DE102007059490B4 - Rear contact solar cell with integrated bypass diode function and manufacturing method thereof - Google Patents

Abstract

A back contact solar cell comprising: a semiconductor substrate (1), wherein the semiconductor substrate (1) has a basic semiconductor type with a first doping concentration; Emitter regions (5) along a rear surface (3) of the semiconductor substrate (1), the emitter regions (5) having an emitter semiconductor type opposite to the base semiconductor type; highly doped base regions (7) along the rear surface (3) of the semiconductor substrate (1), the highly doped base regions (7) being of the basic semiconductor type with a second doping concentration, the second doping concentration being greater than the first doping concentration; Emitter contacts (11) for making electrical contact with the emitter areas (5); Base contacts (13) for making electrical contact with the base regions (7), an interface (21) at which the highly doped base regions (7) adjoin emitter regions (5) being greater than 5% of the rear surface (3) of the semiconductor substrate (1), wherein emitter regions (5) and highly doped base regions (7) in overlap regions (19) at least partially overlap in planes parallel to the rear surface (3) of the semiconductor substrate (1) and wherein an interface (21) on the highly doped base regions (7) within the overlap regions ...

Description

FIELD OF THE INVENTION

The present invention relates to a back contact solar cell with integrated bypass diode function and a manufacturing method for such a back contact solar cell.

BACKGROUND OF THE INVENTION

A common form of using solar cells is their interconnection to modules. In these modules, in each case a certain number of solar cells are connected in series to so-called "strings". The series connection is desirable since in this way the voltages of the individual solar cells of the string add up and the current intensity flowing through the entire series circuit corresponds to the current intensity generated by a single solar cell. Since resistance losses are a function of the current, the series connection of the solar cells to strings minimizes the loss of electrical energy in the resistances of the current-carrying lines within a module.

However, if one of the solar cells is shaded or defective in such a string, not only in this shadowed cell, no contribution to the generation of electrical energy is made, but this cell blocks the flow of current through the entire string. That is, the light-generated current of the unshadowed cells, as far as the summed voltage of the unshaded cells permits, is driven by the shadowed cell, which in this case acts as a pn-diode in the reverse direction. Here, a possibly significant electrical power is implemented in the shadowed cell, which can lead to strong local heating and ultimately damage the module.

For this reason, so-called bypass diodes are incorporated in module interconnections, which can bridge an entire string, portions of a string or even a single solar cell of a string such that at Teilabschattungen the electrical energy generated in the remaining part of the string through the bypass diode can flow instead of through the shaded or broken solar cell. For this purpose, a normal pn diode is conventionally switched in the forward direction parallel to the string region to be bridged.

This type of interconnection with bypass diodes is a method in which damage to solar cells or the entire solar module can be avoided and which ensures that at least some of the illuminated solar cells can still contribute to the provision of electrical energy.

It should be noted, however, that in the case where a bypass diode is assigned to a whole string or to a subarea of a string consisting of several solar cells, the power of the other solar cells in the string or partial string of the shading of only a single solar cell will also be shaded Power generation in the module will no longer be available. The solar cells in the module are therefore not optimally used for shading individual cells for the provision of electrical energy. The alternative case, to provide each individual solar cell with its associated bypass diode, means in conventional solar cells a considerable additional Verschaltungs- and cost.

In the US 5 641 362 A For example, a structure and method of manufacturing a self-aligned aluminum alloy back contact silicon solar cell is described. In this case, p ⁺ regions and n ⁺ regions are arranged directly adjacent to one another at a rear side of the solar cell, wherein the resulting p ⁺ n ⁺ transitions are to act as zener diodes, which can protect the solar cell against reverse voltages.

In the DE 195 25 720 C2 Another method of producing a back contact solar cell is described.

SUMMARY OF THE INVENTION

There may be a need for a solar cell configured such that, when connected in series with other solar cells into a string, shading of the solar cell causes only a slight loss of power relative to the electrical power provided by the string , Furthermore, there may be a need for a solar cell with the said property, in which no additional Verschaltungsaufwand is necessary. There may also be a need for a manufacturing process for such a solar cell.

