HRP20171417A2 - Photovoltaic solar cell - Google Patents

Abstract

The present invention relates to a photovoltaic solar cell containing at least one semiconductor layer, at least one insulating electrical insulation layer and at least one metal contact structure, wherein the insulating layer is between the semiconductor layer and the contact structure, where the insulation layer has multiple contact recesses in which the contact structure in electrical contact with the semiconductor layer in the contact area, and where an appropriate doping region is formed in the semiconductor layer, at least in the contact area, by contacting the semiconductor layer with metal, of which the contact structure is at least partially formed. It is characteristic of the present invention that the contact structure has multiple contact fingers, each extending over multiple contact areas, where the contact fingers have a locally enlarged cross-sectional area in the contact areas.

Description

The invention relates to a photovoltaic solar cell according to the preamble of claim 1.

Photovoltaic cells are used to convert the energy of incident photons into electrical energy. For this purpose, typical solar cells have a semiconducting layer, an electrically insulating layer, and a metallic junction structure.

Absorbed protons in the semiconductor layer produce a pair of carriers, which are separated at the pn-junction. The metal junction structure is connected to a p- or n-doped region, so that the carriers can be scattered. Through the second metal structure with contacts, the corresponding carriers of the region of the semiconductor structure of the opposite doped type are led away.

An insulating layer is placed between the semiconductor and the junction structure, in order to reduce losses caused by the recombination of minority carriers at the metal/semiconductor interface. In an insulating joint, electrical contact can occur between the joint contact structure and the semiconductor layer.

Furthermore, it is known that in order to dilute the recombination of minority carriers in the remaining border area between the metal and the semiconductor in the semiconductor layer in the junction areas, it is necessary to provide at least one doped region created by doping the semiconductor layer with the metal, which is an integral part of the junction structure. Thus, during the production process of the solar cell, the metal of the metal contact structure can be used in a simple way to create the so-called highly doped areas in the contact areas in the semiconductor layer, and in this way the already mentioned reduction of the recombination of minority carriers is achieved in a more efficient way.

Despite the success in terms of reducing production costs and/or increasing the efficiency of photovoltaic solar cells, there is still pressure on the market related to the high price. Therefore, photovoltaic cells find a wide range of such applications, where optimal application is not always guaranteed with respect to the source of radiation, such as for example the sun.

Therefore, the invention has the task of improving the photovoltaic solar cell with the insulating layer and the contact structure as described above, so that, based on the achieved reductions in losses, the efficiency is increased.

This goal is achieved by the photovoltaic solar cell according to claim 1. More favorable ways of applying the photovoltaic solar cell according to the invention can be found in claims 2 to 15.

This invention is based on the knowledge that, especially in solar cells with a contact structure as described at the beginning, the loss in the contact structure in the area of the contact grooves is determined:

As previously described, the metal of the contact structure is used to create locally doped regions at the contact slots in the semiconductor layer. However, this not only causes local doping of the semiconducting layer by the metal, but also typically integrates the semiconducting material into the metal contact structure. This reduces the conductivity of the contact structure in this region. Research has shown that, especially when making a contact structure using known per se contact leads, the conductivity resistance of the contact leads of previously known solar structures in the area of the contact grooves increases through the semi-conductive material stored in the contact lead, and based on the increased electrical conductivity resistance and corresponding ohmic power losses there is a significant reduction in the overall efficiency of the photovoltaic solar cell.

Photovoltaic solar cell according to the invention avoids or at least reduces these losses:

A photovoltaic solar cell according to the present invention has at least one semiconductor layer, at least one insulating layer that is electrically insulating, and at least one methane contact thereon. An insulating layer is placed between the semiconducting layer and the contact structure.

In order to make an electrical connection of the semiconductor layer in the middle of the contact structure, the insulating layer must have a plurality of contact grooves, where the contact structure makes electrical contact with the semiconductor layer in the contact area.

Furthermore, as described at the beginning, at least one doped region is formed in the semiconductor layer on the contact areas by doping the semiconductor layer with a metal, the metal of which is a complete or partial component of the metal contact structure. Therefore, as described above, losses caused by surface recombination of carriers in the semiconductor layer at the contact areas can be reduced.

It is essential that the contact structure has a greater number of contact leads, and the contact leads extend over several contact areas and/or extend along several contact areas, whereby the contact leads on the contact areas lead to an increase in cross-sectional areas.

