JPH0334582A - Solar cell fitted with cover glass - Google Patents

Abstract

PURPOSE:To thin the thickness of an adhesive inside a cell so as to relax the weight by thickening the thickness of the adhesive at the periphery of the bonding face between the cell and the cover glass than the thickness of an adhesive at the inner bonding face. CONSTITUTION:When the thickness of an adhesive at a cell inner region A is t1, the thickness of an adhesive at a peripheral region B on the side where it does not has an interconnector, is t2, the thickness of an adhesive, which includes the thickness of an interconnector 2, at the peripheral region C on the side where it has an interconnector, is t3, and the thickness of the interconnector is defined as t4, it is given a relation of, for example, t1<t2<=(t3-t4). The thickness t3 includes the thickness of a surface electrode 14. The thickness of the surface electrode 14 is usually extremely thin. According to this structure, the thickness of the adhesive at the region A inside the cell is thinned as far as possible, and to prevent the exfoliation of the adhesive arising at the periphery of the cell by the thermal stress by the temperature cycle circumstance in space, the thickness of the adhesive at the peripheral regions B and C is thickened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the structure of a solar cell having a cover glass adhered to its surface.

(Prior Art) A cover glass is used to bond the surface of a solar cell (hereinafter also referred to as a cell) to block radiation exposure and ultraviolet rays. It is especially used in solar cells for space applications. The thickness of the adhesive is made as thin as possible due to demands for weight reduction, and also due to demands for improved reliability to prevent adhesive peeling from the periphery of the cell due to thermal stress caused by temperature cycle environments. There are cases where the thickness is made as thick as possible, and cases where an intermediate thickness is used to satisfy both requirements.

The method of applying adhesive to bond the case and cover glass to the cell is to use a syringe to drop one or several drops of the adhesive onto the cell or cover glass, and then bond the cell and cover glass to spread the adhesive. Using a manufacturing method and a mesh screen with a constant aperture ratio, Cell! Alternatively, there is a method of applying adhesive to the entire cover glass.

The adhesive thickness of cells with cover glasses manufactured using the adhesive application method using a syringe depends on the shapes of the cells and cover glasses, especially their It is greatly affected by the state of warpage. The thickness of the adhesive is controlled by adjusting the amount discharged per drop using a syringe.

The adhesive thickness of the cover glass-equipped cell manufactured by the adhesive application method using a mesh screen with a constant aperture ratio is almost uniform. The adhesive thickness is controlled by adjusting the aperture ratio of the mesh screen.

FIGS. 4 to 6 are diagrams illustrating a case where a cell and a cover glass are bonded by dropping an adhesive using a syringe. As shown in the cross-sectional view of FIG. 4, using a cell 8 having a convex curvature in the direction of the cover glass 7, apply one or several drops of adhesive with a syringe onto the surface of the cell 8 or the surface of the cover glass 70. When the adhesive is discharged and bonded together by pressure bonding, the thickness of the adhesive is greatly influenced by the shape of the cell 8 and the cover glass 7, especially the warp, and as shown in the plan view of FIG. For example, the adhesive constant pressure 1s18 inside the cell has a substantially elliptical shape centered near the center of the cell. 6th
The figure is a sectional view taken along line YY' in FIG. 5, and the thickness of the adhesive 6 is thinner at the center and slightly thicker at the periphery. In the figure, the cover glass 7 is curved and the cell 8 is flat, but the opposite may be true, or both may be curved. In these figures, 2 is an interconnector, and 14 is a front electrode.

The vg1 table below has a 2×4c!
Data on the overall thickness of a cell with a cover glass 1 is shown when a cover glass 7 with a size of 2×43 and a thickness of 100 μm is adhered to a cell 8 with an R dimension. A to ■ in Table 1 correspond to each point A-1 of cell 8 shown in FIG.

Table 1: Cell thickness: 50 m Cover glass thickness: 100 m As is clear from Table 1, the thickness of the adhesive 6 applied to the center of the cell 8 is approximately 10 to 87 μm, while the circumferential portions A, B , C, E, F, and G, it can be seen that the thickness is 50 to 187 μm.

It has been confirmed that a solar cell with a cover glass of this structure can sufficiently withstand a temperature cycle test (-180°C to +140°C, held for 1 hour, 5 cycles) that depicts the temperature cycle environment in space. ing.

