EP4591365A1 - Solar module with three-terminal tandem solar cells - Google Patents

Abstract

The invention relates to a solar module (19) and a solar installation (37) made of multiple solar modules. The solar module has multiple 3TT solar cells (11), which are wired together in order to form at least one string (21), and at least two current input connections (27) at a current input of the solar module and/or at least two current output connections (29) at a current output of the solar module. Each 3TT solar cell has a stack comprising a top cell (3) and a bottom cell (5) arranged under the top cell, and each 3TT solar cell has a top contact (13), a bottom contact (15), and a central tap contact (17) as terminal contacts. A first current input connection (27') of the current input connections (27) is at least connected to one of the terminal contacts of a first 3TT solar cell (11') lying closest to the current input, and a second current input connection (27") of the current input connections (27) is at least connected to one of the terminal contacts of a second 3TT solar cell adjoining the first 3TT solar cell, and/or a first current output connection (29') of the current output connections is at least connected to one of the terminal contacts of a final 3TT solar cell (11") lying closest to the current output, and a second current output connection (29") of the current output connections is at least connected to one of the terminal contacts of a penultimate 3TT solar cell adjoining the final 3TT solar cell. The aforementioned wiring allows, among others, a substantial prevention of string end losses as well as an advantageous integration of bypass diodes (33, 35).

Description

SOLAR MODULE WITH 3-TERMINAL TANDEM SOLAR CELLS

FIELD OF THE INVENTION

The present invention relates to a solar module with tandem solar cells.

TECHNICAL BACKGROUND

Solar modules are used to convert light, particularly that emitted by the sun, into electrical energy. Such solar modules are also referred to as photovoltaic modules or PV modules. A solar module comprises a large number of solar cells connected in series and/or parallel. The solar module also conventionally has a power input connection and a power output connection in order to be able to connect the solar module with other solar modules in series and/or parallel to form a solar system and ultimately to be able to supply the electrical energy generated in the solar module to an external circuit with consumers connected to it.

Traditionally, solar cells have typically been used in solar modules, in which pairs of charge carriers that were generated by absorption of incident light are separated at a single potential difference generated, for example, by a pn junction. The performance or efficiency of the solar cells depends, among other things, on the potential difference and thus on the (semiconductor) material used to generate the potential difference. The efficiency of the solar cells is limited, among other things, by the fact that, depending on a band gap of the semiconductor material used, a low-energy portion of the irradiated light cannot be absorbed and a high-energy portion can only be converted into electrical energy with considerable energy losses. In order to increase the efficiency of solar cells, solar cells were developed in which two or more partial solar cells are stacked on top of each other. Such solar cells are referred to as tandem solar cells or sometimes as multi-junction solar cells or stacked solar cells. The two partial solar cells differ in terms of their materials and therefore their band gaps. A partial solar cell facing the incident light, which is also referred to as a top cell, typically has a larger band gap and is therefore designed to absorb and convert a high-energy portion of the incident light with relatively little energy loss. A further partial solar cell arranged underneath, which is also referred to as a bottom cell, then has a smaller band gap and is therefore designed to absorb and convert a low-energy portion of the irradiated light with relatively little loss.

Tandem solar cells are preferably monolithic. This means that a tandem solar cell is designed as a single component in which all components, such as various semiconductor layers and contacts, are firmly connected to one another. For this purpose, several layers can be deposited on top of one another over the entire surface and/or in partial areas. The tandem solar cell has at least two terminal contacts, but in some implementations, as explained below, three, four or more terminal contacts. A terminal contact is understood to be an electrical contact on the tandem solar cell that is accessible from the outside and via which the solar cell or its partial solar cells can be electrically connected to other solar cells or their partial solar cells.

Various wiring configurations are known for tandem solar cells.

So-called 2-terminal tandem solar cells, also referred to as 2TT solar cells, have only two terminal contacts, with a so-called top contact typically being provided on a front side and a so-called bottom contact on a back side of the tandem solar cell. Such 2TT solar cells are easy to connect in a solar module, i.e. essentially like conventional non-tandem solar cells. However, the fact that a total current that flows through the 2TT solar cell must be the same for both partial solar cells means that this is limited by the weaker of the two partial solar cells. Accordingly, losses due to current mismatch occur regularly. The reason for this can be, on the one hand, that the band gaps of the two partial solar cells are caused by technological framework conditions are not optimally chosen and one partial solar cell generates a higher current than the other, with the lower current of the weaker partial solar cell then limiting the total current of the tandem solar cell. On the other hand, even if the band gaps are optimally selected, current mismatch effects can occur due to a change in the irradiated light spectrum.

Losses due to current mismatches can be largely avoided if the individual solar cells of the tandem solar cells can be contacted and connected separately. For this purpose, a tandem solar cell can have four terminal contacts, i.e. be designed as a so-called 4TT solar cell. Each individual partial solar cell has its own two terminal contacts and can therefore be operated at its optimal operating point independently of the other partial solar cell. However, all partial solar cells must be processed, contacted and connected separately, which requires increased effort and increased optical shading can occur.

As a sort of middle ground between the 2TT solar cells and the 4TT solar cells, tandem solar cells with three terminal contacts were developed, which are accordingly referred to as 3TT solar cells. In addition to a top contact and a bottom contact, 3TT solar cells have an additional terminal contact, which is referred to as a center tap contact. The center tap contact contacts both the top cell as a second terminal contact in addition to the top contact and the bottom cell as a second terminal contact in addition to the bottom contact. On the one hand, 3TT solar cells allow electrical interconnection within a solar module, in which losses due to mismatches in the current can be significantly reduced. On the other hand, connecting the 3TT solar cells within the module can be less complex than with 4TT solar cells and/or losses due to optical shading due to a large number of terminal contacts can be lower than with 4TT solar cells.

3TT solar cells and solar modules constructed with them have been studied both theoretically and experimentally for a long time. Considerations and findings on their internal structure as well as their arrangement and interconnection in solar modules are presented, among others, in the documents listed below, some of which are referenced in the following text: [1] Sakai, S. and Umeno, M., “Theoretical analysis of new wavelength-division solar cells,” Journal of Applied Physics, vol. 51, no. 9, pp. 5018-5024, 1980. [2] Gee, JM, “A comparison of different module configurations for multi-band-gap solar cells,” Solar Cells, vol. 24, no. 1-2, pp. 147-155, 1988.

[3] Jimeno, J.C., Gutierrez, R., Fano, V., Habib, A., del Canizo, C., Rasool, M.A., and Otaegi, A., “A 3 terminal parallel connected silicon tandem solar cell,” Energy Procedia, vol. 92, pp. 644-651, 2016.

[4] Nagashima, T., Okumura, K., Murata, K., and Kimura, Y., “Three-terminal tandem solar cells with a back-contact type bottom cell,” 2000. In Proceedings of the 28th IEEE PVSC , 1193-96. http://ieeexplore.ieee. org/servlet/opac?punumber=7320.

[5] McMahon, William; Schulte-Huxel, Henning; Buencuerpo, Jeronimo; Geisz, John; Young, Michelle; Klein, Talysa et al. (2021): Homogenous Voltage-Matched Strings Using Three-Terminal Tandem Solar Cells: Fundamentals and End Losses. In: IEEE J. Photovoltaics 11 (4), pp. 1078-1086. DOI: 10.1109/JPHOTOV.2021.3068325.

[6] Jimeno Cuesta, J., Luque Lopez, A., Recart Baranano, F., Lago Aurrekoetxea, R, Gutierrez Serrano, R, Varner, K., Ikaran Salegi, C. et al. “Photovoltaic device and photovoltaic panel,” WO/2011/045462, filed Oct. 14, 2010, issued Apr. 21, 2011.

[7] Borden, P. G. “Three-terminal solar cell circuit,” US4513168 A, filed April 19, 1984, issued April 23, 1985.

[8] H. Uzu, G. Koizumi, “SOLAR CELL MODULE”, WO/2020/196288, March 19, 2020, issued October 1, 2020.