This embodiment is based on the knowledge that there is a structure with contacts, which includes the previously described doped areas, and whose structure is not completely metallized, like, for example, the previously known complete side metallizations. There is a need for such a structure with contacts that is partially transparent to incident photons due to the incomplete coverage of the surface with a metal layer. Using such a structure with a larger number of contact leads, it is possible to apply a structure with contacts to the front side of the solar cell facing the sunlight.

It is also possible to use the back side of the solar cell, for example, to form a bifacial photovoltaic solar cell, which will be described in more detail below.

Here, research has shown that unlike the fully metallized design, contact structures with multiple contact leads carry the risk of the previously mentioned ohmic power losses due to locally increased resistance in the contact leads themselves.

According to the embodiment of the photovoltaic solar cell according to the invention, the contact leads are provided across and/or along several contact areas, where the leads on the contact areas create a local increase in cross-sectional areas. Likewise, leads on the contact areas create electrically parallel connected conductive structures, which do not cover the contact areas.

Through a local increase in the cross-sectional area, undesirable increases in the conductivity of the contact lead at the contact slots can be compensated for, or at least diluted. As a result, through this design of contact leads with multiple cross-sectional areas, the aforementioned ohmic power losses are avoided, or at least reduced. Contact leads on the contact areas preferably create extensions parallel to the surface of the insulating layer and to the right in the longitudinal direction of the contact lead.

As a result, the local expansion of the contact lead in the contact area achieves a simpler and technically undemanding realization of the local increase of the cross-sectional area.

It is particularly desirable in this case that the contact leads on the contact area are made so that they overlap the insulating layer. This results in a double effect of reducing the aforementioned ohmic power losses.

Through the expansion of the contact areas, on the one hand, the increase in the cross-sectional area is facilitated, so that the conduction resistance of the contact leads themselves decreases due to the increase in the cross-sectional area, in contrast to the contact leads without an increase in the cross-sectional area.

In addition, in the areas of those contact leads that overlap the insulating layer, semiconductor material is not installed or rarely installed, because during the production process these areas are not in contact, or at least in direct contact, with the semiconductor layer. As a result, the specific conduction resistance is reduced in the areas of those contact leads that overlap the insulating layer (based on reduced storage of semiconductor material), as opposed to areas directly on or across the contact surfaces (based on increased storage). In the corresponding diagram, the parallel connection of one contact lead with an increased specific resistance and a reduced specific resistance can be excluded, so that due to the storage of semiconductor material, there is no or a very small increase in the conduction resistance in the contact leads, and in this way efficiency losses are avoided, or at least reduced .

In a particularly preferred embodiment, the contact leads cover the insulating layer. Through this, on the one hand, the described effect of parallel connection is enhanced. In addition, the production of a solar cell requires a certain precision in processing, because there is an overlap of the insulating layer around the surface of the contact joint using metallized leads, and in this way a greater tolerance is ensured in relation to improper adjustments.

The basic task of the invention is fulfilled by the fact that the contact leads create electrically parallel connected metallized conductive structures on the contact areas, without covering the contact areas. These electrically paralleled metallic conductive structures store very little or no semiconducting material, and do not cover the contact areas. Based on the parallel connection of the contact lead area, which covers the contact area, the electrically parallel connected metallic conductive structure compensates, or at least reduces, the increases in conduction resistance that occur due to the storage of the semiconducting material.

Electrically parallel connected metal conductive structures are primarily made as local, parallel side leads. These secondary branches are an integral part of a single branch, but extend into the areas of contact areas separately but parallel to the main branch of the branch.

In this case, it is particularly preferable that the main branch does not cover the contact areas, but only the side branches of the contact area.

The result is that the current in the main branch is not, or only slightly, disturbed by deposits of semiconducting material. For this reason, the side lines in the area of the contact areas are spaced so that, due to the wideness of the gap, during the production of such a semi-conductive material of the contact lead which is embedded in the metal of the side lead, the material of the main line of the contact lead cannot be reached.

The contact slots are arranged in pairs, where one pair of slots is assigned a contact outlet on the opposite side.

In this advantageous embodiment of the invention, the main line or the main branch of the contact lead extends between the pair of contact grooves of the contact lead, whereby an extension occurs in the region of the contact groove of the contact lead, so that the main branch covers the contact grooves.

