SOLAR CELL AND SOLAR CELL MODULE WITH ONE-SIDED CONNECTIONS
The invention relates to a solar cell, in particular, to the interconnection in a solar-cell module,
according to the preamble of Claim 1.
Solar cells typically consist of a semiconductor structure that has a base and an emitter area. In
the semiconductor structure, light is typically coupled via the front side of the solar cell, so that
after absorption of the coupled light, a generation of electron-hole pairs takes place in the solar
cell. A pn-junction is formed between the base and emitter area, with the generated charge-
carrier pairs being separated at this pn-junction. Furthermore, a solar cell comprises a metallic
emitter contact and also a metallic base contact that are each connected in an electrically
conductive way to the emitter and to the base, respectively. By means of these metallic contacts,
the charge carriers separated at the pn-junction can be discharged and thus fed to an external
circuit or to an adjacent solar cell in the case of module interconnection.
Different solar-cell structures are known, wherein the present invention relates to those solar-cell
structures in which both the metallic emitter contact and also the metallic base contact are
arranged on one contacting side of the solar cell, typically the back side of the solar cell. This
stands in contrast to standard solar cells in which typically the metallic emitter contact lies on the
front side and the metallic base contact lies on the back side of the solar cell.
Solar cells in which the metallic emitter contact and base contact are arranged on one contacting
side have the advantage that they can be contacted on one side, i.e., they can be connected to
other solar cells in a module or to an external circuit by interconnections on only one side of the
solar cell.
Such solar cells that can be contacted on one side typically have, on the back side, comb-like,
interdigitated metallization structures, wherein a first comb-like metallization structure is
connected in an electrically conductive way to the emitter area and the second metallization
structure engaging in the first metallization structure like a comb is connected in an electrically
conductive way to the base.
The positive and also the negative charge carriers are guided via the comb-like metallization
structures laterally, that is, parallel to the contacting side of the solar cell, to one or more
collection points of the metallization structures and tapped there by means of cell connectors or
other contacting types.
Such a solar-cell structure is described, for example, in [1] (see "References").
Starting from here, the present invention is based on the objective of creating a solar cell that can
be contacted on one side and a corresponding solar-cell module, wherein the potential for
optimization with respect to the efficiency of the solar cell relative to the previously known
solar-cell structures should be increased and the failure probability of the solar cell and
especially of the solar-cell module due to external influences should be reduced.
This task is achieved by a solar cell according to Claim 1 and a solar-cell module according to
Claim 19. Advantageous embodiments of the solar cell are found in Claims 2 to 18;
advantageous embodiments of the solar-cell module are found in Claims 20 to 24.
The solar cell according to the invention comprises at least one metallic base contact, at least one
metallic emitter contact, and also a semiconductor structure. The semiconductor structure has at
least one base area and at least one emitter area.
The base area and emitter area are arranged bordering each other at least partially, so that a pn-
junction is formed between the base area and emitter area at least in the boundary area.
The base area and emitter area have opposite doping. Doping types are the n-doping and the
opposite p-doping.
Typically, in the solar cell according to the invention, the base area is n-doped and the emitter
area is p-doped. An inversion of the doping types also lies within the scope of the invention, that
is, a p-doped base and an n-doped emitter.
The semiconductor structure can here consist of a single silicon wafer that has an underlying
doping as the base doping and, for example, in a sub-area close to the surface, an emitter with a
doping type opposite the doping type of the base doping.
The emitter could be generated, for example, by diffusion of a dopant.
Similarly, other types of semiconductor structures for the construction of a solar cell also lie in
the scope of the invention, for example, multi-layer systems in which, for the production on a
first layer, a second layer is deposited with different doping, so that a pn-junction or hetero-
structures are constructed at the layer boundary between the first and second layer.
The base contact is connected in an electrically conductive way to the base area and the emitter
contact is connected in an electrically conductive way to the emitter area.
In the sense of the present application, in the phrase "connected in an electrically conductive
way," those currents or recombination events are neglected that occur at or above a pn-junction.
Thus, in the sense of the present application, the emitter area and base area are not connected in
an electrically conductive way via the pn-junction and accordingly, the emitter contact is also not
connected in an electrically conductive way to the base contact.
In the sense of this application, the phrase "base contact" designates a metallic structure that is
connected in an electrically conductive way to a base area. Accordingly, in the sense of this
application, "emitter contact" designates a metallic structure that is connected in an electrically
conductive way to an emitter area. For electrical connection to the emitter area, an emitter
contact has a continuous contact surface between the emitter contact and emitter area and
likewise a base contact for the electrical connection to the base area has a continuous contact
surface between the base contact and base area.
It is essential that the solar cell according to the invention comprises several metallic emitter
contacts that are each connected in an electrically conductive way to at least one emitter area and
likewise several metallic base contacts that are each connected in an electrically conductive way,
in turn, to at least one base area.
Here, it lies within the scope of the invention that several emitter contacts are connected in an
electrically conductive way to an emitter area. Similarly, it lies in the scope of the invention that
the solar cell has several emitter areas, wherein each emitter area is connected in an electrically
conductive way to one or to several emitter contacts. A corresponding situation applies to the
base contacts and the base areas.
Furthermore, it is essential that the emitter contacts are not connected in an electrically
conductive way to each other or only via an emitter area and likewise the base contacts are not
connected in an electrically conductive way to each other or only via a base area.
If the solar cell according to the invention is constructed such that it has several emitter areas,
then the condition named above means that for each arbitrary pair of two emitter contacts it is
valid that the two emitter contacts are not connected in an electrically conductive way or only via
an arbitrary emitter area. A corresponding situation applies to the base contacts, as long as the
solar cell according to the invention has several base areas.
A typical, previously known solar cell that can be contacted on one side comprises, as described
before, comb-like, interdigitated metallization structures on the back side, with these structures
being connected in an electrically conductive way on one hand to the base and on the other hand
to the emitter. Here it is known that an insulating layer that has several recesses is arranged
between the metallic contacting structures and the semiconductor surface, with the metallic
structures being led through these recesses for contacting the semiconductor lying underneath. In
this previously known solar cell, a plurality of emitter contact areas is connected in an
electrically conductive way on the semiconductor surface of the emitter area by a metallic
structure and similarly a plurality of base contact areas on the corresponding semiconductor
surface of the base area are connected in an electrically conductive way by means of another
metallic structure.
The solar cell according to the invention differs from this configuration in that the emitter
contacts have no electrically conductive connection among each other on the side facing away
from the emitter area and the base contacts likewise have no electrically conductive connection
on the side facing away from the base area. Thus, in particular, the emitter contacts are not
connected in an electrically conductive way among each other by a metallic contact structure and
the same applies to the base contacts.
The invention is based on the realization of the applicant that, for the optimization and creation
of a solar-cell structure that is not sensitive relative to disruptive influences, the lateral current
flow of charge carriers outside of the semiconductor structure is not to be performed in the
metallic contact structures of the solar cell, but instead in the external contact structures that are
not an integral component of the solar cell, such as, for example, the cell connectors in the
module interconnection of the solar cells.