This need can be met by the subject-matter of the independent claims. Advantageous embodiments of the present invention are described in the dependent claims.

According to a first aspect of the present invention, there is proposed a back contact solar cell comprising: a semiconductor substrate having a base semiconductor type having a first doping concentration; Emitter regions along a backside surface of the semiconductor substrate, the emitter regions having an emitter semiconductor type opposite to the base semiconductor type; highly doped base regions along the backside surface of the semiconductor substrate, the base regions having the basic semiconductor type have a second doping concentration, wherein the second doping concentration is greater than the first doping concentration; Emitter contacts for electrically contacting the emitter areas; and base contacts for electrical contacting of the base areas. In this case, an interface on which highly doped base regions adjoin emitter regions should be larger than 5% of the backside surface of the semiconductor substrate.

In this case, emitter regions and base regions overlap in overlapping regions at least partially in planes parallel to the backside surface of the semiconductor substrate. In other words, there may be overlapping regions in which emitter regions and base regions not only adjoin one another laterally, but the emitter regions and the base regions extend substantially parallel to one another and parallel to the back surface of the semiconductor substrate and directly adjoin one another.

Both the emitter regions and the base regions are usually formed as thin layers with a thickness of at most a few microns due to their production, for example by diffusion of dopants. The fact that the emitter areas and the base areas are not only arranged next to one another and only contact one another at their lateral edges via a height of a few μm corresponding to the layer thickness but are arranged flat adjacent to one another and to the rear side surface adjacent to one another, can be used to form a bypass Diode property important interface between the emitter regions and the heavily doped base regions can be increased in a simple manner.

According to the present invention, this interface between parallel emitter regions and base regions arranged parallel to one another is greater than 5%, preferably greater than 10%, and more preferably greater than 20%, of the backside surface of the semiconductor substrate.

This first aspect of the present invention may be considered to be based on the following idea: in the described back contact solar cell, emitter regions contacted by emitter contacts border on highly doped base regions contacted by base contacts, these base regions having a higher doping concentration than the base doping concentration of the semiconductor substrate forming the solar cell. Thus, at least the highly doped base regions, but preferably also the emitter regions, have a relatively high doping concentration. At the interfaces, that is, where highly doped base regions are adjacent to emitter regions, a pn diode is thus formed in which at least one, but preferably both, doping regions are highly doped, that is, a p ⁺ n junction is formed. a pn ⁺ -junction or a p ⁺ n ⁺ -junction. The resulting diode can be regarded as connected in parallel and in the same polarity direction to a the actual solar cell forming planar pn-junction. Such parallel-connected diodes, in which at least one doping region, but preferably both doping regions, are heavily doped, can permit relatively high currents even at relatively low voltages in the reverse direction. In particular embodiments described in more detail below, such diodes may exhibit a sudden increase in conductivity even above certain reverse bias voltages.

The strength of the reverse-possible currents depends inter alia linearly on the available interface between the base regions and the emitter regions. If the interface is large enough, for example, greater than 5% of the backside surface of the semiconductor substrate, the reverse current allowed in this manner may be of the order of magnitude approximately that of the solar cells at applied voltages, as typically occur in a series cell solar cell string provided current corresponds. The p ⁺ n ⁺ junctions generated by the heavily doped emitter and / or base regions and connected in parallel with the actual pn junction of the solar cell can thus act as an integrated bypass diode for the back contact solar cell.

Further features, details and possible advantages of embodiments of the back contact solar cell according to the invention are explained below.

In the present case, a back contact solar cell can be understood as meaning a solar cell in which both the emitter contacts and the base contacts are arranged on a rear side, that is to say a side of the solar cell remote from the incident light in use. For this purpose, at least parts of the emitter forming the current-collecting pn-junction are formed on the rear-side surface of the solar cell, where they are contacted by the emitter contacts. In addition to the general advantages of back contact solar cells, shading losses are avoided due to the absence of emitter contacts on the solar cell front surface, and because of the fact that both the emitter contacts and the base contacts are located on the cell back side, the cells are easily interconnected can be, has the presented here back-contact solar cell due to the flat design of adjacent emitter and highly doped base regions the Possibility of integrating a bypass diode function in the solar cell.