The contact lead thus has a main branch that extends between both pairs of slots. In the area of the contact slots, the main branch of the contact lead has an extension in the form of side branches or laterally connected extensions, which cover at least the contact slots.

The main branch of the contact finger is guided between the contact depressions on the insulating layer itself, and thus there is no or only relatively small storage of semiconductor material in this area, and thus no or a relatively small increase in the specific conductive resistance. Due to the covering of the contact recesses, the carriers are brought laterally to the main branch of the contact outlet. However, the overall current density in this lateral approach is relatively low, since only the main charge carriers from the respective contact pits need to be brought to the main branch of the contact lead within these areas. In contrast, the carriers of adjacent pairs of contact pits pass through the main branch of the contact lead which, as described above, is not, or only slightly, weakened by semiconductor material deposits.

Alternatively and/or in addition to forming a local cross-section through local extensions of the contact lead, the contact lead creates a thickening at the contact areas. Thus, in the case of a constant width created solely by thickening, a local increase in cross-sectional area can be achieved to reduce ohmic power losses as described above.

Likewise, through a combination of widening and thickening, an increase in the cross-sectional area of equal strength and an increasing reduction in resistance can be achieved.

Preferably, the contact structure comprises several contact leads and at least one bus, wherein it is preferable that the contact leads are connected to the bus in such a way that they are electrically conductive and enclose the material.

The bus is part of the area of the contact structure, which collects a large number of carriers from the contact terminals and brings them to a connection such as a cell connector.

Preferably, the busbar does not cover the contact areas, h. the bus is connected to the semiconductor structure exclusively through the contact leads and the contact surfaces it covers. The advantage of this connection is that there is no reduction of conductivity in the bus due to the storage of semiconductor material.

Contact fingers and busbars can have the structure of known contact grids, especially the structure of grids in the form of a comb or a double comb. Preferably, the contact leads extend parallel and the busbar extends perpendicular to the contact leads. Accordingly, the busbar and contact lead (or the busbar and the main branch of the constant lead in the preferred embodiment as described above) can be used for known geometries and manufacturing methods. In a further embodiment, the contact structure comprises a plurality of contact leads, where the leads do not have metallic electrically conductive connections with each other. An electrically conductive connection of the contact leads exists through a semiconductor layer or through an external circuit, or for example, after the completion of the production of the solar module and the connection of the solar cell with several neighboring solar cells via additional components.

This results in cheap and efficient manufacturing because the busbars are not made as a component of the solar cell that connects the contact leads.

At least a partial amount of the contact surfaces, which preferably of all the contact surfaces, has an elongated stretch, and the contact surfaces are placed perpendicular to the longitudinal circumference of the contact finger. In this advantageous embodiment, the contact outlet can be viewed as an integral part of the main branch, on which there are laterally located contact surfaces, which preferably extend roughly perpendicular to the main branch of the contact outlet. In this case too, the contact lead covers at least the contact surfaces, and what is desirable, the area of the insulating layer surrounding the contact surface. With regard to the conduction lines, the contact surfaces, based on their long extensions and covered lead areas, can be considered as "MikroFinger" (citation from the text, micro-lead) whose carriers supply the main branch.

This results in the already mentioned advantage that very little or no increase in resistance occurs in the main branch of the contact lead due to the storage of semiconductor material. For this reason, the extension of the contact surface provides the possibility of good coverage of the semiconductor layer through the contact surfaces, which additionally reduces losses due to conduction resistance in the semiconductor layer, the so-called resistance losses in series connections within the semiconductor layer due to shorter flow paths of the majority charge carrier in the semiconductor layer.

An additional reduction of ohmic power losses in the contact structure is achieved in a further embodiment, in which the contact lead on the contact surfaces with extensions has a cross-sectional area along the extensions themselves in the direction of the contact lead, of increased width, which is desirable. The mentioned "micro-excerpts" are thus made in the self-known form of "condensed extract". This ignores the fact that the carriers of all contact surfaces enter the metallization covered by the contact surfaces, which increases the total current in the contact structure along the contact surface in the direction of the current flow of the main current. The continuous or gradual quasi-continuous growth of cross-sectional areas along this main current direction, present in the direction of the main branch of the contact lead, leads to optimization in that, on the one hand, the current density does not increase very little or at all, while on the other hand, the shading of the upper surface of the solar cell maintains as little as possible with regard to the contact structure.

