products with a uniform polymeric material, i.e. the entire moulded product generally consists of the thermosetting polymer. Therein, RIM is known to provide several advantages such as low-cost tooling, rapid production of the tooling, enabling the production of thin-walled components with varying wall thicknesses allowing sharp edges, short lead-times for large components, low capital investment, minimum setup requirements, cosmetic surface finishing, enabling processing of various polymer materials having positive physical characteristics such as being flame retardant or having high sheet deflection, etc. In some appliances, small parts such as pins, screws, brackets, etc. may be arranged within the cavity of the mould such as to be moulded into the polymer material and form part of the final product.

In the embodiment presented herein, it has been found that RIM may be beneficially used for preparing a cover structure for a PV label in a way such that a risk of damaging the PV label and particularly the solar cells comprised therein is minimised. At the same time, using the RIM technology enables providing a very reliable, resistant, aesthetic and/or cost efficient PV panel. Optionally, the PV panel may have a curved surface and may serve for example as a vehicle body panel with PV integration. Furthermore, RIM may be specifically beneficial for integrating PV labels into solar panels, particularly into vehicle body panels, as it enables preparing thin walled structures and/or sharp edges.

The thermosetting polymer may be processed such that, during being applied to the PV label, it has a sufficiently low viscosity such as to enable spreading the thermosetting polymer along the front surface of the PV label without exerting excessive forces onto the PV label.

For example, the thermosetting polymer may be a mixture of two or more components. At least one of these components may be a liquid having a low viscosity. For example, the viscosity at room temperature (25°C) may be below 1000 mPa*s, preferably below 300 mPa*s or even below 150 mPa*s. The components are adapted such as, upon being mixed with each other, a chemical reaction is initiated which results in a successive solidification of the mixture. In other words, upon being mixed, the components cure and solidify due to chemical reactions. However, initially, i.e. directly after having been mixed, the mixture of the components is highly fluid and may therefore easily be applied and spread along a surface of the PV label. Such application and spreading of the fluid polymer mixture may be done during a can-time (also referred to as potlife) of the mixture. Such can-time may be in a range of several seconds to several minutes. Typically, the can-time may be shorter than five minutes or shorter than one minute. The thermosetting polymer mixture then continuously solidifies until, after a demoulding time, being sufficiently solid for being stable. The demoulding time may be typically more than a few minutes, for example more than ten minutes. The thermosetting polymer may then require another period of for example a few days until reaching a final solidification status. The thermosetting polymer may be based e.g. on a two-component polyurethane system. For example, the thermosetting polymer may be a mixture of polyol and isocyanate. It may contain glassfiber or carbonfibers for improving the material properties, as described in more details further below.

Alternatively, the thermosetting polymer may comprise only one component and may be configured to cure and solidify upon energy being induced into the polymer. For example, such energy may be induced by heating the polymer beyond a specific curing temperature and/or by irradiating the polymer with energetic radiation such as UV-radiation. The thermosetting polymer is applied to the front surface of the PV label, i.e. to the surface which is directed towards light being incident onto the PV label in normal operation. Optionally, the thermosetting polymer may also be applied to edges of the PV label. The thermosetting polymer may be spread along the entire front surface of the PV label.

For forming the front cover structure, the thermosetting polymer is applied onto the PV label in a vicious condition and is then formed into an intended shape of the panel at its front side by using the second mould. In other words, in order to define a final shape of the cover structure and of the entire panel, the second mould has an inner surface with a shape being complementary to the intended shape of surface contour of the cover structure. In other words, the second mould may form the front side cavity, an inner surface of such cavity corresponding to the intended shape of the cover structure. Accordingly, upon arranging the PV label together with the rear support structure in the cavity and filling the remaining volume of the front side cavity with the thermosetting polymer, the cover structure for the PV label may be prepared. Alternatively, the second mould may have an inner surface with the intended shape and may be pressed onto a thermosetting polymer mass which has been applied to the front surface of the PV label in a preceding processing step, thereby forming and shaping the second mouldable polymer.

Upon the thermosetting polymer being formed and shaped in such manner, it may then solidify at least to a degree in which it is sufficiently stable before being removed from the second mould.

Specifically, the thermosetting second mouldable polymer may be prepared by mixing two or more chemical components which may then chemically react with each other. Accordingly, the thermosetting polymer may also be referred to as a reactive polymer. Therein, at least one first chemical component may act as a base material or matrix material, whereas at least one second chemical component may act as a binder material or hardener material. For example, the first chemical component may be polyol and the second chemical component may be isocyanate. The first and second chemical components may be stored separate from each other, for example in separate reservoirs, and may be brought together and mixed only immediately before injecting the thermosetting polymer generated thereby into the mould. Therein, the term “immediately” may be interpreted as relating to a time period within which the mixture obtained by mixing the at least two chemical components remains sufficiently liquid, i.e. remains at a low viscosity, for being easily injected into the mould. For example, the viscosity of the mixture should not increase within the time period being interpreted as being “immediately” by more than 20% relative, preferably not by more than 10% relative. For example, “immediately” may relate in this context to a time period being shorter than 1 min, preferably being shorter than 30 s shorter than 15 s or even shorter than 5 s.

