JPS60234379A - Formation for electrode of solar cell - Google Patents

Abstract

PURPOSE:To increase the thickness or wall thickness of the striped part of each of the patternized electrodes of a solar cell and to lower their series resistance values by a method wherein the evaporating material on the surface of the evaporated resist layer formed on the main surface of the photoelectric converting body according to the prescribed pattern is removed and the evaporated resist layer, which is reexposed, is performed a plating treatment as a plated resist layer. CONSTITUTION:An evaporated resist layer 4 is formed on the main surface of a photoelectric converting body 3 according to the prescribed pattern by a printing method and so forth. After that, firstly, Cr layers 51, which are respectively used as a first layer, are evaporated, then Cu layers 52, which are respectively used as a second layer, are evaporated and evaporated layers 5, which are respectively used collectively as one layer, are formed. The evaporating material adhered on the surface of the evaporated resist layer 4 is removed by a method, desirably by a mechanical grindstone grinding, and the evaporated resist layer 4 is reexposed. After that, when such a layer as a Cu layer is electroplated on each evaporated layer 5 in the thickness of 10mum, for example, as a first plated layer, and furthermore, such a layer as an Ni layer is electroplated thereon in the thickness of 2mum, for example, as a second plated layer, a plated layer 6 is formed on only each of the evaporated electrode layer parts 5 as an electrode base layer to conform to the prescribed pattern. The plated layers 60 are formed in such a manner as not to adhere on a plated resist layer 40, which is the former evaporated resist layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming electrodes in a solar cell, and in particular, in a pair of front and back electrodes of a solar cell, electrodes are formed on the side (which is the light incident side) in accordance with a predetermined pattern. The present invention relates to a method for forming patterned electrodes.

In a solar cell element having a photoelectric converter such as a pn junction or an nn heterojunction, a total of a pair of electrodes are formed on both main surfaces of the photoelectric conversion specimen in order to extract electric power. Since the electrode on the incident surface side must allow light to efficiently enter the photoelectric converter below, it is necessary to use a pattern that exposes as much of the main surface as possible, rather than the entire main surface of the photoelectric converter, such as a narrow stripe. It is formed into a lattice-like or comb-like pattern consisting of a combination of shaped parts.

However, if this is done, the series resistance value of the patterned electrode inevitably becomes high, which is therefore undesirable in terms of effectively extracting the converted power.

Therefore, in order to eliminate the conflict between these two requirements and lower the series resistance value of the patterned electrode, it is a simple method to increase the thickness or wall thickness of each striped portion of the patterned electrode. Conceivable.

Prior to filing this application, the applicant conducted an experiment to increase the electrode thickness by a plating method, particularly an electroplating method, as a specific method for this purpose. The plating method is not only the cheapest and simplest method, but also requires a low-temperature process.
This is because it was considered to be an advantageous method even for devices that cannot employ high-temperature processes, such as SI+02/Si solar cells, which are separately disclosed by the applicant.

However, the results showed that simply adopting a plating method could not achieve the objective.

One reason for this is that when an electrode layer is suddenly deposited on the main surface of the photoelectric converter using a plating method, good physical and electrical compatibility between the bottom layer of the electrode and the material of the photoelectric converter is obtained. I was at the point where I couldn't do it. If only an inexpensive plating treatment was used, peeling or the like could occur.

Therefore, one of the findings obtained is that an electrode layer is first formed as a base layer on the main surface of the photovoltaic specimen by vapor deposition to ensure good ohmic contact and mechanical adhesion strength with the photovoltaic specimen. Only then can the deposition of the Menki layer begin.

However, it is also possible to perform plating treatment on the electrode material layer formed by vapor deposition in a series of steps without removing the resist layer during vapor deposition, thereby achieving a considerably thick plating as desired. When a resist layer is formed, the plated layer is formed on the entire surface of the vapor deposited layer, so another problem arises when trying to remove the remaining resist layer along with the vapor deposited layer and plating layer above it. However, the problem has arisen that this is no longer possible.

This will be explained in more detail with reference to FIGS.