As stated above, production processes, which in such contact structures have local doping in the area of the contact surfaces with metal that is a complete or partial component of the metallization structure, lead to the storage of semiconductor material in the metallization structure in the area of the contact surfaces. The contact leads can thus contain the semiconducting material of the semiconducting layer in the contact area.

The described contact structure is intended for placement on the back side of the salt cell. As a result, the known and desirable structure of local contact (via local grooves in the insulating layer to create contact surfaces) and local high doping in the semiconductor layer can be maintained in the region of the contact surfaces, and at the same time a biphase solar cell can be formed:

Due to the formation of a contact structure with a larger number of contact fingers, it is not necessary to ensure the metallization of the back side of the full surface.

On the areas of the backside that are not covered by the contact structure, photons can penetrate the semiconducting layer and contribute to carrier recovery. Preferably, the photovoltaic solar cell according to the invention is therefore designed as a bifacial solar cell, so that photons generated on the solar cell from the front side as well as those from the back side can contribute to the generation of electricity.

The contact structure is partially used to create a contact of one p-doped region. A typical metal for making a contact structure is, for example, aluminum. With the help of these metals, as previously described, local high doping can take place in the p-doped region of the solar cell, but not in the oppositely doped, n-doped regions.

Most currently manufactured solar cells have an n-doped emitter and a corresponding p-doped base. Therefore, a contact structure is used to make the contact between the base and the solar cell.

Of interest are those solar cells with improved material properties that have an n-doped base. In the case of such solar cells, contact structures are used to create a p-doped emitter contact, such as when using a medium p-doped aluminum emitter.

A photovoltaic cell made as a PERC solar cell is particularly advantageous. The basic structure of such a solar cell is Blakers, et al. (1989): 22.8% efficient Silicon solar cell. In: Appl. Phys. Lett. 55 (13), S. 1363. DOI: 10.1063/1.101596, beschreibung.

The local increase of the cross-sectional area is designed in such a way that the area of the cross-sections in the spaces of the contact areas is increased by at least a factor of 1.2, preferably it is increased by at least a factor of 1.5, and especially by at least a factor of 2, for difference from the cross-sectional areas of the contact lead areas, which are separated from the contact areas in the direction of the main current flow. Local elevations of the cross-sectional areas are primarily designed in such a way that in the areas of the contact areas the cross-sectional areas are increased by a maximum of a factor of 10, preferably by a maximum of a factor of 7, and preferably by a maximum of a factor of 5, in contrast to the cross-sectional areas of the area contact leads, which are separated from the contact areas in the direction of the main current flow.

In the direction of the flow of the main current of the contact lead, i.e. the main branches of the contact lead, local increases in cross-sectional areas extend, as is preferably a maximum of twice the length of that of the contact surfaces in the direction of the flow of the main current, preferably a maximum of the length of the contact surface itself, and especially preferably at least half the length of the contact surface.

Typically, the contact lead or at least one main branch of the contact lead has an extension. In this case, the direction of flow of the main current extends along this extended extension. extended measures.

As mentioned above, the present invention avoids the negative effects caused by the semiconductor material embedded in the contact leads. Typically, contact leads in the region of the contact surfaces have local deposits of semiconductor material in a concentration greater than 20% (by weight), especially greater than 12.6%, and such concentrations in the contact lead are obtained especially during the epitaxial growth of the doped region on the semiconductor of one liquid phase created by mixing metals and semiconductors, especially preferably metal-contacting structures.

The contact surfaces, over which and/or along which the contact leads extend, are separated from each other. It is desirable that the distance between the contact areas is at least 100 μιη, especially preferably that the distance is at least 200 μιη in order to reduce the negative impact due to recombination effects on the contact areas. The optimality between series resistance and recombination effects is achieved by realization in which the typical distances of the contact areas are in the range of 100 μιη to 4 mm, and especially by realization with a range of 200 Mm to 3 mm. Disturbance in the quality of electrical conductivity caused by the storage of semi-conductive material due to the process of contact formation of the contact structures themselves with the p-doped semi-conductive material, and especially with the p-doped base. Therefore, a contact structure was designed to create a contact (joint) between the p-doped region of the solar cell and the base. Special attention is paid to the fact that the contact structure is located on the back side of the solar cell facing the sun.