Furthermore, the thermosetting polymer may be injected into the mould at pressures being preferably lower than 150 bar, i.e. lower than 15000kPa. Due to such injection at relatively low pressures, a risk of cell breakage in the PV label may be minimised. However, the thermosetting polymer should be injected into the mould at pressures being preferably higher than 50 bar, i.e. higher than 5000 kPa. With such sufficiently high injection pressures, the mould may be filled within a sufficiently short time period, thereby, inter-alia, increasing a throughput in a production procedure.

As a further characteristics, the thermosetting polymer may be injected into the mould while having a temperature of more than 80 °C, more preferably more than 40 °C. At such temperatures, chemical reactions between the chemical components comprised in the thermosetting polymer may solidify the thermosetting polymer within a sufficiently short time period, thereby, inter-alia, increasing the throughput in the production procedure. However, the injection temperature should preferably be lower than 80°C or higher than 40 °C, more preferably 65°C. By avoiding excessively high injection temperatures, it may be avoided that the PV label is excessively heated upon coming into contact with the hot thermosetting polymer, thereby preventing damaging the PV label due to excessively high temperatures.

In an exemplary embodiment, the thermosetting polymer may be injected with an injection pressure of 60 bar +/- 20 bar at room temperature (i.e. 60 °C +/- 10°C). It may then solidify within a time period of 40sec +/- 20 sec. In an optional subsequent tempering step, the thermosetting polymer may be heated to 50 °C +/- 10 °C for a time period of 6 h +/- 2 h and subsequently to 80 °C +/- 10 °C for a time period of 6 h +/- 2 h.

According to an embodiment, the second mouldable polymer is a polyurethane-based material.

In principle, the second mouldable polymer may be any polymeric material having sufficient optical transparency in order to serve as a front cover structure in a PV panel, i.e. enabling transmitting incident light with very low absorption losses. However, it has been found that, for the PV panels proposed herein, polyurethane-based material may show superior characteristics. Such material, which is also referred to as PU material or PUR material, shows a very high transparency enabling transmission losses through the front cover structure of generally substantially less than 5%, in most cases even less than 1%. Furthermore, such material may provide for high scratch resistance, chemical resistance, long-lasting performance, high hardness range (74 Shore A to 82 Shore D). Each of these characteristics, and particularly a combination of these characteristics, result in PU-based material being a perfect candidate for preparing the front cover structure of the PV panel. Furthermore, such material may enable processing advantages such as self-demoulding (i.e. with no additional mould measures like a surface coating being required), short curing times and/or low processing temperatures of typically substantially below 100°C. These characteristics may beneficially support the preparation of the PV panel’s front cover structure as, for example, due to the low processing temperatures, a risk of damaging or even delaminating the PV label during preparation of the front cover structure may be minimised. Furthermore, the short curing times may enable a high-throughput production. PU- based materials typically have a density of about 1.15 g/cm, a shrinkage of 2 - 3.5 %, a gel time of 5 - 10 s and/or a cross-linking time of 0.5 - 4 min. Furthermore, such materials may have a very low viscosity of about 10 - 100 mPas, wherein this characteristics may beneficially help in reducing any pressures exerted onto the PV label upon injecting the second polymer material into the front side cavity of the second mould.

According to an embodiment, the first mould and the second mould are comprised in a common moulding tool and, between preparing the rear support structure and preparing the front cover structure, the photovoltaic label together with the rear support structure is rearranged from the first mould to the second mould internally to the common moulding tool.

In other words, the first mould and the second mould are preferably not comprised in separate moulding tools, such separate tools being operated independently from each other and generally being spaced from each other by distances larger than the tools themselves, therefore requiring transportation of any semifinished products between the separate tools. Instead, the first and second mould are preferably included in a common moulding tool. Such common moulding tool may also be referred to as two-component moulding tool or 2K moulding tool. Accordingly, the operation of the first and second mould may be coupled and/or synchronised. Thereby, an efficiency of the production procedure may be increased.

Furthermore, after having been processed in the first mould for preparing the rear support structure, the semifinished PV panel may be transferred internally within the moulding tool to the second mould for preparing the front cover structure. In other words, the semifinished PV panel does not have to be transported external to the moulding tool and/or along substantial distances. This may enable shortened production cycles.

Furthermore, and possibly particularly beneficial for the production method described herein and as described in more detail further below, the semifinished PV panel, having its rear support structure prepared for example by injection moulding with the first mouldable polymer being injected at substantially elevated temperatures, may be transferred to the second mould while still being relatively hot. Such elevated temperature may help during the preparation of the front cover structure in generating a strong adherence between the first mouldable polymer of the rear support structure, on the one side, and the second mouldable polymer of the front cover structure, on the other side. Further possible details and implementations of the common moulding tool are described below with respect to an exemplary embodiment shown in the accompanying figures.

According to an embodiment, the front cover structure is a layer having an average layer thickness of between 0.1 mm and 3 mm, preferably between 0.3 mm and 1 mm.

