DE102007035883A1 - Solar module, has rear contact solar cells arranged at distance along translation direction, where contact surface is not overlapped with another contact surface when former surface is shifted to distance in translation direction - Google Patents

Abstract

The module has rear contact solar cells (1) arranged at distance (C) along a translation direction. Each cell has bus bars (9, 11) at a rear side. A cell binder (3) electrically interconnects one of the cells and an adjacent cell in the translation direction. The former cell electrically contacts to a contact surface (13A) and the latter cell contacts to another contact surface (13B). The contact surface (13A) is not overlapped with the contact surface (13B) when the surface (13A) is shifted to the distance in the translation direction.

Description

The The invention relates to a back contact solar cell and a solar module in which back contact solar cells interconnected with each other in series.

solar cells serve to convert light into electrical energy. For this purpose points a solar cell forming semiconductor regions of different polarity. For example an emitter region having a first polarity is formed from an n-type semiconductor, whereas a base region having a second polarity consists of a p-type semiconductor is formed. By at the interface between The pn junctions formed in the two regions can be charge carrier pairs, the light incident upon absorption is separated become. To the so separated charge carriers an external circuit respectively to be able to Both the base and emitter regions are electrically powered by base and emitter contacts contacted.

at Back contact solar cells are both the base and the emitter contact on the back of the Solar cell, d. H. the light side facing away from the operation, arranged. As a result, shading of the solar cell front side and thus Efficiency losses avoided. In addition, adjacent in a solar module Solar cells easier together from back to back be interconnected as in conventional Solar cells in which a front-side emitter contact a solar cell with the base contact located at the back a neighboring cell must be interconnected.

Examples of contact patterns of conventional back-contact solar cells 101 are in 1a and 1b shown. In order to keep the distances which charge carriers have to cover laterally in the plane of the solar cell in order to arrive at an emitter or base contact as low as possible, conventional back-contact solar cells usually have base contacts and emitter contacts, each with a pattern of parallel metal fingers 105 . 107 which, like a comb, each have a so-called busbar 109 . 111 connected to each other. The finger 105 . 107 Depending on the manufacturing process usually have a width of about 10 to 1500 microns and a distance of about 5 microns to 1 mm and are substantially over the entire back of the back-contact solar cell 101 equally distributed. The fingers 105 . 107 connecting busbars 109 . 111 have a width of, for example, about 1 to 4 mm. Neither the fingers nor the busbars have to have a constant width. Their width can be advantageously adapted to the expected during operation local amperage. The busbars 109 . 111 serve in the contact fingers 105 . 107 to collect guided charge carriers and a cell connector 103 such as B. supply a solder strip, which connects adjacent solar cells with each other electrically.

Between the fingers 107 of the emitter contact are the fingers 105 the base contact, so the fingers 105 . 107 arranged like a comb (so-called "rear interdigitated contacts") 105 Base bus bar connecting the base contact 109 and the fingers 107 Emitter busbar connecting the emitter contact 111 are located on opposite side edge regions of the solar cell 101 are located.

In the 1a / b shown schematically conventional back-contact solar cells can be easily interconnected in a module with each other in series by being arranged next to each other in the same orientation offset in a translation direction and the Basisbusbar 109 a solar cell with the emitter bus bar 111 a translationally adjacent solar cell z. B. is connected by means of a solder strip.

At the in 1a / b shown back contact pattern extend the contact fingers 107 essentially from a side edge of the solar cell 101 starting almost to the opposite side edge, ie the contact fingers 107 have about the same length as the edge length of the solar cell 101 , Further, the entire over the contact fingers 107 collected carrier current each a single Basisaktbusbusbar 109 and a single emitter contact bus bar 111 fed. The long contact fingers 107 and the high current density in the busbars 109 . 111 contribute to efficiency losses due to series resistances especially in large-scale solar cells, as they are preferred for industrial production. To minimize these efficiency losses, the contact fingers 107 and busbars 109 . 111 be as thick as possible to increase the line cross section. The production of such thick contacts is material and laborious.

It Therefore, back-contact solar cells have been proposed, which have a plurality of base and / or multiple emitter contact busbars. That way, the length can be the single contact finger and the one collected from a single busbar Carrier power be reduced, which in turn allows lower contact thicknesses.