[9] E. L. Warren et al., “A taxonomy for three-terminal tandem solar cells,” ACS Energy Lett., vol. 5, no. 4, pp. 1233-1242, Apr. 2020

[10] M. Zehnder et al., “Module interconnection for the three-terminal heterojunction bipolar transistor solar cell,” AIP Conference Proceedings 2012, 040013 (2018); https://doi.org/10.1063/L5053521, Published Online: September 13, 2018

[11] H. Schulte-Huxel et al., “String-Level Modeling of Two, Three, and Four Terminal Si-Based Tandem Modules,” IEEE JOURNAL OF PHOTOVOLTAICS, VOL. 8, NO. 5, SEPTEMBER 2018, p. 1370 - 1375

[12] R. Witteck et al., “Partial shading of one solar cell in a photovoltaic module with 3-terminal cell interconnection,” Solar Energy Materials & Solar Cells 219 (2021) 110811

It has been observed that efficiencies or power yields in solar modules constructed with 3TT solar cells can be suboptimal, ie in particular they can be lower than would be expected based on the efficiencies of the individual solar cells and the number of solar cells in a solar module. SUMMARY OF THE INVENTION AND EMBODIMENTS

There may therefore be a need for solar modules that enable higher efficiencies or power outputs. In particular, there may be a need for solar modules based on 3TT solar cells, in which a high efficiency of the individual solar cells leads to a high efficiency of the entire solar module due to a suitably selected configuration of the solar cells within the solar module. Furthermore, there may be a need for a highly efficient solar system with such solar modules.

The stated needs can be at least partially met with the subject matter of one of the independent claims of the present application. Advantageous embodiments are specified in the dependent claims as well as the following description and the figures.

According to a first aspect of the present invention, a solar module is described which has a plurality of 3TT solar cells and at least two power input connections on a power input of the module and/or at least two power output connections on a power output of the module. The 3TT solar cells are connected to each other to form at least one string. Each 3TT solar cell has a stack with a top cell and a bottom cell arranged underneath, the top cell and the bottom cell differing from each other in terms of an electrical voltage generated when irradiated with light. Each 3TT solar cell has three terminal contacts with a top contact, which electrically contacts a side of the top cell facing away from the bottom cell, a bottom contact, which electrically contacts a side of the bottom cell facing away from the top cell, and a center tap contact, which connects the 3TT solar cell to an interface electrically contacted between the top cell and the bottom cell. A first of the power input connections is connected to at least one of the terminal contacts of a first of the 3TT solar cells closest to the power input and a second of the power input connections is connected to at least one of the terminal contacts of a second of the 3TT solar cells adjacent to the first 3TT solar cell. Furthermore, a first of the current output connections is connected to at least one of the terminal contacts of a last of the 3TT solar cells closest to the current output and a second of the current output connections is connected to at least one of the terminal contacts of a penultimate of the 3TT solar cells adjacent to the last 3TT solar cell. According to a second aspect of the present invention, a solar system is described which has a plurality of solar modules according to an embodiment of the first aspect of the invention, with each of the power output connections of one of the solar modules being electrically connected to an assigned power input connection of the adjacent one of the solar modules in neighboring solar modules.

In the introduction, a basic idea for embodiments of the invention described herein will be briefly explained, whereby this explanation is to be interpreted as merely a rough summary and not restrictive of the invention:

The present invention describes in particular a solar module in which, due to a special type of arrangement and interconnection of the 3TT solar cells accommodated therein, losses, in particular so-called string-end losses, such as those in conventional solar modules in which the 3TT solar cells are arranged in a conventional manner and are connected, occur, can largely be avoided. As explained in more detail below, a main feature of the solar module presented here can be seen in the fact that the solar module does not only have a single power input connection and a single power output connection, as is usually the case with conventional solar modules, but rather two or more such power input connections and power output connections and these connections are connected in a specific way to the 3TT solar cells within the solar module. Due to the special type of interconnection and the plurality of current input connections and current output connections, it is no longer possible for string end losses due to partial solar cells, which due to the interconnection do not contribute to the efficiency of the module or do not contribute to an optimal extent to the efficiency of the module, to occur on every interconnected solar cell string , ie at least once in every solar module. Instead, a large number of solar modules can be interconnected in such a way that corresponding end losses are only caused once in the entire large number of solar modules and thus have a significantly smaller reducing influence on the overall efficiency of a solar system. In addition, an embodiment of a solar module with 3TT solar cells is described, in which a suitable connection of bypass diodes ensures the reliable operation of the solar module and at the same time enables the aforementioned end losses to be avoided. Possible configurations and advantages of embodiments of the solar module and a method for producing it are described in more detail below:

A solar module as described here includes a large number of solar cells in the form of 3TT solar cells. For example, the solar module typically comprises more than ten solar cells, usually more than 50 solar cells, but usually less than 300 solar cells, usually less than 150 solar cells. Each individual solar cell is a flat diode, with an area typically between 10 cm ² and 1000 cm ² , usually between 100 cm ² and 500 cm ² . A thickness of a solar cell is typically in the range between 10 pm and 1000 pm, usually between 50 pm and 400 pm. At least part of the solar cell can be formed on the basis of a crystalline, that is to say monocrystalline, multicrystalline or polycrystalline, semiconductor substrate such as a silicon wafer. Alternatively or additionally, part of the solar cell can be formed with amorphous semiconductor material, for example in the form of one or more thin layers.

The solar cells are connected to one or more strings. The entire solar cells or the partial solar cells forming these solar cells can be connected in series and/or parallel to one another. A string here is understood to be a smallest unit made up of a plurality of solar cells connected to one another, whereby the entire solar module can comprise several such strings connected to one another in series and/or parallel. A number of solar cells that are combined in a string can depend on various influencing factors. In particular, this number is typically chosen such that an electrical voltage generated by the string when illuminated does not exceed a reverse voltage strength of each of the solar cells in the string. Typically, such strings comprise between three and 50 solar cells connected in series, usually between six and 30 solar cells connected in series.

The 3TT solar cells installed in the solar module consist of a first partial solar cell and a second partial solar cell. The first partial solar cell is arranged on a side of the solar cell that faces the incident light during use, which is considered to be the upper side, which is why this first partial solar cell is referred to as the top cell. The second partial solar cell is arranged below the first partial solar cell and is therefore referred to as the bottom cell. Each of the partial solar cells can in turn be connected via a single pn junction or Application of special cell concepts with several pn junctions, which are preferably located one behind the other along the direction of light incidence.

The top cell and the bottom cell differ in terms of the semiconductor materials that form them. For example, the semiconductor material of the top cell typically has a larger energy band gap than that of the bottom cell, with the two band gaps being able to differ in magnitude from one another by, for example, more than 20%, preferably more than 40% or even more than 80%. Due to the different band gaps, different electrical voltages arise in the two partial solar cells when illuminated at a potential difference formed therein by suitable local doping (for example due to a respective pn junction). In other words, the open-circuit voltages (which are sometimes also referred to as open-terminal voltages Voc) differ significantly in the top cell and the bottom cell. For example, the Voc of the top cell may be 30% or more, 50% or more, or even 100% or more greater than that of the bottom cell.

Each 3TT solar cell has exactly three terminal contacts through which it is connected to other 3TT solar cells. A terminal contact is generally formed by an electrically conductive layer, such as a metal layer, which is attached to the solar cell or integrated into the solar cell. A terminal contact can be formed with a single layer, but the terminal contact can also be composed of a plurality of sub-areas or sub-layers.

The three terminal contacts can be configured according to a convention described by Warren et al. (see document [9] in the list of documents mentioned in the introduction to the description). A first contact is typically arranged on a front surface of the solar cell that faces the incident light and electrically contacts that side of the top cell that faces away from the bottom cell (whereby “electrical contact” herein generally means direct electrical contact, ie without Interposition of other electrical components should be understood, ie in particular an ohmic contact). The first contact is referred to herein as the top contact, but may also be referred to as a T-contact (with “T” for top) according to Warren convention. A second contact is typically arranged on a back surface of the solar cell facing away from the incident light and electrically contacts that side of the bottom cell, which faces away from the top cell. The second contact is referred to herein as the bottom contact, but may also be referred to as the R contact (with "R" for raiz or root) following Warren's convention. A third contact can be arranged, for example, in a plane between the top cell and the bottom cell. However, as stated in more detail below, the third contact can also be spatially arranged on the back surface of the solar cell, wherein the bottom cell and the third contact can be designed in such a way that via the third contact there is an interface between the top cell and the bottom cell prevailing electrical current can be derived. In both cases, the third contact electrically contacts the interface between the top cell and the bottom cell. In doing so, it electrically contacts a side of the bottom cell, which is opposite to the side contacted by the bottom contact and has an opposite polarity relative to the area of the bottom cell contacted by the bottom contact, so that a voltage generated at the bottom cell is tapped via the bottom contact and the third contact can. In addition, the third contact electrically contacts a side of the top cell which is opposite to the side contacted by the top contact and has an opposite polarity relative to the area of the top cell contacted by the top contact, so that a voltage is generated at the top cell via the top contact and the third contact can be tapped. The third contact is referred to herein as the center tap contact, but may also be referred to as the Z contact (with "Z" for additional) according to Warren's convention.

