INTERCONNECT MEMBER

Abstract

The disclosure relates to a metallic interconnect member for connecting a first solar cell to a second solar cell. The interconnect member includes one or more serpentine paths having substantially perpendicular loops. The interconnect member may include two connection pads for connecting to the first solar cell. A further connection pad for connecting to a bypass diode may be included. The disclosure further relates to a string of solar cells including a first and a second solar cell connected by an interconnect member.

Claims

1. A metallic interconnect member having a first side for connecting to a first solar cell, and a second side for connecting to a second solar cell, the first and second solar cells being spaced apart along a first axis; one or more serpentine paths extending from the first side to the second side; wherein each of the serpentine paths has at least one longitudinal loop, and at least one transverse loop; the longitudinal loop of a first serpentine path comprising two parallel longitudinal portions extending along the first axis, and a curved portion extending between the two parallel longitudinal portions; the transverse loop of the first serpentine path comprising two parallel transverse portions extending along a second axis, the second axis being substantially perpendicular to the first axis, and including a curved portion extending between the two parallel transverse portions.

2. The metallic interconnect member according to claim 1, wherein the first side comprises two electrical connection pads for connecting to and making electrical contact with an upper side of the first solar cell.

3. The metallic interconnect according to claim 2, wherein the second side comprises two connection portions for connecting to and making electrical contact with a lower side of the second solar cell.

4. The metallic interconnect according to claim 1, wherein the first side comprises two connection pads for connecting to a cathode of the first solar cell, and a third pad for connecting to a cathode of a bypass diode.

5. The metallic interconnect according to claim 3, further comprising a longitudinal loop extending between the two connection portions of the second side of the interconnect member.

6. The metallic interconnect according to claim 1, wherein an inner wall of a curved portion extending between two parallel portions forms a substantially circular segment.

7. The metallic interconnect according to claim 1, wherein a curved portion of at least one of the loops has a width that is smaller than a width of the parallel portions of the at least one loop.

8. The metal interconnect according to claim 1, wherein the interconnect member comprises a silver-plated metal.

9. The metal interconnect according to claim 1, further comprising a bypass diode that is arranged in a cropped corner of the first solar cell.

10. The metal interconnect according to claim 1, further comprising a metallic layer on a bottom side of the second solar cell.

11. The metal interconnect according to claim 1, wherein the first and the second solar cells are III-V compound semiconductor multijunction solar cells.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:

[0034] FIG. 1 discloses a top view of a first example of an interconnect member;

[0035] FIG. 2 discloses a side view of the interconnect member shown in FIG. 1;

[0036] FIG. 3 discloses a top view of the first example of an interconnect member in assembly with two solar cells;

[0037] FIG. 4 discloses a bottom view of the first example of an interconnect member in assembly with two solar cells;

[0038] FIG. 5 discloses a top view of a second example of an interconnect member;

[0039] FIG. 6 discloses a top view of two series connected solar cells, connected through the second example of the interconnect member;

[0040] FIG. 7 discloses a bottom view of the assembly of solar cells shown in FIG. 6;

[0041] FIG. 8 discloses a side view of the same assembly; and

[0042] FIG. 9 discloses a prior art interconnect member.

DETAILED DESCRIPTION OF EXAMPLES

[0043] With reference to FIGS. 1-4, a first example of an interconnect member will now be described in more detail. Also, a string of solar cells incorporating such an interconnect member will now be described.

[0044] FIGS. 1-4 show an interconnect member 100 for connecting a first solar 101 to a second solar cell 102. The interconnect member 100 may be connected to a cathode of the first solar cell, and an anode of the second solar cell. The first solar cell may be separated from the second solar cell along first longitudinal direction 104. A second direction 106 is defined as perpendicular to the first longitudinal direction 104, in a top view. The interconnect member may connect a top surface of first solar cell 101 with a bottom surface of second solar cell 102.