In addition, when the mesh screen with a fixed aperture ratio is used and the adhesive 6 is applied to the cover glass 7t or the cells 8, the adhesive 6 is applied as shown in the cross-sectional view of FIG. A fairly uniform thickness can be obtained. Table 2 below shows that for cell 8 of 4 x 60 dimensions with a thickness of 50 μm,
Data on the total thickness of a cell with a cover glass when a cover glass 7 of 4×651 dimensions with a thickness of 100 μm is adhered is shown.

A'-l' in Table 2 correspond to points A'-l' of cell 8 shown in FIG.

As is clear from Table 2 of Margin Table 2, according to this method, the thickness of the adhesive is almost uniform throughout the cell, ranging from 14 to 75 μm.
You can see that it is getting thinner.

(Problems to be Solved by the Invention) In the method of dropping adhesive using a syringe as shown in Figures 4 to 6, when the size of the cell becomes large, unless a large amount of adhesive is dropped, the entire cell There is a manufacturing problem in which the adhesive does not spread, and when the thickness of the adhesive is reduced to reduce weight, the shear core force generated at the periphery of the cell increases, and repeated temperature cycles cause the adhesive to weaken. Peeling of the agent may occur.

Furthermore, when using a mesh screen with a constant opening ratio as shown in FIG. Therefore, when the thickness of the adhesive 6 is reduced, the thickness of the adhesive 6 on the interconnector becomes even thinner by the thickness of the interconnector. Therefore, thermal stress due to temperature cycles increases, and adhesive peeling is likely to occur. Also, if the thickness of the adhesive near the interconnector 2 is to be more than a certain level, the overall weight will increase! However, the weight reduction required for recent solar cells with cover glasses cannot be achieved.

As described above, it has been difficult to satisfy both the requirements for weight reduction and reliability.

(Means for Solving the Problem) In the present invention, in order to solve the above-mentioned problem, the thickness of the adhesive at the periphery of the adhesive surface between the cell and the cover glass is adjusted to the thickness of the adhesive on the inner adhesive surface. I made it thicker than the thickness.

(Function) According to the present invention, by increasing the thickness of the adhesive in the portion where a large shear stress acts, it is possible to increase the adhesive strength and at the same time reduce the weight.

(Embodiment) Figure 1 is a plan view of an embodiment of the present invention, and as shown in the cross-sectional view of Figure 2, the thickness of the adhesive in the cell inner area A is tl, and there is no interconnector. Side peripheral area B
When the thickness of the adhesive is +2, the thickness of the adhesive including the thickness of the interconnector 2 in the peripheral area C on the side with the interconnector is °t8, and the thickness of the interconnector 2 is [4]. , for example, tl<tg≦(+3-+4)...+1)
The relationship is as follows. X −X′ in Figure 1
A cross-sectional view is shown in FIG. The thickness +8 also includes the thickness of the front electrode 14. The thickness of Table 'Etf14 is usually very thin. According to this structure, the thickness of the adhesive in the area A inside the cell is made as thin as possible, and in order to prevent the adhesive from peeling off at the periphery of the cell due to thermal stress caused by the temperature cycle environment in space. The thickness of the adhesive in areas B and C is increased. In particular, the thickness of the adhesive (t
B-+4) is desirably thicker than the thickness of the adhesive in the other peripheral areas +2.

Such a change in the thickness of the adhesive is performed by applying the adhesive to the surface of the cell 8 or the surface of the cover glass 7 using a mesh screen 9 as shown in FIG. . Area A inside cell 8 or cover glass
Pl is the aperture ratio of the inner area a of the mesh screen 9 corresponding to Assuming that the aperture ratio of is P2 and the aperture ratio of the peripheral region C of the mesh screen 9 corresponding to the peripheral region C of the cell 8 or the cover glass 7 on the side having the interconnector 2 is P8, then, for example, Pl<P2 <P8...(2
). When adhesive is applied using such a mesh screen, the desired thickness of adhesive is applied to each of areas A, B, and C, but the boundary between these areas is sequentially applied with an intermediate thickness. Change. The area between area A and area B is area (A a B), and the area between area B and area C is area (B).
#C), the middle between area A and area C is area (A, C),
The area between area A, area B, and area C is the area (A, B, C)
shall be. In addition to equation (1), these relationships are as follows: [1≦fineness of area (A, B)≦t2≦area<B, c)
Thickness≦t8...(3
) and tl ≦thickness of region (A e c )≦t3 ・
...(4) and tl≦Thickness of region (A, B, C)≦[8 ...(5
).