In conventional solar modules, each individual solar module typically has only one power input connection and only one power output connection, via which the solar cells integrated in the solar module can be connected to an external circuit. Several solar modules can be connected to one another in series and/or parallel via their individual power input connections and power output connections in order to form a solar system overall.

In contrast to this, the solar module described herein should have at least two power input connections and/or at least two power output connections. Preferably, each solar module should have at least two power input connections and two power output connections. At least theoretically, however, it is conceivable that a solar module, which serves as the first solar module within a solar system, only has one power input connection but two power output connections or a solar module, which serves as the last solar module within a solar system, has two power input connections but only one power output connection.

The power input connections and power output connections are electrically connected in a special way to the terminal contacts of the various solar cells within the solar module.

In particular, a first power input connection is electrically connected to at least one of the terminal contacts of that solar cell that is closest to the power input in the solar module, that is, which has no further solar cell connected upstream on the power input side and which can therefore be viewed as the first solar cell of the solar module. A second power input connection is electrically connected to at least one of the terminal contacts of that solar cell that is adjacent to the first solar cell, i.e. to the second solar cell within the solar module. The first and second solar cells are components of one and the same string. Preferably, the first power input connection is directly electrically connected exclusively to the first solar cell. The second power input connection can only be electrically connected directly to the second solar cell. In addition, the second power input connection can also be connected to one of the terminal contacts of the first solar cell, although this terminal contact differs from the terminal contact to which the first power input connection is connected. Accordingly, there is no direct ohmic electrical connection between the first and second power input terminals.

In a similar manner, a first current output connection is connected to at least one of the terminal contacts of a last solar cell closest to the current output and a second current output connection is connected to at least one of the terminal contacts of a penultimate solar cell adjacent to the last solar cell. The last and the penultimate solar cell are components of one and the same string. In this case too, the first power output connection is preferably electrically connected directly exclusively to the last solar cell of the solar module. The second current output connection can only be electrically connected directly to the penultimate solar cell. In addition, the second current output connection can also be connected to one of the terminal contacts of the last solar cell, although this terminal contact is different from the terminal contact with which the first Power output connection is connected, differs. Accordingly, there is no direct ohmic electrical connection between the first and second current output connections.

The provision of at least two electrically separate power input connections and/or at least two separate power output connections and the special way in which these connections are connected to the various solar cells within the solar module enables, among other things, the various partial solar cells, i.e. the top cells and the bottom cells, within the solar module to be connected to one another in an advantageous manner such that within an entire solar system with several solar modules almost all partial solar cells can be operated optimally, i.e. contribute to the overall efficiency of the solar system. In particular, string end losses, such as those that typically occur in each individual solar module of a solar system or even in each individual string in conventional solar modules with 3TT solar cells, can be largely avoided or their occurrence can be limited to a first solar module and/or a last solar module within a solar system with a large number of solar modules. This is explained further below with reference to specific exemplary embodiments.

According to one embodiment, the top cell and the bottom cell of each of the 3TT solar cells are arranged in an r-type configuration with reverse polarity. Further, the first power input terminal is connected to the center tap contact of the first 3TT solar cell and the second power input terminal is connected to the center tap contact of the second solar cell. Alternatively or additionally, the first current output connection is connected to the top contact of the last 3TT solar cell and the second current output connection is connected to the top contact of the penultimate 3TT solar cell.

In other words, in this embodiment, the top cell and the bottom cell of a 3TT solar cell are aligned with opposite polarities, that is, for example, the forward direction of the top cell is directed from the center tap contact toward the top contact and the forward direction of the bottom cell is directed from the center tap contact toward the bottom contact. Such a configuration is also referred to as an r-type configuration, where “r” stands for “reverse”. In contrast, in a so-called s-type configuration, the top solar cell and the bottom solar cell are aligned in the same way and are therefore connected in series. The r-type configuration enables a particularly advantageous connection for the solar modules described here of the 3TT solar cells with each other and with the at least two power input connections or at least two power output connections.

In particular, in this case, the first power input connection can preferably be electrically contacted exclusively with the center tap contact of the first 3TT solar cell of the solar module. The second power input connection is then electrically contacted with the center tap contact of the second 3TT solar cell of the solar module, wherein this second power input connection can also be electrically contacted with the bottom contact of the first 3TT solar cell. Alternatively or additionally, the first power output connection is preferably electrically contacted exclusively with the top contact of the last 3TT solar cell of the solar module. The second current output connection is then electrically contacted with the top contact of the penultimate 3TT solar cell of the solar module, whereby this second current output connection can also be electrically contacted with the bottom contact of the last 3TT solar cell of the solar module.

The r-type configuration described, together with the special way of connecting the connections, makes it possible to connect the 3TT solar cells to one another and to the multiple input and output connections in an advantageous manner, in particular in a manner with relatively few electrical lines required to interconnect so that the occurrence of losses, in particular the occurrence of string end losses, can be largely limited.

This is particularly true in the case that the electrical voltages generated by the top cells and the electrical voltages generated by the bottom cells have a certain relationship to one another.

For example, according to one embodiment, the electrical voltage of the top cell generated when irradiated with light and the electrical voltage of the bottom cell generated when irradiated with light can essentially be in a ratio of m to n, m and n being natural numbers. “Substantially” can be understood here, for example, to mean that the ratio of the electrical voltages actually occurring in the top cell and the bottom cell differs from a ratio (m: n), for example by less than 25%, preferably less than 15%, more preferably less than 5%. In this case, n top cells connected in series can be connected in parallel to m bottom cells connected in series. In other words, the top cell and the bottom cell can be designed, for example due to a suitable choice of materials and/or dopings used to produce them, in such a way that their electrical voltages generated under common illumination, ie preferably their electrical voltages V _mp p at the point of maximum power, im Essentially have an integer ratio to each other. Accordingly, the n top cells connected in series can generate essentially the same voltage under illumination as the m bottom cells connected in parallel in series with one another. The described adjustment of the voltages between the partial solar cells is also referred to as voltage matching of the strings.

According to a specific embodiment, m>2 and n>1 can be. A number of the current input connections and/or a number of the current output connections then corresponds (in the case of an r-type configuration) to a larger of the two values m and n or is larger (in the case of an s-type configuration) to the larger of the two values m and n.

In other words, a number of the power input terminals and/or power output terminals provided on the solar module can correlate with the way in which the top cells and the bottom cells are matched with respect to the electrical voltages they generate and can thus be matched in groups of several series-connected top cells in parallel with groups of several series-connected bottom cells.

According to a specific embodiment, for example m=2 and n=1. In this case, with the exception of the last 3TT solar cell, each bottom contact of a solar cell can be connected to the center tap contact of the next adjacent 3TT solar cell, and, with the exception of the last and the penultimate 3TT solar cell, each top contact of a solar cell can be connected to the center tap contact of the be connected to the next but one subsequent 3TT solar cell.

Such coordination of the voltages generated by the top cells and bottom cells in a ratio of (2:1) together with the described interconnection of the top cells and bottom cells of the several 3TT solar cells with one another can result in a particularly simple overall interconnection within the solar module while at the same time being highly efficient due to the avoidance of losses , especially final losses. According to one embodiment, a first bypass diode is connected in parallel to the 3TT solar cells of the string in each of the strings. Furthermore, in each of the strings, a second bypass diode is connected in parallel to the top cell of a last 3TT solar cell in the string.