[0045] A top side of the solar cell shall herein be defined as a side of the solar cell that is irradiated by the sun. A bottom side of the solar cell is not irradiated by the sub. Typically, the cathode of a solar cell will be at a top side, whereas the anode of a solar cell will usually be on a bottom side.

[0046] The interconnect member 100 in this example comprises a first connection pad 110A and a second connection pad 110B at a first side 110. The interconnect member 100 also includes a first connection portion 120A and a second connection portion 120B for connecting to the second solar cell on a second side 120 of the interconnect member.

[0047] In this example, the first connection pad 110A is connected with the first connection portion 120A through a first serpentine path, schematically indicated in interrupted lines on the right hand side of the top view. Similarly, a second serpentine path extends from second connection pad 110B to second connection portion 120B, schematically indicated in interrupted lines on the left hand side of the top view.

[0048] In this example, both the first serpentine path, and the second serpentine path include a longitudinal loop 130, 160, and a transverse loop 140 and 150. Although both serpentine paths only include a single transverse loop and a single longitudinal loop it should be clear that in other examples multiple loops could be included in either one of the serpentine paths.

[0049] Each of the loops has a shape corresponding to a section of a partial obround, in other words a section of a stadium shape. The longitudinal loops 130 and 160 include a first i.e. a longitudinal portion 130A, 160A, a second longitudinal portion 130A, 160A (parallel to the first) and a curved portion 130C, 160C in between these two portions. Transverse loops 140, 150 include a first transverse portion 140A, 150A, extending along second (transverse) direction 106, a second transverse portion 140B, 150B, parallel to the first portion and a curved portion 140C, 150C in between.

[0050] The serpentine paths including loops that are substantially perpendicular to each other introduce sufficient flexibility to withstand shear and normal loads by increasing the flexibility in various directions. The longitudinal loops introduce flexibility particularly in the transverse direction 106 and vertical direction (perpendicular to the plane of FIG. 1) by a gap in between the longitudinal parallel portions. Similarly, the transverse loops increase flexibility in the longitudinal direction and in the vertical direction.

[0051] Since one side (e.g. top surface) of the first solar cell is connected to a bottom of the second solar cell, a vertical step 190 may be included relatively close to the connection pads 110A, 110B. In this particular example, only the connection pads 110A, 110B are in a first substantially horizontal plane, whereas the remainder of the interconnect member including serpentine paths are in a second substantially horizontal plane. In this example, the first horizontal plane is arranged on top of the solar cells, whereas the second horizontal plane is arranged at the bottom of the solar cells.

[0052] One or more of the curved portions of the loops of the interconnect member may have an inner wall between the two parallel portions of the loop forming a substantially circular segment. The local width of the serpentine path in the curved portion is reduced as compared to the parallel portions. The resulting half dog bone or half dumbbell structure has been found to reduce stress concentrations in the curved portico of the loops. Without wishing to be bound to any theory, it is believed that the cracks in the prior art interconnect member were at least partly caused by stress concentrations in the curved portions. It has been found, that by locally reducing the width or in spite of locally reducing the width, high stress can be avoided in the curved portions.

[0053] In the particular example of FIGS. 1-4, further flexibility is introduced in the interconnect member by land portions 181, 182, i.e. by further gaps in between the lands 181, 182 and the connection portions 120A and 120B. In this particular example also, a further longitudinal loop 170 having parallel portions 170A and 170B and curved portion 170C is included in between the two connection portions 120A and 120B.

[0054] Starting from connection pad 110A, the first serpentine path first includes longitudinal loop which is transversally displaced with respect to connection pad 110A and connection portion 120A. In the top view of this example, the longitudinal loop is displaced to the right side. The serpentine path then includes a transverse loop 140. The second serpentine path extending between second connection pad 110B and second connection portion 120B on the other hand first has a transverse loop, and then a longitudinal loop transversally displaced with respect to second connection pad 110B and second connection portion 120B. The longitudinal loop of this serpentine path is displaced to the opposite lateral side, i.e. in the top view of this example it is displaced to the left. Thanks to this design, the transverse loops 140, 150 fit in between the connection pads 110A and 110B on the first side 110 and the connection portions 120A and 120B on the second side. A compact design may thus be achieved.