In this way, the advantage is produced that emitter contacts can be optimized only with respect to
the contacting properties of the corresponding semiconductor area, that is, in particular, with
respect to the contact resistance and a low surface recombination rate in the area of the contacted
semiconductor surface and, on the other hand, the lateral current flow takes place outside of the
semiconductor structure in additional connection elements, such as, for example, the cell
connectors in module interconnection, so that these can be optimized separately for lowest
possible losses, such as, for example, ohmic intermediate resistance losses, for the lateral charge-
carrier transport.
In addition, the solar cell according to the invention has the advantages that for an external effect
that leads to a fracture in the semiconductor structure, as a rule the electrically conductive
connection of the emitter contacts to the external connection structures, such as, for example, the
cell connectors, remain intact, so that even the areas of the solar cell separated electrically by the
fracture in the semiconductor can still contribute to the power generation.
In the solar cells noted above that can be contacted on the back side, a fracture in the
semiconductor structure typically likewise leads to a fracture of the comb-like, interdigitated
metallic contacting structures on the contacting side of the solar cell, so that the lateral current
transport is interrupted, on one hand, by the fracture in the semiconductor structure and, on the
other hand, by the fracture in the comb-like metallic connection structure and thus at least parts
of the solar cell can no longer contribute to the power generation.
The contacting side is advantageously the back side of the solar cell. This allows a simple
module interconnection, as well as the reduction of shading losses on the front side of the solar
cell by metallic structures.
Advantageously, the solar cell therefore has a plurality of emitter contacts and/or base contacts
according to the construction according to the invention, in particular, at least 10, advantageously
at least 100, furthermore, at least 1000 emitter contacts and/or base contacts.
Advantageously, the emitter and the base contacts are arranged and constructed such that the
emitter contacts and base contacts are not interdigitated according to the following condition:
The solar cell according to the invention is advantageously constructed such that the emitter
contacts are arranged and constructed such that, around each emitter contact, an imaginary
convex surface can be defined that completely contains the emitter contact and contains no base
contact and also no sub-area of a base contact, and
the base contacts are each arranged and constructed such that, around each base contact, an
imaginary convex surface can be defined that completely contains the base contact and contains
no emitter contact and also no sub-area of an emitter contact.
A surface is then convex when it is applicable for two arbitrary points of the surface that the
straight-line connection between these two points lies completely within the surface.
The previously mentioned condition thus defines an advantageous construction of the solar cell
according to the invention in which the emitter contact and base contact are not interdigitated.
For a construction of emitter contacts and base contacts engaging one in the other there is the
risk that a fracture of a solar cell leads to a fractured piece in which there is a contact of one
polarity and parts of a contact of the opposite polarity engaging with this contact. Such fractured
pieces suffer a loss in efficiency and thus reduce the total efficiency of all fractured pieces. This
is ruled out in the mentioned condition.
In the sense of this application, the phrase "completely" with reference to contacts means that the
entire metallic contact structure of the contact lies within the imaginary circle or the imaginary
surface and not, for example, only a center point of the metallic contact structure.
Advantageously, emitter contacts and/or base contacts are constructed and arranged such that a
sufficient density of the contacts is reached on the contacting side of the solar cell. In this way,
intermediate resistance losses within the solar cell due to the direct routing of charge carriers are
reduced.
The emitter contacts and base contacts are therefore advantageously arranged and constructed
such that for each emitter contact it is applicable that at least this complete emitter contact and at
least one complete base contact lie within an imaginary circle with diameter d1. An arbitrary
emitter contact thus fulfills the condition that it lies completely in an imaginary circle with
diameter d1 around this emitter contact and also at least another emitter contact lies completely in
this imaginary circle. Accordingly, for each base contact it is applicable that at least this
complete base contact and at least one complete emitter contact lie within an imaginary circle
with diameter d1.
The diameter d1 is here selected such that a condition according to Formula 1 is fulfilled:

with a scaling factor k1 and the surface area Ak [cm2] of the contacting side of the solar cell. By
specifying the scaling factor k1, for a given surface area of the contacting side Ak, an upper limit
for the diameter d1 is thus given and thus a minimum density for the previously mentioned
contact arrangement, as well as a maximum size for the contact construction.
Studies of the applicant have resulted in that the scaling factor is selected as k1 = 0.13,
advantageously k1 = 0.06, especially k1 = 0.03, more advantageously k1 = 0.014. In this way, a
sufficient density of the emitter contacts and base contacts is guaranteed.
The advantageous constructions of the solar cell according to the invention according to the
condition with respect to Formula 1 and according to the following conditions with respect to
Formulas 2, 3, and 4 are thus such that an imaginary circle with the specified properties for the
specified contacts or contact groups must absolutely be able to be defined.
Furthermore it is advantageous to guarantee a sufficient density between the contacts of one
polarity, i.e., between the emitter contacts on one side and/or the base contacts on the other side.
Advantageously, the emitter contacts are therefore arranged and constructed such that, for each
emitter contact, at least this complete emitter contact and at least one additional complete emitter
contact lie within an imaginary circle with diameter d2.
Alternatively or additionally it is advantageous that the base contacts are arranged and
constructed such that, for each base contact, at least this complete base contact and at least one
additional complete base contact lie within an imaginary circle with diameter d2.
For the previously named conditions with respect to the emitter contacts among each other
and/or the base contacts among each other, the diameter d2 is selected such that a condition
according to Figure 2 is fulfilled:

with a scaling factor k2 and the surface area Ak [cm2] of the contacting side of the solar cell.
Studies of the applicant have resulted in that the scaling factor is advantageously selected as k2 =
0.26, preferably k2 = 0.13, especially k2 = 0.06, more advantageously k2 = 0.028.
Advantageously, emitter contacts and base contacts are distributed approximately uniformly
across the contacting side of the solar cell according to the invention.
Here it is especially advantageous that the emitter contacts and the base contacts are arranged on
the intersection points of an imaginary, right-angle lattice, especially a lattice with square cells.
Emitter contacts and base contacts are here arranged such that emitter contacts and base contacts
alternate along each line of the imaginary lattice. Thus, this has the result that the four closest
neighbors for an emitter contact are each base contacts and vice versa.
Typical solar cells have approximately the shape of a flat right parallelepiped and the contacting
side correspondingly has a square shape. Advantageously, the solar cell according to the
invention has a square contacting side and the previously described imaginary lattice is arranged
such that the lattice lines are at an angle of 45° relative to the edges of the contacting side.
Through this arrangement it is possible to connect to each other either a row of base contacts or,
in parallel to this, a row of emitter contacts to a metallization line running parallel to an edge of
the contacting side. Thus, in this way, through comb-like, interdigitated cell connectors, a
contacting of all of the emitter contacts can be carried out via a first comb-like cell connector and
a contacting of all of the base contacts can be carried out via a second comb-like cell connector
that is interdigitated with the first cell connector.
It likewise lies in the scope of the invention to arrange the lattice lines at a different angle to the
edges of the contacting side.
Furthermore, it lies in the scope of the invention that emitter contacts and base contacts are
arranged on the intersection points of an imaginary lattice that has diamond-shaped lattice
elements. It likewise lies in the scope of the invention to arrange the emitter contacts and base
contacts on two separate lattices, i.e., to provide one imaginary lattice for the emitter contacts
and one imaginary lattice for the base contacts.
In order to keep intermediate resistance losses low within the solar cell due to the direct routing
of charge carriers, it is advantageous that two adjacent emitter contacts have a distance less than
1 cm, especially less than 5 mm.
