WO2014114708A2

WO2014114708A2 - A photovoltaic device with a highly conductive front electrode

Info

Publication number: WO2014114708A2
Application number: PCT/EP2014/051314
Authority: WO
Inventors: Ko Hermans
Original assignee: Dsm Ip Assets B.V.
Priority date: 2013-01-23
Filing date: 2014-01-23
Publication date: 2014-07-31
Also published as: WO2014114708A3

Abstract

A photovoltaic device is disclosed. The photovoltaic device comprises a relief textured transparent cover layer; a front electrode comprising a transparent conductive material and a reflecting grid of electrodes that is in electrical contact with the transparent conductive material, wherein the reflecting grid of electrodes reflects at least 20% of light having a wavelength in the range from 400 to 750 nm; and a photovoltaic active layer.

Description

A PHOTOVOLTAIC DEVICE WITH A HIGHLY CONDUCTIVE FRONT ELECTRODE Background

Photovoltaic devices are commonly used to convert light energy into electrical energy. Photovoltaic devices contain several components, such as a cover layer, an electrode, and a photovoltaic active layer.

The photovoltaic active layer is a light absorbing material that generates charge carriers upon exposure to light. A typical example of such a material is mono- (m-Si) and poly- (p-Si) silicon. Since silicone is expensive, it is important to keep the layer thickness to a minimum. In the case of m-Si and p-Si, the layer thickness is relatively thick because the material is also used as a substrate for creating the photovoltaic device. The total layer thickness of the silicon is therefore around Ι δθμηη. To overcome this and other problems thin film photovoltaic devices were developed. Said devices use another material (e.g. glass, plastic or metal foil) as a substrate and only a thin layer (± 0.1 -8 μηη) of the active material is applied to this substrate. Examples of photovoltaic active layer materials that are used in thin film photovoltaic applications are amorphous silicon (a-Si), microcrystalline silicon (μο-Si), copper indium gallium selenide (CIGS), cadmium telluride (CdTe) and dye-sensitized solar cell (DSC).

A photovoltaic device contains electrodes to collect the charge carriers that are created in the photovoltaic active layer. The electrodes are placed on the front (light receiving side) and back (non-light receiving side) of the photovoltaic active layer. Because the back electrode is on the non-light receiving side of the photovoltaic device, the back electrode can be made of highly conductive materials, such as metals like silver or aluminum that do not have high light transmittance.

However, because the front electrode is between the light source and the light receiving surface of the photovoltaic active layer, the front electrode is not only required to have a suitable conductivity, but also should show a high overall light transmittance over the entire light receiving surface of the photovoltaic active layer. Otherwise the photovoltaic active layer would not receive sufficient light and would thus yield a photovoltaic device with reduced efficiency.

A grid of metallic electrodes is sometimes used as the front electrode in a photovoltaic device. The grid of metallic electrodes provides both good conductivity and good overall light transmittance. However, light transmittance is completely blocked in the areas directly underneath the grid of metallic electrodes. Consequently, attempts have been made to reduce the light blocking function of the grid of metallic electrodes.

One such technique is evidenced in US4053327, assigned to

Communications Satellite Corporation. In this technique a relief textured transparent cover layer is placed between the grid of metallic electrodes and the light source. When aligned correctly, the relief textured cover plate is said to direct the light away from the grid of metallic electrodes and toward unblocked portions of the photovoltaic active layer of the photovoltaic device. Although this technique may increase the overall light transmittance of the front electrode, it requires careful alignment of the relief textured transparent cover layer and the grid of metallic electrodes. Perhaps consequently, this technique is not widely used in modern photovoltaic devices.

In photovoltaic devices which use a highly crystalline (mono- crystalline, multi-crystalline or poly-crystalline) photovoltaic active layer, the charge carrier is relatively mobile within the photovoltaic active layer. Consequently, a grid of metallic electrodes that covers only a small percentage of the total area of the light receiving surface of the photovoltaic active layer can adequately capture the generated charge carriers. Grids of metallic electrodes are the preferred front electrode in highly crystalline photovoltaic active layers.