Like all diodes, bypass diodes only allow a significant flow of current in one direction, i.e. in their forward direction. In solar modules, bypass diodes are typically connected anti-parallel to the solar cells, e.g. of a string, so that in normal operating mode, i.e. when all solar cells are functioning correctly and generating electricity, they are polarized in the reverse direction. However, if one (or more) of the solar cells does not deliver any current, for example due to shading, it acts like an electrical consumer. The current generated by the other solar cells would have to flow through this consumer, which can generate considerable heat and lead to so-called hotspots. In addition, the total current flowing through a solar module generally depends on the weakest solar cell within the solar module, so that a single shaded solar cell could significantly limit the efficiency of the solar module. In order to avoid hotspots and reduced yields, bypass diodes in solar modules are therefore typically connected anti-parallel to strings of solar cells connected in series. A blocking voltage of the bypass diode corresponds approximately to an open circuit voltage of the solar cells connected in the string.

In the solar modules made of 3TT solar cells described here, as explained above, the individual top cells and bottom cells of the multiple 3TT solar cells can be connected in such a way that a first number of top cells are connected in series with one another and a second number of bottom cells that are different from them are also connected in series, with both series connections being connected in parallel to one another. For example, the top cells of the 3TT solar cells can not be connected in series with the top cell of a next-to-next 3TT solar cell, but only with the top cell of the next-but-one 3TT solar cell. In this case, a first bypass diode can be connected in parallel to the 3TT solar cells of a string. However, the top cell of the last 3TT solar cell of the string is not protected by this first bypass diode in the connection described. Accordingly, it is advantageous to provide a separate, second bypass diode for this top cell, which is connected in parallel to this top cell. In principle, such a second bypass diode can have different properties than the first bypass diode, since it only has to protect a single top cell. For example, the blocking voltage of the second bypass diode can be lower than that of the first bypass diode. However, it can also be provided that all bypass diodes in the solar module are designed in the same way.

According to a specific embodiment, the first bypass diode can be electrically connected on the one hand to the center tap contact of the first 3TT solar cell of the string and on the other hand to the bottom contact or the top contact of the last 3TT solar cell of the string. Furthermore, the second bypass diode can be electrically connected on the one hand to the top contact or the bottom contact of the last 3TT solar cell of the string and on the other hand to the center tap contact of the last 3TT solar cell of the string.

Such a type of connection of the first and second bypass diodes can, as described below with reference to a specific exemplary embodiment, be particularly advantageous for an embodiment of the solar module in which the 3 TT solar cells are designed in an r-type configuration and with regard to the voltages of their top cells and bottom cells are coordinated with one another in a ratio of (2:1).

According to an alternative embodiment, the solar module can have at least one bypass diode connected across strings, the bypass diode connected across strings being connected, on the one hand, to a 3TT solar cell in front of the last 3TT solar cell (i.e., for example, a penultimate 3 TT solar cell) of an adjacent substring and, on the other hand, to the last solar cell of the substring to be saved.

In other words, a connection of bypass diodes to the 3TT solar cells can be designed in the solar module in such a way that at least one last 3TT solar cell in one of the substrings is connected to two bypass diodes, namely the bypass diode assigned to the substring in question and connected in parallel to it and the bypass diode assigned to an adjacent substring. The bypass diodes can be connected to the relevant 3TT solar cell in such a way that at least one of the two bypass diodes protects the bottom cell and at least the other of the two bypass diodes protects the top cell of this 3TT solar cell. In this way, it is preferable to provide a separate bypass diode only to protect a single top or bottom cell of an individual 3TT solar cell, as discussed above with the second bypass diode, can be avoided.

According to an alternative embodiment, the solar module can have at least one further power input connection and/or at least one further power output connection. At least one bypass diode that can be connected across modules is accommodated in the solar module. The bypass diode to be connected across modules can be connected on the one hand to the further power input connection and on the other hand to one of the terminal contacts, in particular the bottom contact, of one of the 3TT solar cells in the solar module. Alternatively or additionally, the center tap contact of the last 3TT solar cell of the solar module can be connected to the other power output connection.

With this design of the solar module, the previously described provision of a second bypass diode to protect the top cell of a last 3TT solar cell in a string can be dispensed with. Instead, this top cell can be protected by the or one of the first bypass diodes of the following string, i.e. a bypass diode connected in this way can work across strings. For this purpose, the subsequent first bypass diode contacts the last top cell of the previous string, for example in the case of the r-type configuration, contacting the center contact of the last cell in the string. However, if the top cell to be protected is that of the last 3TT solar cell not only within one of several strings in the solar module but also the very last 3TT solar cell in the entire solar module, this cannot be protected via a first bypass diode from the same solar module become. Instead, this top cell is protected using a first bypass diode from a neighboring solar module. In order to enable cross-module interconnection of the bypass diode, at least one further power input connection and/or at least one further power output connection is provided on the solar module, via which said top cell can be connected to the first bypass diode in an adjacent solar module. An explanatory example of such a design of the solar module is set out below.

According to a further specific embodiment, several 3TT solar cells are arranged side by side across the entire width of the solar module and are electrically connected to form a substring. The first bypass diode and, if present, the second bypass diode are each arranged laterally next to the substring. In other words, the solar module can be designed with regard to a geometric arrangement of the 3TT solar cells accommodated therein in such a way that several of the solar cells that form a substring are arranged side by side along the entire width of the solar module. The substring accordingly contains a relatively large number of solar cells connected in series.

This type of connection into cell-rich substrings is particularly suitable for the case where the individual partial solar cells each have a relatively high reverse voltage resistance. In this case, it can be advantageous to arrange the first and second bypass diodes laterally next to the substring, i.e. on an outer edge of the solar module. There, the bypass diodes can be particularly easily accessible and/or arranged in a space-saving manner, for example in the area of a frame of the solar module that locally covers the edge of the solar module.

According to an alternative, more specific embodiment, several 3TT solar cells are arranged laterally next to one another over a first half of the width of the solar module and are electrically connected to a first substring, and several other 3TT solar cells are arranged laterally next to one another and electrically over a second half of the width of the solar module connected to a second substring. The first substring and the second substring are connected in parallel to each other. Furthermore, the first bypass diode and, if present, the second bypass diode are each spatially arranged between the first substring and the second substring.

In other words, the solar module can be designed with regard to the geometric arrangement of the solar cells accommodated therein in such a way that only a relatively small number of solar cells are connected to form a substring. The solar cells connected to form a substring are geometrically arranged side by side in such a way that they only extend over half the width of the solar module. Two spatially adjacent substrings can therefore be arranged next to one another across the entire width of the solar module. The two substrings are preferably connected in parallel to one another.

Since with this type of interconnection the number of solar cells within a substring is relatively small, this configuration is particularly suitable for the case that at least some of the sub-solar cells have a relatively low reverse voltage resistance. In this case, it can be advantageous to geometrically sandwich the first and second bypass diodes the first substring and the second substring. The bypass diodes can therefore be arranged, for example, in or near a geometric center of the solar module. A single first bypass diode can be provided for the two substrings connected in parallel to one another, which in turn is connected in parallel to both substrings. Furthermore, a separate second bypass diode can be provided for each of the two substrings, with a second bypass diode being connected anti-parallel to the top cell of the last 3TT solar cell in one of the two substrings and a further second bypass diode being connected anti-parallel to the top cell of the last 3TT solar cell in the other of the two substrings is connected. Overall, due to the central arrangement of the bypass diodes between the substrings, a favorable overall circuit can be achieved in the solar module with, for example, short connection distances and correspondingly low electrical resistance losses.

According to a further specific embodiment, the first and, if present, the second bypass diode can be accommodated in a common diode box.

A diode box can be, for example, a housing in which the bypass diodes can be accommodated and through which the bypass diodes can be protected from environmental influences, for example. By accommodating both bypass diodes in a common diode box, the number of diode boxes required can be kept low. In addition, the design of the solar module with regard to the diode boxes to be provided therein can be the same or similar to that of conventional solar modules, in which there is only one bypass diode per solar cell string. Accordingly, the solar modules can be manufactured and/or assembled in the same way as conventional solar modules with regard to their diode boxes.

According to one embodiment, the top cell is a perovskite solar cell and the bottom cell is a silicon solar cell.

Silicon solar cells are known for their longevity, reliability and high efficiency. For example, silicon solar cells are commercially available that can reliably deliver an efficiency of well over 20% over a lifetime of 20 years or more. However, the efficiency of silicon solar cells is limited, among other things, by the fact that silicon has a relatively small band gap, so that high-energy light can generally only be converted into electrical energy with relatively high energy losses in the form of heat generation. More recently, perovskite solar cells have been developed that can now also deliver high levels of efficiency, although longevity and reliability depend heavily on the exact composition of the perovskites used. Perovskites generally have a significantly larger band gap than silicon, for example, so solar cells made from them are ideal for low-loss absorption of high-energy light.