The same applies for the base contacts: advantageously the base contacts are arranged such that
the distance of two adjacent base contacts corresponds to the previously named conditions.
It likewise lies in the scope of the invention to cover the contacting side of the solar cell
essentially by the base contacts and/or the emitter contacts, wherein adjacent contacts are
separated from each other by narrow intermediate spaces and thus electrically insulated. In
particular, it is advantageous that the intermediate spaces between adjacent contacts equal a
maximum of 1 cm, especially 5 mm.
Advantageously, the emitter contacts and the base contacts are constructed such that each contact
covers a total surface area of less than 16 mm2, advantageously less than 5 mm2, especially less
than 1 mm2, more advantageously less than 0.4 mm2. The projection of an arbitrary contact on
the contacting side thus covers a surface area less than the listed limits.
In particular, it is advantageous that the emitter contacts and base contacts have approximately
circular or approximately square or approximately star-shaped constructions.
In another advantageous embodiment, the contacting side of the solar cell according to the
invention is improved with respect to its recombination properties, such that on the contacting
side, the semiconductor structure has an electrically non-conductive insulation layer.
Advantageously, this insulation layer likewise has passivation properties with respect to the
surface recombination of the semiconductor structure. The insulation layer has recesses at the
locations of the base contacts and emitter contacts and the base contacts and emitter contacts are
arranged on the insulation layer and are led through the recesses of the insulation layer for the
electrical contacting of the surface of the semiconductor structure lying underneath.
In this advantageous embodiment, the base contacts and emitter contacts thus penetrate the
insulation layer at each of its recesses. The recesses in the insulation layer are advantageously
already present before the solar cells are connected to the insulation layer. It likewise lies in the
scope of the invention that the insulation layer is arranged on the solar cells first without recesses
and the recesses are produced also in the processing step in which the contacts are produced.
This is possible, for example, through use of lasers, according to the known method of "Laser
Fired Contacts" (LFC), as described in DE 100 46 170 A1. Alternatively, the recesses are
produced such that the contacts are first applied to the insulation layer and are heated in a
subsequent firing step, so that the insulation layer is penetrated by the contacts and therefore the
recesses are produced and the contact connects to the semiconductor in an electrically conductive
way.
The contacts are advantageously applied by vacuum deposition, screen printing, sputtering,
stencil printing, inkjet printing method, or dispersion. The solar cell according to the invention is
suitable, in particular, for production by a screen-printing method, because the dimensions
especially of the base contacts are suitable for screen-printing conditions.
Here it is advantageous that the recesses of the insulation layer have a surface area less than 16
mm2, advantageously less than 5 mm2, especially less than 1 mm2, more advantageously less
than 0.4 mm2, so that the contact surface area of the metallic base contacts and emitter contacts
on the semiconductor surface also has a correspondingly dimensioned surface area. On the
insulation layer, however, the surface area of the base contacts and emitter contacts can be
selected to be larger, without the surface recombination rate of the semiconductor structure on
the contacting side being increased in this way. For the simpler contacting of the base contacts
and emitter contacts, it is advantageous that the base contacts and emitter contacts on the
insulation layer each cover an area with a surface area less than 16 mm2, advantageously less
than 5 mm2, especially less than 1 mm2, more advantageously less than 0.4 mm2. The contacts
advantageously cover an approximately circular or approximately square area or an
approximately star-shaped area.
It lies in the scope of the invention to construct the solar cell according to the invention with
several base areas and/or several emitter areas, wherein at least one base and one emitter area at
least partially bordering this base are constructed according to the structure according to the
invention.
In the previously described embodiments of the solar cells according to the invention, the base
contacts are connected in an electrically conductive way to each other only via the base area of
the semiconductor structure and likewise the metallic emitter contacts are connected only via the
emitter area of the semiconductor structure.
In one advantageous embodiment of the invention, the emitter contacts are divided into groups,
wherein each group comprises a number of at least 2 and a maximum of 30, especially a
maximum of 20, advantageously a maximum of 10 emitter contacts. The emitter contacts of one
group are connected in an electrically conductive way via a metallization; in contrast, the
different groups of emitter contacts are not connected in an electrically conductive way among
each other or only via an emitter area.
Likewise, the base contacts are divided into groups, wherein each group comprises a number of
at least 2 and a maximum of 30, especially a maximum of 20, advantageously a maximum of 10
base contacts. The base contacts of one group connected in an electrically conductive way via a
metallization; in contrast, however, the different groups of base contacts are not connected in an
electrically conductive way among each other or only via a base area.
Thus, in this advantageous embodiment, only a few base contacts and/or emitter contacts are
assembled into one group, however, the fundamental principle of the configuration of the solar
cell according to the invention is unchanged. In particular, for this advantageous embodiment,
there is only a very low probability that for a fracture of the semiconductor structure, the metallic
connection of one group is also broken. As long as the fracture does not damage the metallic
connection of one group, in this advantageous embodiment, a fracture also does not result in that
significant sub-areas of the solar cell no longer contribute to the power generation.
Also for the advantageous embodiment in which the base contacts and/or emitter contacts are
assembled into groups, it is advantageous when the groups have a sufficiently high density on the
contacting side of the solar cell.
Advantageously, the groups of the emitter contacts and base contacts are therefore arranged and
constructed such that, for each group of emitter contacts, at least this complete group of emitter
contacts and at least one complete group of base contacts lie within an imaginary circle with
diameter d3 and for each group of base contacts, at least this complete group of base contacts and
at least one complete group of emitter contacts lie within an imaginary circle with diameter d3,
wherein the diameter d3 is selected such that a condition according to Formula 3 is fulfilled:

with a scaling factor k3 and the surface area Ak [cm2] of the contacting side of the solar cell.
Studies of the applicant have resulted in that the scaling factor is selected to be advantageously
k3 = 0.40, preferably k3 = 0.26, especially k3 = 0.10, more advantageously k3 = 0.056.
Also with respect to groups, here and in the following the phrase "complete" means that the
entire metallic structure of one group lies within the imaginary circle and not, for example, only
a sub-area or center point of the group. The condition according to the imaginary perimeter thus
defines a minimum density with respect to the named groups, as well as a maximum with respect
to the dimensions of each group.
Furthermore, it is advantageous when the groups of both polarities, i.e., the groups of the emitter
contacts among each other and the groups of the base contacts among each other, have a
sufficiently high density on the contacting side of the solar cell:
Advantageously, the groups of the emitter contacts are therefore arranged and constructed such
that for each group of emitter contacts, at least this complete group of emitter contacts and at
least one additional complete group of emitter contacts lie within an imaginary circle with
diameter d4.
Likewise, in this advantageous embodiment, the groups of base contacts are arranged and
constructed such that, for each base contact, at least this complete group of base contacts and at
least one additional complete group of base contacts lie within an imaginary circle with diameter
d4.
For the two previously named conditions with respect to the groups of emitter contacts and/or
base contacts among each other, the diameter d4 is selected such that a condition according to
Formula 4 is fulfilled:

with a scaling factor k4 and the surface area AK [cm ] of the contacting side of the solar cell.
Studies of the applicant have resulted in that the scaling factor is advantageously selected as k4 =
0.80, preferably k4 = 0.51, especially k4 = 0.20, more advantageously k4 = 0.112.