In FIG. 1(A), a second layer 2, which performs a photoelectric conversion function together with the substrate 1, is formed on a substrate 1, which is generally provided as a wafer with a diameter of 3 inches to 5 inches, using an appropriate thin film forming apparatus. This shows the stage at which the photoelectric converter 3 has been formed.

Of course, materials are selected for the first layer to the substrate 1 and the second layer 2 so that they can perform a photoelectric conversion function by forming a bond with each other. For example, the above-mentioned heterojunction element 5n02/
In a Si solar cell, the substrate 1 is Si, and the second layer 2
is 51102.

Generally, light enters the photoelectric converter 3 from the main surface side of the second layer 2 near the joint, so a patterned electrode is formed in this troublesome manner, but the bottom layer of this electrode is vapor-deposited for the reason mentioned above. The process starts from the state shown in FIG. 1(B).

That is, a resist layer 4 for electrode deposition is applied according to a desired pattern by a printing method or the like, and a second layer principal surface exposed portion 21 is created in a portion corresponding to the pattern, and electrodes are deposited thereon.

The results are shown in FIG. 1(C).

As can be seen from this figure, originally it is sufficient that the electrode material 5 is deposited only on the exposed portion 21 of the second layer main surface where there is no resist layer 4, but as a result, the electrode material 5 is deposited on the entire surface including the resist layer surface.
It looks like it has been attached.

Incidentally, such a vapor deposited layer 5 actually has a multi-layer structure, for example, a first layer 51 . In some cases, the second layer 52 has a two-layer structure.

In the case of the above 5nOz/Si solar cell developed by the applicant,
For the bottom layer 51, Cr is used as a material with good physical and electrical compatibility with the 5nOz layer 2, and then this Cr layer 51
A Cu layer 52 is formed on top of the Cu layer 52 as a material layer that has good contact with the Cu layer, has low resistance, and also exhibits an oxidation prevention function. Incidentally, in terms of the thickness of each layer, the lowest Or layer 51 is 1
The thickness of the Cu layer 52 of the primary layer is about 3000λ.

As shown in Fig. 1(C), if we immediately adopt the step of increasing the electrode thickness by the Menki method as in the experimental example described above in the electrode deposition process and a series of steps, Fig. 1(C) shows that D)
As shown in , since the coating layer 6 always adheres to the area where the vapor deposited layer 5 is located, as the vapor deposition layer 5 covers the entire surface of the photoelectric converter 3, this coating layer also covers the entire surface of the photoelectric converter 3. It is formed by

However, if this happens, the remaining resist layer 4 is removed and the -1- electrode material layer 5 is removed.
, 6 at the same time to obtain a predetermined electrode pattern, this is no longer possible.

This is because, in general, there is no point in providing the plating layer 6 unless it is considerably thicker than the thickness of the vapor deposited layer 5. On the other hand, if it is made this thick,
This is because the lift-off limit that can be removed when removing the resist layer 4 is far exceeded.

For example, in the above-mentioned experimental example by the present applicant, the plating layer 6 was also made to have a two-layer structure, but the thickness of the Cu layer 61 as the first plating layer was approximately 1"104, and the thickness of the Cu layer 61 was approximately 1". The Ni layer 62 has a thickness of approximately C2 and is thick, with the total thickness of the entire coating layer being more than 12 pm.With this, riff-off processing of the resist layer 4 together with the resist layer 4 is completely impossible.

The reason why the plating layer 6 also has a two-layer structure is that the Cu layer 61 as the first coating layer mainly has the function of lowering electrical resistance, and the Ni layer 62 as the second coating layer has the function of preventing oxidation and the external circuit. This is because it has the function of improving soldering when connecting solar cells.

The present invention has been made based on the above knowledge, and employs an inexpensive and simple plating method to increase the thickness of the main part of the patterned electrode in order to reduce its series resistance value. While adhering to the principle that the experiment should be carried out, it was an attempt to overcome the shortcomings of the conventional experimental examples described. As a result, we have disclosed a configuration in which the vapor-deposited resist layer used to form the vapor-deposited layer at the bottom of the electrode, which is necessary to improve compatibility with the photoelectric converter, can also be used as a subsequent plating resist layer. It is something that

Hereinafter, the characteristic parts of the method of the present invention will be explained with reference to FIGS.

