EP2153471A2

EP2153471A2 - Transparent substrate with advanced electrode layer

Info

Publication number: EP2153471A2
Application number: EP08805722A
Authority: EP
Inventors: Guillaume Counil; Michele Schiavoni; Fabrice Abbott
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2007-05-04
Filing date: 2008-04-28
Publication date: 2010-02-17
Also published as: US20100116332A1; WO2008148978A2; FR2915834B1; WO2008148978A3; CN101681937A; MX2009011912A; BRPI0810891A2; JP2010526430A; FR2915834A1; KR20100016182A

Abstract

The invention relates to a substrate having a glazing function and associated with a textured electrode, including at least one conducting transparent layer containing metal oxide(s), said layer being covered by at least one functional layer of an element capable of collecting light, characterised in that the substrate is covered with an interface layer having a textured portion including a repetition of periodical or non-periodical relief patterns.

Description

TRANSPARENT SUBSTRATE WITH ELECTRODE LAYER

IMPROVED

The invention relates to an improvement made to a transparent substrate, in particular glass, which is provided with an electrode. This conductive substrate is more particularly intended to be part of solar cells. This includes using it as the "front face" of the solar cell, that is to say the one that will be directly exposed to solar radiation to convert into electricity.

The invention is particularly interested in solar cells of amorphous or microcrystalline Si type. We briefly recall the structure: This type of product is generally marketed in the form of solar cells mounted in series between two rigid substrates, possibly transparent, whose front face is made of glass. This type of cell is described in the German application DE 10 2004 046 554.1

It is the set of substrates, polymer and solar cells that we designate and that we sell under the name of "solar module".

The invention therefore also relates to said modules. When we know that solar modules are not sold per square meter, but the electric power delivered, each additional percentage of efficiency increases the electrical performance, and therefore the price, of a solar module of given dimensions, each percent of efficiency gained, for a given solar module technology, being mainly a function of a gain obtained in the transmission of light within the substrate associated with said cell.

French patent FR2832706 discloses a glass-function substrate provided with an electrode comprising at least one conductive transparent layer based on metal oxide (s). electrode having the particularity of having an RMS roughness varying from a few nanometers to a few tens of nanometers

Although this textured electrode substrate, when positioned in the immediate vicinity of an element capable of collecting light (for example a photovoltaic cell, a solar collector) fulfills its function and guarantees the achievement of energy conversion efficiency. Interestingly, the inventors have found that the diffusion of the light source within the substrate to a functional layer of the element capable of collecting light can be further improved.

The object of the invention is therefore to find means for improving the photoelectric conversion efficiency of these modules, means having more specifically the "front" glasses provided with electrodes mentioned above. We will look for simple ways to implement on an industrial scale, not disrupting the structures and configurations known for this type of product.

The invention first of all relates to a glass-function substrate associated with a textured electrode having at least one conductive transparent layer based on metal oxide (s), said layer being covered by at least one layer functional element of an element capable of collecting light which is characterized in that the substrate is covered by an interface layer having a textured portion comprising a periodic or non-periodic repeating patterns in relief. For the purposes of the invention, the electrode is known by the abbreviation T. C. O for "Transparent Conductive Oxide". It is widely used in the field of solar cells and electronics.

For the purposes of the invention, the functional layer is defined as any thin layer based on a material that allows the energetic conversion of light into electrical energy or thermal energy within an element capable of collecting light (for example solar cell or photovoltaic, a solar collector). The materials in question for solar cells can be classically amorphous silicon, microcrystalline silicon, CdTe-based layers (cadmium telluride).

If this surface texturing has particular specifications, we will rather obtain an anti-reflection effect between the two environments surrounding the interface layer.

Moreover, thanks to the surface texturing at the level of the interface layer, there is obtained between the interface layer and the materials which surround it, an increased diffusion of the incident light, which "forces" it to have a much longer trajectory through the solar cell.

By thus lengthening the optical path, we increase the chances of absorption of light by the active elements of the cell, and finally we increase the photoelectric conversion rate of the solar cell. This traps light better.

