JP2011204723A - Stainless steel plate for use of solar cell substrate material, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stainless steel plate for use of a solar cell substrate material, which has superior deposition properties.SOLUTION: A steel plate surface has a ten-point average irregularity Rz of a surface roughness parameter of ≤0.3 μm, and a characteristic average parameter Rsk in a height direction of less than 0.7. Irregularities on the steel plate surface for worsening the deposition properties can be controlled by defining Rz and Rsk, thereby improving the deposition properties. In addition, in manufacturing such a stainless steel plate for use of the solar cell substrate material, the plate is rolled so that a total reduction rate of cold rolling to take place until temper rolling is ≥70%. In addition, in cold rolling before finish annealing, the plate is rolled using a pressure roll with a reduction rate of ≥30% and a roughness Ra of ≤0.4 μm in a final path. By manufacturing in such a manner, micro-cracks can be suppressed, and the stainless steel plate for use of the solar cell substrate material with a smooth steel plate surface with Rz of ≤0.3 μm and Rsk less than 0.7 can be easily manufactured.

Description

  The present invention relates to a stainless steel plate for solar ionization substrate material having excellent surface properties as a substrate material for thin film solar cells.

  Conventionally, glass such as soda glass, stainless steel as a metal foil, and polyimide as a synthetic resin are mainly used for a thin film silicon solar cell substrate material. In general, the price per area increases in the order of stainless steel, glass, and polyimide. Moreover, although the high temperature process is passed in the film-forming process of the silicon layer in a solar cell, a polyimide is largely inferior in heat resistance compared with stainless steel or glass. Therefore, stainless steel may be selected as the material for the solar cell substrate material from the viewpoint of price and heat resistance.

  As a configuration in which a stainless steel plate is used as a solar cell substrate material, a configuration in which a stainless steel plate is used as a conductive substrate that is a flexible substrate is known in order to improve corrosion resistance (for example, patents). Reference 1).

JP-A-11-97727 (pages 5 and 9)

  However, in Patent Document 1 and the like, only a stainless steel plate is used as a solar cell substrate material for the purpose of improving the corrosion resistance, and the film formability on the stainless steel plate has not been considered much.

  That is, since the amorphous silicon layer deposited on the solar cell substrate is a thin layer of 1 μm or less and needs to be formed uniformly and continuously, when using a stainless steel plate as the solar cell substrate, the surface of the stainless steel plate surface Wrinkles, microcracks, and the like deteriorate the film formation state and cause a decrease in yield. Further, on the surface of the stainless steel plate, the surface unevenness affects the film formation state, and there is a possibility that the circuit may be short-circuited when a film formation defect occurs. For example, when the height difference of the unevenness is large, there may be a problem that a short circuit or a deterioration in battery characteristics occurs due to the occurrence of pinholes or the like and non-uniform film thickness.

  This invention is made | formed in view of such a point, and it aims at providing the stainless steel plate for solar cell board | substrate materials with favorable film forming property, and its manufacturing method.

  In the stainless steel plate for solar cell substrate material according to claim 1, the steel plate surface has a 10-point average roughness Rz of the surface roughness parameter of 0.3 μm or less, and a feature average parameter Rsk in the height direction. It is less than 0.7.

  The method for producing a stainless steel plate for solar cell substrate according to claim 2 is such that cold rolling performed from hot rolling to temper rolling after finish annealing has a total rolling ratio of 70% or more, The cold rolling performed before annealing is performed using a rolling roll having a rolling rate of 30% or more and a roughness Ra of 0.4 μm or less in the final pass.

  The method for producing a stainless steel plate for solar cell substrate material according to claim 3 is the method for producing a stainless steel plate for solar cell substrate material according to claim 2, wherein the temper rolling is performed without using a lubricant. It is rolled to an elongation of 0.1 to 2.0% using a rolling roll having a roughness Ra of 0.1 μm or less.

  According to the invention described in claim 1, the steel sheet surface has a ten-point average roughness Rz of the surface roughness parameter of 0.3 μm or less and a feature average parameter Rsk in the height direction of less than 0.7. Therefore, it is easy to make the film thickness of the film formation layer uniform, a short circuit of the film formation layer can be suppressed, and the film formation property can be improved.