The steps up to the step shown in FIG. 1(C) may be the same as in the conventional experimental example. That is, after forming the vapor-deposited resist layer 4 on the main surface of the photoelectric converter 3 by a printing method or the like according to a predetermined pattern, first the Cr layer 51 as the first layer is formed to a thickness of about 1,000 mm, and then the second layer is formed to a thickness of about 1,000 mm. For example, the Cu layer 52 as a layer has a thickness of about 30
The vapor deposition layer 5 is formed as a whole by vapor deposition to a thickness of 0.00 mm.

As described, this vapor deposited layer 5 is deposited not only on the predetermined exposed surface portion 21 of the main surface of the photoelectric converter but also over the entire surface of the vapor deposited resist layer 4.

Therefore, in the present invention, as shown in FIG. 2(A), the vapor deposition material adhering to the surface of the vapor deposition resist layer 4 is removed by mechanical grinding, which is preferably an inexpensive and simple method, and the vapor deposition resist layer 4 is removed. Layer 4 is exposed again.

Then, the vapor deposition material remains only in the part necessary as the turned electrode to form the vapor deposited electrode layer portion 5, and the thin resist layer 44 whose surface is re-exposed can be used as the subsequent plating resist layer 40. become.

That is, after that, the entire first plating layer is coated with the above-mentioned C.
If u, etc. are electrically plated to a thickness of, for example, 1 Opn, and N1 etc. are applied as a second metal layer 62 on top of t.
If you apply electric wire to the thickness of the two legs, Figure 2 (13)
j As shown, the metal plating layer 6 is formed only on the vapor-deposited electrode layer portion 5 as an electrode base layer along a predetermined pattern, and the plating resist layer 40, which was the original vapor-deposited resist layer, is
It will not stick to the surface.

Therefore, even if each plating layer is formed to the required thickness -V thick, it is easy to remove the plating/resist layer 40 afterwards, as shown in Figure 2(C)1. In this manner, a patterned electrode 7 having a desired thickness can be obtained according to a predetermined pattern.

In addition, each electrode constituent layer portion 51, 52, 81, 82 described
Any desired specific material may be used in addition to those mentioned above, and both the vapor deposited electrode layer portion 5 and the plated electrode layer portion 6 may have a single layer structure or, conversely, a multilayer structure.

As described in detail above, according to the present invention, a simple and reliable method can be provided for increasing the wall thickness of a multi-turn electrode in order to reduce its series resistance value, thereby increasing efficiency and reducing the This is of great significance for this type of solar cell, which must achieve low cost and become popular in the future.

[Brief explanation of the drawing]

Figure 1 is a process diagram illustrating a conventional experiment carried out by the applicant to increase the thickness of a patterned electrode in order to reduce its series resistance value, and Figure 2 is a process diagram illustrating an example of a conventional experiment carried out by the applicant. FIG. 3 is a process diagram illustrating the characteristic parts of the electrode forming method. In the figure, 1 is the first layer or substrate, 2 is the second layer, 3 is the photoelectric change specimen, 4 is the vapor deposited resist layer, 5 is the vapor deposited electrode layer portion, 6 is the plated electrode layer portion, and 7 is the completed patterned electrode. , 40 is a plating resist layer.

Claims (1)

[Claims] A method for forming an electrode on one main surface of a solar cell according to a predetermined pattern, the method comprising vapor deposition through a vapor deposition resist layer formed on the main surface according to the pattern. After that, the evaporation material deposited on the surface of the evaporation resist layer is removed to re-expose the surface of the evaporation resist layer, and the re-exposed evaporation resist layer is plated as a plating resist layer to form the above pattern. A method for forming an electrode for a solar cell, comprising depositing a plated electrode layer portion only on the remaining vapor-deposited electrode layer portion.