Solar cell string

Abstract

Provided is a solar cell string (1) comprising: a plurality of solar cells (10) that each have a front surface electrode pattern (16) which has a plurality of front surface finger electrodes (161), a perovskite photoelectric conversion layer (14), a crystalline silicon photoelectric conversion substrate (11), and a rear surface electrode pattern (13) which has a plurality of rear surface finger electrodes (131) and a rear surface bus bar electrode (132), and that are disposed such that ends thereof overlap; a plurality of conductive adhesives (21) that are respectively disposed on the plurality of front surface finger electrodes (161) to connect the front surface finger electrodes (161) to the rear surface bus bar electrodes (132) of the solar cells (10) facing each other; and an insulating adhesive (22) that are disposed between the front surface finger electrodes (161) to connect the solar cells (10) facing each other.

Description

Solar cell string

[0001] The present invention relates to a solar cell string.

[0002] As an energy source with low environmental impact, the use of solar cell modules is expanding. A solar cell module is generally formed by sealing a plurality of solar cells between a pair of protective materials. When installing solar cells in various devices, vehicles, buildings, etc., the installable area is limited, so the photoelectric conversion efficiency of the solar cell module can be important. For this reason, a technique is known that eliminates gaps between solar cells and increases the effective area of solar cells in a solar cell module by means of a so-called shingling structure in which ends of solar cells are arranged overlapping each other (see, for example, Patent Document 1).

[0003] Furthermore, as solar cells with high photoelectric conversion efficiency, development is progressing on tandem-type solar cells formed by stacking two types of photoelectric conversion layers having different absorption wavelengths. As an example, a monolithic tandem solar cell has been proposed in which a perovskite photoelectric conversion layer excellent in photoelectric conversion efficiency in the short wavelength region is laminated on the surface of a silicon photoelectric conversion substrate having a wide absorption wavelength range (see, for example, Patent Document 2).

[0004] Japanese Unexamined Patent Application Publication No. 11-186577, Japanese Unexamined Patent Application Publication No. 2017-168500

[0005] When monolithic tandem solar cells having a perovskite photoelectric conversion layer laminated on the front side are connected in a shingling structure, a relatively large stress can act on electrodes disposed on the perovskite photoelectric conversion layer and connected to adjacent solar cells. The perovskite photoelectric conversion layer is relatively prone to peeling; in particular, the region where the electrode of the perovskite photoelectric conversion layer is formed may have residual stress due to electrode formation, so there is a risk of peeling due to the stress acting on the electrode. Therefore, an object of the present invention is to provide a solar cell string having a shingling structure that can suppress peeling of the perovskite photoelectric conversion layer.

[0006] (1) A solar cell string according to one aspect of the present invention comprises a plurality of solar cells arranged with their ends overlapping, each having a surface electrode pattern having a plurality of surface finger electrodes, a perovskite photoelectric conversion layer, a crystalline silicon photoelectric conversion substrate, and a back electrode pattern having a plurality of back finger electrodes and a back busbar electrode, and a plurality of conductive adhesives arranged on the plurality of surface finger electrodes and connecting the surface finger electrodes to the back busbar electrodes of the opposing solar cells, and an insulating adhesive arranged between the surface finger electrodes and connecting the opposing solar cells.

[0007] (2) In the solar cell string of (1), the length of the conductive adhesive along the surface finger electrode may be 2 times or more and 20 times or less the widthwise length of the surface finger electrode.

[0008] (2) In the solar cell string of (1) to (2), the back electrode pattern has a plurality of back busbar electrodes, and the length of the conductive adhesive along the front finger electrodes may be greater than or equal to the distance between the back busbar electrodes.

[0009] According to the present invention, a solar cell string with a single-ring structure that can suppress the peeling of the perovskite photoelectric conversion layer can be provided.

[0010] This is a schematic cross-sectional view of a solar cell string according to one embodiment of the present invention. This is a schematic cross-sectional view of the solar cell string of Figure 1 taken along the line X-X. This is a schematic plan view of the solar cell of Figure 1. This is a schematic back view of the solar cell of Figure 1. This is a schematic enlarged plan view showing an example of the arrangement of conductive adhesive and insulating adhesive in Figure 1. This is a schematic enlarged plan view showing a different arrangement of conductive adhesive and insulating adhesive in Figure 1 than that shown in Figure 4.