Having such thickness, the front cover structure of the PV panel proposed herein is generally substantially thicker than conventional coatings prepared by spraying, spinning or other similar procedures. Therein, the thickness of the front cover structure should not fall below 0.1 mm, preferably not below 0.2 mm or 0.3 mm in order to provide, inter-alia, for a sufficient protection capability, i.e. in order to enable e.g. sufficient scratch resistance. On the other hand, the front cover structure should generally not have an excessive thickness of more than 1 mm, more than 2 mm or even more than 3 mm in order to avoid, inter-alia, excessive weight of the front cover structure, excessive optical absorption upon light transmission through the front cover structure, etc. At least in an area corresponding to an area of the solar cell arrangement or an area corresponding to the entire PV label, the thickness of the front cover structure should not fall below or exceed the above-mentioned lower and upper limits.

Generally, the thickness of the front cover structure may vary along its lateral extension. Particularly, the thickness of the front cover structure may vary such that a form or contour of the front side surface of the front cover structure differs from a form or contour of a rear side surface of this front cover structure. For example, the form or contour of the rear side surface of the front cover structure may be defined by the form or contour of the front side surface of the PV label which it abuts. Such contour may be uneven and/or wavy. In contrast to the rear side surface of the front cover structure, the form or contour of its front side surface is generally defined by the form or contour of the inside surface of the second mould defining the front side cavity during the procedure for preparing the front cover structure. This form or contour may be independently set and may therefore differ from the form or contour of the PV label. Accordingly, at the end of the production method, the outside surface of the PV panel, which is defined by the front side surface of its front cover structure, may for example be set independently from e.g. any waviness of the PV label comprised in the PV panel.

According to an embodiment, the second mould comprises a micro-texture at a surface defining the front side cavity. Accordingly, the PV panel prepared with such second mould may comprise a front cover structure having a micro-texture at an outside surface.

In other words, an inner surface of the second mould used for preparing the front cover structure may not be microscopically smooth but may be provided with a micro -texture. Such microtexture comprises three-dimensional structures having dimensions in a sub-millimetre range. For example, the three-dimensional structures may have lateral extensions and/or a height of between 1 pm and 1 mm, preferably between 5 pm and 500 pm or between 10 pm and 100 pm. The three- dimensional structures may have any shape. The three-dimensional structures may be arranged in an arbitrary pattern. Optionally, the three-dimensional structures may be arranged in a repetitive or periodical pattern.

Having such micro-texture at its surface defining the front side cavity, the second mould may be used for preparing the front cover structure for the PV label such that this front cover structure has a complementary micro-texture at its outside surface, i.e. at the surface directly abutting to the micro-textured surface of the second mould. Such micro-texture may provide for various beneficial optical, mechanical and/or other physical characteristics for the PV panel.

In an exemplary embodiment, the micro-texture has an average arithmetic roughness value Ra of between 5 pm and 50 pm, preferably between 15 pm and 35 pm.

Due to the micro-texture being provided such as to generate such microscopic roughness at the outside, front side surface of the cover structure, the PV panel may provide for a desired visual appearance and/or functional characteristics for the PV panel.

For example, instead of having a glossy finish, the PV panel may be provided with a matt visual appearance due to the micro-texture. Such matt appearance may provide for incident light being not reflected directly but in a diffuse manner. Such optical characteristics may help “hiding” the solar cell arrangement within the PV label, i.e. enable that details of the solar cell arrangement and of its solar cells are less visible from outside, thereby providing the PV label with a more uniform appearance.

Furthermore, the micro-texture may be generated such as to provide the front side of the PV panel with a lotus effect. Such lotus effect may induce self-cleaning properties that are a result of ultrahydrophobicity wherein e.g. dirt particles may be picked up by water droplets due to the micro- and nanoscopic architecture on the surface, which minimizes the droplet's adhesion to that surface. Such self-cleaning properties may be beneficial for the PV panel described herein as avoiding any deposition of dirt or of other light absorbing material on top of the PV panel generally helps keeping the PV panel’s efficiency high during long-term operation thereof.

According to an embodiment, the micro-texture is configured such as to form a light-trapping structure.

Generally, upon light being incident on a surface of an object such as a PV panel, at least a portion of the incident light is reflected from the surface. Accordingly, in case of a planar surface, the reflected portion of the light may not enter the PV panel and, in the end, may not reach and be absorbed by the solar cells comprised therein. Accordingly, the more incident light is reflected, the higher are the optical losses of the PV panel and the lower is the efficiency of the PV panel.

Light-trapping structures are known for reducing such reflection losses. For example, silicon solar cells are often provided with light-trapping structures at a surface of their silicon wafers in order to reduce reflection losses which would otherwise occur to a significant extend at the surface of the silicon wafers due to the relatively high refraction index of silicon.

Such light-trapping structure is typically created by a non-planar, e.g. micro-textured surface in which partial areas are arranged in different angles with respect to the incident light. Therein, such light-trapping structures generally include at least microscopic areas which are not arranged orthogonal to the direction of the incident light. Accordingly, light being incident on such areas at shallow angles is not reflected in a direction opposite to the incident direction but at an angle thereto. Thus, having neighbouring microscopic areas being arranged at different angles, such reflected light portions may impinge onto such neighbouring microscopic areas, i.e. may be incident onto the surface of the PV panel for a second time. Thereby, a portion of the incident light not being reflected but being transmitted into the cover layer of the PV panel may be increased. Overall, reflection losses may be significantly reduced due to the light-trapping structures, thereby increasing the efficiency of the PV panel.