The semiconductor substrate may be, for example, a silicon wafer. For example, it may be doped with boron in a first relatively low doping concentration of about 0.1-5 x 10 ¹⁶ cm ^-3 such that the base semiconductor is a p-type semiconductor. Alternatively, the semiconductor substrate may be doped with phosphorus so that the basic semiconductor type is an n-type semiconductor.

Alternatively, the semiconductor substrate may also be made of any other semiconductor. It can also be provided as a semiconductor thin film.

The emitter regions may extend along the back surface of the semiconductor substrate directly at the surface, but also parts of the emitter regions, in particular in overlapping regions with the base regions, may not directly adjoin the surface, but may extend slightly deeper inside the semiconductor substrate. These emitter regions which are "buried" in the interior can be in electrical contact with the regions of the emitter regions adjoining the backside surface, so that they can also be contacted electrically therefrom by the emitter contacts.

The emitter regions can be produced by diffusing dopants into the semiconductor substrate. For example, in a p-type semiconductor substrate, by locally diffusing phosphorus, an n-type emitter region can be formed. Alternatively, however, the emitter regions can also be produced by other methods, such as by ion implantation or alloying, so that a so-called homo-junction, that is a pn junction with oppositely doped regions of a same semiconductor base material, for example silicon, results. Alternatively, the emitter regions can also be epitaxially deposited, for example vapor-deposited or sputtered on, so that homo- or so-called hetero junctions result, that is to say that in the case of hetero junctions pn junctions are present between a first semiconductor material of the basic semiconductor type and a second semiconductor material of an emitter semiconductor type. One possible example is emitter regions made of PECVD-deposited amorphous silicon layers (a-Si) on a crystalline silicon (c-Si) semiconductor substrate.

The base regions can also be produced by means of one of the abovementioned production methods, although production by local in-diffusion of a dopant to form the base regions may be preferred.

The emitter regions and the base regions, when viewed in a plan view of the back surface of the semiconductor substrate, may each have a comb-like structure in which each of the linear finger-like emitter regions is adjacent to adjacent linear finger-like base regions. Such a nested structure is also referred to as "interdigitated".

Both the emitter contacts and the base contacts can each be designed in the form of a local metallization, for example in the form of finger-like grids. For this purpose, metals such as silver or aluminum can be locally deposited, for example, by a mask or using photolithography or screen printing or other methods on the base or emitter regions, for example by vapor deposition or sputtering or by using screen printing or dispensing. In general, all methods can be used which make it possible to form contacts locally, for example finger or grid-shaped, on a substrate back, including the possibility of applying full-area metal layers, which are subsequently patterned by local removal. In order to avoid short circuits between the emitter contacts and the base contacts, an electrically insulating gap may be provided between the two.

An essential feature of the back contact solar cell according to the invention is the large boundary surface at which highly doped base regions adjoin emitter regions on the rear side of the semiconductor substrate. The larger this interface is, the more pronounced the bypass diode function will be, ie the higher currents can flow even at low voltages of a few volts in the reverse direction through the p ⁺ n ⁺ junction. The interface may be greater than 5%, preferably greater than 10%, more preferably greater than 20%, and even more preferably greater than 30% of the back surface of the semiconductor substrate. In general, the interface required for a sufficient bypass diode function depends strongly on the properties of the adjacent emitter and heavily doped base regions, in particular their doping concentration and their doping profile. Ideally, these properties should be chosen so that the adjacent emitter and heavily doped base regions, although the efficiency of the solar cell under normal lighting operating conditions, eg. B. at a voltage applied across the cell voltage of about 0.45-0.65 V, barely negatively affect that but in shading of the cell due to the then applied to the cell, of the adjacent cells in the string generated voltage of, for example, more than 0.5 V or a few volts, a sufficiently high current in the reverse direction through the cell can flow, for example, approximately equal to the short-circuit current of a corresponding solar cell (eg 30-40 mA / cm ² × area of the solar cell).