Accordingly, perovskite solar cells are ideally suited to serve as partners for silicon solar cells in tandem solar cells and to be used there as top cells. The exact composition of the perovskites used correlates strongly with their band gap and thus indirectly with the open-circuit voltage supplied by the perovskite solar cell.

In the approach described here for a solar system, perovskite solar cells can be used as top cells in the 3TT solar cells and can be optimized in terms of their longevity and reliability, for example. The electrical voltage of the top cells that arises when illuminated depends on the perovskites used. Depending on the resulting electrical voltage, the interconnections within the solar module as well as the number of power input connections and power output connections can then be adjusted as described herein in order to be able to realize a favorable voltage matching between the top cells and the bottom cells within the solar module.

According to one embodiment, the bottom solar cell can be a back contact solar cell, in which terminal contacts of both polarities are arranged nested on a rear side of the bottom solar cell directed away from the top solar cell, with one of the terminal contacts of the bottom solar cell acting as the center tap contact.

Back contact solar cells, in which contacts of both polarities are arranged nested on a back side of a semiconductor substrate facing away from the light, have been known for a long time and are sometimes also referred to as IBC solar cells (interdigitated back contact). With suitable adaptation of the structures used in them, in particular the layer thicknesses, such back contact solar cells can be adapted in such a way that they function as a bottom cell in a tandem solar cell and the two types of contacts not only serve to extract the generated current from the bottom cell, but also one of the Contacts are also electrically connected to the top cell, for example via tunnel contacts, in such a way that the one generated in the top cell is also generated via it together with the top contact Electricity can be extracted. The contact mentioned acts as a center tap contact for the 3TT solar cell, but is not arranged spatially in the middle between the top cell and the bottom cell but rather on the back of the bottom cell. Corresponding concepts have already been presented, for example in the document [4] cited in the introduction to the description. Because the center tap contact is provided on the back of the bottom cell, it can be manufactured relatively easily and contacted from the outside. This makes it possible to significantly simplify the production of the 3TT solar cells and/or the interconnection of the 3TT solar cells within the solar module.

Embodiments of the solar modules described herein can be used to build a solar system according to the second aspect of the present invention. The property that each solar module has at least two power input connections and/or two power output connections can be used to interconnect adjacent solar modules in such a way that losses such as string end losses, such as those in conventionally designed and connected solar modules with 3TT - Solar cells occur can be largely avoided. For this purpose, each of the power output connections of one of the solar modules is electrically connected to an assigned power input connection of the neighboring solar module. In other words, for example, the first power output of a solar module is connected to the first power input of the neighboring solar module and the second power output of the solar module is connected to the second power input of the neighboring solar module.

In this way, as explained in more detail below using an exemplary embodiment, it can be avoided that in each of the solar modules at least one of the first 3TT solar cells closest to the power input and/or one of the last 3TT solar cells closest to the power output cannot be operated optimally and accordingly the final losses mentioned occur. Instead, due to the special interconnection proposed herein between adjacent solar modules via the at least two output and input connections, such end losses no longer occur in each individual solar module but ideally only in a first solar module and/or a last solar module of the entire solar system. Accordingly, the influence of these final losses on the efficiency of the entire solar system can be significantly reduced. According to one embodiment, with the exception of the power input connections of a first of the solar modules and the power output connections of a last of the solar modules, the power input connections of each of the solar modules are electrically separated from one another and the power output connections of each of the solar modules are also electrically separated from one another.

Furthermore, according to one embodiment, in a first of the solar modules the at least two power input terminals are electrically short-circuited or connected to one another and/or in a last of the solar modules the at least two power output terminals are electrically short-circuited or connected to one another.

In other words, each of the power input connections of a solar module is electrically connected to only one of the power output connections of the neighboring solar module, but not to the other power input connection of the same solar module or the other power output connection of the neighboring solar module. This preferably applies to all solar modules in the solar system with the exception of the first solar module and the last solar module. For these two solar modules, which are at opposite ends of the series connection of solar modules within the solar system, the power input connections of the first solar module and the power output connections of the last solar module are used to connect the entire solar system to a single external circuit. Accordingly, these two “extremal” power input connections and power output connections are electrically connected to one another. Accordingly, final losses cannot be avoided on the first solar module and the last solar module, but are avoided on all solar modules in between.

It should be noted that possible advantages and refinements of embodiments of the invention are described herein partly with reference to a solar module according to the invention or partly with reference to a solar system composed of several such solar modules. A person skilled in the art will recognize that the features described can be appropriately transferred, adapted, exchanged or modified in order to achieve further embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below with reference to the accompanying drawings, whereby neither the drawings nor the description are to be construed as limiting the invention.

Figs. l(a)-(d) illustrate a connection of 2TT solar cells, 4TT solar cells, 3TT solar cells in an s-type configuration and 3 TT solar cells in an r-type configuration.

Fig. 2(a) shows a schematic sectional view of a 3TT solar cell with a back contact solar cell as a bottom cell in an r-type configuration.

Fig. 2(b) shows a schematic sectional view of a 3TT solar cell with a back contact solar cell as a bottom cell in an s-type configuration.

Fig. 3 illustrates a conventional connection of 3TT solar cells in an r-type configuration with end losses occurring.

4 illustrates a circuit in a solar module according to the invention with 3TT solar cells in an r-type configuration, each with two separate power input and output connections and with several first and second bypass diodes.

Fig. 5 illustrates two solar modules connected to form a solar system according to the invention.

6 illustrates a connection in a solar module according to the invention with 3TT solar cells in an r-type configuration with a bypass diode connected across strings and with three separate current input and output connections to enable a bypass diode to be connected across modules.

Fig. 7 shows a geometric arrangement and connection of bypass diodes in a solar module according to the invention.

Fig. 8 shows an alternative geometric arrangement and connection of bypass diodes in a further solar module according to the invention.

The figures are only schematic and not to scale. In particular, it should be noted that the dimensions shown in the figures are not realistic are reproduced, but are only intended to illustrate basic principles. Same

Reference numerals designate features that are the same or have the same effect in the various figures.

DESCRIPTION OF PREFERRED EMBODIMENTS

Multiple, stacked or tandem solar cells 1, as shown in various configurations and circuits in the figures. l(a)-(d) are shown as partial areas of a respective solar module (19), offer the possibility of achieving significantly higher efficiencies than solar cells through the absorption of different spectral components in partial solar cells lying one above the other in the form of a top cell 3 and a bottom cell 5 with only one p-n junction.

If, as shown in Fig. 1(a), the partial solar cells 3, 5 are stacked on top of each other and connected in series to form 2-terminal tandem solar cells 7 (i.e. a cell with two connections or contacts), losses can occur Current mismatch occurs. The reasons for this are, on the one hand, that the band gaps of the two partial solar cells 3, 5 are usually not optimally selected due to technological conditions and one partial solar cell generates a higher current than the other. The lower partial cell current then limits the entire current of the 2TT solar cell. On the other hand, even if the band gaps are optimally selected, current mismatch effects can occur, for example due to a change in the irradiated spectrum.

Losses due to mismatching of the current can be avoided if the individual partial solar cells 3, 5 are contacted and connected separately, as shown in Fig. 1(b). For this purpose, a tandem solar cell 1 has four connections or contacts, i.e. two connections for each partial solar cell 3, 5 and is therefore referred to as a 4-terminal tandem solar cell 9. The respective partial solar cells 3, 5 can work at the optimal operating point. However, all partial solar cells must be processed, contacted and connected separately, which usually means increased effort and optical shading.

Tandem solar cells 1 with three terminal contacts, ie 3TT solar cells 11, as shown in Figs. 1(c) and 1(d), also make it possible to significantly reduce losses due to mismatching of the current. Fig. 1(c) shows a so-called s-type configuration in which the top cell 3 and the bottom cell 5 are polarized in the same direction and thus connected in series. Fig. 1(d) shows a so-called r-type configuration in which the top cell 3 and the bottom cell 5 are polarized in the opposite direction, ie “reverse”.

An attractive variant of a 3TT solar cell 11 offers the use of a bottom cell 5 as an IBC solar cell with two nested rear contacts and a contact on the front, which enables contact with the top cell 3. A concept for such a 3TT solar cell 11 is explained, for example, in the document [4] mentioned in the introduction to the description.