In preferred embodiments of the invention, one or more of the following may also be used:

the interface layer is situated on the rear face of the substrate and has a textured portion which comprises a repetition of periodic or non-periodic patterns in relief of pitch w, and of height h satisfying the following relations: w <λ, and preferably w <λ / 2, and more preferably w <λ / 4 and h ≥ λ / 4 and preferably h ≥ λ and more preferably h ≥ 2λ, λ belonging to the solar spectrum and being located at the maximum of energy conversion efficiency of the solar cell.

The interface layer is situated on the rear face of the substrate and has a textured portion which comprises a repetition of periodic or non-periodic patterns in relief of pitch w, and of height h satisfying the following relations: λ / 4 <w <2λ and h is between 20 nm and 1 μm and preferably between between 30 nm and 500 nm and more preferably h between 50 nm and 200 nm, with λ being located at a wavelength in which the solar spectrum is important but the conversion efficiency of the cell n ' is not its optimal.

the conductive layer is deposited on the interface layer,

the interface layer is situated on the front face of the substrate and has a textured portion which comprises a repetition of periodic or non-periodic patterns in relief of pitch w, and of height h satisfying the following relations: λ / 4 <w <2λ and h is between 20 nm and 1 μm and preferably between 30 nm and 500 nm and more preferably h between 50 nm and 200 nm, with λ being situated at a wavelength in which the Solar spectrum is important but the conversion efficiency of the cell is not its optimum.

- The interface layer has a refractive index close to that of the substrate

- The interface layer has a refractive index n <Substrate if the interface layer is placed on the front face of the substrate

- The interface layer has an index n such that <Substrat≤ n≤ nτco if the interface layer is placed between the substrate and the conductive layer the conductive layer is conforming with respect to the interface layer

- The conductive layer has a roughness different from that of the interface layer The interface layer is located on the rear face of the substrate and has a textured portion which comprises a repeating periodic or non-periodic patterns of pitch w substantially close to 300 nm for which it has a combined effect for antireflection for a first range of wavelengths and light trapping for a second wavelength range, the relief patterns comprise parallel lines the relief patterns comprise non-parallel lines and / or pads,

the textured surface is obtained by embossing a sol-gel or polymer layer

the textured surface is obtained by a photolithography technique. Other features, details, advantages of the present invention will appear better on reading the description which follows, made by way of illustration and in no way limiting, with reference to the appended figures on FIG. which:

- Figure 1 is a sectional view of a solar cell incorporating a substrate according to the methods of the invention according to a first embodiment, the interface layer being positioned on the rear face of the substrate.

- Figure 2 is a sectional view of a solar cell incorporating a substrate according to the methods of the invention according to a second embodiment, the interface layer being positioned on the front face of the substrate.

FIG. 3 illustrates the energy conversion efficiencies E (λ) of two typical photovoltaic cells (amorphous Si, and microcrystalline Si) as a function of the wavelength of the light.

FIG. 4 illustrates a first variant embodiment of the invention with an anti-reflective effect,

FIG. 5 illustrates a second variant embodiment of the invention with a light trapping effect. FIG. 6 illustrates, for different step values, the evolution of the optical path as a function of the wavelength. In Figure 1, there is shown an element capable of collecting light (a solar or photovoltaic cell) incorporating a substrate object of the invention.

The transparent substrate 1 with glass function can for example be entirely of glass. It may also be a thermoplastic polymer such as a polyurethane or a polycarbonate or a polymethylmethacrylate.

Most of the mass (that is to say at least 98% by weight), or even the entire glass-function substrate consists of material (x) having the best possible transparency and preferably having a linear absorption. less than 0.01 mm ¹ in the part of the spectrum useful for the application (solar module), generally the spectrum ranging from 380 to 1200 nm.

The substrate 1 according to the invention can have a total thickness ranging from 0.5 to 10 mm when used as a protective plate of a photovoltaic cell of various technologies (amorphous silicon, micro-crystalline silicon). In this case, it may be advantageous to subject this plate to a heat treatment (of the quenching type for example). In a conventional manner, A defines the front face of the substrate directed towards the light rays (this is the external face), and B the rear face of the substrate directed towards the rest of the solar module layers (it is acts of the internal face).

