Patent Description:
<CIT> relates to a solar cell module comprising: a semiconductor substrate; a plurality of solar cells having different polarities on a rear surface of the semiconductor substrate, and having a plurality of first electrodes and a plurality of second electrodes, respectively, which are arranged in a first direction; a plurality of first conductive wirings overlapping the first electrodes and connected thereto and a plurality of second conductive wirings overlapping the second electrodes and connected thereto, each connected to each of the solar cells and arranged in a second direction crossing the first and second electrodes; and an interconnector arranged in the first direction between two first and second solar cells adjacent to each other among the solar cells, and connecting the first and second solar cells in series with each other. The interconnector includes an insulation substrate having elasticity, and a metal layer, which is patterned on the insulation substrate, and to which a plurality of first conductive wirings connected to the first solar cell and a plurality of second conductive wirings connected to the second solar cell are commonly connected.

<CIT> discloses a solar cell module, sometimes also called photovoltaic module, comprising several solar cell strings, wherein each solar cell string comprises several solar cells connected in series. The solar cells are arranged between a front-side encapsulation layer and a back-side encapsulation layer.

Further, <CIT> proposes a method for connecting several rear contact solar cells, in particular interdigitated back contact (IBC) solar cells. In particular, solar cell strings may be formed by electrically connecting several solar cells in series using a plurality of parallel connecting wires.

Typically, interconnectors are used to connect solar cell strings together, either in series or in parallel. The interconnectors comprise an interconnector core having a coating. The coating may be melted for electrically connecting the interconnectors to the connecting wires. It has been found that occasionally parts of the molten coating may not stick to the interconnector and lead to visual and/or electrical degradation of the solar cell module.

Thus, there may be a need for a solar cell module being less prone to failure.

Said need has been addressed with the subject-matter of the independent claim. Advantageous embodiments are described in the dependent claims.

Examples disclose a solar cell module comprising a first solar cell string, wherein the first solar cell string includes a first solar cell and a second solar cell electrically connected in series, wherein the first solar cell and the second solar cell are electrically connected via a plurality of parallel connecting wires; and an interconnector crossing at least some of the connecting wires, in particular being arranged perpendicular to the connecting wires, and electrically connecting the at least some connecting wires; wherein the interconnector comprises an interconnector core having a first surface facing the connecting wires and a second surface; wherein the first surface is covered with a first coating and the second surface is covered with a second coating, wherein the first coating is thicker than the second coating.

In an embodiment of the solar cell module, the first coating may be made of a first coating material, the connecting wires may comprise a wire core and a wire coating, the wire coating is made of a wire coating material, and the first coating material differs from the wire coating material. This may allow for adapting the wire coating material specifically for the connection with the solar cells and the first coating material for the connection with the connecting wires. In some examples, the first coating material may also be the same as the wire coating material. Thus, the number of materials required for manufacturing the solar cell module may be reduced.

Some embodiments may prescribe that the second coating is made of a second coating material, wherein the second coating material differs from the first coating material. For example, the first coating material may be optimized for providing a good electrical and mechanical contact to the connecting wires while the second coating material may be optimized to improve the optical appearance of the solar cell module. For example, an Sn- or In-based first coating material may be used and an Ni-based second coating material.

The first coating material and/or the wire coating material comprises a solder. Soldering may provide a good electrical and, optionally mechanical, connection between the parts soldered together. In examples, the solder may be SnPb consisting of <NUM> weight-% Sn and <NUM> weight-% Pb and having an eutectic temperature of <NUM>. Preferably, the solder is a lead-free solder. Examples of lead-free solders include InSn consisting of <NUM> weight-% In and <NUM> weight-% Sn and having an eutectic temperature of <NUM>, SnBi consisting of <NUM> weight-% Sn and <NUM> weight-% Bi and having an eutectic temperature of <NUM> as well as SnBiAg consisting of <NUM> weight-% Sn, <NUM> weight-% Bi and <NUM> weight-% ag. Further examples of useable solders are disclosed in <NPL> and <NPL>.