Figs. 2(a) and 2(b) show embodiments of such a 3TT solar cell 11, wherein the contact arrangement and designation are carried out according to the convention according to Warren et al. (see document [9] mentioned in the introduction to the description). Similar dopings are represented by a similar type of hatching in the figures. The 3TT solar cells can be manufactured in different types, which can be classified into "reverse" connection, i.e. as an r-type configuration as shown in Fig. 2(a), and "series" connection, i.e. as an s-type configuration as shown in Fig. 2(b). Due to the simpler connection, the "reverse" variant is mainly discussed below. The terminal contacts of the 3TT solar cells 11 are named according to their properties. The top contact 13 or T-contact is the only accessible contact on the top cell 3. The top contact 13 contacts the side of the top cell 3 facing away from the bottom cell 5. The bottom contact 15 or R-contact (for “raiz” or “root”) is the contact of the two rear contacts of the bottom cell 5 with the opposite polarity of the front contact of the bottom cell. The bottom contact 15 contacts the side of the bottom cell 5 facing away from the top cell 3. The center tap contact 17 or Z-contact (for “additional”) is the rear contact with the same polarity as the front of the bottom cell, i.e. the additional contact for extracting the charge carriers. The center tap contact thus electrically contacts a side of the bottom cell 5 which is opposite to the side contacted by the bottom contact 15 and has an opposite polarity relative to it. The center tap contact 17 is thus also able to extract charge carriers that were separated in the top cell 3 from the interface between the top cell 3 and the bottom cell 5. The center tap contact 17 can be arranged geometrically between the top cell 3 and the bottom cell 5, but in the case of a rear-side contact similar to an IBC solar cell, the center tap contact 17 can alternatively be arranged geometrically on the rear of the bottom cell 5, ie laterally adjacent to the bottom contact 15. and thereby act as electrically connected to the interface between the top cell 3 and the bottom cell 5.

In Figs. 2(a) and 2(b) additionally indicate the electrical voltages prevailing between the various terminal contacts 13, 15, 17. Vt _op is the voltage generated by the top cell 3 and Vbot is the voltage generated by the bottom cell 5. VRT is the voltage present between the bottom contact 15 and the top contact 13, VZT is the voltage present between the center tap contact 17 and the top contact 13 and VRZ is the voltage present between the bottom contact 15 and the center tap contact 17.

Advantages of 3TT solar cells include:

(i) solar modules formed with this can be operated as bifacial tandem modules in the open field, since the top and bottom solar cells do not have to have the same current. This avoids a major market entry hurdle, as the additional yield of tandem modules must not only be compared to monofacial silicon modules but also to bifacial silicon modules. These have an additional yield compared to monofacial PV modules with the same efficiency of approx. 5%-20% depending on the method of use and location;

(ii) low losses are possible when the band gap or voltage at the point of maximum power is not optimally adjusted. This allows the selection of the top cell 3 to be made with regard to other criteria such as the reliability or efficiency of the top cell;

(iii) the voltage per additional solar cell in a string of solar cells only increases by the voltage of the bottom cell and not by the combined voltage of the bottom plus top cell. This enables more photovoltaic modules per module string and therefore fewer cables are necessary in the system structure.

As in Figs. 1(c) and 1(d) illustrated as a partial view, 3TT solar cells 11 can be integrated into a solar module 19 through a combination of series and parallel connection. Since the top cells 3 generate a significantly higher voltage than the bottom cells 5, for example a single top cell 3 is connected in parallel to two bottom cells 5. For this purpose, a top contact 13, i.e. a contact of the top cell 3 facing away from the bottom cell 5, is led to a contact of the opposite polarity of the next but one 3TT solar cell 11, which is a center tap contact 17.

Since there is no 3TT solar cell 11 at the end of a string, losses occur there in the order of magnitude of the power of one to two 3TT solar cells, depending on Cell design or configuration and/or type of interconnection. The losses at the ends of the strings have been investigated theoretically, for example in the document mentioned in the introduction to the description [5], and the considerations for adjusting the voltage by interconnecting the cells have been discussed since the introduction of 3TT solar cells, for example in the document mentioned in the introduction to the description [2]. A possible way of interconnecting technology for 3T tandem PV modules was presented in the document [10]. There is therefore a practically implementable solution for interconnecting 3TT solar cells in the solar module. It is pointed out that instead of interconnecting 3TT solar cells by means of a common connector structure, to which different terminal contacts of the 3TT solar cells are then connected or interconnected using different methods, as described in document [10], continuous connectors can alternatively be used, by means of which typically neighboring solar cells within a module are contacted and interconnected, whereby a single connector is usually led from a front side of a 3TT solar cell to a back side of a neighboring 3TT solar cell.

Fig. 3 shows a possible conventional connection of 3TT solar cells 11 in a combination of series and parallel connection for module integration. There are two wiring ends 23 at both ends of a string 21. These are conventionally connected to one another by electrical connectors 25 in order to be able to extract the power generated by the string 21 from the solar module 19 at a power input connection 27 and a power output connection 29. In other words, the connectors 25 at each string end ensure that the current generated in the string 21 can be extracted from the string 21.

However, these connectors 25 short-circuit the bottom cell 5' of the first 3TT solar cell 11' of the string 21 (far left in FIG. 3) and its power is not extracted. Furthermore, at each string end, ie at the first 3TT solar cell 11' and the last 3TT solar cell 11", the top cell 3', 3" there is only operated at around 50% of its voltage. This leads to losses, also known as string-end losses, which in the case shown are equivalent to the output of approximately a 3TT solar cell. By connecting the wiring ends 23 with the connectors 25, a common bypass diode 31 can also be connected in parallel to all 3TT solar cells 11 of the string 21 including all top cells 3 and all bottom cells 5. This means that string end losses occur when integrating each bypass diode. This procedure results in a currently typical string length of 20 Cells suffer a power loss of around 5%, which often more than compensates for the advantage of 3TT solar cells over, for example, 2TT solar cells. In the case of perovskite solar cells, often only a small string length is possible per bypass diode and the influence of the final losses is therefore even greater.

With the approach discussed in this patent application, both methods are discussed to reduce the string end losses from a module level (with typically approx. 60 cells) or a substring level (typically a 1/3 module with approx. 20 cells) to one System level e.g. a solar system (typically with up to 2000 cells) in order to minimize their relative contribution, as well as an advantageous possibility of integrating bypass diodes.

In particular, embodiments of the invention address the following aspects:

(i) An electrical connection between solar modules to a solar system with, for example, a cable with two wires or with two cables;

(ii) An integration of bypass diodes without the need to bring together contacts or wiring ends at the end of strings;

(iii) A module design for modules in the middle and at the ends of strings through the external combination of the contacts (e.g. module contacts combined outside the module), e.g. through suitable plugs or connectors.

4 shows an embodiment of a solar module 19 according to the invention, in which 3TT solar cells 11 are wired to one another in a special way and to two power input connections 27 ', 27 "and two power output connections 29 ', 29". Furthermore, at least a first bypass diode 33 and a second bypass diode 35 are provided in each of two substrings 21′, 21″ shown as examples.

Fig. 5 illustrates how two solar modules 19 according to the invention can be connected to form a solar system 37 according to the invention. It is noted that real solar systems naturally generally comprise more than two solar modules 19, but that a principle of the wiring is clearly visible in this reduced example.

Regarding aspect (i) above, Figs. 4 and 5 all string ends of different potentials are led out to terminal contacts in the form of the two current input connections 27 and current output connections 29. This creates the substrings 21', 21" of several neighboring solar modules 19 are connected beyond the physical boundaries of the solar modules 1 to form an overall string. By connecting the solar modules 19 to one another via the two current input connections 27 and current output connections 29, it is possible to provide all top cells 3 in the overall string (with the exception of the top cell 3 of a very last 3TT solar cell 11) with a bottom cell 5 after that for parallel connection and to expand the interconnection concept beyond the module boundaries. As a result, the string end losses, as they would otherwise occur in each of the substrings 21 ', 21 "in parallel with a bypass diode 31 (ie with typically 20 or fewer cells each), are pushed to a system level (typically with up to 2000 and more cells) with a large number of interconnected solar modules 1, which reduces a relative contribution of the string end losses by two orders of magnitude (ie from 1/20 = 5% to 1/2000 = 0.05%).