The large interface may be created in a variety of ways, as described below for specific embodiments. Both the emitter regions and the base regions may in this case extend very close to the rear side surface of the semiconductor substrate, in particular in view of the thickness of the emitter or base regions of z. B. a few microns usually large thickness of the semiconductor substrate, which may amount to about 200 microns, for example, in a silicon wafer. However, the emitter region, in particular in overlapping regions with the base regions, can extend deeper into the semiconductor substrate than the base regions. For example, the emitter region may extend to a depth of more than 1 .mu.m, preferably more than 2 .mu.m below the back surface, whereas the base regions, for example, only less than 1 .mu.m deep, for example about 0.5 .mu.m deep, extend into the semiconductor substrate.

In this case, the emitter regions do not extend along the entire rear side surface of the semiconductor substrate in the finished solar cell, but there remain small local regions which do not have the emitter semiconductor type and which later for the electrical connection between the highly doped base regions formed on the rear surface and the base regions in the interior serve the semiconductor substrate. These connection regions in which either no corresponding emitter doping was effected during the generation of the emitter regions or in which a previously generated emitter doping was subsequently removed again, for example by etching away or path lasers, or in which in the subsequent formation of the back base regions Emitter layer has been locally overcompensated so that there is a passage from the back base regions to the base-doped main volume of the semiconductor substrate may be linear, such as parallel or perpendicular to the base contacts to be formed later, or punctiform.

According to one embodiment of the present invention, the base regions and the emitter regions are formed in such a way that a pn junction with the properties of a zener diode results at the interface on which highly doped base regions adjoin emitter regions.

Diodes generally have the property of transmitting current when a forward voltage is applied, the current magnitude being exponentially dependent on the applied voltage, whereas at a reverse biased voltage, at least up to a threshold voltage referred to as the breakdown voltage, quasi do not allow current to flow. The breakdown voltage and the breakdown mechanism depend on the band gap of the semiconductor material used and on the doping of the diode-forming semiconductor layers in the vicinity of the pn junction. With double-sided very high doping, for example of the order of 10 ¹⁹ cm ^-3 or higher, it comes with pn diodes of silicon when applying a blocking voltage of, for example, only a few volts to such a high field strength in the space charge zone that electrons from the valence band of Semiconductor can "tunnel" into the conduction band and this may result in a breakthrough current increase. Named after his discoverer as a "Zener breakthrough", this effect is the physical basis for Zener diodes commonly used in electronics.

By the zener diode characteristic, it can be understood that while the diode behaves like a diode at a voltage applied in the forward direction, that is. H. the conducted current is not linear but, for example, depends exponentially on the voltage, but on the other hand the diode does not behave like a conventional diode when the voltage applied in the reverse direction and blocks the current, but conducts well even at low blocking voltage.

Diode types that behave similarly to Zener diodes are the so-called back diodes or the tunnel diodes. These diode types can thus also have a Zener diode property in the sense of this application.

According to the presently described embodiment, in particular the doping concentrations and profiles in the emitter and / or base regions can be selected such that the zener diode properties or tunneling or backbone properties which are suitable in the interface regions of the resulting p ⁺ n ⁺ -junction. Have diode properties for the realization of a bypass diode. For example, the Zener diode properties can be selected such that a breakthrough can already occur at low reverse voltages, for example the single or double open terminal voltage of the solar cell, but preferably at even lower voltages, so that in the case of shading of the solar cell already the voltage generated by one or two other intact solar cells in the same string is sufficient to cause the Zener diodes to Break and thus give them a property of a bypass diode.

According to a further embodiment of the present invention, emitter regions and base regions are intermeshed in toothed regions in a tooth-like manner. By the comb-like toothing, which may be formed parallel or transverse to the back surface of the semiconductor substrate, also important for the bypass diode characteristic interface between the emitter and base regions can be increased.

