JPS60160180A - Master plate for solar cell board - Google Patents

Abstract

PURPOSE:To obtain the preferable surface conditions at low cost by performing skin-pass rolling after forming a plated layer with a stainless steel thin plate as a core plate. CONSTITUTION:An Ni and/or Cr plated layer is formed on a stainless steel thin plate as a core plate. Consequently, when using it for a solar cell, the cell characteristics can be maintained to be stable for a long term. However, regarding Al, Ag or Cu, the elements cause diffusion in an amorphous layer during usage as a cell and there is possibility of deterioration of the cell characteristics. Meanwhile, Ni and Cr do not cause such phenomenon. Next, the core plate on which the above plated layer is formed is subjected to skin-pass rolling to form a smooth surface. Thus the preferable surface conditions for a parent material for solar cell board can be obtained at low cost.

Description

[Detailed Description of the Invention] (Technical Field) The technical content described in this specification relates to improving the surface quality of a stainless steel thin plate as a substrate material for a solar cell. This paper attempts to propose development results for achieving excellent adaptation to amorphous layers.

(Technical background) A solar cell has a 0.1
Form an amorphous layer ~1 μm thick.

Because the film thickness of this amorphous layer is extremely thin, it is strongly influenced by the substrate material in terms of battery manufacturing reliability and battery characteristics such as the conversion efficiency of sunlight into electrical energy. Selection is important, including economic efficiency, which is strongly related to manufacturing method.

Conventionally, materials such as quartz glass, soda lime glass, and stainless steel have been used as substrate materials for solar cells.

Glass-based materials have the advantage of simultaneously protecting the battery surface because the substrate itself has optical transparency, but they also suffer from the disadvantage of being easily damaged, which is the fate of glass.In particular, silica glass is alkali-free. There is a problem that it is expensive and that a roll-to-roll method with high mass production efficiency cannot be adopted when manufacturing solar cells.

On the other hand, stainless steel has high mechanical strength and toughness, so thin plates of about 0.8 IIm or less can be used, and since it is flexible, it can be mass-produced using coiled materials. Furthermore, it is excellent in that it is advantageously suitable for use as a solar cell with a curved structure.

However, the surface of rolled stainless steel usually has many defects such as oil bits and scratches that occur during rolling, and if this is used as a substrate material for solar cells, the amorphous layer will be thin. Therefore, they tend to be non-uniform in their formation, and in some cases, electrical short circuits may occur around defects, and they may even fail to function as a battery.

For this reason, the current situation is that the surface roughness is generally adjusted by performing several steps of abrasive polishing to about #1000 to #1500, followed by electrolytic polishing. However, in such a method, the process operation is complicated and the treatment takes a long time, and the processing cost is high, and even though stainless steel itself is cheap, the final price is very high.

In order for solar cells to become popular as a power source on par with existing power generation methods, it is necessary to significantly reduce costs from the current situation, and there is a need for substrate materials that are inexpensive and have excellent material properties that can overcome the current situation. ing.

(Problems with the Prior Art) Recently, in view of the above-mentioned circumstances, regarding the surface polishing method of stainless steel, abrasive grains added to the anodic dissolution of the base surface of the substrate by electrolytic action using a neutral salt aqueous solution as the electrolyte have been developed. A manufacturing method has been developed in which the surface of the substrate is mirror polished by scratching (see Japanese Patent Laid-Open No. 71077/1983).

In this case, conventional mechanical polishing and electrolytic polishing are combined and performed at the same time, so it is disclosed that the operation time can be significantly shortened. The yield of stainless steel itself is decreasing and the processing cost remains at a high level, which does not essentially solve the above-mentioned concerns.

(Problem to be solved by the invention) By the way, the desirable characteristics that a substrate material for solar cells should have are (1) small surface roughness and as few small bit-like defects as possible, and (2) cell properties that are transferred from the substrate surface to the amorphous layer. (3) It has excellent corrosion resistance and heat resistance and is durable for long-term use as a solar cell; (4) It has excellent thermal conductivity; (5) It can be summarized as follows: (6) It is possible to mass-produce batteries using a roll-to-roll method with high strength and flexibility, and (6) It is inexpensive.

(Objective of the invention) As a substrate material for solar cells, the most basic from the viewpoint of cell characteristics and reliability is low surface roughness, no impurity diffusion into the amorphous layer, excellent durability, and meets all the requirements listed in item 1. It is an object of the invention to provide an advantageously satisfying and inexpensive substrate material.

(Structure of the Invention) This invention comprises a substrate made of a thin stainless steel plate, at least one side of which is provided with a plating layer, and the plating layer has a smooth surface formed by skin bath rolling after plating treatment. This is a base plate for a pond substrate, and as an embodiment thereof, it is desirable that the plating layer is Ni and/or Cr plating.

This invention is based on the fact that stainless steel, which has been used as a substrate material for solar cells, is inexpensive and advantageous, and the requirements for a solar cell substrate material as described in the problem of the invention section are as follows. The thin plate of the substrate material is limited to a thin stainless steel plate because of the excellent feature of improved surface quality that satisfies the above requirements. This stainless steel thin plate is cold rolled to a predetermined thickness, annealed if necessary, and further skin bath rolled to obtain an original plate for plating according to the present invention.

The surface condition of stainless steel before and after this plating treatment and the improvement effect when further skin bath rolling is applied after plating were investigated.
An example in which mm > is used as a plating original plate will be described in detail below.

The sample classification is as follows.