This invention is particularly suitable for known embodiments of contact structures with multiple contact leads that are found on the invention itself. Accordingly, all the contact leads of the contact structures extend over a greater number of mutually spaced contact areas and/or along a greater number of mutually spaced contact areas, whereby the contact leads on the contact areas have a local increase in the cross-sectional area, and/or the contact leads on the contact areas have electrically parallel conductive metal structures that do not cover the contact areas.

Further desirable features and performance are explained below with performance examples and images. It shows:

Figure 1 is the first example of the performance of the inventive photovoltaic cell, which is performed as a PERC solar cell, in a perspective view

Fig. 2 contact structure of the solar cell shown in Fig. 1;

Fig. 3 is an alternative contact structure shown by another exemplary embodiment comprising micro-leads.

Figure 4 further alternative embodiment of the contact structure based on the third example of the embodiment which does not have a busbar.

Figure 5 is a cross-section of another further embodiment example, where the cross-section view passes through one contact lead

Figure 6 is the sixth example of the design, in which the contact leads are located on the contact area of the electrically parallel connected conductive structure, while not covering the contact areas.

The various images show schematic designs that are not authoritative. Identical reference symbols in Figures 1 to 5 denote the same or equivalent elements.

Figure 1 shows the first example of the performance of a photovoltaic solar cell according to the invention, which has a PERC structure:

The solar cell has a semiconductor layer 1, which is made of p-doped silicon. In the illustration according to Figure 1, the back side of the solar cell is at the top and therefore the front side of the solar cell is shown at the bottom.

An n-doped emitter 2 is formed on the front side of the solar cell. For passivation and improvement of optical properties (reduction of reflection), an anti-reflection layer 3 is additionally placed on the front side, which is constructed as a dielectric layer and is therefore additionally electrically insulated. On the anti-reflective layer 3 (not shown), a metal frontal contact grid is placed, which passes through the anti-reflective layer 3, in order to form an electrically conductive connection with the emitter 2 in a known manner.

An electrically insulating insulating layer 4 is placed on the back side of the solar cell, which is constructed as a silicon nitride layer.

A contact structure 5 is placed on the insulating layer 4, which thus represents a metal structure for creating a contact on the back side of the solar cell, which is shown in Figure 1. The insulating layer 3 has a larger number of depressions, or grooves for contact (for example, a depression for forming a contact 6). This plurality of contact grooves is produced, for example, by local laser ablation of the insulating layer.

On these contact grooves 6, the contact structure 5 penetrates the insulating layer 4 and, together with the semiconductor material 1, builds an electrically conductive contact for contacting the p-doped base of the photovoltaic cell.

During production, the semiconductor material of the semiconductor layer 1 in the area of the contact grooves is dropped into the molten metal in a process called "contact melting". During the contact melting cooling process, the released semiconductor material on the semiconductor layer 1 is recrystallized, and in this way it is doped with metal, primarily aluminum, so that on the one hand, the metal of the contacting structure 5 is present as a dopant in the semiconductor layer 1, thereby creating local doped areas 7. On the other hand, semiconductor material is also incorporated into the contact structure in the area of the contact slots.

The contact structure is primarily made of aluminum, so that the doped regions 7 represent aluminum-doped regions, and therefore, p-doped regions. The doping of these areas is greater than the basic doping of the base of the semiconductor layer 1, so that the doped areas 7 represent local highly p-doped areas (denoted as p++ areas).

The design of the contact structure 5 is explained in more detail below with reference to Figure 2:

Figures 2 to 4 and 6 show partial sections of various contact structures viewed from above. Figure 2 shows the contact structure 5 of the solar cell given in Figure 1.

Additionally, Figures 2 to 4 and Figure 6 show enlarged sections of the local enlargement of the cross-sectional areas of the contact structure.

The contact structure 5 shown in Fig. 2 has a busbar 8 and a larger number of contact leads, whereby in this case three contact leads 9 are shown. The contact leads extend over several mutually spaced contact areas 10, with a distance of 500 μιη:

As can be seen in the enlarged section, the insulating layer 4 of the contact lead 9 penetrates into the contact groove and thereby creates electrical contact with the semiconductor layer 1 in this area. Thereby there is a contact surface 11 in the contact area 10 on which contact surface 11 the contact structure 5 and the semiconductor layer 1 directly touch and form an electrical contact.