  According to the invention described in claim 2, the cold rolling performed after hot rolling to temper rolling after finish annealing has a total rolling ratio of 70% or more, and cold rolling performed before finish annealing is Since the rolling rate is 30% or more and rolling is performed using a rolling roll having a roughness Ra of 0.4 μm or less in the final pass, the ten-point average roughness Rz of the surface roughness parameter of the steel sheet surface is 0. A stainless steel plate for solar cell substrate material having a film forming property of 3 μm or less and having a characteristic average parameter Rsk in the height direction of less than 0.7 and having good film formability can be easily produced.

  According to the invention described in claim 3, temper rolling is performed without using a lubricant and rolled to an elongation of 0.1 to 2.0% using a rolling roll having a roughness Ra of 0.1 μm or less. Therefore, it is possible to easily manufacture a stainless steel plate for solar cell substrate material having good film forming properties.

It is sectional drawing which shows the structure of a solar cell typically.

  Hereinafter, the configuration of an embodiment of the present invention will be described in detail.

  The stainless steel plate for solar cell substrate material is formed in a plate shape from stainless steel such as ferritic stainless steel and austenitic stainless steel.

  The stainless steel plate for solar cell substrate material has a ten-point average roughness Rz of the surface roughness parameter of 0.3 μm or less and a feature average parameter Rsk in the height direction of less than 0.7 on the surface of the steel plate.

  Rz is specified in JIS B 0601: '94, and is a ten-point average roughness indicating the difference in level of the irregularities on the surface of the steel sheet, and in the roughness curve, from the peak showing the highest convex part to the fifth highest Is the sum of the average height of the convex portions and the average depth of the concave portions up to the fifth in the deepest order from the bottom showing the deepest concave portion.

  If the 10-point average roughness Rz of the steel sheet surface is larger than 0.3 μm, the unevenness of the unevenness will be large, causing not only unevenness of the film thickness and short circuit of the film formation layer, but also trapping dirt such as particles in the recess Therefore, the film formability deteriorates.

  Rsk is defined in JIS B 0601: '01, and is a feature average parameter in the height direction indicating the acute angle of the convex part and concave part of the steel sheet surface. When Rsk> 0, the convex part shape is acute and concave. When the shape is an obtuse angle and Rsk <0, the convex shape is an obtuse angle and the concave portion is an acute angle. Further, the convex shape becomes more acute as the numerical value of the feature average parameter Rsk becomes positive, and the concave shape becomes sharper as the value of the characteristic average parameter Rsk becomes negative.

  In the unevenness on the surface of the steel sheet, if the characteristic average parameter Rsk on the surface of the steel sheet is 0.7 or more and the convex part has an acute angle, the film thickness of the film forming layer becomes non-uniform and short-circuiting easily occurs. Resulting in.

  Here, when the concave portion on the surface of the steel plate is acute, depending on the depth of the concave portion, dirt such as particles can be easily trapped. That is, when the depth of the acute concave portion is deep, it is easy to trap dirt, and the film formability may be deteriorated.

  However, by setting the ten-point average roughness Rz to 0.3 μm or less, the height difference between the convex portion and the concave portion can be defined, and therefore the depth of the concave portion can be controlled. That is, even when the feature average parameter Rsk shows a large negative value and an acute concave portion is formed on the steel plate surface, the ten-point average roughness Rz is 0.3 μm or less, and the depth of the acute concave portion is Since it is shallow, it is difficult to trap dirt, and the film formability does not deteriorate.

  Therefore, the steel sheet surface was made to have a surface property having a ten-point average roughness Rz of 0.3 μm or less and a feature average parameter Rsk of less than 0.7.

  For example, as shown in FIG. 1, a lower electrode layer, a pin-type solar cell, and an upper electrode layer are sequentially formed on a stainless steel plate for a solar cell substrate material to form a solar cell. The lower electrode layer is formed by sequentially depositing ZnO, Ag, and ZnO on the stainless steel plate surface by sputtering. In the pin type solar cell, an n-type amorphous silicon layer, an i-type amorphous silicon layer, and a p-type microcrystalline silicon layer are sequentially deposited on the lower electrode layer by a plasma chemical vapor deposition (CVD) method. To be formed. Further, the upper electrode layer is formed by sequentially depositing an Indium Tin Oxide (ITO) film and Ag on a pin type solar cell by sputtering.