On the B side of the substrate, an interface layer 2 is deposited. This interface layer 2 is obtained by spin coating, flow coating, spray coating, screen printing or any other liquid layer deposition technique. thin, and is based on a polymer or sol gel.

The sol-gel layers that can be used are generally liquid layers of inorganic oxide precursor such as SiO 2, Al 2 O 3, TiO 2, for example in solution in a water-alcohol mixture. These layers harden on drying, with or without auxiliary heating means.

Examples of precursors of SiO 2 are tetraethoxysilane (TEOS) or methyltriethoxysilane (MTEOS). Organic functions can be included in these precursors and the silica finally obtained. For example, fluorinated silanes have been described in the document

EP 799,873 to obtain a hydrophobic coating.

Among the polymers can be cited

poly (ethylene terephthalate) (PET),

polystyrene, polyacrylates such as poly (methyl methacrylate), poly (butyl acrylate), poly (methacrylic acid), poly (2-hydroxyethyl methacrylate) and their copolymers,

polyepoxy (meth) acrylates,

polyurethane (meth) acrylates, polyimides such as polymethylglutarimide,

polysiloxanes, such as polyepoxysiloxanes,

poly (vinyl ethers),

polybisbenzocyclobutenes ... alone or in copolymers or mixtures of several of them. The said patterns are then produced on the surface of this interface layer 2 by either an embossing technique, or by a photolithography technique, or by any texturing technique (chemical etching, laser transfer ablation, ion exchange, photorefractive effect or electro-optical). The embossing method consists in structuring a surface portion of the glass-function substrate by forming an array of patterns according to sub-millimetric characteristic dimensions, the surface structuring by plastic or viscoplastic deformation being performed by contact with a structured element called a mask and by exerting pressure, the structuring being effected by a continuous movement of the mask parallel to the surface of the product and / or by a continuous movement of said product parallel to the surface of the product. The speed of the movement and the duration of the contact, under pressure, between the product and the mask are adjusted according to the nature of the surface to be structured in particular: its viscosity, its surface tension; and possibly depending on the type of desired patterns (most faithful reproduction of the pattern of the mask, or deliberately truncated ...).

The mask pattern is not necessarily the negative of the replicated pattern. Thus, the final pattern can be formed with several masks or by several passes.

The mask may have a plurality of areas with distinct patterns in size (width and height) and / or orientation and / or distance. Another possible method of manufacturing the network according to the invention comprises a photolithography. This method generally consists in first providing the transparent substrate with a first layer in which said raised patterns can be formed. This first layer is comparable to the sol-gel or polymer layer reported from the embossing process. It can also be of the same nature as this one, in particular silica. In a second step of the process, a second layer of a photoresist is deposited. This is hardened in defined locations, by exposure to targeted radiation. Thus is formed a mask, above the first layer to be etched, after removal of the uncured portions of the photoresist. Then, in the same manner as described above, in the optional step of the embossing process. Any residues of the photoresist can be removed.

Another method of manufacturing the network according to the invention comprises the transfer of a nanostructured layer. A layer in adhesion on a first support is put in adhesion on a second, so as to constitute a device according to the invention. The layer may be of plastics material or the like.

Another useful method is based on ion exchange, for example Na ⁺ ions by Ag ⁺ in a mineral glass. Finally, it is possible to use a photorefractive effect, according to which a modulated light induces a spatial modulation of the refraction index of the material (example: photorefractive crystal in barium titanate). It is also possible to use an electro-optical effect in which an electric field induces a spatial modulation of the refractive index of the material.

Depending on the shape of the desired structure, this process may not necessarily lead to perfect geometric shapes. In particular, in the case of sharp-angled patterns, the pattern can be rounded without affecting the required performance.