With regard to aspect (ii) above, Figs. 4 and 5 schematically show the integration of the first bypass diodes 33 and second bypass diodes 35. The first bypass diodes 33 (shown running down in the figures) protect the respective substring 21 ', 21' ', similar to a current 2TT solar cell or single junction solar cell solar module. However, the last top cell 3" of each substring 21 ', 21" is not protected and is therefore protected by a separate second diode 35.

At the end of the overall string, which extends through the described interconnection over several solar modules 19, the overall string ends 43 must generally be brought together for connection to power electronics or an inverter in order to derive the generated current from three parallel strands make possible. A first strand comprises a first plurality of top cells 3 connected in series, each next to the next, a second strand comprises a second plurality of top cells 3, each connected in series, also connected in series, and a third strand comprises a plurality of top cells 3, each connected in series , each next bottom cell.

It is noted that the ones shown in Figs. 3 to 5 each apply to the case that the voltages Vt _op generated by the top cells 3 when illuminated are approximately twice as large as those voltages Vbot of the bottom cells 5, that is to say that a ratio Vtop / Vbot is an integer ratio ( m: n), which in this specific case is equal to (2:1). Accordingly, the circuit described includes n = 1 in series connected top cells 3, which are connected in parallel to m = 2 bottom cells 5 connected in series. In this case, m = 2 mutually parallel strands of top cells 3 connected in series are provided.

It should be noted that in general the voltage ratios of the top and bottom cells can be coordinated (ie "matched") in integer ratios m: n in another way, e.g. Vt _op / Vbot = (m: n) = (3: 2 ) (not shown in the figures).

Fig. 6 shows an alternative embodiment of a solar cell module 1, which differs from the one in Figures in particular with regard to the provision and interconnection of bypass diodes and with regard to the way in which this solar cell module 1 is to be interconnected with neighboring modules. 4 and 5 differs.

In particular, this solar cell module 1 has a bypass diode 34 connected across strings in the middle of the solar module 19. This is on the one hand with a penultimate cell 3TT solar cell 11' "in front of the last 3TT solar cell 11" of the previously adjacent substring 21" and on the other hand with the last Solar cell 11" of the substring 21 'to be secured is connected. In the example shown, the bypass diode 34 connected across strings is connected to the bottom contact 15 of the penultimate cell 3TT solar cell 11'' of the previously adjacent substring 21'' on the one hand and to the bottom contact 15 of the last solar cell 11'' of the substring 21' to be secured on the other hand. In this way, the last solar cell 11" in the previously adjacent substring 21" is connected both to the bypass diode 36 assigned to its substring "and to the cross-string bypass diode 34 assigned to the adjacent substring 21 '. As a result, its top cell 3'' is also protected, so that a second bypass diode 35, as proposed for the exemplary embodiment in FIG. 4, can be dispensed with.

Furthermore, this solar cell module 1 has, in addition to the first and second power input connections 27', 27", a further power input connection 27"' and/or, in addition to the first and second power output connections 29', 29", a further power input connection 29"'. Furthermore, the solar module 1 has at least one bypass diode 36, which is connected in such a way that it can protect both 3TT solar cells 11 of the relevant solar module 1 and at least one 3TT solar cell 11 of an adjacent solar module. This bypass diode is therefore also referred to herein as a bypass diode 36 to be connected across modules. In the example shown, this bypass diode 36, which is to be connected across modules, is electrically contacted on the one hand with the further power input connection 27"' and on the other hand with the bottom contact 15 of one of the 3TT solar cells 11 in the solar module 1. Furthermore, in addition to the bypass diode 36, which is to be connected across modules, the entire solar module also comprises a further bypass diode, which is connected as a cross-string bypass diode 34 as described above. This bypass diode 34 is connected between the center tap contact 17 of the 3TT solar cell 11" of the substring 11" shown on the left in the example, the bottom contact 15 of which is contacted by the cross-module bypass diode 36, and the bottom contact 15" of the last 3 TT solar cell 11" of the substring 21' shown on the left in the example. However, since this does not protect the top cell 3" of the last 3TT solar cell 11", the center tap contact 17" of this last 3 TT solar cell 11" is connected to the further current output connection 29"'.

By now interconnecting the additional power input connection 27" between adjacent solar modules 1 with the additional current output connection 29" of the adjacent solar module 1, the bypass diode 36, which is to be interconnected across modules, can also be the top cell 3" of the last 3TT solar cell 11" in the adjacent solar module 1 secure. The provision of one or more second bypass diodes 35 can therefore be dispensed with in this exemplary embodiment.

Figs. 7 and 8 show possible geometric arrangements of the bypass diodes 33, 35 in respective substrings 21 of a 3TT solar module 19 for 3TT solar cells 11 with high dielectric strength (Fig. 7) and low dielectric strength (Fig. 8).

In the embodiment shown in Fig. 7, several 3TT solar cells 11 are arranged in rows across the entire width B of the solar module 19, side by side, with two such rows being electrically connected to form a substring 21' in the example shown. The first bypass diode 33 and the second bypass diode 35 are each arranged laterally next to the substring 21'. The bypass diodes 33, 35 can be arranged, for example, close to a lateral edge of the solar module 19, for example on or under a frame enclosing the solar module 19 (not shown).

In the figure, the squares represent the 3TT solar cells 11. The lines 39 along the edge of the 3TT solar cells 11 symbolize a 3-pole connection between the solar cells. A practical solution for this 3-pole connection was explained in [10]. Vertical hatched dots symbolize a bottom contact 15 (R contact) to the bottom cell 5, horizontally hatched dots symbolize a top contact 13 (T contact) to the top cell 3, diagonally hatched dots symbolize a center tap contact 17 (Z contact) of the 3TT solar cell 11. In order to keep the contact diagram for the bypass diodes 33, 35 simple, only the contacts to the geometrically closest 3TT solar cell 11 are shown. By connecting the 3TT solar cells 11 (symbolized by line 39), the terminal contacts are continued to other 3TT solar cells 11 in the string 21. This arrangement has two parallel rows of solar cells that are connected in series. This geometric arrangement is suitable for solar cells with high reverse voltage resistance.

8, however, several 3TT solar cells 11 are arranged laterally next to one another over a first half B/2 of a width B of the solar module 19 and are electrically connected to a first substring 21 'and several other 3TT solar cells are above a second half of the width of the solar module 19 is arranged side by side and electrically connected to a second substring 21". The first substring 21' and the second substring 21" are connected in parallel to each other. The first bypass diode 33 and the second bypass diode 35 are each arranged laterally between the first substring 21 ' and the second substring 21 ". Such a type of connection is particularly suitable for 3TT solar cells 11 with low reverse voltage resistance.

In other words, as with half-cell modules, the bypass connection for 3TT solar cells 11 with low reverse voltage strength can be carried out in the middle of the module (FIG. 8). However, the 3TT solar cells 11 are virtually connected in series within a double string (symbolized by the surrounding line 39). A further connection can be made from the contacts brought out either to the next substring 21 or to the next solar module 19. A center contact 17 (Z contact) is picked up by a 3TT solar cell 11 that is not located directly in the middle of the module. This contact is made via a wire connection, which is routed as standard to the next but one top cell 3 for further interconnection. This connection can be used as a power tap.

The special feature of the geometric arrangement of solar cells 11 and bypass diodes 33, 35 in FIG. 7 is that two of the bypass diodes 33, 35 lying next to a double string 21 are in a common diode box 41 (shown in dashed lines in FIG. 7 for better clarity). can be summarized. For example, it is possible with the usual three Diode boxes 41 to build a solar module 19. Likewise, with the geometric arrangement of solar cells 11 and bypass diodes 33, 35 in Fig. 8, two bypass diodes 33, 35 can be connected in a diode box (not shown in Fig. 8 for better clarity), so that it is again possible to carry out the diode connection using the usual three diode boxes 41 in the middle of the module.

If you connect the proposed solar modules 19, you can optionally short-circuit the two power output connections 29', 29" to a common negative contact and the two power input connections 27', 27" to a common plus contact while accepting string end losses, in order to achieve only a single-wire connection between the solar modules 19. In this case, the solar modules 19 are wired together in series so that the minus contact is connected to a plus contact of an adjacent solar module 19. If you want to utilize the full potential of the circuit, a first power output connection 29' with a first power input connection 27' and a second power output connection 29" with a second power input connection 27" of an adjacent solar module 19 must be connected via a two-wire connection, i.e. for example with a two-wire cable or with two cables, connected in series.