Thus, contrary to conventional coatings being prepared by spraying or painting and generally having a microscopically smooth, non-textured surface, the method proposed herein allows for generating the front cover structure with microscopic light-trapping structures by simply suitably adapting the inner surface of the second mould in an area adjacent to the front side cavity. Particularly, such inner mould surface may be provided with a microscopic texture being inverse to the intended light-trapping structure required at the PV panel’s front side. For example, such light-trapping structure may be composed of multiple grooves, recesses and/or protrusions. Such structures may be arranged in a repetitive or periodical pattern. Flanks included in such microscopic texture may be arranged at an angle, particularly an angle of between 10° and 80°, more preferably an angle of between 30° and 60°, with respect to an overall or average surface plane of the front cover structure. Particularly, the light-trapping structures may include pyramids or inverse pyramids in order to generate a particularly strong light-trapping effect.

According to an embodiment, the second mouldable polymer is applied along the front surface of the photovoltaic label such as to extend beyond lateral edges of the photovoltaic label and to directly contact the rear support structure in an overlapping area. Thus, in the final PV panel, the front cover structure covers the entire front surface of the photovoltaic label, extends beyond lateral edges of the photovoltaic label and directly contacts the rear support structure in an overlapping area.

Expressed differently, upon producing the PV panel, the second mould used for preparing the front cover structure is formed and dimensioned such that, and the PV label is arranged in such second mould such that the front side cavity defining the final front cover structure not only extends along the entire PV label but even beyond a lateral circumference of the PV label. Accordingly, upon the second mouldable polymer being injected into such front side cavity, it covers not only the PV label but also comes into direct contact with portions of the rear support structure in circumferential areas laterally protruding beyond the PV label. Such circumferential areas therefore form the overlapping area between the rear support structure and the front cover structure. Thus, the front cover structure formed by such second mouldable polymer may not only adhere to the PV label but also to the circumferential areas of the rear support structure, thereby improving an overall adherence and mechanical integration within the entire PV panel. The overlapping area may typically have a width of between a few millimetres and a few centimetres, e.g. between 2 mm and 10 cm, preferably between 5 mm and 3 cm.

According to an embodiment, the second mouldable polymer is applied upon the rear support structure and/or the PV label being at an elevated temperature of more than 40°C, preferably more than 80°C.

In other words, the second mouldable polymer is preferably not injected into the front side cavity formed by the second mould while portions of the semifinished PV panel to be covered by the front cover structure are at relatively low temperatures. Instead, it is preferred that such portions of the semifinished PV panel are at an elevated temperature substantially above room temperature. Such elevated temperature may help in establishing an improved adherence between the front cover structure formed by the second mouldable polymer, on the one hand, and at least one of the PV label and the overlapping area at the circumference of the rear support structure, on the other hand.

Preferably, such elevated temperature results from the fact that, in the preceding manufacturing step, the rear support structure has been prepared by applying the first mouldable polymer to the PV label, wherein such first mouldable polymer is typically applied at elevated temperatures of e.g. more than 100°C or even more than 150°C. Accordingly, in case the first mouldable polymer and the PV label being in thermal contact therewith have not yet completely cooled down after the rear support structure having been formed but are still at an elevated temperature, the remaining heat within the rear support structure and/or the PV label may help in obtaining an intense and stable contact and adherence with the front cover structure. Therein, as indicated further above, it may be helpful to prepare both, the rear support structure as well as the front cover structure, in a common moulding tool, thereby enabling a quick transfer of the semifinished product from the first mould to the second mould and therefore enabling relatively low temperature losses between both moulding steps.

Alternatively or additionally, the second mould may include a heater for specifically heating the PV label and/or the rear support structure before applying the second mouldable polymer.

According to an embodiment, the method further comprises at least one of the following steps: - applying a layer of primer material on top of the rear surface of the photovoltaic label prior to applying the first mouldable polymer onto the rear surface of the photovoltaic label, and - applying a layer of primer material on top of the front surface of the photovoltaic label prior to applying the second mouldable polymer along the front surface of the photovoltaic label.

It has been observed that a rear support structure applied onto the rear surface of the PV label may suffer from insufficient adhesion or adherence unless the respective surface is specifically prepared in a preceding processing step before applying the respective first or second mouldable polymer material thereon. In order to prevent such insufficient adhesion or adherence, optinally, a thin layer of a primer material may be applied to the respective surface of the PV label at least at those locations where the rear support structure is to be adhered to this surface.