According to a first variant embodiment, a so-called "fly-eye" profile is produced, namely that the plurality of periodic or non-periodic reliefs has the following geometrical characteristics: the pitch w and the height h of the pattern satisfy the following relations: w <λ, and preferably w <λ / 2, and more preferably w <λ / 4 and h ≥ λ / 4 and preferably h ≥ λ and more preferably h

≥ 2λ

In this configuration λ belongs to the solar spectrum and more particularly is located at the maximum of the efficiency of the solar cell, in particular λ = 500 nm for the amorphous silicon (cf Figure 3), and λ = 700 nm for the micro-crystalline silicon. (see Figure 3).

The patterns may, for example, be cone-shaped or pyramid-shaped polygonal in shape such as triangular or square or rectangular or hexagonal or octagonal, said patterns being convex, that is to say protruding from the general plane of the layer. interface or be concave, that is to say coming hollow in the mass of the interface layer. All of these patterns can extend on the surface and form parallel or non-parallel lines (in fact generate pads).

The material chosen to constitute the material of the interface layer has a refractive index substantially similar to or close to that of the material constituting the glass-function substrate (approximately 1.50).

On this interface layer 2, there is deposited a conductive layer 3 called TCO for "Transparent Conductive Oxide". It may be chosen from the following materials: doped tin oxide, in particular fluorine or antimony (the precursors that can be used in the case of CVD deposition may be organo-metallic or tin halides associated with a fluorine precursor of the hydrofluoric acid or trifluoroacetic acid type), doped zinc oxide, in particular with aluminum (the precursors that can be used, in the case of CVD deposition, may be organometallic or zinc and aluminum halides), or doped indium oxide, in particular with tin (the precursors that can be used in the case of CVD deposition can be organo-metallic or tin and indium halides).

The conductive layer 3 has a resistance per square of at most 30 ohms / square, in particular at most 20 ohms / square, preferably at most 10 or 15 ohms / square. It is generally between 5 and 12 ohms / square.

It may be noted that the interface layer has an index n such that <n _V erre≤ n≤ nτco if the interface layer is placed between the glass and the conductive layer 3 in TCO

In this way, an antireflection effect will be obtained between the glass-based substrate 1 (glass-based) and the conductive layer 3. This results in an increase of the transmission of the order of 2 to 3%, TCO of conventional index close to 2.0 The conductive layer 3 is covered by a functional layer 4 of a solar cell. Depending on the nature of the contact zone between the conductive layer 3 and the functional layer 4, different optical properties can be obtained within the solar cell:

If the contact zone is compliant (conductive layer 3 has followed in a manner consistent with the geometry of the interface layer

2 from the reliefs), a second anti-reflection effect is obtained between the conductive layer 3 and the functional layer 4. For a TCO of index 2 and a functional layer of index 3, the increase in transmission will be of the order from 3 to 4% - If the contact zone is not in conformity (that is to say that the conductive layer 3 has a different texturing (formation of grains for example) than that of the interface layer 2), this second texture can help light trapping and extend the path of light in the functional layer of the solar cell.

According to a second variant embodiment, a structure is produced which diffuses or diffracts the light. The textured portion of the interface layer 2 comprises a plurality of periodic or non-periodic reliefs that have the following geometrical characteristics: the pitch w, and the height h satisfy the following relations: λ / 4 <w <2λ and h is included between 20 nm and 1 μm and preferably between 30 nm and 500 nm and more preferably h between 50 nm and 200 nm.

In this configuration the wavelength λ which is chosen corresponds to a wavelength in which the solar spectrum is important but the conversion efficiency of the cell is not its optimum. In this way the wavelengths travel a longer distance in the solar cell and the probability of being converted is greater. We will choose wavelengths for which the conversion efficiency is not too low, (if we take λ for which the conversion efficiency is too low, the extension of the optical path will have a large relative increase but a small absolute increase. For example, for solar cells based on amorphous silicon (see FIG. 3), λ will be chosen between 550 and 750 nm (efficiency too low beyond this value). For μcrystalline silicon (see FIG. 3), λ will be chosen between 500 and 650 nm and between 800 and 1000 nm.

The patterns may, for example, be cone-shaped or pyramid-shaped polygonal in shape such as triangular or square or rectangular or hexagonal or octagonal, said patterns being convex, that is to say protruding from the general plane of the layer. interface or be concave, that is to say coming hollow in the mass of the interface layer.