The previously named advantageous arrangements of the emitter contacts and/or base contacts
with respect to the imaginary lattice is likewise advantageous for the arrangement of the
previously described groups of the emitter contacts and/or base contacts, wherein, in this case,
the groups with a reference point predefined for each groups, such as, for example, the geometric
center point of a group, lie on the crossing lines of the imaginary lattices.
Advantageously, the groups of the emitter contacts have, among each other, identical geometries,
i.e., the metallic structures have identical constructions with respect to their expansion and
geometric dimensions. This likewise applies advantageously for the groups of the base contacts
among each other and, in particular, the groups of the emitter contacts advantageously have
identical constructions like the groups of the base contacts.
Advantageously, all of the emitter contacts and/or all of the base contacts of the solar cell are
constructed and/or arranged according to the previously described structure according to the
invention. Likewise, however, it lies in the scope of the invention that only one sub-area of the
solar cell, i.e., a part of the emitter contacts and/or base contacts is constructed according to the
invention. Advantageously, the sub-area on the contacting side of the solar cell in which the
emitter contacts and/or base contacts are constructed according to the invention comprises at
least 70%, preferably at least 80%, especially at least 95% of the surface area of the contacting
side.
The solar cell according to the invention represents a solar cell that can be contacted on one side.
The additional design of the solar cell can here be constructed according to already known solar-
cell structures that can be contacted on one side, especially according to the basic design of a
back-side contact cell (described, for example, in [1]), the basic design of an emitter-wrap-
through solar cell (described, for example, in [2]), or a metal-wrap-through solar cell (described,
for example, in [3]).
The emitter of the solar cell according to the invention is advantageously generated by diffusion
of a dopant into the semiconductor material. Likewise, however, other methods or structures for
the construction of the emitter also lie in the scope of the invention. In particular, the use of
aluminum as a doping source for generating a p-doping is advantageous, in connection i) on one
hand with a vacuum-deposited aluminum layer as dopant source and ii) on the other hand with
printed aluminum-containing pastes. In a subsequent firing step (heating of the structure), it can
result in ii) a very complex process profile in which a partially molten layer is present that
contains aluminum and silicon and in which solidification forms essentially a eutectic mixture.
Simultaneously it results in a doping of the semiconductor with aluminum. This process cannot
be attributed solely to diffusion, but instead could also be a result of the solidification of the
aluminum/silicon mixture. This formation of the emitter is thus especially advantageous for the
construction of a solar cell according to the invention starting from an n-doped semiconductor
wafer.
The solar cell according to the invention allows novel types of interconnection for combinations
of several solar cells in a solar-cell module:
The invention therefore further comprises a solar-cell module according to Claim 19.
The solar-cell module according to the invention comprises at least one first and one second
solar cell that are each solar cells according to the invention according to at least one of the
previously described embodiments.
The first solar cell is arranged in the solar-cell module next to the second solar cell, wherein as is
typical in such modular arrangements, each contacting side is arranged in the module lying
underneath.
On the contacting side, a cell connector is arranged that is constructed such that the emitter
contacts of the first solar cell are connected in an electrically conductive way to the base contacts
of the second solar cell. The solar cells are thus connected in series. Likewise, it lies in the scope
of the invention to connect the solar cells in parallel, i.e., the emitter contacts of the first solar
cell are connected in an electrically conductive way to the emitter contacts of the second solar
cell and likewise the base contacts of the first solar cell are connected in an electrically
conductive way to the base contacts of the second solar cell.
Advantageously, the cell connector is flexible, in particular, it has a film-like construction. In this
way, the risk that the contact to the cell connector is likewise interrupted for a fracture of a solar
cell is also reduced, because the cell connector yields to the movement of individual fracture
pieces of the solar cell due to the flexibility of the cell connector during a fracture process.
Likewise the use of a non-flexible cell connector lies within the scope of the invention, for
example, a cell connector constructed like a circuit board.
Advantageously, the solar-cell module comprises at least two solar cells arranged on next to the
other like a row and the cell connector has metallization structures that engage in each other like
combs and are arranged such that, for solar cells arranged like rows with the contacting side on
the cell connector, the emitter contacts of one solar cell are connected in an electrically
conductive way to the base contacts of the adjacent solar cell by means of the comb-like
metallization structures. The solar cells are thus connected in series. Likewise it lies in the scope
of the invention that the metallization structures engaging in each other like combs are arranged
such that the solar cells are connected in parallel.
In one advantageous embodiment of the solar-cell module, the cell connector is constructed as an
electrically insulating film that has metallic connection structures on both sides. Thus, in this
way, the electrical interconnection on the two sides of the films can be selected independently
from each other, in particular, crossing of the conductive paths is also possible.
The metallic connection structure of one side of the cell connector is guided onto the other side
via recesses of the film and recesses of the metallic connection structure of the opposite side.
The cell connector is constructed such that the film has a first metallic connection structure on
the side facing the solar cell for modular interconnection and a second metallic connection
structure on the side facing away from the solar cell and the second metallic connection structure
is guided through recesses of the film and the first metallic connection structure to the other side.
Advantageously, the second metallic connection structure is guided via solder or conductive
adhesive in the described recesses to the other side. The first metallic connection structure is
advantageously likewise pre-allocated with solder or conductive adhesive, in order to provide an
electrically conductive connection to the solar cell.
The metallic connection structures are arranged such that, for solar cells arranged with the
connecting side on the film, the base contacts of the solar cells are each connected in an
electrically conductive way via the recesses to the one metallic connection structure and the
emitter contacts of the solar cells are each connected in an electrically conductive way to the
other metallic connection structure or vice versa.
For simpler component insertion and handling of the solar cells set on the cell connector, it is
advantageous when the cell connector has recesses for the application of a vacuum for the
component insertion of the cell connector with solar cells.
Here, the solar cells are placed with the contacting side on the corresponding side of the cell
connector and on the side of the cell connector opposite the solar cell, a vacuum is established
via the recesses, so that the solar cell is suctioned onto the cell connector. In this way, a simple
handling of the cell connector is possible together with the solar cell for the production of the
solar-cell module. Likewise, a conductive adhesive for the electrical connection of the emitter
contacts and base contacts with the metallic structures of the cell connector could be previously
deposited on the cell connector and/or the metallic contacts of the solar cell and after component
insertion of the cell connector, the application of the vacuum leads to a contact pressure between
the cell connector and contacting side of the solar cell, so that a qualitatively high-quality
connection is established by means of the conductive adhesive.
Alternatively, in another advantageous embodiment, another connection technology could also
be selected, such as, for example, soldering. For this purpose, the cells and/or the cell connector
are supplied with solder appropriately in advance and then soldered.
In another advantageous embodiment, the cell connector is constructed as a field from
electrically conductive wires arranged essentially in parallel and solar cells are arranged on the
wires such that the emitter contacts of one solar cell are connected in an electrically conductive
way by the wires to the base contacts of the adjacent solar cell. The connection of the wires to
the contacts is realized advantageously via bonding with conductive adhesive, solder, or welding.
Likewise, it lies in the scope of the invention to generate a parallel circuit by connecting the
contacts of the same polarities of adjacent solar cells.
Other preferred features and embodiments of the solar cell according to the invention and the
solar-cell module according to the invention are described below with reference to the figures.