The primer may be applied in liquid form. The primer may have a low viscosity. The primer may consist of or comprise an adhesion promoting material. The primer may be solvent-borne and/or pigmented. For example, the primer may be a prime coat comprising a solvent and being based on polyurethane. The primer may be configured for chemically reacting with humidity comprised in air in order to thereby cure or solidify. Initially, the primer may comprise a solid-state content and a solvent. The solid-state content may be for example between 10% and 50%, preferably between 20% and 40% or approximately 30% ± 5%. The primer may be specifically configured for enhancing adhesion to for example base surfaces or substrates comprising for example PMMA, PC (polycarbonate), PS (polystyrene), GFK, ABS, PVC or others. The primer may be applied onto the surface with simple tools such as a brush, a felt or a foam. The primer layer may be applied such as to have a thickness of preferably less than 1 mm or even less than 200 pm. The primer may have a flash-off time or airing time of between 1 min and 120 min, preferably between 5 min and 20 min. Excessively short flash-off times or excessively long flash-off times may negatively affect an adhesion induced by the primer. The primer layer may serve as an interface layer between the rear surface of the PV label and an adjacent surface of the rear support structure formed by the first polymer or between the front surface of the PV label and an adjacent surface of the front cover structure formed by the second polymer. The primer layer may provide a sufficient degree of elasticity. Accordingly, the primer layer may absorb or compensate slight motions between the PV label and the rear support structure and/or the front cover layer, respectively, such motions occurring for example due to different thermal expansion coefficients of the materials of both components and therefore due to thermal stress.

It shall be noted that possible features and advantages of embodiments of the invention are described herein partly with respect to a method of producing a PV panel and partly with respect to a PV panel producible with such method. One skilled in the art will recognize that the features may be suitably transferred from one embodiment to another and features may be modified, adapted, combined and/or replaced, etc. in order to come to further embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, advantageous embodiments of the invention will be described with reference to the enclosed drawings. However, neither the drawings nor the description shall be interpreted as limiting the invention.

Figs. 1 (a) - (e) visualise processing steps during producing a PV panel in accordance with an embodiment of the present invention.

Fig. 2 shows an enlarged visualization of a partial area “A” as indicated in Fig. 1(e).

Figs. 3(a) - (f) visualise processing steps during producing a PV panel using a common two- component moulding tool in accordance with an embodiment of the present invention.

The figures are only schematic and not to scale. Same reference signs refer to same or similar features.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1(a) - (e) shows a sequence for producing a PV panel 1. Fig. 2 shows an enlarged view with details in a partial area “A” indicated in Fig. 1(e). Fig. 3(a) - (f) shows a sequence of processing steps for producing the PV panel 1 using a common two-component moulding tool 101.

The PV panel 1 is produced by first providing a PV label 3, then preparing a rear support structure 17 at a rear surface 4 of the PV label 3 and finally preparing a transparent front cover structure 23 at an opposite front surface 6 of the PV label 3. Therein, the rear support structure 17 as well as the front cover structure 23 are prepared using moulding techniques.

The PV label 3 comprises a front side polymeric stabilisation foil 5, a front side polymeric lamination foil 7, a rear side polymeric lamination foil 9 and a rear side polymeric stabilisation foil 11. A solar cell arrangement 13 comprising several rigid wafer-based solar cells 15 is interposed between the front and rear side polymeric lamination foils 7, 9, which themselves are interposed between the front and rear side stabilisation foils 5, 11- The entire stack of polymeric foils 5, 7, 9, 11 including the solar cell arrangement 13 is laminated to form the PV label 3. Initially, this PV label 3 is prepared with a planar first geometry (see Fig. 1(a)).

Subsequently, the initially planar PV label 3 may optionally have to be deformed into a curved three-dimensional shape (see Fig. 1(b)). In order to simplify such deformation, the PV label 3 may be heated to an elevated temperature of for example 70 - 90°C. At such elevated temperature, the polymeric foils 5, 7, 9, 11 come increasingly deformable.

In such optionally heated state, the PV label 3 is introduced into a first mould 103 of the moulding tool 101 (see Fig. 3(a)). It is to be noted that, for simplifying the visualisation, Fig. 3 shows the moulding tool 101 in a version in which the PV label 3 as well as the entire PV panel 1 to be produced comprise a planar shape. However, as evident for those skilled in the art and as also shown in various prior patent applications filed by the applicant, the moulding tool 101 may easily be adapted for accommodating a curved PV label 3 for forming a three-dimensional PV panel 1.

The moulding tool 101 comprises a first mould 103 including at least a first moulding portion 105 and a second moulding portion 107. These first and second moulding portions 105, 107 are displaceable relative to each other between an open state, in which the moulding portions 105, 107 are spaced from each other, and a closed state, in which the moulding portions 105, 107 generally abut to each other at least along a circumferential rim 111 and enclose a first cavity 109 between each other and inside the circumferential rim 111. For forming the first cavity 109, a first recess 113 is provided at the first moulding portion 105 and, additionally, a second recess 115 is provided at the second moulding portion 107.

As schematically visualised in Fig. 3(a), the PV label 3 may be arranged within the second recess 115 prior to closing the first mould 103. Particularly, the PV label 3 may be positioned using a positioning arrangement and/or a prefixation arrangement (not shown in detail), such positioning arrangement and/or prefixation arrangement possibly comprising for example fixation pins, clamps, suction cups, etc. Upon the PV label 3 being interposed between the first moulding portion 105 and the second moulding portion 107, the two moulding portions 105, 107 are then pressed together. Thereby, the PV label 3 is deformed into an intended curved geometry. This geometry at least roughly corresponds to a contour of the first cavity 109 of the first mould 103 and therefore to the contour of the PV panel 1 to be produced (see figure 1(b)). Subsequently, a first layer 19 of primer may optionally be applied onto the rear surface 4 of the PV label 3 (see figure 1(c)). Therein, the primer is preferably deposited onto the rear surface 4 upon the PV label 3 being cooled down to ambient temperatures.