It is obvious that the contact fingers 9 have a local increase in cross-sectional area at the contact areas 10:

As in the floor plan shown in Fig. 2, the contact leads 9 have a local expansion parallel to the surface of the insulating layer 4 in the contact areas 10. This is a local increase in the cross-sectional area of the contact lead 9 in the area of the contact surface 11 opposite the cross-sectional area of the contact lead in front of and behind the contact surface 11. The cross-sectional area present in the area of the contact surfaces (area "A1") is increased by a factor of approximately 1.7, compared to the cross-sectional area in front of and behind the contact surface (positions "A2" and "A3"). The first is the increase in cross-sectional areas with a factor in the range of 1, 10 to 3, and especially in the range of 1.2 to 2.

In the area outside the contact surfaces (outside the cross-sectional areas), the leads have a width of about 300 μm, where it is important that this width is approximately within the desired range (100 μm to 500 μm). In the area of contact surfaces (in the area of increased cross-sectional area), the leads have a width of approximately 500 μm. First of all, the increase in the cross-sectional area is limited approximately to the area of the contact surface. Likewise, the increase in cross-sectional area may extend slightly in front of and behind the contact surface, but preferably by less than half the length of the contact surface.

The term "length" refers to the extension of the contact surface in the direction of the main current flow. Since the extension is made larger than the width of the contact surface 11, the contact lead 9 on the contact area 10 is made so that it overlaps the insulating layer 4. The contact lead overlaps the insulating layer 4 in particular in the area that includes the contact surface 11, i.e. in the view from above it is the contact surface 11 covered by the area covered by the insulating layer 4 of the contact outlet 9 is closed. The contact lead 9 covers the contact area 10 and thus also the contact surface 11.

When using a solar cell, the current flow in the contact structure takes place in the direction of the bus 8, which is electrically conductively connected to the neighboring solar cell during the production of the solar module via the cell connector.

Current flows from left to right in contact lead 9, shown in Figure 2. In one contact area, the specific conductivity resistance of contact lead 9 is increased because the semiconducting material of the semiconducting layer is stored in that area in the contact leads.

On the basis of the increase of the cross-sectional areas, primarily on the basis of the expansion of the contact lead in the contact area, this increase in the specific conduction resistance is compensated. Because of this, the marginal areas of the contact lead 9, which include and close the contact area 10, have very little or no concentration of semiconducting material, and also have very little or no increase in conduction resistance.

As a result, the efficiency loss caused by the local increase in the conduction resistance of the contact structure 5 caused by the storage of the semiconductor material is avoided or at least significantly reduced.

Figure 3 shows an alternative embodiment of the contact structure 5' with a corresponding alternative embodiment and arrangement of contact recesses and contact surfaces 11' presented by another embodiment example. The contact structure 5' shown in Fig. 3 can replace the contact structure 5 in Fig. 1 corresponding to the assigned contact recesses 6, i.e. the contact structure 5' is partially usable as the contact structure of the rear side of the bifacially constructed PERC solar cell.

The contact lead 9' of the contact structure 5' shown in Figure 3 has one main branch 12' on it, from which micro leads 13 extend, as can be seen in the enlarged cross-sectional view. The micro-leads 13 extend perpendicular to the main direction of extension of the main branch 12 of the contact lead 9.

The contact surfaces 11' have elongated extensions thereon and are placed perpendicular to the gap and are placed perpendicular to the direction of extension of the main branch 12 of the contact lead 9'. The microleads 13 cover the contact surfaces 11' completely and therefore overlap the insulating layer enveloping the contact surfaces 11'.

With the contact structure 5' shown in Figure 3, during the use of the solar cell in the contact outlet 9', the current essentially flows in the direction of the bus 5', i.e. in the main branch 12 of the contact outlet 9' from left to right shown in the embodiment in Figure 3.

In the micro-outlets, current flows perpendicular to the main branch 12 and in the direction of the main branch 12.

The contact lead 9' creates local increases in cross-sectional areas on the contact surfaces 11', which are formed by micro leads 13 and local extensions (in the direction of the main branch 12). The cross-sectional area is increased through one pair of microextracts by a factor of 3. In this version, the cross-sectional area is increased by a factor ranging from 2 to 5.

Accordingly, the main branch 12 does not cover the contact surfaces 11', so there is very little or no concentration of semiconductor material in the main branch 12, and in this way the current flow of the main branch 12' in the direction of the busbar 5' is greatly, little or not hindered at all. by increasing the conduction resistance caused by the deposition of semiconducting material.