2a , b show solar cell arrangements with a conventional back-contact solar cell 201 with two base contact busbars 209 and two emitter contact busbars 211 , It can be seen that such back-contact solar cells 201 not as easy to interconnect as the ones in 1 shown solar cells 101 with only one busbar each 109 . 111 , because be neighboring solar cells 201 each oriented through 180 ° must be arranged oriented to work with conventional straight cell connectors 203 can be electrically connected. This alternating twisting of the solar cells 201 Before the interconnection, the production of solar modules means an additional work step and represents an additional source of error. It should be noted that the in 2a shown cell connectors may alternatively extend over the entire length of the contacted busbars (see 26 ). If there are several contacts along this route, where there is an overlap between the cell connector and the busbar, the cell connector can support the transport of electricity along the busbar in this case.

One another problem with conventional Solar cell modules are mechanical voltages that are subject to temperature fluctuations due to different thermal expansion coefficients the solar cell substrates, the metal contacts and the cell connector occur. Especially for large-area solar cells can These voltages become so strong that cell connectors tear off the busbars or even pieces break out of a solar cell.

It can be considered as an object of the present invention in particular, the above-described problems of conventional ones Back contact solar cells to avoid. It may in particular as an object of the present Be considered invention, a back-contact solar cell and a Plurality of back contact solar cells providing solar module, wherein adjacent solar cells be interconnected or can be such that Efficiency losses due to series resistance and temperature fluctuations conditional mechanical stresses remain low.

These Task can by a solar module or by a solar cell according to a the independent one claims solved become.

According to one The first aspect of the present invention is a solar module with a plurality of along a translation direction by a distance C offset arranged back-contact solar cells proposed, wherein each of the back-contact solar cells at the back Contacts of a first and a second polarity respectively connected by busbars, preferably has parallel contact fingers, each of the Back contact solar cells Your back has at least three busbars, wherein a cell connector is a first Back contact solar cell and a second, in the translation direction adjacent back-contact solar cell electrically connects and the first back-contact solar cell in one first contact surface A electrically contacted and the second back-contact solar cell in a contact area B electrically contacted and wherein the first contact surface A, when it is not offset by the distance C in the translation direction with the contact surface B overlaps.

characteristics and advantages of the solar module according to the invention will be explained in more detail below.

Under a solar module herein is an arrangement of a plurality of neighboring solar cells in a common plane understood. For example can several solar cells in a row along a translation direction be arranged side by side. Adjacent solar cells are included arranged offset laterally by a distance C, d. H. the middle-point a solar cell is one from the center of its neighbor cell Distance C away. The distance C may be selected so that a gap between remains in the direction of translation adjacent solar cells, so adjacent solar cells do not overlap. Alternatively, neighboring Solar cells also at their edges abutting or almost abutting one another, to be able to compensate for thermal expansion can be arranged.

The in the solar module used back-contact solar cells can Be solar cells, in which both the emitter contact and the Basic contact exclusively on the back side the solar cell is arranged. An example of conventional back-contact solar cells are high-efficiency solar cells based on high quality crystalline silicon, by which Light generated minority carriers substantially solely by diffusion processes to one on the back the cell formed pn junction reach and be collected there and fed to the emitter contact.

One Another example is so-called EWT solar cells (emitter wrap Through) or MWT solar cells (Metal Wrap Through), where an emitter on the front a silicon wafer is formed and charge carriers, the at the front of the solar cell were generated and separated by small holes in the solar cell, through which the emitter or a metallization passes through, led to contacts on the back of the solar cell can. Another possible Example are thin-film solar cells, where both the n-type region and the p-type region of the back are contacted.

The used solar cells preferably have a square shape, can but also a right-angled, pseudo-right angle (i.e., with rounded Corners), round or any other outline.