In some examples, a melting point of the first coating material is higher than a melting point of the wire coating material. This may avoid that the first coating material is re-molten when the connecting wires are soldered to the solar cells. However, in other examples, a melting point of the first coating material may also be equal to a melting point of the wire coating material. Some examples may also prescribe that a melting point of the first coating material is lower than a melting point of the wire coating material.

The first coating may have a thickness above <NUM>, in particular above <NUM>, more particularly above <NUM>. This may ensure a sufficient adhesion force between the connecting wires and the interconnector.

Some examples may prescribe that the first coating has a thickness below <NUM>, in particular below <NUM>. This may keep the costs for the first coating material reasonably low. In some examples, the first coating may also have a thickness below <NUM>.

The interconnector and the solar cells may be arranged on a same side of the connecting wires. This may facilitate manufacturing of the solar cell module in case the solar cells are rear contact cells. However, it is also conceivable that the interconnector and the solar cells are arranged on opposite sides of the connecting wires.

The solar cell module may comprise a cover laminate and a back laminate, wherein the solar cell string is laminated between the cover laminate and the back laminate, wherein the cover laminate and the back laminate are configured to be laminated together at a laminating temperature being higher than the melting temperature of the wire coating material. Accordingly, the connecting wires may be soldered to the solar cells upon laminating.

The laminating temperature may be lower than the melting temperature of the first coating material. Hence, a pre-soldered connection between the interconnector and the connecting wires may be maintained during laminating.

The solar cell module may comprise a second solar cell string, wherein the interconnector electrically connects connecting wires associated with a first polarity of the first solar cell string and connecting wires associated with a second polarity of the second solar cell string.

Alternatively or in addition, the solar cell module may also comprise a second solar cell string, wherein the interconnector electrically connects connecting wires associated with a first polarity of the first solar cell string and connecting wires associated with the first polarity of the second solar cell string.

In some examples, the solar cell string and module comprises foil segments; wherein the connecting wires are arranged between the foil segments and the solar cells, wherein the foil segments adhere to the solar cells and fix a position of the connecting wires with respect to the solar cells.

The solar cells of the solar cell module may be rear contact solar cells, in particular interdigitated back contact solar cells.

The interconnector may have an essentially rectangular cross-section.

Examples of the proposed solar cell module are described with respect to the drawing in which:.

<FIG> shows a first solar cell module <NUM> with a plurality of solar cell strings <NUM>, <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM>. The solar cell module may also be called a photovoltaic module. The solar cell string <NUM>, <NUM>, <NUM>, <NUM> may also be considered as a first solar cell string. The first solar cell string comprises a plurality, in particular at least two, solar cells <NUM>, <NUM>, <NUM>, and <NUM> connected in series. <FIG> shows four solar cells connected in series per solar cell string. However, it is also conceivable that each solar cell string comprises eight, ten, twelve or, in particular, twenty solar cells. The solar cells of the first solar cell string are arranged in two columns. One column comprises the solar cells <NUM> and <NUM> whereas the other column comprises the solar cells <NUM> and <NUM>. The further solar cells strings of the solar cell module <NUM> are constructed equally, wherein the solar cell strings <NUM>, <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> are arranged mirror symmetrically to the solar cell strings <NUM>, <NUM>, <NUM>, <NUM>; <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM>. Accordingly, the solar cell module <NUM> may comprise six times twenty solar cells, which are arranged in twenty lines and six columns. The number of lines and, accordingly, the number of solar cells per solar cell string may be varied. Likewise, more or less solar cell strings may be used such that the number of columns may also deviate. Examples may also provide that the solar cell strings of the lower half of the solar cell module <NUM> as it is shown in <FIG> may be omitted.