Then, the PV label 3 is introduced into the first mould 103 again. Upon the first and second moulding portions 105, 107 of the first mould 103 being closed with the PV label 3 being arranged in the first cavity 109, a rear side cavity 119 is formed adjacent to the rear surface 4 of the PV label 3. This rear side cavity 119 forms part of the first cavity 109 and includes a volume of the first cavity 109 not been occupied by the PV label 3. A first mouldable thermoplastic polymer 121 such as PC, ABS, ASA, PET or a combination of all is then introduced into the first cavity 109 via an introduction channel 117. The first polymer 121 spreads throughout the rear side cavity 119 and may cover portions of the rear surface 4 or the entire rear surface 4 of the PV label 3. Upon at least partially cooling down, the thermoplastic first polymer may then solidify and thereby form the support structure 17 (see Figs. 1(d) and 3(b)).

Particularly, the first cavity 109 of the first mould 103, the shape of the PV label 3 and/or the manner in which the PV label 3 is arranged within the first mould 103 may be specifically configured such that at least a small portion of the first polymer 121 may flow around a rim 25 of the PV label 3 to the front side 6 of the PV label 3. Thereby, an undercut structure 27 forming a positive joint between the PV label 3 and the support structure 17 may be formed.

For example, the PV label 3 may have a step structure 29 along its rim 25. Such step structure 29 may result for example from using a rear side polymeric stabilisation foil 11 which has slightly larger dimensions than the front side polymeric stabilisation foil 11. Upon being suitably held within the first cavity 109 of the first mould 103, the first polymer may then flow around the rim 25 of the PV label 3 and fill an empty space in such step structure 29 in a way such that, finally, the solidified polymer forms the undercut structure 27 with the PV label’s step structure 29 while forming a flush surface or a smooth transition between an outer surface of the support structure 17 and an outer surface of the PV label 3. Alternatively, the rim 25 of the PV label 3 may be formed with a slanted, bevelled or chamfered edge geometry. Again, polymer may then flow around such rim 25 and form the undercut structure 27 with the PV label’s edge geometry.

After solidification of the first polymer 121 to a sufficient degree such as to become sufficiently mechanically stable and self-supporting and form the rear support structure 17, a second stage of the production method may be initiated in order to prepare the front cover structure 23. For such purpose, the semifinished product including the PV label 3 together with the rear support structure 17 is arranged in a second mould 123. In principle, such second mould 123 could be provided in a separate moulding tool. However, in such case, the semifinished product would need to be transported to such separate tool, therefore requiring additional efforts and logistics. In order to avoid this, a common two-component (2K) moulding tool 101 as shown in Fig. 3 may include both the first mould 103 as well as the second mould 123.

In the embodiment shown in Fig. 3, the common moulding tool 101 comprises a rotatable central component 125. This rotatable central component 125 comprises, on the one side, the second moulding portion 107 of the first mould 103 and, on the other side, a third moulding portion 127 of the second mould 123. Accordingly, in a first configuration of the rotatable central component 125, a combination of the first moulding portion 105 and the second moulding portion 107 forms the first mould 103, whereas, in a rotated second configuration of the rotatable central component 125, a combination of the first moulding portion 105 and the third moulding portion 123 forms the second mould 123. The third moulding portion 127 comprises a third recess 129. This third recess 129 is larger than the second recess 115 comprised in the second moulding portion 107.

As visually indicated in Figs. 3(c) and (d), at the beginning of the second stage of the production method, the first mould 103 is first displaced into its open state and, subsequently, the rotatable central component 125 is rotated by 180°. Accordingly, the third recess 129 in the third moulding portion 127 is directed towards the semifinished product comprising the PV label 3 and the rear support structure 17 which is still held at the first moulding portion 105.

In such rotated configuration, as shown in Fig. 3(e), the second mould 123 comprising the first moulding portion 105 and the third moulding portion 127 may be closed by bringing the first and third moulding portions 105, 127 together. Due to the third recess 129 in the third moulding portion 127 being larger than the second recess 115 in the second moulding portion 107, a front side cavity 131 is thereby formed adjacent to the front surface 6 of the PV label 3.

A transparent second mouldable polymer 133 is then injected into this front side cavity 131. Such second mouldable polymer 133 is preferably a thermosetting material such as a polyurethane- based material. Therein, the thermosetting material may be composed of two or more chemical components which are mixed immediately before injection into the front side cavity 131 using e.g. a mixing and injection unit 135. In the example shown in Fig. 3(e), the mixing and injection unit 135 is arranged at a lower end of the second mould 123 and injects the second mouldable polymer 133 via an injection channel 137 such that the second mouldable polymer 133 may then spread throughout the front side cavity 131 and thereby cover the front side 6 of the PV label 3.

Preferably, the second stage of the production method and particularly the injection of the second mouldable polymer 133 is executed while the PV label 3 and the rear support structure 17 prepared in the preceding first stage are still at an elevated temperature of e.g. 60°C to 100°C. Thereby, an adhesion between the second mouldable polymer 133, on the one side, and the first mouldable polymer 121 of the rear support structure 17 and/or the polymer material forming the front side polymeric stabilisation foil 5 of the PV panel 3 may be enhanced.