[0011] Embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions of various components in the drawings have been adjusted for ease of viewing. Furthermore, in embodiments described later, components similar to those described earlier are denoted by the same reference numerals, and redundant explanations may be omitted.

[0012] Figure 1 is a schematic cross-sectional view of a solar cell string 1 according to one embodiment of the present invention. Figure 2 is a schematic cross-sectional view of the solar cell string 1. The solar cell string 1 comprises a plurality of solar cells 10 arranged in a row in a first direction with their ends overlapping, a plurality of conductive adhesives 21 that mainly electrically connect the solar cells 10, and a plurality of insulating adhesives 22 that mechanically connect the solar cells 10. The solar cell string 1 has a so-called single-ring structure.

[0013] The solar cell 10 comprises a crystalline silicon photoelectric conversion substrate 11, a back surface transparent electrode layer 12, a back surface electrode pattern 13, a perovskite photoelectric conversion layer 14, a front surface transparent electrode layer 15, and a front surface electrode pattern 16. The solar cell 10 is a so-called monolithic tandem type solar cell in which the perovskite photoelectric conversion layer 14 is laminated on the crystalline silicon photoelectric conversion substrate 11.

[0014] The crystalline silicon photoelectric conversion substrate 11 absorbs light that has passed through the perovskite photoelectric conversion layer 14 to generate carriers (charges: electrons and holes), and outputs charges of different polarities on its front and back sides. The crystalline silicon photoelectric conversion substrate 11 is formed from a single-crystal silicon material and may be, for example, an n-type semiconductor substrate doped with an n-type dopant or a p-type semiconductor substrate doped with a p-type dopant. The crystalline silicon photoelectric conversion substrate 11 may have semiconductor layers stacked on its front and back sides to select the polarity of the carriers passing through. These semiconductor layers may be formed by film deposition techniques such as CVD or PVD.

[0015] The back surface transparent electrode layer 12 collects carriers of one polarity from the carriers generated in the crystalline silicon photoelectric conversion substrate 11 and outputs them to the outside. The back surface transparent electrode layer 12 is formed from a conductive material such as transparent conductive oxide (TCO). Examples of transparent conductive oxides include indium oxide, tin oxide, zinc oxide, titanium oxide, and composite oxides thereof, among which ITO (Indium Tin Oxide), which is indium oxide with added tin, is preferred. Depending on the material, the back surface transparent electrode layer 12 can be formed by film deposition techniques such as CVD or PVD.

[0016] As shown in Figure 3, the back electrode pattern 13 is a relatively low-resistance conductor for outputting the charge collected by the back transparent electrode layer 12 as an electric current to an adjacent solar cell 10 or external wiring. The back electrode pattern 13 has a plurality of back finger electrodes 131 extending in a first direction, and a back busbar electrode 132 extending in a second direction intersecting the first direction along one end of the solar cell 10 in the first direction. The back finger electrodes 131 compensate for the high electrical resistance of the back transparent electrode layer 12 in the planar direction by serving as a charge movement path in the first direction. The back busbar electrode 132 connects the plurality of back finger electrodes 131 to maintain an equal potential and is used as an external terminal for connecting to an adjacent solar cell 10 or external wiring. The back electrode pattern 13 may have one or any number of back busbar electrodes 132 so as to easily increase the adjustment range of the overlap width of the solar cells 10 in order to obtain a solar cell string 1 of a desired length without unnecessarily increasing its area. The back-side finger electrodes 131 may further have compensating electrodes (not shown) that intersect with the back-side finger electrodes 131 in order to enhance the potential equalization effect between the back-side finger electrodes 131. The back-side electrode pattern 13 is formed from, for example, metal, conductive paste, etc. Depending on the material, the back-side electrode pattern 13 can be formed by film deposition techniques such as CVD and PVD using a mask, or by printing techniques such as screen printing and dispensing.