In photovoltaic devices which have low or no crystallinity (amorphous, nano-crystalline or micro-crystalline) photovoltaic active layers, such as thin film photovoltaic devices, the charge carrier is relatively immobile. Consequently, a grid of metallic electrodes cannot adequately capture the generated charge carriers while covering only a small percentage of the total area of the light receiving surface of the photovoltaic active layer. For this reason, grids of metallic electrodes are not generally used in thin film photovoltaic devices. Instead, a transparent conductive front electrode is used to capture the charge carriers.

The transparent conductive front electrode is typically formed using a transparent conductive material. The most common transparent conductive material is a transparent conductive oxide (TCO). Examples of TCO materials are indium tin oxide (ITO), fluorinated tin oxide (FTO) or (aluminum) zinc oxide (AZO). Also other transparent conductive materials such as Poly(3,4-ethylenedioxythiophene) (PEDOT) or carbon nanotubes doped polymers can be used as a transparent conductive front electrode.

Thus current photovoltaic devices containing transparent conductive front electrodes made of transparent conductive materials have an increased efficiency compared to those same photovoltaic devices if those photovoltaic devices instead contained a front electrode made of a grid of metallic electrodes. Moreover, the light transmittance of transparent conductive materials is typically further increased by imparting a texture to the transparent conductive material in order to reduce the reflection of light by the transparent conductive material.

In US2008/0308151 , assigned to Guardian Industries Corp., a multilayer transparent conductive front electrode is disclosed. The multi-layer transparent conductive front electrode comprises a transparent conductive material and a 3 to 18 nm thick metallic IR reflecting layer. The layers are sputter deposited. The 3 to 18 nm thick metallic IR reflecting layer is said to be thin enough to reflect a substantial portion of IR light while being substantially transparent to light with wavelengths that can be converted to electricity by the photovoltaic active layer. It is stated that the multi-layer transparent conductive front electrode may enhance transmission in selected photovoltaic active regions of the electromagnetic spectrum, such as the visible and near IR regions.

Even in view of these advances, a photovoltaic device with higher efficiency and manufacturability is desirable.

Summary

The known photovoltaic devices of the prior art have sought to improve the efficiency of a photovoltaic device by maximizing the light transmittance of the front electrode, thereby allowing more light to reach the active layer where the light can be converted to electricity, while retaining the function of the front electrode. By light transmittance it is meant light transmittance in the photovoltaic active region, the area of the electromagnetic spectrum that can be converted to electricity by the photovoltaic active layer. This has generally been accomplished by the prior art by limiting the area of the photovoltaic active layer that is covered by a grid of metallic electrodes, or by completely substituting the grid of metallic electrodes with a transparent conductive front electrode made from transparent conductive materials.

Although completely substituting the grid of metallic electrodes with a transparent conductive front electrode made from transparent conductive materials has increased the efficiency of those photovoltaic devices, such as thin film photovoltaic devices, by maximizing the light transmittance of the front electrode, the conductivity of transparent conductive front electrodes used to achieve this increase in light transmittance is actually less than the conductivity of a front electrode made of a grid of metallic electrodes. This relatively low conductivity of the transparent conductive front electrode limits the efficiency of a photovoltaic device, but has been seen as a necessary consequence of improving the overall efficiency of a photovoltaic device through increasing the light transmittance of the front electrode. In US2008/0308151 , which mentions a multi-layer transparent conductive front electrode comprising a transparent conductive material and an IR reflecting metallic material, the metallic material has a thickness that is greatly limited to allegedly transmit a substantial portion of visible light while reflecting a substantial portion of IR light. Although this may increase the conductivity of the front electrode, the technique relies on slow

manufacturing processes and a complicated multi-layer design. These characteristics limit the manufacturability and commercial feasibility of such a photovoltaic device.