Shown each in schematic representation herein are:
Figure 1, the contacting side of one embodiment of a solar cell according to the invention,
Figure 2, a section perpendicular to the plane of the drawing in Figure 1 on the section line
designated with A, wherein only one sub-area of the section figure is shown, comprising an
emitter contact and a base contact,
Figure 3, three solar cells according to Figure 1 that are connected to cell connectors,
Figure 4, the contacting side of a second embodiment of a solar cell according" to the
invention in each of which six emitter contacts and six base contacts are assembled into groups,
Figure 5, a partial cutout of a contacting side of a third embodiment of a solar cell
according to the invention in each of which five emitter contacts and five base contacts are
assembled into groups,
Figure 6, a partial cutout of the contacting side of a fourth embodiment of a solar cell
according to the invention in which, for the base contacts on one side, and for the emitter
contacts on the other side, a lattice with diamond-shaped lattice elements is predetermined and
the contacts are each arranged on the crossing points of the lattice lines,
Figure 7, the contacting side of a fifth embodiment of a solar cell according to the invention
in each of which six emitter contacts and six base contacts are assembled into groups,
Figure 8, the contacting side according to Figure 4, wherein several types of electrical
contacting of the individual groups of contacts by cell connectors are shown,
Figure 9, the contacting side according to Figure 7, wherein straight-lined cell connectors
for the electrical contacting of the groups of emitter contacts on one side and groups of base
contacts of base contacts on the other side are shown,
Figure 10, an embodiment of a modular interconnection of solar cells according to the
invention by a wire field,
Figure 11, an embodiment of a cell connector for modular interconnection, wherein the cell
connector is constructed as a flexible film and has metal structures engaging in each other like
combs on the side facing the solar cells,
Figure 12, an embodiment of a cell connector for modular interconnection with recesses for
vacuum suctioning during the module production,
Figure 13, an embodiment of a cell connector for modular interconnection, wherein the cell
connector is constructed as an insulating film that has metallic structures on both sides,
Figure 14, an exemplary arrangement of the cell connector from Figure 3 in a solar-cell
module, and
Figure 15, a section perpendicular to the plane of the drawing in Figure 13a along the line B.
The solar cell shown in Figure 1 as an embodiment is constructed as a back-side contact cell that
was produced from a block silicon wafer with a square surface area. Accordingly, the solar cell
has a square contacting side 1. The angle a between two lattice lines equals 90° accordingly.
Likewise, constructions with lattices with diamond-shaped elements lie in the scope of the
invention in which the angle a is selected as less than 90°.
The embodiment of the solar cell according to the invention has an n-doped base. Accordingly,
in Figure 1, on the contacting side 1, there are several metallic emitter contacts (shown with
vertical stripes, an emitter contact is designated, as an example, with reference symbol 5) and
metallic base contacts (shown with horizontal stripes, a base contact is designated, as an
example, with reference symbol 6).
Figure 1 is merely a schematic diagram. Typically, a solar cell according to the invention has an
edge length of 10 to 20 cm and the distance between an emitter contact and base contact equals
less than 5 mm, so that there is a significantly higher density of metallic contacts, as shown in
Figure 1. Likewise, however, the solar cell according to the invention is also advantageous in
smaller dimensions, for example, in order to construct the solar cell according to the invention as
a concentrator solar cell for use with radiation concentrators.
The emitter contacts and base contacts are arranged on the crossing points of an imaginary, right-
angle lattice G that is shown dotted in Figure 1. Emitter contacts and base contacts here alternate
along each line of the imaginary lattice. In addition, the lattice is arranged such that the lattice
lines are at an angle of 45° to the edges of the contacting side.
In Figure 1, two imaginary circles 8 and 9 are also shown dashed for illustrating the conditions
listed above for the arrangement and construction of the emitter contacts and/or base contacts.
The circle 9 comprises two emitter contacts (shown with vertical stripes). For the diameter of the
circle 9, the contacting side shown in Figure 1 thus fulfills the conditions that, for each emitter
contact, these emitter contacts lie within a circle with the shown diameter and also another
emitter contact lies within this circle, wherein both emitter contacts lie completely, i.e., with
respect to the entire extent of their metallic structure, within the circle 9. The identical condition
also applies for the base contacts, i.e., around each base contact in Figure 1, an imaginary circle
with the diameter of the circle 9 can be arranged such that this base contact and at least one other
base contact lie completely in this circle.
Accordingly, the circle 8 illustrates the condition that for an emitter contact (shown with vertical
stripes), at least one base contact (shown with horizontal stripes) lies within a circle with the
diameter of the circle 8, wherein the emitter contact and base contact each lie completely within
this circle. An analogous condition applies for the base contacts.
Figure 2 represents a section perpendicular to the plane of the drawing on the section line A
shown in Figure 1, wherein only one sub-area comprising one emitter contact and one base
contact is shown.
The solar cell according to the invention is formed of an n-doped silicon wafer and thus has an n-
doped base area 2. An emitter area 3 that is p-doped was generated by diffusion on the contacting
side 1. Another p-doped emitter area 3a was generated by means of diffusion on the front side
over the entire surface. This emitter area 3a, however, is not connected to the metallic emitter
contacts, it is used only for improving the recombination properties of the front side of the solar
cell. Alternatively, for improving the recombination properties of the front side of the solar cell,
a so-called "front surface field" is advantageous, i.e., instead of the emitter area 3a, an n-doped
area that has a significantly higher doping concentration compared with the base.
The light coupling is carried out across the front side in the solar cell according to the invention.
Likewise, light can penetrate into the solar cell via the back side, especially re-reflected IR
radiation.
An electrically non-conductive insulation layer 4 that is constructed as a silicon-dioxide layer is
deposited on the silicon wafer on the contacting side 1 of the solar cell according to the
invention. This insulation layer 4 has recesses that are penetrated by the metallic emitter contacts
and base contacts.
Alternatively, a construction of the insulation layer from silicon nitride, aluminum oxide, silicon '
carbide, or as a multi-layer system from the mentioned materials is also advantageous, especially
also containing amorphous silicon.
In Figure 2, as an example, two recesses of the insulation layer 4 and correspondingly a metallic
emitter contact 5 and a metallic base contact 6 are shown.
The recesses of the insulation layer 4 are approximately circular (perpendicular to the plane of
the drawing in Figure lb) and have a surface area of approximately 0.1 mm2 on the
semiconductor surface. The metallic contacts S and 6 pass through the recesses of the insulation
layer 4 for contacting the emitter 3 on one hand and the base 2 on the other hand. The surface
between the metallic contact and semiconductor surface thus likewise equals approximately 0.1
mm2 for each metallic contact.
On the side of the insulation layer facing away from the semiconductor, the metallic contacts
cover a surface area that corresponds at least to the surface area between the metallic contact and
semiconductor.
Advantageously, however, the metallic contacts on the side of the insulation layer facing away
from the semiconductor cover a larger surface area of the insulation layer. Also here, the metallic
contacts have an approximately circular shape and cover a surface area of advantageously at least
1 mm2 , especially at least 5 mm2 , furthermore at least 10 mm2 .
In this way it is guaranteed that, due to the, for example, 1 mm2 large surface area of the metallic
contacts, a permanent connection can be achieved with a cell connector for a simultaneously low
output resistance.