[0055] FIG. 2 illustrates a side view of an assembly of a first solar cell 101 and a second solar cell 102 with interconnect member 100 connecting both. FIG. 3 illustrates how the first connection pad 110A and the second connection pad 110B connect respectively to a first and a second cathode portion 101A and 101B of the first solar cell 101. The cross-sectional side view of FIG. 2 is indicated in FIG. 3. The solar cells may be covered by a protective glass cover.

[0056] FIG. 4 illustrates a bottom view of the interconnect member 100. The connecting portions 120A, 120B may be connected to a metallic layer on the bottom side of the second solar cell 102. The step portion 190 perpendicular to the plane is also illustrated. In some examples, the metallic layer may be a solid metallic foil having a thickness between 0.001 and 0.005 inches (between 0.0254 mm and 0.127 mm).

[0057] FIGS. 5-8 illustrate a second example of an interconnect member 200. As opposed to the first example, the second example has a three toe design including two connection pads 210A, 210B for connecting to a cathode of a first solar cell 201, and a connection pad 210C to connect to a cathode of a bypass diode.

[0058] At the opposite side of the interconnect member 200, there are three connecting portions 220A, 220B, 220C for connecting to an anode of a second solar cell. The first connection pad 210A is connected to first connecting portion 220A through a first serpentine path. The second connection pad 210B is connected to a second connecting portion 220B through a second serpentine path. And the bypass connection pad 210C is connected to the third connecting portion 220C through a third serpentine path.

[0059] In this example, each of the serpentine paths includes a loop or partial obround section including parallel portions along a first direction 204 and a curved portion in between. Each of the serpentine paths furthermore includes parallel portions along a second direction 206, perpendicular to the first direction 204, and a curved portion in between. The loops we provided substantially in the same plane. The metallic interconnect member 200 further includes a step portion 209 perpendicular to this plane. The step portion may be more clearly appreciated in FIG. 8.

[0060] The first serpentine path includes a longitudinal loop 230 with straight portions 230A, 230B and curved portion 230C, and a transverse loop 240 with portions 240A, 240B and 240C. The second serpentine path includes a transverse loop 245 with portions 245A and 245B extending along the second direction 206 and a curved portion 245C in between, and a longitudinal loop 250 including parallel portions 250A and 250B extending along the first direction 204 with a curved portion 250C in between.

[0061] In this example, the first and second serpentine paths are nested in between each other. In particular, the transverse loops 240 and 245 are arranged in between the longitudinal loops 230 and 250, and the transverse loop 240 is arranged longitudinally between the transverse loop 245 and the connection portions 220 on the second side. The third serpentine path is transversely offset from the first and second serpentine paths and includes a longitudinal loop 265 and one and a half transverse loops 270, 275.

[0062] Similarly to the first example, the interconnect member includes longitudinal loops 255, 290 and 295 in between the different connection portions, thereby introducing several gaps in between the connection portions. Similarly also to the first example, one or more or all of the curved portions may include a partial dumbbell shape as explained before.

[0063] The bypass diode may be arranged in a cropped corner 208 of the first solar cell 201. The bypass diode may have a substantially triangular shape with two acute angles. The bypass diodes may be silicon semiconductors, and may have a thickness of e.g. 140 microns. This may be seen particularly in FIG. 6 (showing a top view of a portion of a string of solar cells) and in FIG. 7 (showing a bottom view of the same).