In accordance with the invention, a photovoltaic device is provided comprising a relief textured transparent cover layer; a front electrode comprising a transparent conductive material and a reflecting grid of electrodes that is in electrical contact with the transparent conductive material, wherein the reflecting grid of electrodes reflects at least 20% of light having a wavelength in the range from 400 to 750 nm; and a photovoltaic active layer. Such a photovoltaic device may attain improved conductivity over the current state of the art, but the light transmittance of the front electrode will be reduced. The reduced light transmittance of the front electrode may be compensated for by the relief textured transparent cover layer. Moreover, as the reflecting grid of electrodes can be formed using a relatively fast and cost-effective technique, such as printing processes, the manufacturability and commercial feasibility limitations of prior art designs may be overcome.

The relief textured transparent cover layer contains an array of optical relief structures that trap light that is reflected from the reflecting grid of electrodes.

Therefore, the reduction in light transmittance caused by the presence of the reflecting grid of electrodes is at least partially compensated for by the relief textured transparent cover layer.

Thus the reflecting grid of electrodes can increase the conductivity of a front electrode of a photovoltaic device without the efficiency of the device being overly hampered by the increased reflectivity caused by the reflecting grid of electrodes. Surprisingly, the significant portion of the light incident to the photovoltaic device that is reflected away from the photovoltaic active layer is retained. Detailed Description

As noted above, the present invention may provide an increase in efficiency of a photovoltaic device even though the light transmittance of the front electrode itself is lower than the current state of the art. This is accomplished using a front electrode comprising a transparent conductive material and a reflecting grid of electrodes that is in electrical contact with the transparent conductive material. This lowering of light transmittance of the front electrode moves in the opposite direction of recent advances in the art of photovoltaic devices which have sought to increase the light transmittance of the front electrode. Despite this reduction, the efficiency of a photovoltaic device may be increased through a corresponding increase in conductivity of the front electrode, and by a relief textured transparent cover layer which enables some of the light that would otherwise be blocked from reaching the photovoltaic active layer by the reflecting grid of electrodes to still reach the photovoltaic active layer of the photovoltaic device and be converted to electricity.

Preferably, the relief textured transparent cover layer comprises an array in optical contact with a light receiving side of the photovoltaic active layer.

Whether optical contact is achieved does not depend on the distance between the relief textured transparent cover layer and the photovoltaic active layer. Instead, optical contact depends on the medium or media that connect the relief textured transparent cover layer and the photovoltaic active layer. This medium or media comprises the front electrode. Optical contact does not need to be achieved over the entire media between the relief textured transparent cover layer and the photovoltaic active layer. For example, optical contact will not be achieved in areas where the reflecting grid prohibits light from reaching the photovoltaic active layer. However, optical contact can still be achieved if there is optical contact over some portion of the total area of the light receiving side of the photovoltaic active layer. Preferably, optical contact is achieved over at least 80% of the photovoltaic active layer, more preferably over 85%.

As mentioned above, whether optical contact is achieved depends on the refractive index (n_d) of the medium or media that connect the relief textured transparent cover layer and the photovoltaic active layer. To determine the refractive index of a medium an Abbe refractometer should be used. Optical contact is achieved when the refractive index of some portion of the medium or media that connect the relief textured transparent cover layer and the photovoltaic active layer is on average at least 1.2. More favorably, the refractive index of the medium or media is on average at least 1.3, and most favorably the refractive index of the media or medium is at least 1 .4.

The relief textured transparent cover layer contains an array of optical relief structures that trap light that is reflected from the reflecting grid of electrodes. The optical relief structures can have many shapes and sizes. Examples are linear V grooves, pyramids, domes or cones. The optical relief structures could also be with and without an apex (i.e. flat peak or a point peak), or have multiple apexes. Preferably, the optical relief structures are characterized in that at least one individual optical relief structure from the array comprises a base and a single apex that are connected by at least three n-polygonal surfaces where n is equal to 3 or higher. Preferably, at least one of the individual optical relief structures from the array comprises a base and a single apex that are connect by at least three n-polygonal surfaces where n is equal to 4 or higher, such as in US8283560 which is hereby incorporated by reference in its entirety. Preferably the base of an individual optical relief structure comprises an m- sided polygonal shape and the optical relief structure contains in total of at least m+1 surfaces. The optical relief structure may also have a flat peak apex as in

US20120204953, which is hereby incorporated by reference in its entirety.