A first bridging element <NUM> is connected in parallel to the first solar cell string <NUM>, <NUM>, <NUM>, <NUM>. Similarly, a second bridging element <NUM> and a third bridging element <NUM> are connected in parallel to the second solar cell string <NUM>, <NUM>, <NUM>, <NUM> and the third solar cell string <NUM>, <NUM>, <NUM>, <NUM>, respectively. The bridging elements <NUM>, <NUM>, <NUM> shown in <FIG> are diodes. However, the diodes may be replaced with different bridging element, e.g. active switches.

<FIG> shows a solar cell string comprising three solar cells <NUM>, <NUM>, <NUM> connected in series. The solar cells <NUM>, <NUM>, <NUM> are provided with backside contacts <NUM>, <NUM> of opposite polarity. A plurality of parallel connecting wires <NUM> and <NUM> connect the solar cells <NUM>, <NUM>, <NUM> in series. Interconnectors <NUM>, <NUM> are crossing the connecting wires <NUM>, <NUM>. In the example shown in <FIG> the interconnectors <NUM>, <NUM> are arranged perpendicular to the connecting wires <NUM>, <NUM>. The interconnector <NUM> electrically connects a first group of connecting wires <NUM> and the interconnector <NUM> connects a second group of connecting wires. The interconnectors <NUM>, <NUM> may correspond to the connectors <NUM>, <NUM> shown in <FIG>. The interconnectors <NUM><NUM> may also be called ribbons or "Querverbinder" (German) or "Stringverbinder" (German).

<FIG> shows an interconnector <NUM> crossing a plurality of connecting wires <NUM>. The interconnector <NUM> comprises an interconnector core <NUM> having a first surface facing the connecting wires <NUM> and a second surface. The first surface is covered with a first coating <NUM> and the second surface is covered with a second coating. The first coating <NUM> is made of a first coating material. The interconnector core <NUM> may have an essentially rectangular cross-section. The connecting wires <NUM> may comprise a wire core <NUM> and a wire coating <NUM>. The first coating material and/or the wire coating material comprise a solder. In examples, the wire coating <NUM> may be molten to provide solder contacts between the connecting wires and the contacts of the solar cells. Likewise, the first coating <NUM> may be molten to provide solder contacts between the connecting wires <NUM> and the interconnector <NUM>. In the example shown in <FIG>, the thicknesses of the first coating <NUM>, the second coating <NUM> and the wire coating <NUM> are equal. Said thickness may amount to <NUM> +/-<NUM>.

<FIG> shows an interconnector <NUM> crossing a plurality of connecting wires <NUM>. The interconnector <NUM> comprises an interconnector core <NUM> having a first surface facing the connecting wires <NUM> and a second surface. The first surface is covered with a first coating <NUM> and the second surface is covered with a second coating <NUM>. The first coating <NUM> and the second coating <NUM> are made of a first coating material and have the same thickness. The interconnector core <NUM> may have an essentially rectangular cross-section. The connecting wires <NUM> may comprise a wire core <NUM> and a wire coating <NUM>. The first coating material and/or the wire coating material comprise a solder. In examples, the wire coating <NUM> may be molten to provide solder contacts between the connecting wires and the contacts of the solar cells. Likewise, the first coating <NUM> may be molten to provide solder contacts between the connecting wires <NUM> and the interconnector <NUM>.

Recently, it has been observed that the soldering adhesion may be improved by increasing the thickness of the first coating <NUM> with respect to the thickness of the wire coating <NUM>. The increase in adhesion force with increasing thickness is illustrated in Table <NUM>. In the experiment, the connecting wire had a wire coating with a thickness of <NUM> +/-<NUM>.