  Next, the manufacturing method of the stainless steel plate for solar cell substrate materials is demonstrated.

  The stainless steel plate for solar cell substrate material, for example, after refining and casting, hot rolling, intermediate rolling (cold rolling), intermediate annealing, finish rolling (cold rolling), finish annealing, as with conventional stainless steel plates And temper rolling is performed sequentially.

  In intermediate rolling and finish rolling, which are cold rolling performed after hot rolling to temper rolling after finish annealing, rolling is performed so that the total rolling ratio in each cold rolling is 70% or more. In addition, since hot rolling is appropriately passed through steps such as annealing, cold rolling, and polishing, the total rolling rate of cold rolling performed after hot rolling to temper rolling after finish annealing is 70. % Or more.

  Further, finish rolling, which is cold rolling performed before finish annealing, is an important process that greatly affects the surface properties of the stainless steel plate. In the case of cold rolling performed before such finish annealing, the rolling rate is 30% or more, and in the final pass of this cold rolling, the arithmetic roughness Ra is 0.4 μm or less. Roll using a rolling roll.

  Further, the temper rolling is preferably performed by rolling to an elongation of 0.1% or more and 2.0% or less using a rolling roll having an arithmetic roughness Ra of 0.1 μm or less without using a lubricant.

  Here, if the depth of the microcracks, which are fine depressions on the surface of the steel plate, is deep, the surface properties of the surface of the steel plate deteriorate and cause a short circuit when a solar cell is formed. Therefore, in order to obtain a surface property with a ten-point average roughness Rz of 0.3 μm or less and a feature average parameter Rsk of less than 0.7, the surface defects that cause microcracks are stretched by cold rolling. Therefore, it is important to reduce the depth of the microcracks.

  If the total rolling ratio of each cold rolling until temper rolling is lower than 70%, the surface properties of the steel sheet surface are adversely affected, for example, microcracks having a depth of 0.5 μm or more are likely to be generated. The ten-point average roughness Rz is 0.3 μm or less and the feature average parameter Rsk is difficult to control below 0.7. Therefore, the total rolling reduction of each cold rolling from hot rolling to temper rolling after finish annealing is set to 70% or more.

  In addition to managing the total rolling rate of each cold rolling performed before temper rolling, cold rolling before finish annealing can be performed under specific conditions and extended so that traces of microcracks do not remain. It is important for improving surface properties. In cold rolling before finish annealing, if the rolling rate is lower than 30%, microcracks that adversely affect the surface properties are likely to remain. Therefore, the rolling rate of cold rolling before finish rolling is set to 30% or more.

  Furthermore, the rolling roll used in the final pass of cold rolling before finish annealing tends to affect the unevenness of the steel sheet surface, and if a rolling roll having a roughness Ra coarser than 0.4 μm is used, the unevenness of the unevenness of the steel sheet surface is different. The ten-point average roughness Rz on the steel sheet surface tends to be larger than 0.3 μm. Therefore, in cold rolling before finish annealing, rolling is performed using a rolling roll having an arithmetic roughness Ra of 0.4 μm or less in the final pass.

  The temper rolling is a step of finally determining the surface of the steel sheet, and the temper rolling may cause micro cracks and may deteriorate the surface properties.

  Specifically, in temper rolling, when using lubricants such as rolling oil, lubricating oil and rust preventive agent with additives for the purpose of imparting luster to the steel sheet surface and preventing rust, When the oil film of the lubricant enters between the roll and the steel plate surface, microcracks are generated during temper rolling.

  Therefore, in temper rolling, it is preferable to perform rolling without using a lubricant such as a lubricating oil and a rust inhibitor. In addition, since it is only necessary to prevent the oil film from entering between the roll and the steel sheet surface, for example, the work of cleaning the roll with a cleaning liquid or the like for removing foreign substances from the roll, or the work of wiping with a wiper using a cleaning liquid or the like As described above, an oil film or a foreign substance may be prevented from entering between the roll and the steel sheet surface using a cleaning liquid.

  Moreover, since the roughness of the rolling roll in the temper rolling and the elongation of the stainless steel plate in the temper rolling also affect the generation of microcracks, it is preferable to stretch under specific temper rolling conditions.