Furthermore, as shown in Fig. 1(e) as well as in Fig. 3(e), the third recess 129 in the third moulding portion 127 is formed and dimensioned such that, upon filling the resulting front side cavity 131 with the second mouldable polymer 133, the second mouldable polymer 133 is not only applied to the front surface 6 of the PV label 3 but also extends beyond lateral edges of the PV label 3 such as to directly contact the rear support structure 17 in an overlapping area 31.

After the second mouldable polymer 133 having sufficiently solidified, the final PV panel 1 including the rear support structure 17 at the rear side of the PV label 3 as well as the front cover structure 23 at the front side of the PV label 3 may be removed from the opened second mould 123 of the moulding tool 101 (see Fig. 3(f)).

Optionally, before preparing the front cover structure 23, a second layer 21 of primer may be applied to the front surface 6 of the PV panel 1. Such second layer 21 of primer may be applied in an area including the exposed surface of the PV label 3 as well as a surface of the overlapping area 31 of the support structure 17. By applying such second layer 21 of primer, an adherence between the second mouldable polymer 133 forming the front cover structure 23, on the one hand, and the polymer materials of the PV label 3 and the rear support structure 17, on the other hand, may be enhanced.

Furthermore, it may be noted that, while the common moulding tool 101 is shown in the figures to be implemented with the rotatable component 125, other techniques may be used for providing a single moulding tool with two different moulds, i.e. a first mould 103 and a second mould 123 having a shape different from the one of the first mould 103. For example, different second and third moulding portions 107, 127 may be provided on a common table which may then be translated or rotated between a first configuration, in which the second moulding portion 107 cooperates with the first moulding portion 105, and a second configuration, in which the third moulding portion 127 cooperates with the first moulding portion 105.

Fig. 2 visualises, in an enlarged view, details of the final PV panel 1 in a partial area "A” indicated in Fig. 1(e).

Therein, it is visible that the front cover structure 23 comprises a micro-texture 33 at its outside surface. Such micro-texture 33 is formed such as to generate an average arithmetic roughness value of about 25pm +/- 10pm. Thereby, the outside surface of the front cover structure 23 provides for a matt visual appearance of the PV panel 1.

The micro-texture 33 is specifically provided with microscopic pyramids 35 or invers pyramids, thereby generating a light-trapping structure 37. Due to such light-trapping structure 37, incident light 39 is partly reflected at an inclined flank 41 of a pyramid 35 in a direction such as to impinge onto the outside surface of the front cover structure 23 for a second time, thereby increasing the portion of light being transmitted through the front cover structure 23 towards the solar cells 15 comprised in the PV label 3.

The micro-texture 33 and, particularly, the light-trapping structure 37 in the front cover structure 23 may be easily prepared by providing the second mould 123 and particularly an inside surface of the third moulding portion 127 at its third recess 129 with a geometry which is complementary to the intended micro -texture 33.

Furthermore, as the outside surface of the front cover structure 23 prepared with the method described herein is predetermined by the inside surface of the third moulding portion 127, an uneven surface of the PV label 3 and particularly any waviness in the PV label 3 (not shown in the figures) or any uneven surface structures in the overlapping area 31 of the rear support structure 17 (such as the indentation 39 exemplarily shown in Fig. 2) may be compensated.

The resulting PV panel 1 may be specifically configured such as to form a car body panel. Such car body panel generally has a three-dimensional curved outer contour. Using the approach described herein, high-efficiency photovoltaics including wafer-based solar cells may be easily and reliably integrated into such car body panel.

Embodiments of the method and device described herein may be used for various appliances. For example, PV integrated vehicle body panels may be provided. For example, PV panels forming an outer cover of a vehicle body, a vehicle roof element, a battery cover or a bus shoulder may be provided. As a specific example, for example a PV integrated tonneau or lid for covering e.g. a cargo area of a truck may be provided. As a further example, a PV integrated and potentially movable or deployable roof component for a campervan may be provided.

Finally, it should be noted that the term “comprising” does not exclude other elements or steps and the “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE SIGNS

1 PV panel

3 PV label

4 rear surface of PV panel

5 front side polymeric stabilisation foil

6 front surface of PV panel

7 front side polymeric lamination foil

9 rear side polymeric lamination foil

11 rear side polymeric stabilisation foil

13 solar cell arrangement

15 solar cell

17 support structure

19 first layer of primer

21 second layer of primer

23 front cover structure

25 rim of the PV label

27 undercut structure

29 step structure

31 overlapping area

33 micro-texture

35 microscopic pyramid

37 light-trapping structure

39 indentation

41 flank

101 moulding tool

103 first mould

105 first moulding portion

107 second moulding portion

109 first cavity

111 circumferential rim

113 first recess

115 second recess introduction channel rear side cavity first mouldable polymer second mould rotatable central component third moulding portion third recess front side cavity transparent second mouldable polymer mixing and inj ection unit

