JPH03250673A - Compound semiconductor photoelectric conversion element on si substrate - Google Patents

Abstract

PURPOSE:To permit connection of an external connector without destroying a GaAs solar battery on an Si substrate or degrading its characteristics by forming a welded assembly part of a p-electrode and a welded assembly part of an n-electrode outside the GaAs solar battery itself. CONSTITUTION:A p-electrode 7 is joined to a p-type GaAs layer 4 with a hole opened in ARC 6 and p-type AlGaAs 5 as well as wired on the side of an Si substrate via an insulating film 9 and is further extended continuously to the outside on the same plane as a second principal surface. An-electrode 8 is continuously extended to the outside of the second principal surface on the second principal plane and the same plane as the second principal plane. A welded part 7b of the p-electrode 7 and a welded part 8b of the n-electrode exist outside a GaAs layer of a GaAs solar battery on the Si substrate and the Si substrate. When an external connector is to be welded, thermal and mechanical stress accompanying the welding does not affect the GaAs layer, so that no crack will occur on the GaAs layer as well as no crack of the Si substrate due to the stress will occur.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a compound semiconductor photoelectric conversion device on a Si substrate, and particularly relates to the structure of a photoelectric conversion device having an m-v group compound semiconductor layer on a Si substrate. .

[Conventional technology]

FIG. 4 shows, for example, a conventional compound semiconductor photoelectric conversion element on a Si substrate, as shown on page 196 of the collection of papers presented at the 3rd International Conference on Photovoltaic Power Generation held in 1987.

Here, a GaAs solar cell on a Si substrate will be described as an example of a compound semiconductor photoelectric conversion element on a Si substrate.

In FIG. 4, 1 is a Si substrate, and 2 is an n-type GaAs epitaxially grown on the first main surface of the Si substrate 1.
, 3 is GaAs and AlGaA grown on top of it.
s (or InGaAs) superlattice (hereinafter referred to as Ga A
s/A 7! (referred to as G a As superlattice), 2
' is n-type GaAs as the active layer of the solar cell, 4 is G
a As / A j! It is formed on the n-type GaAS 2' formed on the GaAs superlattice 3, and absorbs light energy and generates electricity as the active layer of the solar cell.
n-type GaAs for n-junction formation, 5 is n-type GaAs4
p-type A is formed on top of the solar cell and serves as the window layer of the solar cell.
fGaAs, 6 is an anti-reflection coating (hereinafter referred to as A RC) to allow as much light as possible to enter the inside of the solar cell.
Abbreviation for Reflection Coating”
), 7 is a hole formed in ARC6 and p-type A#GaAs5, and patterned to contact n-type GaAs4, to effectively collect the photocurrent generated by light irradiation and take it out to the outside. Side metal electrode, 8 is Si
This is an n-side metal electrode formed on the back side of the substrate 1.

Next, the operation will be explained.

The light is A, R, C6 and p-type Aj! When the light enters n-type GaAs4 and n-type GaAs 2' through GaAs 5, the incident light is absorbed in this region and converted into carriers of electrons and holes, and the electrons generated in n-type GaAs4 are p
through n-junction to n-type GaAs2', n-type GaAs2
The holes generated at 7.' diffuse into the n-type GaAs4 through the p-n junction, and positive charges are transferred to the n-side metal electrode 7. Negative charges are collected on the n-side metal electrode 8, a voltage is generated between these terminals, and a current can be extracted from between these terminals.

[Problem to be solved by the invention]

Conventional GaAs solar cells on Si substrates are constructed as described above, so in principle there seems to be no problem in extracting current, but when actually used as a solar cell,
It is necessary to connect an interconnector for current extraction to the n-electrode 7 and n-electrode 8 sides. This connection has G
Parallel gear welding is generally used in aAs solar cells, etc., as it has high reliability at connection points, but when this method is applied to a GaAs solar cell on a Si substrate with the structure shown in Figure 4, Thermal damage causes thermal damage to the GaAs layer below the weld of the n-electrode 7, resulting in problems such as a decrease in adhesive strength of the interconnector at that location and a decrease in solar cell characteristics due to p-n junction breakdown. Furthermore, the thermal expansion coefficients of Ga A, s and SiO are
is 2.4X10'(K-'), GaAs is 5.7X
10-6 (K-'), and the deformation of the element due to the difference between the two, that is, the deformation that causes the solar cell in FIG. 4 to become convex upward when viewed with the n-electrode 8 facing upward. Yes, Figure 2 (
When welding a connector to this n-electrode side, as shown in Figure 2(a), welding head 1 is placed on this convex side.
From 5 onwards, mechanical and thermal stress will be applied.
Cracks occur in the GaAs layer in the parts of the product corresponding to the welded parts, and in severe cases, the Si substrate is also cracked, making it unusable as a solar cell.