In Figure 3, a cell connector for the construction of an embodiment of a solar-cell module
according to the invention is shown. The cell connector 7 has four comb-like structures 7a to 7d
that have a comb-like, interdigitated construction.
The dashed lines in Figure 3 indicate the positions at which three solar cells according to Figure
1 are placed with the contacting side on the cell connector 7. Here, for example, through the
comb-like metallization structure 7b, an electrically conductive connection to the base contacts
of the solar cell arranged on the left is formed, while the right side of the comb-like metallization
structure 7b has an electrically conductive connection to the emitter contacts of the solar cell
arranged in the middle, so that the base contacts of the solar cell arranged on the left are
connected via the cell connector in an electrically conductive way to the emitter contacts of the
solar cell arranged in the middle. The same applies with respect to the comb-like metallization
structure 7c and the solar cell arranged in the middle with the solar cell arranged on the right.
The comb-like metallization structures 7a and 7d represent termination connections for each end
of a solar-cell row, with each connection being connected to external circuits or other solar-cell
rows (so-called "strings").
Figure 3 is also only one schematic diagram of a cell connector. Typically, a larger number of
solar cells are arranged in a row, for example, 15 to 20 solar cells in a row in which the base
contacts of one solar cell are connected to each other in an electrically conductive way to the
emitter contacts of the adjacent solar cell by comb-like metallization structures 7d, 7c.
The cell connector 7 shown in Figure 3 advantageously has (not shown) recesses. For the
production of a solar-cell module according to the invention, initially conductive adhesive is
deposited on the emitter contacts and base contacts point by point. Then the solar cells are
moved with the contacting side onto the cell connector according to the positions shown with
dashed lines in Figure 2 and a vacuum is applied by means of the recesses, so that the solar cells
are pressed onto the cell connector 7 and accordingly a qualitatively high-quality connection is
constructed between the emitter contacts and base contacts by the conductive adhesive to the
comb-like metallic structures. Likewise, the connection of the emitter contacts and base contacts
with other methods lies in the scope of the invention, such as, for example, by soldering,
welding, or alloying.
In Figure 4, one embodiment of the solar cell according to the invention is shown in which, on
the contacting side, 6 base contacts are combined into a group of base contacts 10, wherein the
individual base contacts are connected to each other in an electrically conductive way by a
comb-like metallic structure.
Likewise, 6 emitter contacts are combined into a group of emitter contacts 11, wherein the
individual emitter contacts are connected to each other in an electrically conductive way by a
comb-like metallic structure.
In Figure 4, analogous to Figure 1, two imaginary circles 12 and 13 are shown with dashed lines
for illustrating the conditions with respect to the arrangement and construction of the groups of
contacts by fixing a maximum diameter of such circles:
The circle 12 represents an example in which, within a circle around a group of emitter contacts
(shown with vertical stripes), at least one group of base contacts (shown with horizontal stripes)
lies, wherein both groups of contacts lie completely within the circle 12.
Accordingly, the circle 13 illustrates the condition that, within the circle 13, a group of emitter
contacts and at least one other group of emitter contacts each lie completely. Likewise, one
group of base contacts and at least one other group of base contacts each lie completely in
another circle with this diameter, wherein, in the illustrated case, both circles are identical for the
selected groups.
In Figure 5, a cutout of a contacting side is shown, wherein emitter contacts and base contacts
are arranged analogous to Figure 1 and Figure 4. In Figure 5, however, another example for the
formation of groups of emitter contacts and base contacts is shown:
Every five emitter contacts are combined by a cross-like metal structure into a group (solid line)
and likewise every five base contacts are combined by a cross-like metal structure into a group
(dotted line).
In Figure 6, another embodiment of a contacting side with a different arrangement of the emitter
contacts and base contacts relative to each other is shown.
For this purpose, two imaginary lattices G5 (dashed lines) and G6 (solid lines) were defined that
each have diamond-shaped lattice elements. The emitter contacts each lie on the crossing points
of the lattice G5 and the base contacts each lie on the crossing contacts of the lattice G6.
The imaginary lattices G5 and G6 are pushed against each other, so that a hexagonal distribution
of the emitter contacts and base contacts is produced.
In Figure 7, an embodiment is shown that has an arrangement of emitter contacts and base
contacts according to Figure 6. Here, however, every six emitter contacts are connected into a
group by crow's feet-like metallic connection structures (shown dashed) and every six base
contacts are likewise connected into a group by the crow's foot-like connection structures shown
in solid lines.
In Figure 8 it is shown how a contacting side according to Figure 4 is connected in an electrically
conductive way by cell connectors.
Advantageously, initially a conductive adhesive point (designated with reference symbol 14 as
an example) is deposited in the middle in each comb-like metallic structure of the groups of
emitter contacts and base contacts (10 and 11). This is shown in the first line a) in Figure 8.
Then, as shown in line b), linear cell connectors 7a and 7b are placed above the comb-like
metallization structures of the individual groups and the conductive adhesive points, so that, at
the conductive adhesive points, there is an electrically conductive connection between the comb-
like metallization structures and the cell connectors. The linear cell connector 7b thus contacts
the base contacts and the linear cell connector 7a contacts the emitter contacts of the contacting
side shown in Figure 8.
Alternatively, it is possible, as shown in line c), to connect the linear cell connector via the entire
contact surface to the metallic comb-like structures, for example, by bonding, soldering, or
welding.
In Figure 9 it is shown that the contacting side shown in Figure 7 can likewise be connected by
linear cell connectors, wherein the linear cell connectors alternately connect in an electrically
conductive way emitter contacts and base contacts or the metallization structures of the groups of
emitter contacts and base contacts.
Advantageously, for this purpose, in the middle on the crow's foot-like metallic connection
structures, points with conductive adhesive are deposited by which the cell connectors are
connected in an electrically conductive way to the metallic crow's foot-like connection
structures. Such points are shown in Figure 9 as examples by the filled circles.
In Figure 10, an embodiment of a modular interconnection is shown in which the solar cells (one
solar cell is designated with 15 as an example) are connected by a wire field. For this purpose,
individual linear wires are arranged such that the base contacts of one solar cell are connected in
an electrically conductive way to the emitter contacts of an adjacent solar cell. As an example, a
wire 20 is designated. For the production of a module, the wire field and the contacts of the solar
cells are pre-soldered or provided with conductive adhesive and connected to each other.
Advantageously, the wire field is arranged on a carrier formed advantageously from the material
EVA.
In Figure 11, an embodiment of a cell connector is shown that is constructed as a flexible,
electrically insulating film 21 and has comb-like, interdigitated metal structures 22 on one side
and on the side facing the solar cells. The arrangement of a solar cell on the cell connector is
shown as an example by dashed lines. Advantageously, an electrically non-conductive filler
material is arranged on the flexible film between the comb-like metal structures, with this filler
material preventing the formation of air bubbles between the solar cell and flexible film 21.
In Figure 12, a refinement of the cell connector from Figure 11 is shown that has additional
recesses 23, so that by applying a vacuum on the side facing away from the solar cells through
the recesses, the solar cells can be drawn to the cell connectors. Advantageously, the cell
connector is pre-soldered at points 24 on the metal structures or provided with conductive
adhesive, wherein the points are arranged such that for the application of a solar cell on the cell
connector, the pre-soldered points contact the emitter contacts or base contacts. The arrangement
of a solar cell is indicated as an example by the dashed line.