Figure 4 shows an example of a design for a contact structure 5'' that can be used as a contact of the rear side of a solar cell, similar to the design in Figure 1. The dimension of the local cross-section can be made analogously to the example of the design according to Figure 3.

The contact structure 5'' is special in that the solar cell does not have electric lines to connect the individual contact leads 9'':

The contact structure 5'' contains a large number of contact leads'', which are provided with one main lead branch along a large number of contact surfaces 11''. The contact surfaces 11'' are, as seen in Figure 3, in pairs, where the contact surfaces associated with one pair are made (and correspondingly associated contact depressions in the insulating layer) on the opposite side of the main branch of the corresponding contact outlet 9'.

The enlarged section shows the contact lead 9' with one pair of contact surfaces 11'', which are oppositely attached to the main branch 12'' of the contact lead 9''. Likewise, within the framework of the invention, it is necessary to create a contact surface from several contact surfaces, which are extended under the main branch of the contact lead.

The contact structure 5'' also contains micro leads 13':

As can be seen in the enlarged view, laterally on the main branch 12'' of the contact lead 9'', microleads 13'' are attached, which completely cover the contact surfaces 11''. Accordingly, the micro leads 13' are made as "narrowed leads", where the width of the micro leads expands in the direction of the main branch 12''. Since during the use of the solar cell, current is continuously fed through the contact surfaces 11", the current flow of the micro outlet 13" in the direction of the main branch 12" also increases.

In order to prevent, or at least reduce, conduction losses due to an increase in current flow, the micro-lead'' 13 expands in the direction of the main branch 12''.

When connecting the solar cells to the solar module, the contact leads 9'' are electrically conductively connected via external components to each other and/or to the contact leads 9'' of neighboring solar cells. Accordingly (and based on the lack of one busbar), the contact leads 9'' shown in Figure 4 are partially called busbars in further literature.

Figure 5 shows a further implementation example, in which a local increase in the cross-sectional area is achieved by means of local thickening:

Basically, the implementation example given in Figure 5 can be designed based on the structure of the solar cell given in Figure 1 and on the basis of the contact structure given in the floor plan in Figure 2. The version shown in Figure 5 shows a section perpendicular to the isolation layer 4 and along and approximately centrally through one contact outlet 9. The local increase in the cross-sectional area of the contact lead 9''' is not only realized on the basis of the local thickening shown in Figure 2, but also additionally through the local thickening shown in Figure 5. The thickness increases locally by approximately a factor of 2. The local increase takes place with a factor in the area of 1 ,2 to 4.

Figure 6 shows the fifth embodiment, in which the contact leads are formed from an electrically parallel connected metallic conductive structure:

The illustrated contact structure from the partial view in Fig. 6 can be used to make the contact of the PERC solar cell shown in Fig. 1. Here, too, multiple contact leads 9'' emerge from one busbar 8'''. Unlike the previous embodiments, these contact leads 9'' have so-called "side leads": as can be seen in the enlarged section shown on the right, the main branch 12'' of the contact lead which does not cover any contact areas is centrally placed. Laterally next to the main branch 12'', secondary leads 14a and 14b are placed parallel to the main branch, which are separated from the main branch 12'' in the area of the contact area 10, due to which there is no electrically conductive connection in these areas. An electrically conductive connection exists only between the side terminals 14a and 14b of the main branch 12''' due to the metal bar.

The advantages are evident from this, that when making such a contact structure, the semiconducting material on the contact areas 10 really diffuses into the metal, not reaching the main branch due to the wide distance from the main branch 12''. The current flow along the main branch 12'' up to busbar 8''' is not, or is very little hindered by the storage of semi-conductive material.

The width of the side branch covers about 75% of the width of the main branch. The main branch spans a width of approximately 200 μm.