[0017] The perovskite photoelectric conversion layer 14 absorbs incident light of a different wavelength than that absorbed by the crystalline silicon photoelectric conversion substrate 11, generating photocarriers and outputting charges of different polarities on its front and back sides. The polarity of the perovskite photoelectric conversion layer 14 is oriented in the same direction as the polarity of the crystalline silicon photoelectric conversion substrate 11. The perovskite compound contained in the perovskite photoelectric conversion layer 14 includes an organic atomic group A containing at least one of monovalent organic ammonium ions and amidinium-based ions, a metal atom B that generates a divalent metal ion, and a halogen atom X containing at least one of iodide ions I, bromide ions Br, chloride ions Cl, and fluoride ions F, and ABX ３ Compounds represented by can be used. The perovskite photoelectric conversion layer 14 may have a configuration comprising a perovskite compound and an excitation layer that generates photocarriers, a first charge transport layer interposed between the excitation layer and the crystalline silicon photoelectric conversion substrate 11 that selectively extracts charges of one polarity, and a second charge transport layer interposed between the excitation layer and the surface transparent electrode layer 15 that selectively extracts charges of the other polarity. Each layer of the perovskite photoelectric conversion layer 14 may be formed by film deposition techniques such as coating, CVD, or PVD, depending on the material.

[0018] The surface transparent electrode layer 15 collects charges of a different polarity from the charges extracted by the back transparent electrode layer 12 from the crystalline silicon photoelectric conversion substrate 11, among the carriers generated in the perovskite photoelectric conversion layer 14, and outputs them to the outside. The surface transparent electrode layer 15, like the back transparent electrode layer 12, is formed from a conductive material such as a transparent conductive oxide, and depending on the material, it can be formed by a film deposition technique such as CVD or PVD.

[0019] As shown in Figure 4, the surface electrode pattern 16 is a relatively low-resistance conductor for outputting the charge collected by the surface transparent electrode layer 15 as an electric current to an adjacent solar cell 10 or external wiring. The surface electrode pattern 16 has a plurality of surface finger electrodes 161 extending in a first direction, which serve as a charge movement path in the first direction and compensate for the high electrical resistance of the surface transparent electrode layer 15 in the planar direction. The surface finger electrodes 161 are preferably formed in parallel lines with a constant and sufficient spacing between them to reduce the area that blocks light. The surface electrode pattern 16 may have compensation electrodes (not shown) to equalize the potential of the surface finger electrodes 161, but it is preferable that there are no portions extending in a second direction, such as busbars or compensation electrodes, in the area where an adjacent solar cell 10 is superimposed on the front side. The surface electrode pattern 16 is formed from, for example, metal, conductive paste, etc. The surface electrode pattern 16 can be formed by film deposition techniques such as CVD and PVD using a mask, or by printing techniques using a screen plate, dispenser, etc., depending on the material.

[0020] As shown in Figure 5, the conductive adhesive 21 is placed on each of the multiple surface finger electrodes 161, connecting the surface finger electrodes 161 to the back busbar electrodes 132 of the opposing solar cell 10. The conductive adhesive 21 may extend beyond the surface finger electrodes 161, but space is left between it and the conductive adhesive 21 on the opposing surface finger electrodes 161 for the placement of insulating adhesive 22. The conductive adhesive 21 may be arranged in a substantially circular shape, but it is preferable that the length along the surface finger electrodes 161 is greater than the width of the surface finger electrodes 161 in order to allow for misalignment of the opposing solar cell 10 in the first direction. The length of the conductive adhesive 21 along the surface finger electrodes 161 is preferably 2 to 20 times the width of the surface finger electrodes 161, and more preferably 5 to 10 times. This ensures that the surface finger electrodes 161 are securely connected to the opposing back busbar electrodes 132, while preventing the conductive adhesive 21 from protruding from the front solar cell 10 and impairing its appearance. When the back electrode pattern 13 has multiple back busbar electrodes 132, it is preferable that the length of the conductive adhesive 21 along the surface finger electrodes 161 is greater than or equal to the distance between the back busbar electrodes 132 (the width of the area without back busbar electrodes 132) so that the surface finger electrodes 161 can be connected to any of the back busbar electrodes 132.