In Figure 13, one embodiment of a cell connector is shown that is constructed as an electrically
insulating, flexible film 26 that has a first metallization on the side facing the solar cells and a
second metallization on the side facing away from the solar cells. The side facing the solar cells
is shown in Figure 13a and the side facing away from the solar cells is shown in Figure 13b. The
flexible film and the first metallization have recesses 25 at which the second metallization is
guided through the recesses to the side facing the solar cells. In Figure 13a, shown with dashed
lines as an example, the position of a solar cell is shown. The metallizations and the recesses are
arranged such that the first metallization covers the base contacts and the second metallization
through the recesses covers the emitter contacts of the solar cell and each are connected in an
electrically conductive way. In Figure 13b, it is visible that the cell connector on the side facing
away from the solar cells is divided into individual areas separated from each other electrically.
This allows a series interconnection of the solar cells in the module, as described below with
reference to Figure 14:
In Figure 14, an example arrangement of the cell connector from Figure 13 in a solar-cell module
is shown, wherein Figure 14a shows the side facing the solar cells and Figure 14b shows the side
facing away from the solar cells. In Figure 14a, the arrangement of two solar cells is shown as an
example.
Figure 15 shows a section figure of the cell connector perpendicular to the plane of the drawing
in Figure 13 along the line B. The electrically insulating, flexible film 26 is partially covered on
the side facing the solar cells (shown at the top) with a first metallization 27 and partially
covered on the side facing away from the solar cells with a second metallization 28. In recesses
25 both of the first metallization and also of the flexible film, the second metallization can be
guided to the side facing the solar cells or an electrically conductive contact with the solar cells
can be established by means of conductive adhesive or solder. Furthermore, recesses 29 of the
second metallization and 30 of the first metallization are shown that create a structuring of the
metallizations according to Figures 13 and 14.
References:
[1] Lammert. M.D. end R.J. Sohwartz (1877) The interdigited Back Contact
Solar Cell: A Silicon Solar Cell for Use in Concentrated Sunlight" Transactions
on Electron Devices ED-24 (4): 337-42
[2] Gee, J.M., W.K. Schubert, et al. (1893) "Emitter wrap-through solar cell"
Proceeding of the 23rd IEEE Photovoltaic Specialists Conference, Louisville,
Kentucky, USA. IEEE. New York. NY. USA
(3) Van Kerschever, E., 8. De Wolf, et al. (2000) Towards back contact silicon
solar cells with screen printed metallisation Proceedings of the 28th IEEE
Photovoltaios Specialists Conference, Anchorage. Alaska. USA
WE CLAIM
1. Solar cell, in particular, for interconnection in a solar-cell module, comprising at least one
metallic base contact (6), at least one metallic emitter contact (5), and also a semiconductor
structure that has at least one base area and at least one emitter area (2, 3),
wherein the base area and emitter area (2, 3) have opposite doping types and border each other at
least partially for formation of a pn-junction,
the base contact (6) is connected in an electrically conductive way to the base area (2) and the
emitter contact (5) is connected in an electrically conductive way to the emitter area (3), and
both the base contact and also the emitter contact (6, 5) are arranged on one contacting side (1)
of the solar cell,
characterized in that
the solar cell has several of the metallic emitter contacts (5) that are each connected in an
electrically conductive way to the emitter area (3) and several of the metallic base contacts (6)
that are each connected in an electrically conductive way to the base area (2),
wherein the emitter contacts are not connected among each other or are exclusively connected by
the emitter area (3), in an electrically conductive way, and
the base contacts (6) are not connected among each other or are exclusively by the base area (2),
in an electrically conductive way.
2. Solar cell according to Claim 1,
characterized in that
the emitter contacts (5) are each arranged and constructed such that, around each of the emitter
contacts (5), an imaginary convex surface area can be defined that completely contains the
emitter contact and contains none of the base contacts (6) and also no sub-area of a base contact,
and
the base contacts (6) are each arranged and constructed such that, around each of the base
contacts (6), an imaginary convex surface area can be defined that completely contains the base
contact (6) and contains none of the emitter contacts (5) and also no sub-area of an emitter
contact (5).
3. Solar cell according to at least one of the preceding claims,
characterized in that
the solar cell has a plurality of the emitter contacts and/or the base contacts (5, 6) according to
the construction according to the invention, especially at least 10, advantageously at least 100,
furthermore at least 1000 of the emitter contacts and the base contacts.
4. Solar cell according to at least one of the preceding claims,
characterized in that
the emitter contacts and the base contacts (5, 6) are arranged and constructed such that
for each of the emitter contacts (5) it is valid that at least this complete emitter contact (5) and at
least one complete base contact (6) lie within an imaginary circle (8) with diameter d1 and
for each of the base contacts (6) it is valid that at least this complete base contact (6) and at least
one complete emitter contact (5) lie within an imaginary circle (8) with diameter d1,
wherein the diameter d1 fulfills the following condition according to Formula 1:

with a scaling factor k1 and a surface area Ak [cm2] of the contacting side (1) of the solar cell and
k1 =0.13, advantageously, k1 = 0.06, especially k1 = 0.03, more advantageously k1 = 0.014.
5. Solar cell according to one of the preceding claims,
characterized in that
the emitter contacts (5) are arranged and constructed such that
for each of the emitter contacts (5) it is valid that at least this complete emitter contact (5) and at
least one other complete emitter contact (5) lie within an imaginary circle (9) with diameter d2
and/or
the base contacts (6) are arranged and constructed such that
for each of the base contact (6) at least this complete base contact (6) and at least one other
complete base contact (6) lie within an imaginary circle (9) with diameter d2,
wherein the diameter d2 fulfills the following condition according to Formula 2:

with a scaling factor k2 and the surface area Ak [cm2] of the contacting side (1) of the solar cell
and k2 = 0.26, advantageously k2 = 0.13, especially k2 = 0.06, more advantageously k2 = 0.028.
6. Solar cell according to at least one of the preceding claims,
characterized in that
the emitter contacts (5) and the base contacts (6) are arranged on crossing points of an imaginary,
square lattice (G), wherein the emitter contacts and the base contacts (5, 6) are arranged such that
the emitter contacts and the base contacts (5, 6) alternate along each line of the imaginary lattice.
7. Solar cell according to Claim 6,
characterized in that
the solar cell has a square contacting side (1) and the imaginary lattice (G) is arranged such that
lattice lines stand at an angle of 45° relative to edges of the contacting side (1).
8. Solar cell according to at least one of the preceding claims,
characterized in that
the emitter contacts (5) among each other and likewise the base contacts (6) among each other
have a spacing of less than 1 cm, especially less than 5 mm.
9. Solar cell according to at least one of the preceding claims,
characterized in that
the emitter contacts and the base contacts (5, 6) are constructed such that each of the contacts
covers a total surface area less than 16 mm2, advantageously less than 5 mm2, especially less
than 1 mm , more advantageously less than 0.4 mm .