Claims

1. Method for producing a photovoltaic panel (1), particularly a photovoltaic vehicle body panel, the method comprising: providing a photovoltaic label (3) comprising polymeric foils (5, 7, 9, 11) and a solar cell arrangement (9) interposed between the polymeric foils (5, 7, 9, 11), preparing a rear support structure (17) for supporting the photovoltaic label (3), wherein the rear support structure (17) is prepared by applying a first mouldable polymer (121) to a rear surface (4) of the photovoltaic label (3), including arranging the photovoltaic label (3) in a first mould (103) forming a rear side cavity (119) adjacent to the rear surface (4) of the photovoltaic label (3) and applying the first mouldable polymer (121) onto the rear surface (4) of the photovoltaic label (3) for filling the rear side cavity (119) of the first mould (103) and solidifying the first polymer (121), and preparing a transparent front cover structure (23) covering a front surface (6) of the photovoltaic label (3), wherein the front cover structure (23) is prepared by applying a transparent second mouldable polymer (133) to the front surface (6) of the photovoltaic label (3), including arranging the photovoltaic label (3) together with the rear support structure (17) in a second mould (123) forming a front side cavity (131) adjacent to the front surface (6) of the photovoltaic label (3) and applying the second mouldable polymer (133) along the front surface (6) of the photovoltaic label (3) for filling the front side cavity (131) of the second mould (123) and solidifying the polymer (133).

2. Method according to claim 1, wherein the front cover structure (23) is prepared using a reaction injection moulding procedure in which the transparent second mouldable polymer (133) is a thermosetting polymer and the procedure includes at least one of the following characteristics:

- mixing at least two chemical components for preparing the thermosetting polymer, wherein the two chemical components are mixed immediately before injecting the thermosetting polymer into the second mould (123);

- injecting the thermosetting polymer into the second mould (123) with a pressure of between 30 bar and 100 bar, preferably between 50 bar and 80 bar; - injecting the thermosetting polymer into the second mould (123) with the thermosetting polymer having a temperature of between 20°C and 100 °C, preferably between 50°C and 80°C.

3. Method according to one of the preceding claims, wherein the second mouldable polymer (133) is a polyurethane-based material.

4. Method according to one of the preceding claims, wherein the first mould (103) and the second mould (123) are comprised in a common moulding tool (101) and, between preparing the rear support structure (17) and preparing the front cover structure (23), the photovoltaic label (3) together with the rear support structure (17) is rearranged from the first mould (103) to the second mould (123) internally to the common moulding tool (101).

5. Method according to one of the preceding claims, wherein the second mould (123) comprises a micro-texture at a surface defining the front side cavity (131).

6. Method according to claim 5, wherein the micro-texture has an average arithmetic roughness value of between 5 pm and 50 pm, preferably between 15 pm and 35 pm.

7. Method according to one of claims 5 and 6, wherein the micro-texture is configured such as to form a light-trapping structure (37).

8. Method according to one of the preceding claims, wherein the second mouldable polymer (133) is applied along the front surface (6) of the photovoltaic label (3) such as to extend beyond lateral edges of the photovoltaic label (3) and to directly contact the rear support structure (17) in an overlapping area (31) adjacent to the lateral edges of the photovoltaic label (3).

9. Method according to one of the preceding claims, wherein the second mouldable polymer (133) is applied upon at least one of the rear support structure (17) and the PV label (3) being at an elevated temperature of more than 40°C, preferably more than 80°C.

10. Method according to one of the preceding claims, wherein the method further comprises at least one of the following steps:

- applying a layer (19) of primer material on top of the rear surface (4) of the photovoltaic label (3) prior to applying the first mouldable polymer (121) onto the rear surface (4) of the photovoltaic label (3), and

- applying a layer (21) of primer material on top of the front surface (6) of the photovoltaic label (3) prior to applying the second mouldable polymer (133) along the front surface (6) of the photovoltaic label (3).

11. Photovoltaic panel (1), particularly a vehicle body panel, the panel including: a photovoltaic label (3) comprising polymeric foils (5, 7, 9, 11) and a solar cell arrangement (9) interposed between the polymeric foils (5, 7, 9, 11), a rear support structure (17) supporting the photovoltaic label (3), wherein the rear support structure (17) comprises a first mouldable polymer (121) adhering to a rear surface (4) of the photovoltaic label (3), and a transparent front cover structure (23) covering a front surface (6) of the photovoltaic label (3), wherein the front cover structure (23) comprises a transparent second mouldable polymer (133) adhering to the front surface (6) of the photovoltaic label (3).

12. Photovoltaic panel (1) according to claim 11, wherein the front cover structure (23) is a layer having an average layer thickness of between 0.1 mm and 3 mm, preferably between 0.3 mm and 1 mm.

13. Photovoltaic panel (1) according to one of claims 11 and 12, wherein the second mouldable polymer (133) is a polyurethane-based material.

14. Photovoltaic panel (1) according to one of claims 11 to 13, wherein the front cover structure (23) comprises a micro-texture (33) at an outside surface.

5. Photovoltaic panel (1) according to one of claims 11 to 14, wherein the front cover structure (23) covers the entire front surface of the photovoltaic label (3), extends beyond lateral edges of the photovoltaic label (3) and directly contacts the rear support structure (31) in an overlapping area adjacent to the lateral edges of the photovoltaic label (3).