Preferably, the relief textured transparent cover layer comprises an array of optical relief structures, and a plurality of the optical relief structures comprise an apex, a base, an at least three n-polygonal surfaces made up of n sides, where n is an integer of at least 4. Each n-polygonal surface has at least two sides converging to each other in the direction of the apex and has at least two sides converging to each other in the direction of the base. Preferably, all surfaces of the optical relief structure are converging towards the apex.

When describing the m-polygonal base of the optical relief structure by a circle wherein the edges of the polygonal base lie on the circumferential line of the circle, the diameter D of the circle is preferably less than 30 mm, more preferably less than 10 mm and most preferably less than 3 mm. More preferably, the diameter D of the circle is less than 1 mm, and more preferably less than 0.5 mm and more preferably below 0.2 mm.

The height of structures depends on the diameter D of the base and is preferably between 0.1 ^*D and 2^*D.

Although the relief textured transparent cover layer could contain only one individual optical relief structure, it is preferred that the relief textured transparent cover layer contains an array of optical relief structures. An array is to be understood as a collection or group of elements, in this case individual optical relief structures, placed adjacent to each other or arranged in rows and columns on one substrate. Preferably the array contains at least 4 optical relief structures. In another preferred embodiment of the invention, the relief textured transparent cover layer contains an array of optical relief structures with adjacent structures abutting each other. The optical relief structures can be placed such that the orientation of all optical relief structures is the same, alternating or random with respect to each other. The array may comprise different individual optical relief structures, or each member of the array may be the same optical relief structure. More than one array may be present in the relief textured cover layer, and the arrays may overlap.

The relief textured transparent cover layer could be made of any transparent materials like glass or polymers, or a combination thereof. Examples of polymers that are suitable for carrying out the invention, but that are by no means meant to restrict the invention, are polycarbonate (PC), polymethylmethacrylate (PMMA), polymethylacrylate (PMA), polyurethane (PU), urethane acrylates (UA), urethane methacrylates, polypropylene (PP), polyethylene terephthalate (PET), fluoropolymers, and/or polyethylene and also combinations thereof. The relief textured transparent cover layer can be formed by a polymerization initiated by, e.g. heat or light. Further examples of methods of manufacturing a relief textured transparent cover layer are described in US20120031489 and US20120024355, both hereby

incorporated by reference in their entirety.

The thickness of the relief textured transparent cover layer can be any thickness. Preferably the thickness should be less than 10 mm and more preferably the thickness should be less than 5 mm.

The transparent conductive material can be present at any appropriate thickness, size or shape. Preferably, the transparent conductive material is a layer less than 1 micron thick, more preferably less than 200 nm and most preferably less than 100 nm. Said material can be made of any materials that are at least partially transparent and conductive. Preferably, the transparent conductive material is at least 50% transparent to light having wavelengths from 400 to 750 nm. Preferably, only a single layer of transparent conductive material is present.

The transparent conductive material may be organic or inorganic. In a preferred embodiment, the transparent conductive material is an inorganic material. Examples of transparent conductive materials that are suitable for carrying out the invention, but that are by no means meant to restrict the invention, are indium tin oxide (ITO), fluorinated tin oxide (FTO), and aluminum zinc oxide (AZO).

In yet another preferred embodiment, the transparent conductive material is an organic material such as, for example, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PETDOT:PSS), Poly(3,4-ethyleendioxythiophene)- tetramethacrylate (PEDOT-TMA), poly(p-phenylene vinylene) (PPV), or polymers doped with conductive fillers such as carbon nano-tubes. The transparent conductive material is typically applied via sputtering, or other deposition techniques. In embodiments the transparent conductive material is textured, meaning that the transparent has an RMS roughness of greater than or equal to 80 nm. In other embodiments, the transparent conductive material is present as a layer and is non- textured, meaning that the transparent conductive layer has an RMS roughness of less than 80 nm. In the case that the transparent conductive material is textured, the texturing may be formed by either texturing the transparent conductive material itself, or by texturing the inside of the textured transparent cover which will result in a texturing of the transparent conductive material. In either case, the texturing can be formed by etching.