[0021] As shown in Figure 5, the insulating adhesive 22 is placed on the transparent surface electrode layer 15 between the surface finger electrodes 161, connecting the opposing solar cells 10, more specifically, the transparent back surface electrode layer 12 or back surface electrode pattern 13 (mainly the back surface busbar electrode 132) of the solar cell 10 facing the transparent surface electrode layer 15. The insulating adhesive 22 ensures a mechanical connection between the opposing solar cells 10 and suppresses peeling stress acting on the surface finger electrodes 161 that are connected to the corresponding solar cells 10 by the conductive adhesive 21. In the solar cell 10, residual stress generated during the formation of the surface finger electrodes 161 can easily cause delamination between the layers on the surface or inside the perovskite photoelectric conversion layer 14 directly beneath the surface finger electrodes 161. However, by suppressing the peeling stress acting on the surface finger electrodes 161 with the insulating adhesive 22, damage to the solar cell 10 due to thermal stress, etc., can be suppressed. In a plan view, the area of ​​the insulating adhesive 22 is preferably larger than the area of ​​the conductive adhesive 21 in order to more reliably suppress the peeling stress of the surface finger electrodes 161. Since the insulating adhesive 22 is usually transparent, any overflow from the front side of the solar cell 10 has little effect on the aesthetics. The insulating adhesive 22 may be arranged continuously around multiple conductive adhesives 21, as shown in the alternative diagram in Figure 6.

[0022] As described above, the solar cell string 1 according to this embodiment is highly reliable because, by directly connecting the surface finger electrodes 161 of the back-side solar cell 10 to the back-side busbar electrodes 132 of the front-side solar cell 10 with a conductive adhesive 21, and by mechanically connecting the opposing solar cells 10 between the surface finger electrodes 161 with an insulating adhesive 22, it is possible to prevent large peeling stress from acting on the region where the surface electrode pattern 16 exists and causing the perovskite photoelectric conversion layer 14 to peel off.

[0023] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and variations are possible. The solar cell according to the present invention may have a multilayer structure for each layer, and may further include layers that perform additional functions. For example, the solar cell in the solar cell string according to the present invention may be provided with an intermediate electrode layer that ensures the electrical and mechanical bonding between the crystalline silicon photoelectric conversion substrate and the perovskite photoelectric conversion layer, a passivation layer that suppresses the recombination of photocarriers at the interface between the crystalline silicon photoelectric conversion substrate and the perovskite photoelectric conversion layer, an anti-reflective layer that suppresses light reflection, and the like.

[0024] 1 Solar cell string 10 Solar cell 11 Crystalline silicon photoelectric conversion substrate 12 Backside transparent electrode layer 13 Backside electrode pattern 131 Backside finger electrode 132 Backside busbar electrode 14 Perovskite photoelectric conversion layer 15 Front transparent electrode layer 16 Front electrode pattern 161 Front finger electrode 21 Conductive adhesive 22 Insulating adhesive

Claims

1. A solar cell string comprising: a plurality of solar cells each having a surface electrode pattern having a plurality of surface finger electrodes, a perovskite photoelectric conversion layer, a crystalline silicon photoelectric conversion substrate, and a back electrode pattern having a plurality of back finger electrodes and a back busbar electrode, with their ends overlapping; a plurality of conductive adhesives each disposed on the plurality of surface finger electrodes and connecting the surface finger electrodes to the back busbar electrodes of the opposing solar cells; and an insulating adhesive disposed between the surface finger electrodes and connecting the opposing solar cells.

2. The solar cell string according to claim 1, wherein the length of the conductive adhesive along the surface finger electrode is 2 to 20 times the widthwise length of the surface finger electrode.

3. The solar cell string according to claim 2, wherein the back electrode pattern has a plurality of back busbar electrodes, and the length of the conductive adhesive along the front finger electrodes is greater than or equal to the distance between the back busbar electrodes.

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