According to the invention Solar cells of the solar module at the back of at least three busbars on, the contact fingers of each of the emitter and the base contact connect electrically. For example, two emitter busbars and a base busbar or vice versa be provided. The busbars can extend linearly, with one side or both sides a busbar contact fingers can protrude transversely. The contact fingers of the Emitter and base contact can comb-like nested. The more busbars are provided, the shorter are the distances, the charge carriers in a contact finger have to go back before they reach a bus bar. This reduces series resistance losses. Furthermore can the busbars themselves have a smaller cross-section, d. H. be slimmer and flatter if multiple busbars to forward the charge carrier available. It is therefore preferable to use the solar cells with all the more more busbars, z. B. 4, 5 or 7 busbars to provide, the larger the Area of Solar cell is. It can Busbars of the same polarity be connected to each other on a solar cell.

According to the invention are in Direction of translation adjacent back-contact solar cells of the solar module electrically connected to each other by at least one cell connector. To connect the solar cells of the module in series, contacted the cell connector z. B. the emitter contact of a first solar cell at a first contact surface A and contacts the base contact one in translation direction adjacent solar cell at a contact surface B. The contact surfaces A, B need are not each self-contained surfaces, but can be composed of individual, spaced partial surfaces. The contact surfaces A, B are preferably designed so that they are easy with the Cell connectors can be electrically connected. For example, the contact surfaces as trained as Lötpads Broadening a respective busbar be configured on which soldered a cell connector can be.

One Cell connector can in the simplest case simply an oblong be metallic band, for example, copper. Alternatively, you can a cell connector also a more complex, z. B. curved or have angled geometry and / or from another electrically conductive Material exist.

The inventive solar module is characterized in that the first contact surface A, if they are offset by the distance C to which adjacent solar cells are displaced is translated in the translation direction, not overlapped with the contact surface B. If it is assumed that adjacent solar cells of a module are the same Floor space In other words, that means the cell connector the first solar cell exclusively electrically contacted at positions where it is the adjacent second Solar cell, based on the base area, not contacted.

The contact area A can be connected or divided into individual non-contiguous sub-areas be.

embodiments The invention will become apparent from the dependent claims. characteristics and advantages of the embodiments are explained below.

In an embodiment the cell connectors are designed as rectilinear strips and the cell connectors are skewed aligned to the translation direction. The use of straight stripes z. B. electrically good conductive copper allows a particularly simple and cost-effective Connector manufacturing as well as a good electrical connection between neighboring solar cells. The flat metal strips can z. B. from thin Sheet metal punched or made of wires to be rolled. The prerequisite according to the invention described above not overlapping contact surfaces A and B can be easily achieved with straight metal strips, that the metal strips are sloping be arranged to the translation direction C.

According to one another embodiment are all back contact solar cells of the solar module or at least those solar cells that are not at the edge of the module, with respect to their contact surface geometry essentially identical. Under the contact surface geometry here is the Position and size of the contact surfaces A, B understood, where the cell connectors the base and emitter contacts contact the solar cell. Furthermore, it is preferred that the entire Pattern of base and emitter contacts on all solar cells of the Module is the same. In other words, a single cell type for the whole Module can be used. To have to not, as with conventional Back contact solar cell modules partly common, different solar cell types with different contact geometries be arranged alternately or in alternating orientation in Solar module can be arranged. This reduces manufacturing costs and simplifies the interconnection of the solar cells in the module.

The inventive interconnection the solar cells in the module allows it according to one another embodiment, that the back contact solar cells are oriented substantially the same, d. H. the solar cells need not rotated by 180 ° alternately to be arranged, as is partially conventional Solar modules needed was. This saves costs and effort when aligning the solar cells before switching in the module.

at The solar module according to the invention can be electrically conductive cell connectors above areas of individual solar cells run in which are electrically conductive tracks such. As fingers or busbars the emitter contacts or base contacts are located. In the case of straight Cell connectors that are oblique are arranged to the translation direction, the cell connectors for Example obliquely over several Emitter and base contact fingers run. Thus, the emitter contact is not shorted to the base contact is according to another embodiment in an area outside the contact surfaces A, B is an insulating layer between the contacts of the back contact solar cell and intended for the cell connectors.

Around shorting Preventing the solar cell through the cell connectors would only suffice the area between cell connectors and contacts on the back of the solar cell to isolate through the insulation layer. However, it is mostly easier essentially the entire back of the solar cell together the contacts arranged thereon with an adhesive, electrical to provide insulating layer and only the areas of the contact surfaces A, B auszusparen. The adherent layer can be, for example, using applied by Siebdruck- or Dispenstechniken and then dried become. These techniques allow the application of the insulation layer in a simple, inexpensive way and proven in industrial use.