According to a further embodiment of the present invention, the boundary surface, on which base regions adjoin emitter regions, is distributed substantially homogeneously over the backside surface of the semiconductor substrate. In other words, it may be advantageous not to limit the interface provided for the bypass diode property to a small contiguous area fraction of the back contact solar cell, that is, for example, only one contiguous area occupying 5% of the total area of the back contact -Solar cell is to form as such an interface, but to provide the entire interface in the form of individual smaller partial interfaces, which are arranged uniformly over the entire surface of the back contact solar cell. Since in the case in which the corresponding back-contact solar cell is shaded in a module, these interfaces should act as bypass diodes and thereby flow considerable currents through the interfaces, a heat dissipation can be improved by a homogeneous distribution of the interfaces. In this way it can be avoided that the reverse-biased back-contact solar cell heats up excessively locally, thereby damaging itself or the module.

According to a further embodiment of the present invention, the heavily doped base regions and / or the emitter regions are produced by diffusion of dopants into the semiconductor substrate. Although the base regions and / or the emitter regions can also be produced by other methods, such as epitaxy, alloying or ion implantation, it has been found that base or emitter regions also produced by diffusion of dopants have advantageous properties due to the doping concentration profile typical for the diffusion can have.

According to another embodiment of the present invention, the base regions are phosphorus doped and the emitter regions are boron doped. In this case, for the production of the back contact solar cell according to the invention, first of all surface emitter regions can be produced by diffusion of boron, and then base regions can be introduced by diffusion of phosphorus into partial regions of the back surface of the solar cell. In this case, the so-called emitter-push effect can be exploited, in which in the indiffusion of phosphorus, the previously present in this region boron is pushed in front of him. Accordingly, phosphorus-doped base region layers are formed on the backside surface, and adjacent to it, deeper in the semiconductor substrate, the emitter-push-effect inwardly displaced boron-doped emitter region layers.

According to another aspect of the present invention, there is provided a method of manufacturing a solar cell, the method comprising the steps of: providing a semiconductor substrate having a basic semiconductor type; Forming emitter regions along a backside surface of the semiconductor substrate, the emitter regions having an emitter semiconductor type opposite to the base semiconductor type; Forming heavily doped base regions along the backside surface of the semiconductor substrate, the heavily doped base regions having the base semiconductor type and a second doping concentration, the second doping concentration being greater than the first doping concentration; Forming emitter contacts for electrically contacting the emitter regions; and forming base contacts for electrically contacting the base regions. In this case, the emitter regions and the base regions are formed such that an interface on which base regions adjoin emitter regions is greater than 5% of the backside surface of the semiconductor substrate.

The emitter regions and the heavily doped base regions can be produced by different methods, for example by local in-diffusion using, for example, masks or lithography, by ion implantation, by local alloying, by epitaxial deposition of appropriate layers, etc.

The emitter and base contacts can also be formed by various methods, for example, by locally depositing metals, for example, using masks or lithography, or by using screen printing or dispensing methods. In general, all methods can be used which make it possible to form contacts locally, for example finger or grid-shaped, on a substrate back, including the possibility of applying full-area metal layers, which are subsequently patterned by local removal.

According to another embodiment of the present invention, first the emitter regions having a first depth and a first doping concentration and then the base regions having a second depth and a second doping concentration are formed, wherein the first depth is greater than the second depth and wherein the first doping concentration is smaller as the second doping concentration. In other words, initially a relatively weakly doped, deep emitter is formed, which can then be locally overcompensated locally by a more heavily doped, shallower base region. In this case, deeper emitter regions can remain outside the overcompensated regions, so that the desired large-area interface forms between emitter regions and highly doped base regions.

According to a further embodiment of the present invention, first the emitter regions are formed with a boron doping and then the base regions are formed with a phosphorus doping, in particular by diffusion of phosphorus. In this case, it is not absolutely necessary for the base regions to be generated by overcompensating the emitter regions previously generated. Instead, in this embodiment, the emitter-push effect can be used, wherein during the indiffusion of the phosphorus, the previously present there boron doping is pushed in front of him and forms a lower emitter region. Accordingly, the doping concentration in the base regions need not necessarily be larger than in the original emitter regions, and the depth of the original emitter regions need not be deeper than the depth of the subsequent base-like diffusion from the outset.