The reflecting grid of electrodes can be made in any size, thickness or shape. Preferably, the grid is greater than 50 nm thick, more preferably greater than 100 nm thick. The reflecting grid of metallic electrodes should reflect at least 20% of light having a wavelength in the range from 400 to 750 nm, i.e. the wavelengths of light which will be most effectively converted to electricity by the photovoltaic active layer. More preferably at least 50% of light having a wavelength in the range from 400 to 750 nm is reflected. Even more preferably, at least 80% of light having a wavelength in the range from 400 to 750 nm is reflected. Reflection includes both diffuse and specular reflection. By a grid, it is meant some construction where light is able to reach the photovoltaic active layer without coming into contact with the reflecting grid of electrodes in some locations, and where light is not able to reach the photovoltaic active layer in other locations. For example, a uniform layer of material covering an entire surface is not a grid.

Said reflecting grid of electrodes can be made of any material(s), with the restrictions that the material(s) used should be more conductive than the transparent conductive material and reflecting. Preferably, the reflecting grid of electrodes comprises a metallic material. Examples of metallic materials that are suitable of carrying out the invention, but that are by no means meant to restrict the invention, are silver, copper, gold, aluminum or metal alloys.

The reflecting grid of electrodes could be manufactured via any printing technique like screen-printing, ink-jet printing, offset printing or flexoprinting. Alternatively, it could be made via casting techniques like for example solution casting, spin coating, doctor blading, dip coating, capillary filling or spray coating. It is also possible to make said grid via deposition techniques like sputter coating, chemical vapour deposition or plasma enhanced chemical vapour deposition. Preferably, a printing technique is used. The grid could be made from an ink containing metallic precursors or metal particles, or directly from a metal itself.

It is further preferred that the reflecting grid of electrodes covers more than 1 % of the surface of the photovoltaic active layer. In other embodiments, the reflecting grid of electrodes covers more than 5% of the surface of the photovoltaic active layer. In other embodiments, the reflecting grid of electrodes covers more than 10 % of the surface of the photovoltaic active layer.

The reflecting grid of electrodes can be in any pattern. Examples of patterns are lines, triangular, squares or hexagonal patterns. Preferably, the grid of reflecting electrodes does not require alignment to any feature of the relief textured transparent cover layer.

The thickness of each electrode can vary. This will also depend on the way that the photovoltaic device is built. Although multiple building strategies are possible, roughly speaking one can distinguish between a bottom up approach or top down approach. In the former, one starts with the back side (substrate) of the PV device and deposits each layer on top of the substrate. In the latter, one starts with the front side (superstrate) of the photovoltaic device and deposits each layer at the back of the superstrate.

In the bottom up approach one can use a thicker electrode than in the top down approach. However, in any case the thickness of the electrodes is less than 1 mm. Preferably, the thickness of the electrodes is less than 100 micron, more preferably less than 10 micron and most preferably even less than 1 micron.

The front electrode may be assembled by first placing the transparent conductive material and then placing the grid of reflecting electrodes, or by first placing the grid of reflecting electrodes and then placing the transparent conductive material.

In an embodiment, the front electrode of the photovoltaic device consists essentially of a reflecting grid of electrodes that is in electrical contact with the transparent conductive material, wherein the reflecting grid of electrodes reflects at least 20%, preferably at least 50%, and more preferably at least 80%, of light having a wavelength in the range from 400 to 750 nm. By consisting essentially of it is meant that the only conductive materials present in the front electrode are the transparent conductive material and the reflecting grid of electrodes. In a further embodiment, the front electrode of the photovoltaic device consists essentially of a single layer of transparent conductive material and a reflecting grid of electrodes that is in electrical contact with the transparent conductive material, wherein the reflecting grid of electrodes reflects at least 20% of light having wavelengths from 400 to 750 nm.

A photovoltaic active layer can be made of any material which creates a voltage and a corresponding electric current when it is exposed to light. The photovoltaic active layer can be made from organic or inorganic materials. Examples of photovoltaic active layer materials that are based on inorganic materials that are suitable for carrying out the invention, but that are by no means meant to restrict the invention, are amorphous silicon (a-si), microcrystalline silicon (μο-si), cadmium telluride (CdTe), copper indium gallium selenide (CIGS) and cadmium telluride (CdTe).