10. Solar cell according to at least one of the preceding claims,
characterized in that
on the contacting side (1), the semiconductor structure has an electrically non-conductive
insulation layer (4) that has, at locations of the base contacts and the emitter contacts (5),
recesses and
the base contacts and the emitter contacts (6, 5) are arranged on the insulation layer (4) and
electrical connections pass through recesses in the insulation layer (4) for electrical contacting of
the semiconductor structure.
11. Solar cell according to Claim 10,
characterized in that
the recesses of the insulation layer (4) have a surface area less than 16 mm2, advantageously less
than 5 mm2, especially less than 1 mm2, more advantageously less than 0.4 mm2.
12. Solar cell according to Claim 11,
characterized in that
the base contacts and the emitter contacts (6, 5) on the insulation layer (4) each cover an area
with a surface area less than 16 mm2, advantageously less than 5 mm2, especially less than 1
mm2, more advantageously less than 0.4 mm .
13. Solar cell according to at least one of the preceding claims,
characterized in that
the emitter contacts (5) are divided into groups, wherein each of the groups (11) comprises a
number of at least 2 emitter contacts and a maximum of 30, especially a maximum of 20,
advantageously a maximum of 10 emitter contacts and the emitter contacts (5) of one of the
groups are connected in an electrically conductive way via a metallization, whereas the different
groups of emitter contacts (11) are not connected or are exclusively connected in an electrically
conductive way among each other only via the emitter area (3), and
the base contacts (6) are divided into groups (10), wherein each of the group comprises a number
of at least 2 base contacts and a maximum of 30, especially a maximum of 20, advantageously a
maximum of 10 base contacts and the base contacts (6) of one of the groups (10) are connected
in an electrically conductive way via a metallization, whereas the different groups of base
contacts (10) are not connected or are exclusively connected in an electrically conductive way
among each other only via the base area (2).
14. Solar cell according to Claim 13,
characterized in that
the groups of the emitter contacts and base contacts (11, 10) are arranged and constructed such
that
for each group of the emitter contacts (11), at least this complete group of the emitter contacts
(11) and at least one complete group of the base contacts (10) lie within an imaginary circle (12)
with diameter d3 and
for each group of the base contacts (10), at least this complete group of the base contacts (10)
and at least one complete group of emitter contacts (11) lie within an imaginary circle (12) with
diameter d3,
wherein the diameter d3 fulfills the following condition according to Formula 3:

with a scaling factor k3 and the surface area AK [cm2] of the contacting side (1) of the solar cell
and
k3 = 0.40, advantageously k3 = 0.26, especially k3 = 0.10, more advantageously k3 = 0.056.
15. Solar cell according to at least one of the preceding Claims 13 to 14,
characterized in that
the groups of emitter contacts (11) are arranged and constructed such that
for each group of the emitter contacts, at least this complete group of the emitter contacts (11)
and at least one other complete group of the emitter contacts lie within an imaginary circle (13)
with diameter d4 and/or
the groups of the base contacts (10) are arranged and constructed such that
for each group of the base contacts (10), at least this complete group of the base contacts (10)
and at least one other complete group of the base contacts lie within an imaginary circle (13)
with diameter d4,
wherein the diameter d4 fulfills the following condition according to Formula 4:

with a scaling factor k4 and the surface area Ak [cm2] of the contacting side (1) of the solar cell
and
k4 = 0.80, advantageously k4 = 0.51, especially k4 = 0.20, more advantageously k4 = 0.112.
16. Solar cell according to at least one of the preceding claims,
characterized in that
the solar-cell structure corresponds to a basic design of a back-side contact cell ("RCC") or an
emitter-wrap-through solar cell ("EWT") or a metal-wrap-through solar cell ("MWT").
17. Solar cell according to at least one of the preceding claims,
characterized in that
the solar cell has at least 10, especially at least 100, advantageously at least 1000 of the emitter
contacts and/or the base contacts (5, 6).
18. Solar cell according to at least one of the preceding claims,
characterized in that
only one sub-area of the solar cell is constructed according to the preceding claims, wherein the
sub-area comprises at least 70%, especially at least 80%, furthermore at least 95% of the surface
area of a contacting side (1) of the solar cell.
19. Solar-cell module,
comprising at least one first and one second solar cell each according to at least one of the
preceding claims, as well as at least one cell connector,
wherein the first solar cell is arranged in the solar-cell module next to the second solar cell and
the cell connector (7) is arranged and constructed on the contacting side (1) of the first and the
second solar cell such that the emitter contacts (5) of the first solar cell are connected in an
electrically conductive way to the base contacts of the second solar cell or vice versa.
20. Solar-cell module according to Claim 19,
characterized in that
the cell connector (7) is constructed as a circuit board or flexibly, especially like a film (21, 26).
21. Solar-cell module according to at least one of Claims 19 to 20,
characterized in that
the solar-cell module comprises at least two solar cells arranged one next to the other in a row,
each according to at least one of the preceding Claims 2 to 9, and the cell connector (7) has
comb-like, interdigitated metallization structures (7a, 7b, 7c, 7d) that are arranged such that, for
the solar cells arranged in the row with the contacting side (1) on the cell connector (7), the
emitter contacts (5) of one of the solar cells are connected in an electrically conductive way to
the base contacts of the adjacent solar cell via the comb-like metallization structure.
22. Solar-cell module according to at least one of Claims 19 to 20,
characterized in that
the cell connector is constructed as an electrically insulating film (21, 26),
the film has, on the side facing the solar cell for modular interconnection, a first metallic
connection structure (27) and, on the side facing away from the solar cell, a second metallic
connection structure (28) and
the second metallic connection structure is guided through recesses (25) of the film and the first
metallic connection structure to the other side,
wherein the metallic connection structures are arranged such that, for solar cells arranged with
the contacting side (1) on the film, the base contacts (6) of the solar cells are each connected in
an electrically conductive way via the recesses to the one metallic connection structure and the
emitter contacts (5) of the solar cells are each connected in an electrically conductive way to the
other metallic connection structure.
23. Solar-cell module according to at least one of Claims 19 to 20,
characterized in that
the cell connector is constructed as a field of electrically conductive wires arranged essentially
parallel and the solar cells are arranged on the wires such that the emitter contacts (5) of one of
the solar cells are connected in an electrically conductive way by the wires to the base contacts
(6) of the adjacent solar cell.
24. Solar-cell module according to at least one of Claims 19 to 23,
characterized in that
the cell connector has recesses (23) for the application of a vacuum for component insertion of
the cell connector with the solar cells.

A solar cell, in particular for connecting to a solar cell module, including at least one
metallic base contact, at least one metallic emitter contact (5) and a semi-conductor
structure having at least one base area and at least one emitter area (3). The base
area and emitter area (2,3) are at least partially adjacent to each other forming a
pn-junction, the base contact (6) being connected in an electrically conductive
manner to the base area (2), the emitter contact (5) being connected in an
electrically conductive manner to the emitter area (3), and the solar cells being
arranged on the contact side (1) as a base and emitter contact (6,5). Essentially,
the solar cell includes several metallic emitter contacts which are connected in an
electrically conductive manner to the emitter area (3) and several metallic base
contacts which are connected in an electrically conductive manner to the base area
(2). The emitter contacts (5) do not have an electrically conductive connections
among each other on the side facing away from the emitter area (3) and the base
contacts do not have an electrically conductive connections on the side facing away
from the base area (2). A solar cell module including at least two solar cells is also
provided.