(A): Original plate before plating (B): After electrolytically degreasing the original plate with homezaline and potassium hydroxide aqueous solution, 1 μm thick nickel plating (plating solution:
Ni 804 ・6H20 + NiCA2 ・6H20 + boric acid) (C): Similarly, 1μ thick chromium plating (plating solution: C
rO3+H2804) (D): 0.2μm after 0.5μ thick nickel plating
Thick paste [J Mumetsuki plating solution: (B).

(Same as (C)) (E), (F), (G): (B), (C), (D) were each skinned at a rolling rate of 1% using rolls polished to #1000. The surface of the bus-rolled multi-sample was
The results of observation using a scanning electron microscope at twice the magnification are shown in the first
Shown in the figure. At the bottom of each photo, the surface roughness values Ra and RIaX measured for each case are also listed.

(According to A>, 5US4 has a macroscopically beautiful surface.
When observing the original plate No. 30 at high magnification, the surface shows shallow grooves running parallel to the rolling direction caused by the transfer of the unevenness caused by the grinding of the rolling rolls, and oil bits and pickling caused by the lubricant during rolling. It can be seen that there are many surface defects such as a large number of bits with a diameter of 2 to 3 μm or less, microcracks on the surface, and indentation flaws.

These defects are caused by the battery as mentioned above! During FJ manufacturing, the amorphous layer is extremely thin, which causes various problems and significantly reduces reliability as a battery. In this case, the surface roughness of the original plate (A) is average roughness Ra1 maximum height RII
The value of lax is 0.134μI11, 1,091 respectively
It was μm.

Each sample (B
), (C), and (D), the minute bit-like surface defects seen on the original plate were filled with electrodeposit and an improvement was seen, and the Ra.

The values of Rwax are (B) 0.102μs,
0.954us (C) 0,066μa+, 0.6
7Jczm ([)) 0.085μm, 0.717μm
It was m. However, for relatively large surface defects, although the profile of the defect becomes gentler, its outline can still be observed.

8 trials 11 (E
), (F), and (G) are significantly improved. In other words, the contours of surface defects covered with electrodeposit that remained even after plating are smoothed out and no trace remains. Ra
, Rmax is (E) 0.057μn+
, 0.440 μm (F) 0.028 μm.

0.291μm (G) 0.023μm, 0.28
3. It comes to show an extremely excellent value of cz+++.

As described above, by forming a plating layer using a stainless steel thin plate as a core plate and then applying skin bath rolling, it can be used as a mother plate for solar cell substrates without applying the polishing method, which has complicated process operations and high processing costs. It is clear that favorable surface conditions can be obtained at low cost.

When the substrate surface is plated with Ni and/or Or,
When used as a solar cell, battery characteristics can be maintained stably for a long period of time.

However, Al1. When using Aa or Cu, these elements diffuse into the amorphous layer during use as a battery, potentially deteriorating the battery characteristics, whereas such diffusion development is not observed with Ni and Cr. It is advantageous in this respect.

The thickness of the plating layer is preferably as thin as possible as long as the surface condition required as a mother plate for a solar cell substrate can be obtained, but it must be selected in consideration of the balance between the surface condition of the plated original plate and economic efficiency.

Normally, in the case of stainless steel, Rmax is at most 2 to 5 μ-
Considering the following, it is sufficient for the plating thickness to be in the range of 15 μm or less, particularly 10 μm or less.

Skin pass rolling may be carried out using a skin bath rolling mill commonly used in the manufacture of stainless steel, and the surface of the rolls used in this rolling mill is #1000 to #15.
It is preferable to perform polishing of about 0.00 and rolling rate at a rolling rate of 0.1 to 5%.

Further, skin pass rolling can be applied to both wet skin pass rolling using a lubricant and dry skin pass rolling not using an aSII lubricant.

For the plating operations described above, commonly used continuous electroplating equipment can be used. Furthermore, it is possible to improve the surface condition of a mother plate for a solar cell substrate by a low-order, highly productive continuous method using a skin-pass rolling mill commonly used in stainless steel production.

(Example) SUS-304, SUS 430. and S
A 3.5-4.0 mm thick plate of US 410L was given the processing history shown in Table 1.

That is, (i) after cold rolling the core plate to a predetermined cold-rolled thickness, <ii> (1) remains as cold-rolled (2).

For (3) and (6), bright annealing, (4), (
For 5), air annealing and skin pass rolling were performed.
(iii) These are subjected to anodic electrolytic degreasing in a photometherin + potassium hydroxide aqueous solution,
Electroplating was performed with the plating type and plating thickness shown in the table (the plating bath composition used was the same as described above), and then #10
Skin pass rolling ((1), (2), (4)
The final finishing treatment was performed by performing wet skin pass rolling in (3), dry skin pass rolling (3), (5), and (6).

As shown in the table, the above treatment significantly improved the surface roughness compared to the core board, and also eliminated the various pit forest surface defects observed on the core board.

(Effects of the Invention) This invention uses stainless steel as a core plate and combines plating and skin pass rolling to provide an excellent surface condition at a low cost as a mother plate for solar cell substrates, meeting recent needs. .

[Brief explanation of the drawing]

FIG. 2 is a scanning electron micrograph (magnification: 500 times) showing the surface condition of the core plate before substrate phase and treatment according to the present invention. FIG.

Claims (1)

[Claims] 1. A core plate made of a thin stainless steel plate is provided with a plating layer formed on at least one side thereof, and the plating layer has a smooth surface obtained by skin pass rolling after the plating treatment. Motherboard for solar cell substrates. 2. The base plate according to 1, wherein the plating layer is Ni and/or Cr plating.