In particular organic photovoltaic active layers are suitable for carrying out the invention. These organic materials can be relatively short molecules or large (polymeric) molecules. Examples of photovoltaic cells that are based on organic materials are dye-sensitized solar cells (DSSC) or Gratzel cells, organic photovoltaic cells or polymer photovoltaic cells.

Although the invention is particularly suitable for thin film photovoltaic panels, it can also be used on crystalline photovoltaic panels.

Certain embodiments of the invention may have particular utility when fast, high volume production of photovoltaic devices is desired, such as in the production of organic photovoltaic devices. When fast, high volume production is desired a transparent conductive material that is an organic transparent conductive material, such as PEDOT or PETDOT, can be used as the transparent conductive material. Although organic transparent conductive materials are more quickly processed than their inorganic counterparts in photovoltaic device production, organic transparent conductive materials also possess generally poorer conductivity than inorganic transparent conductive materials. This poorer conductivity can be

compensated for by applying the reflecting grid of electrodes and a relief textured cover plate, which can also be quickly processed. For example, the reflecting grid of electrodes can be printed at high speed. In an embodiment, an organic photovoltaic device comprises a relief textured transparent cover layer; a front electrode comprising an organic transparent conductive material, and a reflecting grid of electrodes that is in electrical contact with the organic transparent conductive material, wherein the reflecting grid of electrodes reflects at least 20% of light having a wavelength in the range from 400 to 750 nm; and an organic photovoltaic active layer.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. While certain optional features are described as embodiments of the invention, the description is meant to encompass and specifically disclose all combinations of these features unless specifically indicated otherwise or physically impossible.

Claims

A photovoltaic device comprising:

a relief textured transparent cover layer;

a front electrode comprising

a transparent conductive material, and

a reflecting grid of electrodes that is in electrical contact with the transparent conductive material, wherein the reflecting grid of electrodes reflects at least 20% of light having a wavelength in the range from 400 to 750 nm; and

a photovoltaic active layer.

The photovoltaic device according to claim 1 , wherein the reflecting grid of electrodes is a grid of metallic electrodes.

The photovoltaic device according to claim 1 or 2, wherein the relief textured transparent cover layer comprises an array of optical relief structures that are not aligned to the reflecting grid of electrodes.

The photovoltaic device of claim 3, wherein the optical relief structures are abutting.

The photovoltaic device according to claim 3 or 4, wherein at least one of the optical relief structures of the relief textured cover layer comprises a base and a single apex that are connected by at least three n-polygonal surfaces where n is equal to 3 or higher.

The photovoltaic device according to claim 5, wherein n is equal to 4 or higher.

The photovoltaic device according to any one of claims 1 to 6, wherein the relief textured transparent cover layer is made of glass.

The photovoltaic device according to any one of claims 1 to 7, wherein the relief textured transparent cover layer is made of a polymer.

The photovoltaic device according to any one of claims 1 to 8, wherein the relief textured transparent cover layer is made partially of glass and partially of a polymer.

The photovoltaic device according to any one of claims 1 to 9, wherein the transparent conductive material is an inorganic material.

The photovoltaic device according to any one of claims 1 to 9, wherein the transparent conductive material is an organic material. The photovoltaic device according to any one of claims 1 to 1 1 , wherein the reflecting grid of electrodes covers more than 1 % of the surface of the front electrode.

The photovoltaic device according to any one of claims 1 to 12, wherein the grid of reflecting electrodes covers more than 5% of the surface of the front electrode.

The photovoltaic device according to any one of claims 1 to 13, wherein the reflecting grid of electrodes reflects at least 50% of light having a wavelength in the range from 400 to 750 nm.

An organic photovoltaic device comprising:

a relief textured transparent cover layer;

a front electrode comprising

an organic transparent conductive material, and

a reflecting grid of electrodes that is in electrical contact with the organic transparent conductive material, wherein the reflecting grid of electrodes reflects at least 20% of light having a wavelength in the range from 400 to 750 nm; and

an organic photovoltaic active layer.