[0064] In any of the examples disclosed herein, the interconnect members may be made of a silver-plated metal material. Useful metals include, for example, molybdenum; a nickel-cobalt ferrous alloy material designed to be compatible with the thermal expansion characteristics of borosilicate glass such as that available under the trade designation KOVAR from Carpenter Technology Corporation; a nickel iron alloy material having a uniquely low coefficient of thermal expansion available under the trade designation Invar, FeNi36, or 64FeNi; or the like.

[0065] In any of the examples disclosed herein the connection pads may be welded to the cathode or top surface of the first solar cell and to a top surface or cathode of the bypass diode. Similarly, the connection portions on the opposite side of the interconnect member may be welded as well.

[0066] In any of the examples disclosed herein, cover glass may be bonded over the top surface of the solar cell, the bypass diode, and a first side of the interconnect member using an adhesive.

[0067] In any of the examples of the present disclosure, the solar cell assembly or glass interconnected cell (CIC) may be about 140 microns in thickness.

[0068] In some examples, a solar cell array comprising a supporting substrate including a molybdenum, KOVAR or FNi alloy having a CTE suitably matched to the CTE of the semiconductor and having a thickness between 0.001 and 0.005 inches (in between 0.0254 mm and 0.127 mm), and an array of solar cells mounted on the supporting substrate.

[0069] KOVAR is a trademark of CRS Holdings, Inc. of Wilmington, Del., and is a nickel-cobalt ferrous alloy designed to be compatible with the thermal expansion characteristics of borosilicate glass in order to allow adjacent disposition of the KOVAR material and the glass to ensure reliable mechanical stability over a range of temperatures.

[0070] In some examples, the semiconductor solar cells may have a thickness of less than 50 microns.

[0071] In some examples of the disclosure, a bypass diode may have a substantially triangular shape adapted to fit into a space left free by at least a portion of the cut corner. That is, the bypass diode can be fit into the space left free due to the absent corner, that is, the space that is formed between, for example, a linear contact member such as a linear bus bar, and the edge of the solar cell that is placed adjacent to the contact member.

[0072] Although described examples of the present disclosure utilizes a triple junction solar cell, i.e. a vertical stack of three subcells, various aspects and features of the present disclosure can apply to semiconductor devices with stacks with fewer or greater number of subcells, i.e. two junction cells, four junction cells, five, six, seven junction cells, etc. In the case of four or more junction cells, the use of more than one metamorphic grading interlayer may also be utilized.

[0073] In addition, although the disclosed embodiments are configured with top and bottom electrical contacts, the subcells may alternatively be contacted by means of metal contacts to laterally conductive semiconductor layers between the subcells. Such arrangements may be used to form 3-terminal, 4-terminal, and in general, n-terminal devices. The subcells can be interconnected in circuits using these additional terminals such that most of the available photogenerated current density in each subcell can be used effectively, leading to high efficiency for the multijunction cell, notwithstanding that the photogenerated current densities are typically different in the various subcells.

[0074] While the solar cell described in the present disclosure have been illustrated and described as embodied in a conventional multijunction solar cell, it is not intended to be limited to the details shown, since it is also applicable to inverted metamorphic solar cells, and various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

[0075] Thus, while the description of the semiconductor device described in the present disclosure has focused primarily on solar cells or photovoltaic devices, persons skilled in the art know that other optoelectronic devices, such as thermophotovoltaic (TPV) cells, photodetectors and light-emitting diodes (LEDS), are very similar in structure, physics, and materials to photovoltaic devices with some minor variations in doping and the minority carrier lifetime. For example, photodetectors can be the same materials and structures as the photovoltaic devices described above, but perhaps more lightly-doped for sensitivity rather than power production. On the other hand LEDs can also be made with similar structures and materials, but perhaps more heavily-doped to shorten recombination time, thus radiative lifetime to produce light instead of power. Therefore, this invention also applies to photodetectors and LEDs with structures, compositions of matter, articles of manufacture, and improvements as described above for photovoltaic cells.

[0076] It is to be noted that the terms front, back, top, bottom, over, on, under, and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the disclosure described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[0077] Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.