This invention was made to solve the above-mentioned problems, and it prevents cracks in the GaAs layer and cracks in the solar cell when welding the n-electrode of the solar cell and the external connector on the n-electrode. An object of the present invention is to obtain a compound semiconductor photoelectric conversion element on a Si substrate that can prevent the above problems.

[Means to solve the problem]

In the compound semiconductor photoelectric conversion device on a Si substrate according to the present invention, the second conductivity type electrode is connected to the second conductivity type m-v group compound semiconductor layer formed on the first main surface of the Si substrate; The part passes over the side surface of the Si substrate through the insulating film, and the
The second major surface is formed on the same surface as the second main surface of the substrate.
is continuously stretched on a portion other than the main surface of the first
The conductivity type electrode is also formed on the second main surface of the Si substrate, and a part thereof is formed so as to be continuously extended to a portion other than the second main surface.

Further, the present invention provides that the portions of the first conductivity type electrode (n electrode) and the second conductivity type electrode (n electrode) that are not on the second main surface of the Si substrate, that is, the portions that protrude to the outside of the solar cell, It has a stress relief structure.

[Effect]

In this invention, the n-electrode and the tip of the n-electrode are present in the region where Si and the m-v group compound semiconductor of the m-v group compound semiconductor solar cell on the Sj substrate are not present, so external connectors are connected at these parts. As a result, mechanical and thermal stress will not affect the m-v group compound semiconductor solar cell, and problems such as deterioration of characteristics and cracking of the shape of the m-v group compound semiconductor solar cell on the Si substrate will occur. Practical assembly can be done without any problems.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional perspective view of a GaAs solar cell on a Si substrate, which is a compound semiconductor photoelectric conversion element on a Si substrate according to an embodiment of the present invention. In the figure, 1 is an n-type Si substrate;
2 is n-type GaAs epitaxially grown on this Si substrate l, 3 is GaA further grown on it, s/
Aj! GaAs (or InGaAs etc.) superlattice,
2' is n-type GaAs as the active layer of the solar cell, 4 is G
a p-type G a A, s, 5 is formed on the a A S /AlGaAs superlattice 3 to form a p-n junction that absorbs light energy and generates electricity as an active layer of a solar cell.
p-type AlGaAs formed on 4-type GaAs and serving as the window layer of the solar cell; 6 is an anti-reflection film (A, RC)
, 7 drilled holes in ARC6 and p-type AAGaAs 5,
A p-electrode connected to the p-type GaAs layer 4, wired on the side surface of the Si substrate via an insulating film 9, and further extended continuously to the outside of the same plane as the second main surface, 7a
7b is the grid electrode portion, and 7b is the bus electrode welding portion.

Reference numeral 8 denotes a second main surface and an n-electrode formed on the same plane as the second main surface and extending continuously to the outside of the second main surface, of which 8a
is an n-electrode formed on the second main surface, and 8b is a helical electrode welding part. 9 is an insulating film for electrically insulating the p-electrode 7 and the n-type GaAs and n-type Si substrates; 10 is the p-electrode 7;
This is an insulating film for preventing a short circuit between the n-electrode 8 and the n-electrode 8.

Since the operation of the solar cell itself of the GaAs solar cell on the Si substrate according to this embodiment is the same as that of the conventional example, the description will be omitted, and the characteristic operation of this embodiment will be described. The welded portion 7b of the p-electrode and the welded portion 8b of the n-electrode according to the present invention are S
Since it exists outside the GaAs layer of the GaAs solar cell on the i-substrate and the Si substrate, when welding an external connector here, the thermal and mechanical stress associated with welding does not reach the GaAs layer, so cracks may occur in the GaAs layer. Not only will this not occur, but the Si substrate will not crack due to the stress described above. As mentioned in the conventional example, Ga is deposited on a Si substrate.
When forming an As layer, epitaxial growth is usually performed at a high temperature of about 700°C, and then stress is alleviated by the movement of dislocations in the high temperature region during the gradual cooling process, but it is not necessary to cool down to about 350°C. If this happens, the dislocations will move, making it impossible to alleviate the stress, and stress will be generated inside due to the difference in thermal expansion coefficient between Si and GaASO, which corresponds to the temperature difference caused by cooling. This inherent stress amount is
A sufficient amount to generate a crank in the As layer (~1,
5 x 109 dyn/cm”) has been accumulated.

If it is static, it may be able to withstand this stress, but if mechanical or thermal dynamic stress is applied, such as when welding an external connector, this will act as a trigger, and the GaAs layer will be damaged. Crank occurs, and this crack breaks the GaAs layer, resulting in a decrease in the photovoltaic properties of the GaAs solar cell.