It has been observed that the increased thickness of the first coating <NUM> (being equal to the thickness of the second coating <NUM>) improves the connection between the interconnector <NUM> and the connecting wires <NUM>. However, the molten first and second coating <NUM>, <NUM> may tend to flow towards an edge of the solar cell module in form of spikes or small coating bubbles. For increased module efficiency the distance from the last current transporting portion of the solar cell module to the edge of the solar cell module, in particular, to the edge of the glass covering the solar cell module should be minimized. The spikes and/or bubbles increase the risk that a required minimum distance between the current transporting portions of the solar cell module and the edge of the solar cell module cannot be maintained without the risk of a failure of the solar cell module. The current transporting portions of the solar cell module may also be called live parts of the module.

Thus, it is proposed a configuration as illustrated in <FIG>. The interconnector <NUM> crosses a plurality of connecting wires <NUM>. The connecting wires <NUM> correspond to the connecting wires <NUM> and <NUM> and comprise a wire core <NUM> and a wire coating <NUM>. The material of the wire core <NUM> may essentially comprise copper and/or aluminium. The interconnector <NUM> comprises an interconnector core <NUM> having a first surface facing the connecting wires <NUM> and a second surface. The first surface is covered with a first coating <NUM> and the second surface is covered with a second coating <NUM>. The first coating <NUM> is thicker than the second coating <NUM>. Thus, the total amount of required interconnector coating material may be reduced. For a given thickness of the first coating <NUM> this may reduce the risk of solar cell module failures due to spikes and/or bubbles. Moreover, the reduced amount of interconnector coating material my reduce the material costs of the solar cell module. The first coating material and/or the wire coating material may comprise a solder. A melting point of the first coating material may be higher than a melting point of the wire coating material. This may ensure that the first coating material is not molten another time when the wire coating material is molten.

The first coating <NUM> is made of a first coating material. The second coating <NUM> is made of a second coating material. The first coating material may be the same as the second coating material. This may ensure that the visual appearance of the interconnector does not depend on the direction from which a person looks at the solar cell module. The material of the interconnector core <NUM> may comprise essentially copper and/or aluminium.

<FIG> shows a solar cell module <NUM> in cross-section. The solar cell module <NUM> comprises a first solar cell string, wherein the first solar cell string includes a first solar cell <NUM>, a second solar cell <NUM> and a third solar cell <NUM> electrically connected in series via a plurality of parallel connecting wires <NUM>, <NUM>. An interconnector <NUM> crosses the connecting wires <NUM> and an interconnector <NUM> crosses the connecting wires <NUM>. The interconnectors <NUM>, <NUM> have a first surface facing the connecting wires <NUM>, <NUM> and a second surface. The first surface of the interconnectors <NUM>, <NUM> is covered with a first coating (not shown) and the second surface is covered with a second coating, wherein the first coating is thicker than the second coating. The connecting wire <NUM> may correspond to the connecting wire <NUM> shown in <FIG> and the connecting wire <NUM> may correspond to the connecting wire <NUM> shown in <FIG>.

Claim 1:
Solar cell module (<NUM>) comprising
a first solar cell string (<NUM>),
wherein the first solar cell string (<NUM>) includes a first solar cell (<NUM>) and a second solar cell (<NUM>) electrically connected in series,
wherein the first solar cell (<NUM>) and the second solar cell (<NUM>) are electrically connected via a plurality of parallel connecting wires (<NUM>, <NUM>);
and
an interconnector (<NUM>) crossing at least some of the connecting wires (<NUM>), being arranged perpendicular to the connecting wires (<NUM>), and electrically connecting the at least some connecting wires (<NUM>);
wherein the interconnector (<NUM>; <NUM>) comprises an interconnector core (<NUM>) having a first surface facing the connecting wires (<NUM>) and a second surface;
wherein the first surface is covered with a first coating (<NUM>) and the second surface is covered with a second coating (<NUM>),
wherein the first coating (<NUM>) is thicker than the second coating (<NUM>), wherein the first coating (<NUM>) is made of a first coating material,
wherein the second coating (<NUM>) is made of a second coating material, wherein the first coating material comprises a solder,
characterized
in that the first coating material is the same as the second coating material.