According to one another embodiment before attaching the cell connectors an insulating film over the back the solar cell are placed. The film may be in the area of the contact surfaces A, B openings or perforations, so that at these points the cell connectors Contact the contacts or the contact pads of the solar cells directly can and so an electrical connection can be made. The Slide can z. B. be a laminating, as standard for Lamination of solar cells used for encapsulation in a module is, except that the film in this case does not have the solar cell back with the attached cell connectors is placed but yourself between the solar cell back and the cell connectors and these against each other electrically isolated. The relatively thick and elastic film leads Yet another advantage: by a slight bending of the cell connector as it occurs when the cell connector soldered to contacts of the solar cell is guided over the film in intermediate isolated areas, will be an increased Tolerance of the module against temperature fluctuations achieved. The at Temperature fluctuations occurring mechanical stresses can through the curved cell connector are at least partially compensated.

In a further embodiment of the location-selective isolation and local Contacting the solar cell can Cell connector integrally incorporated in an insulating film be. The cell connectors generally run within the film and are thus isolated to the outside. Only in the places where the cell connectors contact the contacts of the solar cell are the cell connectors are guided to the surface of the film or an overlying one Foil layer is removed locally.

According to one another embodiment the cell connector is a core of electrically conductive material at least on its side facing the solar cell covered with an insulating material. Preferably, the Core completely encased with an electrically insulating material, with only the areas where the cell connector is in electrical contact with the contacts on the solar cell back to stand, stripped are.

The inventive solar module can advantageously solar cell strands of identical and same-oriented Use solar cells. So it's not necessary, every second Solar cell by 180 ° too turn two more solar cell types / geometries use. Accordingly, for the module interconnection of Solar cells a possible Error source in the production of solar cell strings avoided. Furthermore can in that the cell connectors are preferably not parallel to Direction of translation between adjacent solar cells running can be arranged, thermally induced stress low be held, as oblique arranged cell connectors under thermal stress not only along their own longitudinal direction stretched or compressed but also sheared or twisted can be. The forces exerted by the cell connectors on the solar cell forces Temperature fluctuations are therefore compared to conventional ones Solar cell arrangements reduced.

According to one Another aspect of the present invention is a back-contact solar cell with at the back arranged contacts of a first and a second polarity, respectively proposed with connected by busbars contact fingers, wherein at least two busbars for the contacts of the first polarity and at least one busbar for the Contacts of the second polarity are provided. The back contact solar cell characterized by a the contacts at least partially covering electrically insulating layer in the area of at the busbars located contact surfaces openings has, off.

Such a back-contact solar cell whose rear surface together with the angeord Neten base and emitter contacts is covered over a large area of an insulating layer, is particularly suitable to be connected in a solar module according to the invention according to the first aspect of the invention described above by means of cell connectors with adjacent cells. The cell connectors can be soldered in the region of the openings in the insulating layer to the busbars of the solar cell or the contact surfaces located there. The insulating layer can effectively prevent inadvertent shorting of the cell contacts by the cell connectors.

The Busbars of the solar cell are preferably parallel to each other. The From the busbars comb-like projecting contact fingers are preferably parallel to each other and perpendicular to the bus bars. The contact surfaces can as be formed widened areas of busbars.

In an embodiment are at least two busbars for contacts of the same polarity contact surfaces so are arranged, that a straight line through at least two contact surfaces obliquely to the translation direction adjacent solar cells runs. Preferably closes the straight line with the translation direction an angle α, so that 2 ° <α <88 °, more preferably 10 ° <α <80 °, even more preferable 20 ° <α <70 °. If the contact surfaces are arranged at the busbars and intermediate areas the solar cell back through the insulating layer protected are, just can standard cell connectors aslant to be soldered to the busbars running on contact surfaces of the same polarity and neighboring solar cells are connected to form a solar module, as described above.

In a further embodiment are contact surfaces at busbars for Contacts of the first polarity not mirror symmetric to contact pads on busbars for contacts the second polarity with respect to a plane of symmetry through the center of the back-contact solar cell arranged. This asymmetry is a prerequisite for that the contact surfaces are arranged such that adjacent, identical and similarly oriented solar cells by a preferably straight Cell connectors can be interconnected in series.