All of these patterns can extend on the surface and form parallel or non-parallel lines (in fact generate pads). On this interface layer is deposited a conductive layer 3 called TCO (Transparent Conductive Oxide). It may be chosen from the following materials: doped tin oxide, in particular fluorine or antimony (the precursors that can be used in the case of CVD deposition may be organo-metallic or tin halides associated with a fluorine precursor of the hydrofluoric acid or trifluoroacetic acid type), doped zinc oxide, in particular with aluminum (the precursors that can be used, in the case of CVD deposition, may be organometallic or zinc and aluminum halides), or doped indium oxide, in particular with tin (the precursors that can be used in the case of CVD deposition can be organo-metallic or tin and indium halides).

The conductive layer 3 has a resistance per square of at most 30 ohms / square, in particular at most 20 ohms / square, preferably at most 10 or 15 ohms / square. It is generally between 5 and 12 ohms / square. The conductive layer 3 is covered by a functional layer 4 of a solar cell, there is a diffractive effect (the light rays are scattered or diffracted at the interface layer). If the conducting layer 3 conforms to the texturing coming from the interface layer and in addition has a certain intrinsic roughness, then, in this case, the interface zone between the conductive layer 3 and the functional layer 4 will present a dual-scale texturing, a first scale being given by the textured interface layer, the second scale from the intrinsic roughness of the conductive layer. This double-scale roughness makes it possible to obtain an improved "light trapping" phenomenon.

For some modes the roughness is non-uniform, random. There are no regular patterns at the interface layer surface and the conductive layer, but varying sizes of protuberances and / or troughs at the surface of the layers, distributed randomly over any said surface. This roughness will already allow a diffusion of the light transmitted by the important substrate, and mainly "forwards", that is to say so as to diffuse the light, but mainly towards the inside of the solar cell .

The goal is, again, to "trap" at best the incident solar rays in specific wavelengths λ between 550 and 750 nm for amorphous silicon-based cells, we choose λ between 550 and 750 nm, and for microcrystalline silicon (see FIG. 3), λ will be chosen between 500 and 650 nm and between 800 and 1000 nm.

The functional layer 4 is covered by a conductive layer 5 to serve as a second electrode to the solar module. This conductive layer 5 is made for example of silver by a vacuum sputtering technique (magnetron). Subsequently, this glass plate 1 provided with all the previously explained layers is fixed via a interlayer lamination 6 to a counter glass 7, thus conforming a solar cell or photovoltaic.

FIG. 2 shows another embodiment of the invention which differs from that illustrated in FIG. 1 simply by the position of the interface layer 2 relative to the substrate.

According to this embodiment, the interface layer 2 is on the face A of the substrate 1. In this case, the interface layer has a refractive index n <n _ve rre.It makes it possible to diffuse or diffract the incident light so that the light rays traveling through the substrate 1, then in the conductive layer 3, then the functional layer 4, at high angles of incidence, thereby increasing the phenomenon of light trapping. This scattering or diffraction of light is obtained for specific wavelengths.

Embossings having a pitch w and a height h which satisfy the following relations λ / 4 <w <2λ and h is between 20 nm and 1 μm and preferably between 30 nm and 500 nm and more preferably h are used. between 50 nm and 200 nm. We choose λ between 550 and 750 nm (efficiency too low beyond this value) for amorphous silicon. For microcrystalline silicon (see FIG. 3), λ will be chosen between 500 and 650 nm and between 800 and 1000 nm.

The substrate according to the invention finds its use in a solar cell. Depending on the intended application, it is possible to apply on the face of the most appropriate plate at least one layer conferring on it a particular property. In particular, a barrier layer can be applied at certain wavelengths, for example in ultraviolet light. It is also possible to apply to the plate, preferably at least on the side directly in the ambient air, an anti-fouling layer such as a layer of TiO 2, in particular a layer which is the subject of the patent application EP 1087916, or a SiO 2 antifouling layer or Si oxycarbide or Si oxynitride or Si oxycarbonitride as described in WO 01/32578.