In actual use, solar cells are rarely used alone, and multiple solar cells are connected to each other using external connectors. As shown in Figure 4, in a conventional GaAs solar cell on a Si substrate, the n-electrode is on the second main surface of the Si substrate. As shown in the figure, since the convexly curved solar cell is locally pressurized and heated by the welding head 15 until it comes into flat contact with the welding table 14, a bending moment is first applied to the entire solar cell, and then the bending moment is applied to the entire solar cell, and then Since thermal stress was applied from the welding head, cracks occurred in the GaAs layer corresponding to the areas in contact with the welding head, and the Si substrate broke.

On the other hand, in the above embodiment of the present invention, the n electrode 8 is formed on the first main surface of the Si substrate as shown in FIG. When welding the external connector to the electrode 8b, the solar cell 11 becomes concave upward;
Even when the welding head 15 applies pressure on the n-electrode 8b for welding, the other end of the solar cell lifts up, causing the G on the Si substrate to rise.
No mechanical stress is applied to the aAs layer 11.

Further, since there is no GaAs layer under the n-electrode, local heating from the welding head 15 has no adverse effect on the GaAs layer. Therefore, in this embodiment, external connectors can be connected without deteriorating the characteristics or destroying the structure of the solar cell, and a GaAs solar cell on a Si substrate can be put to practical use.

In the above embodiment, the p-bus electrode welded portion 7b has a flat plate shape, but the p-bus electrode welded portion 7b may have a stress relief structure, and an example thereof is shown in the third example.
As shown in the figure. Figure 3 shows a mesh type. By making the bus electrode welding part a mesh type in this way, when welding external connectors to each electrode, it is possible to release the force applied to the cell when the welding head 15 pressurizes the n-electrode 8b for welding. This makes it possible to obtain more reliable cell connection points when modularized, and to improve the characteristics of solar cells.

Naturally, the shape of the stress relief is not limited to the mesoche type, and may have any other structure as long as it releases the force applied to the cell.

In one embodiment of the present invention, a case of a GaAs solar cell has been described, but similar effects can be obtained with devices using other compound semiconductors.

〔Effect of the invention〕

As described above, the GaAs solar cell on the Si substrate according to the present invention has the p-electrode welding assembly location and the n-electrode welding assembly location outside the GaAs solar cell itself. External connectors can be connected without causing damage or property deterioration, which not only makes it practical, but also allows connectors and connectors to be connected by using the externally protruding p and n electrodes as connectors themselves. Since there is no need for a process to do this, it is possible to reduce assembly costs and increase the cell filling rate when connecting multiple cells into modules. This has the effect of increasing the efficiency of the solar cell module by allowing more power to be obtained.

Furthermore, since the p and n electrodes protruding to the outside have a stress relief structure, there is an effect that a highly reliable cell connection point can be obtained when modularized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional perspective view of a compound semiconductor photoelectric conversion element on a Si substrate according to an embodiment of the present invention, and FIG. 2 (δ), fb
) is a diagram showing the state of assembly of a GaAs solar cell on a conventional Si substrate to an nTK pole, and a diagram showing the state of assembly in one embodiment of the present invention, and FIG. 3 is a diagram showing another embodiment of the present invention. A plan view of an example of a compound semiconductor photoelectric conversion device on a Si substrate, FIG. 4 shows a conventional GaAs on a Si substrate.
FIG. 2 is a cross-sectional structural diagram of a solar cell. 1 is a Si substrate, 2 is an n-type GaAs, 2' is an n-type GaAs as a solar cell active layer, 3 is a GaAs layer A I
Ga As superlattice, 4 is p-type GaAs, 5 is p-type A
&GaAs, 6 is an anti-reflection film, 7 is a p-electrode, 7a is a p-grid electrode part, 7b is an n-bus electrode welding part, 8 is an n-electrode,
8a is an n electrode on the second main surface, 8b is an n bus electrode welding part,
9 is a side insulating film, 10 is a second main surface insulating film, 11 is a GaAs solar cell on a Si substrate of the present invention, 14 is a welding sound, 1
5 is a welding device, and 51 is a conventional GaAs solar cell on a Si substrate. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A first conductivity type Si substrate, a first conductivity type III-V compound semiconductor layer formed on the first main surface of the Si substrate, and a first conductivity type III-V compound semiconductor layer formed on the first main surface of the Si substrate. In a photoelectric conversion element having a second conductivity type III-V compound semiconductor layer formed on a semiconductor layer, a second conductivity type electrode is connected to the second conductivity type III-V compound semiconductor layer, and A part of the Si substrate is formed by extending through an insulating film on the same surface as the second main surface of the Si substrate and not on the second main surface,
A first conductivity type electrode is formed on the second main surface of the Si substrate, and a part thereof is formed on the same plane as the second main surface and extends on a portion not on the second main surface. A compound semiconductor photoelectric conversion device on a Si substrate, characterized in that: (2) The compound semiconductor photoelectric conversion device on a Si substrate according to claim 1, wherein a stress relief structure is provided on a portion of the first conductivity type electrode and the second conductivity type electrode that is not on the second principal surface.