The electrically insulating layer may, for. B. by means of cost, industrially proven screen printing or dispensing techniques on the back the back contact solar cell be upset.

Further Features of the present invention will become apparent from the following Description of preferred embodiments together with the accompanying drawings, wherein:

1a / b show solar cell arrays with conventional back-contact solar cells with only one emitter busbar and one base busbar;

2a / b show a solar cell arrangement with conventional back-contact solar cells with two emitter busbars and two base busbars, wherein adjacent solar cells are in each case arranged rotated through 180 ° to one another;

3 shows the back of a back-contact solar cell, which is suitable for a solar module according to the invention;

4 the back contact solar cell of 3 after printing with an insulator layer;

5 an embodiment of a solar module according to the invention using the in 3 and 4 shows solar cell shown;

6a and 6b to describe a production sequence for a further embodiment of the present invention;

7 that by means of in 6a and 6b 1 shows a manufactured solar module according to an embodiment of the present invention;

8th a further embodiment of a solar cell arrangement for a solar module according to the invention shows with an asymmetrical cell connection with a cell connector per busbar;

9 a further embodiment of a solar cell arrangement for a solar module according to the invention shows with an asymmetrical cell connection with two cell connectors per busbar;

10 a further embodiment of a solar cell arrangement for a solar module according to the invention shows with a symmetrical cell connection with W-shaped arranged cell connectors; and

11 Another embodiment of a solar cell arrangement for a solar module according to the invention shows a quasi-symmetrical cell connection with straight standard cell connectors.

each other corresponding components of the various embodiments are disclosed in the various Figures with corresponding reference numerals.

3 shows the back of a back contact solar cell 1 with interwoven base and emitter contact fingers 5 . 7 before applying an insulator on the back of the cell. The base contact fingers 5 are through three base busbars 9 connected to each other the. The emitter contact fingers 7 are by two emitter busbars 11 connected with each other. The base and emitter bus bars 9 . 11 have widened contact surfaces 13 on.

4 shows the same cell backside after printing with an insulation layer 15 , The insulation layer 15 consists of an electrically insulating material that can be printed in the form of a viscous paste on the back of the cell and then dried. Except for the contact surfaces 13 the entire cell back is printed. The unintentional contact at unintended locations and possibly the resulting short-circuiting of the cell is prevented by the insulating layer.

In 5 is a connected arrangement of several adjacent back-contact solar cells 1 shown. The solar cells 1 are offset in a translation direction in each case by a distance C to each other, so that a small gap remains between them. The solar cells 1 are all identical and the same orientation. Straight standard cell connectors 3 connect neighboring solar cells in translation direction 1 electric. The cell connectors 3 are aligned obliquely to the translation direction. Every cell connector 3 contacts a first solar cell at first contact surfaces 13A the base contact busbars 9 and a second solar cell adjacent in translation direction at second contact surfaces 13B the emitter contact busbars 9 , The cell connectors 3 are flat metal bands and are at the contact surfaces 13 soldered. Through the insulation layer 15 will prevent the cell connector 3 the between the contact surfaces 13 lying areas of the bus bars 9 . 11 or the contact fingers 5 . 7 Contact and short circuit the solar cell.

In 7 is a solar module 51 according to another embodiment, the production thereof with reference to 6a and 6b should be explained. In a first step is on a coverslip 21 , which forms a sun-facing cover plate in the finished solar module, a first laminating film 23 placed. On the lamination film 23 In the example shown, six back-contact solar cells will be used 1 with its back facing upwards arranged in two rows and three columns. The solar cells 1 have a similar structure to those in 3 shown solar cell with multiple contact surfaces 13 for interconnecting the solar cells with each other.

Next is about the solar cells 1 a second laminating film 25 placed. The second lamination film 25 has perforations in the form of openings 27 on. The openings 27 are each provided at the points in the finished laminated state of the solar module 51 over the contact surfaces 13 lie. The lamination film has an electrically insulating material. Conventional EVA (ethylene vinyl acetate) laminating film can be used.