Example 1

Reference is made to FIG. 4 which illustrates an antireflection configuration in "fly-eye" according to the first variant embodiment.

An interface layer 2 is deposited on side B of a glass substrate 1. This layer 2 is structured and has trapezoidal grooves. The bases of the trapezoids have a width of w = 135 nm and p = 15 nm. The grooves are spaced from each other by a distance p = 15 nm. The depth h of the pattern is 900 nm.

On this interface layer 2 is deposited a transparent conductive layer 3.

Table 1 below gives the reflection values between the glass substrate and the conductive layer 3, with the presence of the interface layer 2 and without this interface layer 2. The reflection indices are respectively: = 1.52 for the glass 1, n = 1.52 for the structured interface layer 2, n = 2.01 for the conductive layer (TCO) 3. The reflection was calculated for 3 angles of incidence θ: 0 °, 30 °, 42 ° (this last angle being the total internal reflection angle in the glass) and for a wavelength λ = 450 nm (ideal for an amorphous silicon type cell)

Table 1: Reflection at the glass / conductive layer interface in the presence of an interface layer 2 having an antireflection effect (structured layer in a fly eye) or in the absence of an interface layer.

The antireflection effect of the interface layer appears obvious, with a reflection that goes from about 2% to less than 0.1% for all angles of incidence.

Example 2

Example 2 illustrates the second variant embodiment of the invention, namely the increase of the optical path. Reference can be made to FIGS. 5 and 6. An interface layer 2 is deposited on side B of a glass substrate 1. This interface layer 2 is structured and has grooves having a sinusoidal profile. The pitch of the sinusoid is w and the height h. On this interface layer 2 is deposited a transparent conductive layer 3 forming a TCO, of thickness e, conformably follows the structuring of the textured interface layer 2. This results in an increase in the path of light in the functional layer 4. If a light ray is found in the functional layer 4 with an angle θ relative to the normal to the cell, the optical path in the active medium will increase by a factor l / cos (θ) with respect to a normal radius of the cell.

The increase in the optical path as a function of the wavelength λ of the light is given below, for different steps w of textures. The height h was set at h = 200 nm and the thickness e = 600 nm.

The increase A (in%) of the optical path as a function of the wavelength of the light λ in the layer is given below. functional 4 for different w steps of the texture. The indices are n = 1.52 for media 1 and 2 (glass and textured interface layer), n = 2.0 for media 3 (TCO) and n = 3 for media 4 (functional layer 4). The increase A (in%) was calculated by averaging over a range of angles of incidence in the air, between 0 ° and 50 °.

The results are summarized in FIG. 6. An increase in the optical path due to the diffraction / scattering of light on the structured layers is observed. The increase of the optical path "light trapping" varies with the wavelength of the light. In particular, a texture with w = 300 nm is particularly effective for an amorphous silicon type cell such as that of FIG. 3. Indeed "light trapping" is particularly effective for λ between 600 and 750 nm. Moreover, a texture with w = 400 nm appears particularly effective for a microcrystalline silicon cell such as that of FIG. 3. Indeed "light trapping" is particularly effective for λ between 500 and 650 nm and between 750 and 900 nm, while the "light trapping" is less efficient around 700 nm, the wavelength at which this cell possesses an optimal conversion efficiency, making the phenomenon of light trapping less necessary.

Example 3

Finally, in Example 3, a structure is presented which has both an anti-reflective effect in "fly eye" and a "light trapping" effect.

In this example 3, we take the geometry of Example 2 and in particular the case with w = 300 nm. In this configuration, not only is it possible to obtain a trapping of the light with increase of the optical path (light trapping), but an antireflection effect is obtained between the glass (medium 1) and the functional layer 4. By calculating the transmission between the middle 1 (glass) and the functional layer 4 for a first range of wavelengths between λ = 400 and 600 nm for such a structure, an increase in light transmission of the order of 4% is obtained (value obtained by averaging on incidence angles between 0 ° and 50 °). Moreover, we have already seen (see Fig. 6) that this structure allows an optical path increase of the order of 20% for a second wavelength range between 600 and 750 nm. It follows that this structure will have a double beneficial effect for a functional layer 4 of amorphous silicon type such as that of FIG. 3. For wavelengths between 400 and 600 nm, for which the functional layer 4 is very efficient, the structure induces an anti-reflective effect while for wavelengths between 600 and 750 nm, where the functional layer 4 is less effective, we obtain a "light trapping" effect. "