Claims (15)

1. Photovoltaic solar cell, which contains at least one semiconductor layer (1), at least one electrically insulating insulating layer (4) and at least one metal contact structure (5, 5′, 5′′), where the insulating layer is located between the semiconductor layer and the contact structure and the insulating layer (4) has a number of spaced contact recesses (6), where the contact structure (5, 5′, 5′′) is in electrical contact with the semiconductor layer (1) in the contact area (10) and where the semiconductor layer (1) is formed at least in the contact areas, and in the semiconductor layer there is a doping area obtained by doping the semiconductor layer with a metal from which the metal contact structure (5, 5′, 5′′) is at least partially made, indicated by what the contact structure (5, 5′, 5′′) has several contact fingers, wherein each of said contact fingers (9, 9′, 9′′, 9′′′) extends across multiple spaced contact areas and/or along multiple spaced contact areas, where contact fingers (9, 9′, 9′′, 9′′′) have a locally increased cross-sectional area in the contact areas and/or the contact fingers in the contact areas are electrically connected in parallel metallic conductive structures, which do not cover the contact areas. 2. Solar cell according to claim 1, indicated by what the contact fingers (9, 9′, 9′′, 9′′′) in the contact areas have an extension parallel to the surface of the insulating layer (4) and perpendicular to the longitudinal extension of the contact finger. 3. Solar cell in accordance with patent claim 2, indicated by what the contact fingers (9, 9′, 9′′, 9′′′) are formed overlapping in the contact areas of the insulating layer (4), especially since the contact fingers (9, 9′, 9′′, 9′′′) cover the insulating layer (4) in the area surrounding the contact areas. 4. A solar cell in accordance with any of the previous patent claims, indicated by what the contact recesses are located in pairs, where the pair of contact recesses are located on opposite sides of the main branch of the contact finger. 5. A solar cell in accordance with any of the previous patent claims, indicated by what the contact fingers (9, 9′, 9′′, 9′′′) have a local increase in thickness in the contact areas. 6. A solar cell in accordance with any of the previous patent claims, indicated by what the contact structure (5, 5′, 5′′) has at least one contact finger more, where the contact fingers (9, 9′, 9′′, 9′′′) are preferably parallel. 7. A solar cell according to any of the previous patent claims, indicated by what the contact structure (5, 5′, 5′′) contains several contact fingers and at least one bus (8, 8′, 8′′), where the contact fingers (9, 9′, 9′′, 9′′′) connected in a materially coupled and electrically conductive manner to the busbar, preferably where the contact fingers (9, 9′, 9′′, 9′′′) extend parallel, and the busbar (8, 8′, 8′′) extends vertically in relation to contact fingers. 8. A solar cell according to any of the previous patent claims, indicated by what the contact structure contains several contact fingers, and the contact fingers (9′′) are not electrically electrically conductively connected to each other. 9. A solar cell according to any of the previous patent claims, indicated by what at least a subset of the contact surfaces, preferably all the contact surfaces, extend longitudinally and are located perpendicular to the longitudinal extension of the contact finger, especially what the contact fingers (9, 9′, 9′′, 9′′′) on the contact surfaces extending longitudinally in the longitudinal direction in the direction of the contact finger (9, 9′, 9′′, 9′′′) increase the cross-sectional area , especially preferably increased width. 10. A solar cell in accordance with any of the previous patent claims, indicated by what electrically parallel connected metal conductive structures are formed as local, parallel auxiliary fingers, spaced apart in the area of the contact areas of the main branch of the contact finger, especially the auxiliary fingers cover the contact areas, while the main branch of the contact areas is not covered. 11. A solar cell in accordance with any of the previous patent claims, indicated by what the contact fingers (9, 9′, 9′′, 9′′′) in the contact area (10) contain the semiconductor material of the semiconductor layer (1). 12. A solar cell in accordance with any of the previous patent claims, indicated by what the solar cell is constructed as a double-sided solar cell, where at least the rear side of the solar cell is made as a surface that is at least partially transparent to electromagnetic radiation, especially which is a contact structure (5, 5′, 5′′) formed as a contact structure on the back side (5, 5′, 5′′) and located on the back side of the solar cell. 13. A solar cell according to any of the previous patent claims, indicated by what the contact structure (5, 5′, 5′′) was used to make contact with the p-doped region of the semiconductor layer (1). 14. A solar cell according to any of the previous patent claims, indicated by what the contact structure (5, 5′, 5′′) is formed as the contact structure on the back side (5, 5′, 5′′) and is located on the back side of the solar cell and that on the back side of the solar cell, local areas of high doping are formed in the contact areas in the semiconductor layer (1). 15. A solar cell according to any of the preceding claims, indicated by what the contact fingers have on all contact areas a local increase in cross-section and/or parallel conductive structures, and/or that the solar cell is built as a PERC solar cell.