Table 3 below shows an example of data on the overall thickness of a solar cell with a cover glass manufactured as a prototype according to the present invention. As in the examples in Tables 1 and 2, the cell thickness is 50
The thickness of the μm1 cover glass is 100 μm. however,
The area for both was 4 x 6 cm. A' in MrJB table
-I' correspond to each point A' to ■' in FIG.

As is clear from Table 8, the thickness of the adhesive in the inner region A of the cell, for example at point E' in FIG.
For example, point B I in the circumferential proper region B.

The thickness of the adhesive at cl, vl, Hl, xl is somewhat thick, 44-88/l m, and for example at points A', D' in the peripheral region C.

The thickness of the adhesive at G' is as thick as 82 to 118 μm. Furthermore, if the thickness of the interconnector is 80 μm, the thickness of the adhesive on the interconnector is 52 to 50 μm.
It is 88 μm, which falls within the range of formulas (1) to (5) described above. It has been confirmed that the solar battery cell with a cover glass having this structure does not cause adhesive peeling even in the above-mentioned temperature cycle test.

The fact that the structure according to the present invention is highly reliable with respect to adhesive peeling can be explained using a simple -dimensional stress equation as follows.

In FIG. 10, it is assumed that the cover glass 7 and the cell 8 have high rigidity and are not affected by mutual displacement via the adhesive 6. In addition, the adhesive 6 has low rigidity, and the cover glass 7 and the cells 8 (assuming the effect of curling displacement is 1). Sawo rttT
Let it be slTg. In addition, the transverse elastic constant of the adhesive 6 is 08, and the X-axis stress of the cover glass 7 and cell 8 is g
'1. Let it be g2. Assume that the interfacial shear stress between the casing, the cover glass 7, and the adhesive 6 of the cell 8 is equal to τ.
shall be.

At this time Here, X indicates the distance from the center of the cell.

Each stress is expressed by the formula below.

El and E2 indicate the Young's modulus of the cover glass 7 and the cell 8, respectively.

ul and u2 indicate the displacement of each layer in the X-axis direction, αl and α2 indicate the linear expansion coefficient of each layer, and JT indicates the amount of temperature change.

When the solution to equation (G) is found using equation (Ql), σ2 =
−m g l m=T1/′r2, n=”/E!

When arranged as a function of the adhesive thickness T8, it becomes as follows.

Figure 11 shows the shear core force τ when the thickness of the cell 8, the thickness of the cover glass 7, and the physical property values of each constituent material are arbitrarily fixed.
A relative comparison is shown using the thickness T8 of the adhesive 6 and the distance X from the center of the cell 8 as parameters. Adhesive thickness T2
It can be seen that as the size of the cell becomes smaller and the dimensions of the cell and the cell become larger, the shear stress generated in the adhesive 6 around the cell increases exponentially.

Although the above explanation has been made regarding an example using a mesh screen, it may also be realized by discharging the adhesive from a narrow nozzle and obtaining a distribution of the adhesive that satisfies the condition of formula (2).

(Effects of the Invention) As described above, in the solar cell with a cover glass according to the present invention, since the thickness of the adhesive in the peripheral part is thick, the reliability against thermal settling is improved, and the thickness of the adhesive inside the cell is increased. Since it can be made thinner, the weight can be reduced. This is effective in reducing the weight of the adhesive even as solar cells become larger.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a sectional view taken along line xx' in FIG. 1, FIG. 8 is a plan view of a mesh screen used in the present invention, and FIG. 5 is a plan view of a conventional example, FIG. 6 is a Y-Y' sectional view thereof, and FIG. 7 is a sectional view of another conventional example, Fig. 8 is a plan view showing the position of each point of data measurement in the example of Fig. 5, Fig. 9 is a plan view showing the position of each point of data measurement in the example of Fig. +$7, and Fig. 10 is a plan view showing the position of each point of data measurement in the example of Fig. 5. FIG. 11, a perspective view for explaining the formula, is a graph showing the relationship between shear stress and distance from the cell center. l...Solar cell with cover glass, 2...Interconnector, 6...Adhesive, 7...Cover glass,
8...Cell, 18...Thick edge of adhesive etc., 14...Top electrode diagram diagram diagram diagram

Claims (1)

[Claims] 1. The thickness of the adhesive on the bonding surface between the solar cell and the cover glass is defined as: thickness of adhesive at the center of the cell <thickness of adhesive at the periphery where there is no interconnector ≤interconnector A solar cell with a cover glass, characterized in that the thickness of the adhesive on the periphery of the connector is increased.