It should be noted that terms such as "comprising", "comprising", etc. do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps that have been described with reference to one of the above-described exemplary embodiments can also be used in combination with other features or steps of other above-described embodiments. Reference symbols in the claims are not to be viewed as a limitation.

REFERENCE MARK LIST

I Tandem solar cell

3 top cell

3' top cell of the first 3TT solar cell

3" top cell of the last 3TT solar cell

5' bottom cell of the first 3TT solar cell

5" bottom cell of the last 3TT solar cell

5 bottom cell

7 2TT solar cell

9 4TT solar cell

I I 3TT solar cell

11' first 3TT solar cell

11” last 3TT solar cell

13 top contacts

15 bottom contact

17 Center tap contact

19 solar module

21 strings

21' Substring

21" Substring

23 wiring ends

25 connectors

27 power input connector

27' first power input port

27” second power input connector

27 “‘ another power input connection

29 power output connector

29 ' first power output connection

29” second power output connector

29 “‘ additional power output connection

31 common bypass diode 33 first bypass diode

34 bypass diodes connected across strings

35 second bypass diode

36 Bypass diode to be connected across modules 37 Solar system

39 series connection symbolizing line

41 diode box

43 total string ends

Claims

Expectations: 1. Solar module (19) comprising: a plurality of 3TT solar cells (11), which are interconnected to form at least one string (21), and at least two power input connections (27) on a power input of the solar module (19) and / or at least two power output connections ( 29) at a power output of the solar module (19), each 3TT solar cell (11) having a stack with a top cell (3) and a bottom cell (5) arranged underneath, the top cell (3) and the bottom cell (5) being differ from each other with regard to an electrical voltage generated when irradiated with light, each 3TT solar cell (11) having three terminal contacts with a top contact (13), which electrically contacts a side of the top cell (3) facing away from the bottom cell (5), a bottom contact (15) , which electrically contacts a side of the bottom cell (5) facing away from the top cell (3), and a center tap contact (17), which electrically contacts the 3TT solar cell at an interface between the top cell (3) and the bottom cell (5), where a first (27') of the power input connections (27) is connected to at least one of the terminal contacts of a first (11') of the 3TT solar cells (11) closest to the power input and a second (27") of the power input connections (27) is connected to at least one the terminal contacts of a second of the 3TT solar cells (11) adjacent to the first 3TT solar cell (11 ') are connected and/or wherein a first (29') of the current output connections (29) is connected to at least one of the terminal contacts of a last one (11 ") of the 3TT solar cells (11) is connected and a second (29") of the current output connections (29) is connected to at least one of the terminal contacts of a penultimate of the 3TT solar cells (11) adjacent to the last 3TT solar cell (11") . 2. Solar module according to claim 1, wherein the top cell (3) and the bottom cell (5) of each of the 3TT solar cells (11) are arranged in an r-type configuration in reverse polarity, and wherein the first power input connection (27') is connected to the center tap contact (17) of the first 3TT solar cell (11') and the second power input connection (27") is connected to the center tap contact (17) of the second solar cell (11) and/or wherein the first current output connection (29') is connected to the top contact (3) of the last 3TT solar cell (11") and the second current output connection (29") is connected to the top contact (3) of the penultimate 3TT solar cell (11). 3. Solar module according to one of the preceding claims, wherein the electrical voltage of the top cell (3) generated when exposed to light and the electrical voltage of the bottom cell (5) generated when exposed to light are essentially in a ratio of m to n, where m and n are natural numbers are, and where n top cells (3) connected in series are connected in parallel to m bottom cells (5) connected in series. 4. Solar module according to claim 3, wherein m > 2 and where n > 1, and wherein a number of the power input connections (27) and / or a number of the power output connections (29) is equal to or greater than a larger of the two values n and m . 5. Solar module according to one of claims 3 and 4, where m = 2 and n = l, with the exception of the last 3TT solar cell (11 "), each bottom contact (15) of a 3TT solar cell (11) with the center tap contact (17) of the adjacent next 3TT solar cell (11) is connected, and wherein, with the exception of the last and the penultimate 3TT solar cell, each top contact (3) of a 3TT solar cell (11) is connected to the center tap contact (17) of the next but one subsequent 3TT solar cell (11) is connected. 6. Solar module according to one of the preceding claims, wherein in each of the strings (21) a first bypass diode (33) is connected in parallel to the 3TT solar cells (11) of the string (21) and furthermore in each of the strings (21). second bypass diode (35) parallel to the top cell (3) and / or bottom cell (5). last 3TT solar cell (11') of the string (21) is connected. Solar module according to claim 6, wherein the first bypass diode (33) is connected on the one hand to the center tap contact (17) of a first 3TT solar cell (11') of the string (21) and on the other hand to the bottom contact (15) or the top contact (13) of the last 3TT -Solar cell (11") of the string (21) is electrically connected, and the second bypass diode (35) on the one hand with the top contact (13) or the bottom contact (15) of the last 3TT solar cell (11") of the string (21) and on the other hand is electrically connected to the center tap contact (17) of the last 3TT solar cell (11”) of the string (21). Solar module according to one of the preceding claims, wherein the solar module (19) has at least one bypass diode (34) connected across strings, the bypass diode (34) connected across strings being connected on the one hand to a 3TT solar cell (11'") in front of the last 3TT solar cell (11 ") of a neighboring substring (21") and on the other hand is connected to the last solar cell (11") of the substring (21 ') to be secured. Solar module according to one of the preceding claims, wherein the solar module (19) has at least one further power input connection (27"') and / or at least one further power output connection (29"'), wherein in the solar module (19) at least one bypass diode to be connected across modules ( 36), the bypass diode (36) to be connected across modules being connected on the one hand to the further power input connection (27'') and on the other hand to one of the terminal contacts, in particular to the bottom contact (15), of one of the 3TT solar cells (11) in the solar module (19) is connected and/or the center tap contact (17) of the last 3TT solar cell (11) of the solar module (19) is connected to the further power output connection (29''). Solar module according to one of claims 6 to 9, wherein a plurality of 3TT solar cells (11) are arranged laterally next to one another over an entire width (B) of the solar module (19) and are electrically connected to form a substring (21 '), and wherein the first Bypass diode (33) and, optionally, the second bypass diode (35) are each arranged laterally next to the substring (21 '). Solar module according to one of claims 6 to 9, wherein a plurality of 3TT solar cells (11) are arranged laterally next to one another over a first half of a width (B) of the solar module (19) and are electrically connected to form a first substring (21 ') and several 3TT solar cells (11) are arranged side by side over a second half of the width of the solar module (19) and are electrically connected to a second substring (21"), with the first substring (21 ') and the second substring (21") ) are connected in parallel to each other, and wherein the first bypass diode (33) and, optionally, the second bypass diode (35) are each arranged between the first substring (21 ') and the second substring (21"). Solar module according to one of claims 6 to 11, wherein the first and second bypass diodes (33, 35) are accommodated in a common diode box (41). Solar module according to one of the preceding claims, wherein the top cell (3) is a perovskite solar cell and the bottom cell (5) is a silicon solar cell. Solar module according to one of the preceding claims, wherein the bottom solar cell (5) is a back contact solar cell, in which terminal contacts (15, 17) of both polarities are arranged nested on a rear side of the bottom solar cell (5) facing away from the top solar cell (3) and one of the Terminal contacts of the bottom solar cell (5) acts as the center tap contact (17). Solar system comprising: a plurality of solar modules (19) according to one of the preceding claims, wherein in the case of adjacent solar modules (19), each of the power output connections (29) of one of the solar modules (19) is electrically connected to an assigned one of the power input connections (27) of the adjacent solar module (19). 16. Solar system according to claim 15, wherein, with the exception of the power input connections (27), a first of the solar modules (19) and the power output connections (29) of a last one of the solar modules (19), the power input connections (27) of each of the solar modules (19) are electrically insulated from one another and the power output connections (29) of each of the solar modules (19) are electrically insulated from one another. 17. Solar system according to one of claims 15 and 16, wherein in a first of the solar modules (19) the at least two power input connections (27) are electrically short-circuited or connected to one another and / or in which in a last of the solar modules (19) the at least two Current output terminals (29) are electrically short-circuited or connected to one another.