Claims

1. A substrate (1) with a glass function associated with a textured electrode comprising at least one conductive transparent layer (3) based on metal oxide (s), said layer being covered by at least one functional layer (4) an element capable of collecting light, characterized in that the substrate (1) is covered by an interface layer (2) having a textured part comprising a repetition of periodic or non-periodic patterns in relief

2. Substrate according to claim 1, characterized in that the interface layer (2) is located on the rear face of the substrate (1) and has a textured portion which comprises a repetition of periodic or non-periodic patterns in relief of pitch w , and of height h satisfying the following relations: w <λ, and preferably w <λ / 2, and more preferably w <λ / 4 and h ≥ λ / 4 and preferably h ≥ λ and more preferably h ≥ 2λ, λ belonging to the solar spectrum and being located at the maximum of the energy conversion efficiency of a solar cell.

3. Substrate according to claim 1, characterized in that the interface layer (2) is located on the rear face of the substrate (1) and has a textured portion which comprises a repeating periodic or non-periodic patterns in relief of pitch w , and of height h satisfying the following relations: λ / 4 <w <2λ and h is between 20 nm and 1 μm and preferably between 30 nm and 500 nm and more preferably h between 50 nm and 200 nm , with λ being located at a wavelength in which the solar spectrum is important but the conversion efficiency of a cell is not its optimum.

4. Substrate according to any one of the preceding claims, characterized in that the conductive layer (3) is deposited on the interface layer (2).

5. Substrate according to claim 1, characterized in that the interface layer (2) is located on the front face of the substrate (1) and has a textured portion which comprises a repetition of periodic or non-periodic patterns in relief of pitch w , and of height h satisfying the following relations: λ / 4 <w <2λ and h is between 20 nm and 1 μm and preferably between 30 nm and 500 nm and more preferably h between 50 nm and 200 nm , with λ being located at a wavelength in which the solar spectrum is important but the conversion efficiency of a cell is not its optimum.

6. Substrate according to any one of the preceding claims, characterized in that the conductive layer (3) is consistent with respect to the interface layer (2).

7. Substrate according to one of claims 1 to 5, characterized in that the conductive layer (3) has a roughness different from that of the interface layer.

8. Substrate according to one of claims 1 to 4, characterized in that the interface layer (2) has a refractive index close to that of the substrate.

9. Substrate according to claim 5, characterized in that the interface layer (2) has a refractive index n <n _su bstrat

10. Substrate according to one of claims 1 to 4, characterized in that the interface layer (2) has a refractive index n such that <n _S ubstrat≤ n≤ nrco if the interface layer is placed between the substrate and the conductive layer

1. The substrate according to any one of the preceding claims, characterized in that the relief patterns comprise parallel lines.

12. Substrate according to one of claims 1 to 10, characterized in that the raised patterns comprise non-parallel lines and / or pads.

13. Substrate according to one of the preceding claims, characterized in that it is associated with a solar module, the textured face being directed to the active material of the solar module.

Substrate according to one of the preceding claims, characterized in that the interface layer (2) is situated on the rear face of the substrate (1) and has a textured part which comprises a repetition of periodic or non-periodic step patterns. w substantially close to 300 nm for which it has a combined effect of antireflection for a first range of wavelengths and light trapping for a second wavelength range.

15. Process for producing a substrate according to one of claims 1 to 14, characterized in that the textured surface is obtained by embossing a sol-gel or polymer layer.

16. Process for producing a substrate according to one of claims 1 to 14, characterized in that the textured surface is obtained by a photolithography technique.

17. Use of the substrate according to one of claims 1 to 14 in a solar cell.

18. Solar cell characterized in that it comprises the substrate according to one of claims 1 to 14.