It is noted that the embodiments, features and advantages of the invention have been described mainly with respect to the back contact solar cell according to the invention. However, a person skilled in the art will recognize from the foregoing and also from the following description that, unless stated otherwise, the embodiments and features of the invention can also be transferred analogously to the production method for a solar cell according to the invention. In particular, the features of the various embodiments can also be combined with one another in any desired manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent to those skilled in the art from the following description of exemplary embodiments, which is not, however, to be construed as limiting the invention, and with reference to the accompanying drawings.

1 shows in cross-sectional representation a back contact solar cell according to an embodiment of the present invention with parallel to the back surface of the semiconductor substrate overlapping emitter and base regions.

2 shows a sectional view along the plane AA 1 ,

3 shows in cross-sectional representation a back-contact solar cell according to a werteren embodiment of the present invention with interlocking trained emitter and base regions.

4 shows a sectional view along the plane BB 3 ,

All figures are only schematic and not to scale. In the figures, similar or like elements are numbered with like reference numerals.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the 1 Cross-section of the invention shown in the back contact solar cell has a semiconductor substrate 1 in the form of a silicon wafer. At the backside surface 3 of the semiconductor substrate 1 are both emitter areas 5 as well as heavily doped base areas 7 educated. As in 2 to recognize the emitter areas run 5 and the highly-doped base areas 7 as elongated fingers parallel to each other. At the backside surface 3 there is also a dielectric layer 9 of silicon oxide or silicon nitride, which is used to passivate the surface of the semiconductor substrate 1 and / or can serve as a rear-side reflector. Over the dielectric layer 9 are then the emitter contacts 11 and the base contacts 13 educated. Both the emitter and base contacts 11 . 13 are formed in the form of elongated, finger-shaped, perpendicular to the plane extending contacts and contact by linear openings 15 . 17 the respective underlying emitter or base regions 5 . 7 ,

The emitter areas 5 are from the back surface 3 seen formed deeper than the highly doped base areas 7 and overlap them in the lateral direction. In the overlap area 19 , in which the emitter regions extend beyond the highly doped base regions and adjoin them, a large-area interface is formed 21 between the highly doped emitter region 5 and that as well. heavily doped base area 7 , Due to the high doping of the two adjacent areas 5 . 7 For example, the resulting p ⁺ n ⁺ diode may have characteristics of a zener diode or tunnel diode or back diode and thus act as a bypass diode for the solar cell at a sufficiently high reverse biased voltage, which is preferably low as compared to the open clamp voltage. As in particular in 2 to recognize the overlapping areas run 19 and the resulting interfaces 21 each parallel to all contacts 11 . 13 such that a p ⁺ n ⁺ interface distributed substantially homogeneously over the entire area of the solar cell 21 results.

In the in the 3 and 4 The alternative embodiments shown are the emitter regions 5 and the highly-doped base areas 7 intermeshed like a comb, with elongated narrow "teeth" 23 an emitter area 5 in the adjacent base area 7 protrude to this way in a gearing area 25 the interface 21 between the doped areas 5 . 7 to enlarge.

Finally, it is pointed out that the terms "comprise", "exhibit" etc. do not exclude the presence of further elements. The term "a" does not exclude the presence of a plurality of objects. The reference signs in the claims are only for better readability and are not intended to limit the scope of the claims in any way.

Claims (10)