Subsequently, rectilinear cell connectors as in 7 shown on the solar cells 1 placed and at the contact surfaces 13 soldered. The solar cells at the edges of the module are at their edge side each with a first and two second cell connectors 29 . 31 soldered. The first cell connector 29 connects the two rows of solar cells electrically in series. The second cell connectors 31 connect the solar cell array to an external terminal 33 of the solar module 51 ,

Further embodiments are in 8th and 9 shown. In contrast to the preceding embodiments, solar cells are shown here whose busbars run parallel to the direction of translation of the cell strand. Furthermore, in this exemplary embodiment, a cell connection which is symmetrical to the direction of translation has been dispensed with. With a total of odd number of busbars, of course, a symmetrical cell connection through the cell connector is possible.

In 10 an embodiment with W-shaped cell connectors is shown. In 11 For example, an embodiment with quasi-symmetrical cell connection is shown by straight standard cell connectors.

Claims (13)

Solar module with offset along a translation direction by a distance C arranged back-contact solar cells ( 1 ), wherein each of the back-contact solar cells ( 1 ) at its rear side contacts of a first and a second polarity respectively by busbars ( 9 . 11 ) connected contact fingers ( 5 . 7 ), wherein each of the back-contact solar cells ( 1 ) at least three busbars ( 9 . 11 ), wherein a cell connector ( 3 ) a first back-contact solar cell ( 1 ) and a second, in translation direction adjacent back-contact solar cell ( 1 ) electrically connects and the first back-contact solar cell ( 1 ) at a first contact surface ( 13A ) and the second back-contact solar cell ( 1 ) at a second contact surface ( 13B ), and wherein the first contact surface ( 13A ), when displaced by the distance C in the translation direction, not with the second contact surface ( 13B ) overlaps. Solar module according to claim 1, wherein the cell connectors ( 3 ) are formed as rectilinear strips and wherein the cell connectors ( 3 ) at an angle to the translati are aligned onsrichtung. Solar module according to claim 1 or 2, wherein the back contact solar cells ( 1 ) are oriented substantially the same. Solar module according to one of claims 1 to 3, wherein the back-contact solar cells ( 1 ) are substantially identical in terms of their contact surface geometry. Solar module according to one of claims 1 to 4, wherein in an area outside the contact surfaces A, B, an insulating layer ( 15 ; 25 ) between the contacts of the back-contact solar cell ( 1 ) and the cell connectors ( 3 ) is provided. Solar module according to claim 5, wherein the insulating layer one outside the contact surfaces ( 13 ) at the contacts of the back contact solar cell ( 1 ) adhering electrically insulating layer ( 15 ) having. Solar module according to claim 5, wherein the insulating layer is an electrically insulating film ( 25 ) with openings ( 27 ) in the area of the contact surfaces ( 13 ) having. Solar module according to claim 5, wherein the cell connectors ( 3 ) are coated with an electrically insulating layer. Rear contact solar cell with contacts of a first and a second polarity arranged on its rear side, in each case with busbars ( 9 . 11 ) connected to at least two busbars ( 9 . 11 ) for the contacts of the first polarity and at least one busbar ( 11 . 9 ) are provided for the contacts of the second polarity and wherein the busbars ( 9 . 11 ) Contact surfaces ( 13 ) and with the contacts at least partially covering electrically insulating layer ( 15 ) in the area of the contact surfaces ( 13 ) Has openings. A back-contact solar cell according to claim 9, wherein at at least two busbars for contacts of the same polarity contact surfaces ( 13 ) are arranged so that a straight line through at least two contact surfaces ( 13 ) diagonally to the busbars ( 9 . 11 ) runs. A back-contact solar cell according to claim 9 or 10, wherein contact surfaces ( 13A ) at busbars for contacts of the first polarity not mirror-symmetric to contact surfaces ( 13B ) are arranged at busbars for contacts of the second polarity with respect to a plane of symmetry through the center of the back-contact solar cell. A back-contact solar cell according to claim 9, 10 or 11, wherein the contact surfaces ( 13 ) as widened areas of busbars ( 9 . 11 ) are formed. A back-contact solar cell according to any one of claims 9 to 11, wherein the electrically insulating layer ( 15 ) by screen printing on the back of the back-contact solar cell ( 1 ) is printed.