  Specifically, in temper rolling, if the elongation by temper rolling is lower than 0.1%, the number of remaining microcracks that adversely affect the surface properties of the steel sheet surface increases, and the elongation by temper rolling is 2 If it is higher than 0%, it will encourage the biting of foreign matter. Therefore, in temper rolling, it is preferable to roll the elongation to 0.1% or more and 2.0% or less, and in this temper rolling, it is preferable to use a rolling roll having an arithmetic roughness Ra of 0.1 μm or less. .

  And according to such a stainless steel plate for solar cell substrate materials, the steel plate surface has a 10-point average roughness Rz of the surface roughness parameter of 0.3 μm or less and a feature average parameter Rsk in the height direction. Since it is less than 0.7, there are few microcracks and surface flaws, and the smoothness of the steel sheet surface is good. Therefore, the surface property for performing vapor deposition when forming the solar cell is good, and the film formability on the surface of the steel sheet can be improved.

  When producing a stainless steel plate for solar electric substrate material, cold rolling performed after hot rolling to temper rolling after finish annealing has a total rolling ratio of 70% or more, and is performed before finish annealing. Cold rolling is performed using a rolling roll having a rolling rate of 30% or more and a roughness Ra of 0.4 μm or less in the final pass, so that the number of microcracks is small and the unevenness of the surface of the steel sheet is low. Becomes smaller. Therefore, it is easy to form a stainless steel plate that is a smooth steel plate surface with a ten-point average roughness Rz of 0.3 μm or less and a feature average parameter Rsk of less than 0.7, and a stainless steel plate for a solar cell substrate material having good film formability. Can be easily manufactured.

  The temper rolling is performed using a rolling roll having an arithmetic roughness Ra of 0.1 μm or less without using a lubricant. Generation can be suppressed. Therefore, it is easy to form a stainless steel plate that is a smooth steel plate surface with a ten-point average roughness Rz of 0.3 μm or less and a feature average parameter Rsk of less than 0.7, and a stainless steel plate for a solar cell substrate material having good film formability. Can be easily manufactured.

  In the above embodiment, when producing a stainless steel plate for solar cell substrate material, hot rolling, intermediate rolling, intermediate annealing, finish rolling, finish annealing, and temper rolling are sequentially performed after refining and casting. In temper rolling, a configuration is used in which rolling is performed to 0.1 to 2.0% elongation using a rolling roll having an arithmetic roughness Ra of 0.1 μm or less without using a lubricant. However, the cold rolling performed from hot rolling to temper rolling after finish annealing has a total rolling rate of 70% or more, and cold rolling performed before finish annealing has a rolling rate of 30% or more. And a method of rolling using a rolling roll having an arithmetic roughness Ra of 0.4 μm or less in the final pass.

  Film formation evaluation as a solar cell substrate material was performed using the stainless steel plates of the present examples and comparative examples shown below. Carbon (C): 0.01 mass%, Silicon (Si): 0.52 mass%, Manganese (Mn): 0.2 mass%, Chromium (Cr): 18.2 mass%, Niobium (Nb): 0 .41% by mass, copper (Cu): 0.48% by mass, the balance being ferritic stainless steel sheet with iron (Fe) and inevitable impurities, C: 0.04% by mass, Si: 0.48 Containing mass%, Mn: 0.2 mass%, Cr: 18.4 mass%, nickel (Ni): 8.2 mass%, nitrogen (N): 0.02 mass%, the balance being iron (Fe) And the austenitic stainless steel plate which is an unavoidable impurity was formed on the conditions shown in Table 1. Steel types a, b, d, f, i, and k used ferritic stainless steel as test materials, and steel types c, e, g, h, j, and l used austenitic stainless steel as test materials. .

  In the film formation evaluation of solar cells, these ferritic stainless steel plates and austenitic stainless steel plates were used as test materials, and solar cells were formed by conventional methods to evaluate the film formability.

  Specifically, as shown in FIG. 1, first, a lower electrode layer was formed on the surface of each stainless steel plate by sequentially depositing ZnO at 20 nm, Ag at 250 nm, and ZnO at 20 nm.