A back-contact solar cell, comprising: a semiconductor substrate ( 1 ), wherein the semiconductor substrate ( 1 ) has a basic semiconductor type with a first doping concentration; Emitter areas ( 5 ) along a backside surface ( 3 ) of the semiconductor substrate ( 1 ), the emitter regions ( 5 ) have an emitter semiconductor type opposite to the base semiconductor type; heavily doped base areas ( 7 ) along the back surface ( 3 ) of the semiconductor substrate ( 1 ), whereby the heavily doped basic areas ( 7 ) have the base semiconductor type with a second doping concentration, wherein the second doping concentration is greater than the first doping concentration; Emitter contacts ( 11 ) for electrically contacting the emitter regions ( 5 ); Basic contacts ( 13 ) for electrically contacting the base regions ( 7 ), where an interface ( 21 ), at the heavily doped base areas ( 7 ) at emitter areas ( 5 ) is greater than 5% of the back surface ( 3 ) of the semiconductor substrate ( 1 ), emitter regions ( 5 ) and heavily doped base areas ( 7 ) in overlapping areas ( 19 ) at least partially in planes parallel to the back surface ( 3 ) of the semiconductor substrate ( 1 ) and where an interface ( 21 ), at the heavily doped base areas ( 7 ) within the overlapping areas ( 19 ) at emitter areas ( 5 ) is greater than 5% of the back surface ( 3 ) of the semiconductor substrate ( 1 ). A back contact solar cell according to claim 1, wherein said highly doped base regions ( 7 ) and the emitter areas ( 5 ) are formed such that at the interface ( 21 ), at the heavily doped base areas ( 7 ) at emitter areas ( 5 ) adjoin one another, yielding a pn junction with characteristics of a zener diode. A back-contact solar cell according to one of claims 1 or 2, wherein a doping concentration in the emitter regions ( 5 ) and in the heavily funded base areas ( 7 ) on the back surface ( 3 ) of the semiconductor substrate ( 1 ) is higher than 1 × 10 ¹⁹ cm ^-3 . A back contact solar cell according to any one of claims 1 to 3, wherein emitter regions ( 5 ) and heavily doped base areas ( 7 ) in gearing areas ( 25 ) are meshed together like a comb. A back-contact solar cell according to any one of claims 1 to 4, wherein the interface ( 21 ), at the heavily doped base areas ( 7 ) at emitter areas ( 5 ), substantially homogeneous over the back surface (FIG. 3 ) of the semiconductor substrate ( 1 ) is distributed such that the entire interface is formed in the form of individual smaller sub-interfaces, which are arranged uniformly over the entire surface of the back-contact solar cell. A back-contact solar cell according to any one of claims 1 to 5, wherein the highly doped base regions ( 7 ) and / or the emitter regions ( 5 ) by diffusion of dopants into the semiconductor substrate ( 1 ) are generated. A back contact solar cell according to any one of claims 1 to 6, wherein the highly doped base regions ( 7 ) Are phosphorus-doped and the emitter regions ( 5 ) Are boron-doped. A method for producing a solar cell, comprising: providing a semiconductor substrate ( 1 ) having a basic semiconductor type with a first doping concentration; Forming emitter regions ( 5 ) along a backside surface ( 3 ) of the semiconductor substrate ( 1 ), the emitter regions ( 5 ) have an emitter semiconductor type opposite to the base semiconductor type; Formation of heavily doped base areas ( 7 ) along the back surface ( 3 ) of the semiconductor substrate ( 1 ), whereby the heavily doped basic areas ( 7 ) have the basic semiconductor type and a second doping concentration, the second Doping concentration is greater than the first doping concentration; Forming emitter contacts ( 11 ) for electrically contacting the emitter regions ( 5 ); Forming base contacts ( 13 ) for electrically contacting the base regions ( 7 ), the emitter regions ( 5 ) and the heavily doped base areas ( 7 ) are formed such that an interface ( 21 ), at the heavily doped base areas ( 7 ) at emitter areas ( 5 ) is greater than 5% of the back surface ( 3 ) of the semiconductor substrate ( 1 ), emitter regions ( 5 ) and heavily doped base areas ( 7 ) are formed in such a way that they overlap in overlapping areas ( 19 ) at least partially in planes parallel to the back surface ( 3 ) of the semiconductor substrate ( 1 ) and that an interface ( 21 ), at the heavily doped base areas ( 7 ) within the overlapping areas ( 19 ) at emitter areas ( 5 ) is greater than 5% of the back surface ( 3 ) of the semiconductor substrate ( 1 ). The method of claim 8, wherein first the emitter regions ( 5 ) with a first depth and a first doping concentration and then the highly doped base regions ( 7 ) having a second depth and a second doping concentration, wherein the first depth is greater than the second depth and wherein the first doping concentration is less than the second doping concentration. Method according to one of claims 8 or 9, wherein first the emitter regions ( 5 ) are formed with a boron doping and then the highly doped base regions ( 7 ) are formed with a phosphorus doping.

Images