  Next, a pin type solar cell was fabricated on the lower electrode layer by a plasma CVD method. That is, on the lower electrode layer, an n-type amorphous silicon layer was formed in a thickness of 20 nm, an i-type amorphous silicon layer was formed in a thickness of 300 nm, and a p-type microcrystalline silicon layer was sequentially formed in a thickness of 20 nm.

  Further, an ITO film of 70 nm and Ag of 250 nm were sequentially deposited on the pin type solar cell by sputtering to form an upper electrode layer.

  Moreover, the size of the solar cell was 5 mm × 5 mm, and 16 amorphous silicon solar cells were formed on each stainless steel plate. After the formation of the cell, vacuum annealing was performed at 150 ° C. for 2 hours to obtain a solar cell for evaluation.

  The photoelectric conversion rate was calculated | required using the solar simulator by Yamashita Denso Co., Ltd. with respect to the solar cell formed in this way. In consideration of the result of film formation due to a short circuit, etc., the ratio of the cells in which the photoelectric efficiency was measured out of the 16 cells in which the photoelectric conversion rate was measured, that is, the yield of the cells was calculated to evaluate the film formability. did.

  Moreover, about evaluation of surface property, the 10-point average roughness Rz and the characteristic average parameter Rsk which are surface roughness parameters were measured using the surface roughness measuring apparatus by Tokyo Seimitsu Co., Ltd. The surface roughness is based on JIS'94 standard, the measurement direction is the C direction perpendicular to the rolling direction, the measurement distance is 4 mm, the measurement speed is 0.3 mm / s, and the cutoff value is It was calculated as 0.8 mm. Table 1 shows the surface roughness parameters and cell yields of this example and the comparative example.

  As shown in Table 1, in this example using stainless steels of steel types a, b, c, d, e, h, and k formed under the above specified conditions, the ten-point average roughness Rz is 0. It was 3 μm or less, and the feature average parameter Rsk was less than 0.7. Further, the cell yield is 90% or more, respectively, and it can be said that the film formability is good. In addition, for example, the yield of film formation of a glass substrate conventionally used as a solar cell substrate material is 90% or more, and in this example, the yield of cells was comparable to that of a glass substrate.

  In this example, the ten-point average roughness Rz is 0.3 μm or less, the feature average parameter Rsk is less than 0.7, and the surface properties of the steel sheet surface are smooth. Since a short circuit is unlikely to occur, the film formability is considered to be good.

  On the other hand, the comparative example using the stainless steel plates of the steel types f, g, i formed in the manufacturing process including conditions different from the above-described conditions described above has a ten-point average roughness Rz of 0.3 μm. The cell yield was much lower, 13%, 16% and 0%.

  Moreover, the comparative example using the stainless steel plate of the steel type j formed in the manufacturing process including conditions different from the above-mentioned conditions described above has a feature average parameter Rsk of 0.7 or more and a cell yield of 13 % Was very low.

  Moreover, the comparative example using the stainless steel plate of the steel type 1 formed in the manufacturing process including conditions different from the above-mentioned conditions specified above has a ten-point average roughness Rz larger than 0.3 μm and a feature average. The parameter Rsk was 0.7 or more, and the cell yield was 0%.

  In each comparative example, a manufacturing process different from the above-mentioned conditions is included, a large number of microcracks and the like are generated on the surface of the steel sheet, the unevenness of the unevenness on the surface of the steel sheet is large, and the apex of the convex part is an acute angle shape. For this reason, it is considered that the surface properties were likely to cause a short circuit.

Claims (3)

The steel plate surface has a ten-point average roughness Rz of the surface roughness parameter of 0.3 μm or less and a feature average parameter Rsk in the height direction of less than 0.7. Stainless steel sheet. Cold rolling performed after hot rolling to temper rolling after finish annealing has a total rolling rate of 70% or more,
Cold rolling performed before finish annealing is performed using a rolling roll having a rolling rate of 30% or more and a roughness Ra of 0.4 μm or less in the final pass. Method for manufacturing stainless steel sheet. The temper rolling is performed by rolling to an elongation of 0.1 to 2.0% using a rolling roll having a roughness Ra of 0.1 μm or less without using a lubricant. Manufacturing method of stainless steel sheet for battery substrate material.

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