# US 10,312,385 B2 · Solar cell substrate made of stainless steel foil and method for manufacturing the same

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- Number: US 10,312,385 B2
- Document ID: US10312385B2
- Status: Granted
- Kind: B2
- Application number: 14/402,155
- Filed: 2012-05-23
- Published: 2015-07-23
- Granted: 2019-06-04
- Earliest claimed: 2012-05-23
- Assignees: Jfe Steel Corporation
- Applicants: Yasuhiro Yamaguchi; Atsutaka Honda; Naoki Nishiyama; Tokio Nakada
- Inventors: Yasuhiro Yamaguchi; Atsutaka Honda; Naoki Nishiyama; Tokio Nakada
- Web page: https://patentgrep.com/patent/US10312385B2

## CPC

- H10F 77/219: {Arrangements for electrodes of back-contact photovoltaic cells}
- C21D 1/30: Stress-relieving
- C21D 1/76: Adjusting the composition of the atmosphere
- C22C 38/004: {Very low carbon steels, i.e. having a carbon content of less than 0,01%}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/18: containing chromium
- C22C 38/20: with copper
- C22C 38/22: with molybdenum or tungsten
- C22C 38/26: with niobium or tantalum
- C23C 16/305: {Sulfides, selenides, or tellurides}
- C23C 16/56: After-treatment
- H10F 71/128: {Annealing}
- H10F 77/126: {comprising only Group I-III-VI chalcopyrite materials, e.g. CuInSe2, CuGaSe2 or CuInGaSe2 [CIGS]}
- H10F 77/14: Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies
- H10F 77/1699: {the films including Group I-III-VI materials, e.g. CIS or CIGS on metal foils or polymer foils}
- Y02E 10/541: CuInSe2 material PV cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

Provided are a solar cell substrate made of stainless steel foil which contains 7% to 40% by mass Cr and has a coefficient of linear expansion of 12.0×10−6/° C. or less at 0° C. to 100° C. and a thickness of 20 μm to 200 μm is subjected to the preparatory heat treatment for stress relief in an atmosphere consisting of one or more selected from an N2 gas, an H2 gas, an Ar gas, an AX gas, and an HN gas within the range of 250° C. to 1,050° C.; a back-contact made of a Mo layer is formed on a surface of the stainless steel foil subjected to the preparatory heat treatment or an insulating coating is formed on a surface of the stainless steel foil followed by forming the back-contact including the Mo layer thereon; and an absorber layer made of Cu(In1-xGax)Se2 is formed on the back-contact by performing coating formation heat treatment.

## Claims

### Claim 1

A method for manufacturing a solar cell substrate made of stainless steel foil, comprising stainless steel foil which contains 7% to 40% by mass Cr and 0.36% to 1.5% by mass Nb, and which has a coefficient of linear expansion of 12.0×10−6/° C. or less at 0° C. to 100° C. and a thickness of 20 μm to 200 μm and which is subjected to preparatory heat treatment for stress relief in an atmosphere containing nitrogen within the range of 250° C. to 1,050° C., the preparatory heat treatment being performed before any layer is formed on a surface of the stainless steel foil; forming a back-contact made of a Mo layer on the surface of the stainless steel foil subjected to the preparatory heat treatment or an insulating coating on the surface of the stainless steel foil followed by forming the back-contact made of the Mo layer thereon; and forming an absorber layer made of Cu(In1-xGax)Se2 on the back-contact by performing coating formation heat treatment such that a width and a length of the stainless steel foil before and after the coating formation heat treatment satisfy the following inequalities (1) and (2):
100×|(W1−W0)|/W0≤0.037% (1);
100×|(L1−L0)|/L0≤0.037% (2),
wherein W0 is a width in mm of the stainless steel foil before being subjected to the forming of the back-contact, W1 is a width in mm of the stainless steel foil after being subjected to the forming of the back-contact, L0 is a length in mm of the stainless steel foil before being subjected to the forming of the back-contact, and L1 is a length in mm of the stainless steel foil after being subjected to the forming of the back-contact.

### Claim 2 (depends on 1)

The method for manufacturing a solar cell, substrate made of stainless steel foil according to claim 1, wherein the preparatory heat treatment is performed within the range of 250° C. to 900° C.

### Claim 3 (depends on 1)

The method for manufacturing a sour cell substrate made of stainless steel foil according to claim 1, wherein the preparatory heat treatment is performed within the range of 250° C. to 700° C.

### Claim 4 (depends on 1)

The method for manufacturing a solar cell substrate made of stainless steel foil according to claim 1, wherein the coating formation heat treatment is performed within the range of 450° C. to 700° C.

### Claim 5

A solar cell substrate made of stainless steel foil produced in such a way that stainless steel foil which contains 7% to 40% by mass Cr and 0.36% to 1.5% by mass Nb, and which has a coefficient of linear expansion of 12.0×10−6/° C. or less at 0° C. to 100° C. and a thickness of 20 μm to 200 μm and which is subjected to the preparatory heat treatment for stress relief in an atmosphere containing nitrogen within the range of 250° C. to 1,050° C., the preparatory heat treatment being performed before any layer is formed on a surface of the stainless steel foil; a back-contact made of a Mo layer is formed on the surface of the stainless steel foil subjected to the preparatory heat treatment or an insulating coating is formed on the surface of the stainless steel foil followed by forming the back-contact made of the Mo layer thereon; and an absorber layer made of Cu(In1-xGax)Se2 is formed on the back-contact by performing coating formation heat treatment, wherein width and length of the stainless steel foil before and after being subjected to the coating formation heat treatment satisfy the following inequalities (1) and (2):
100×|(W1−W0)|/W0≤0.037% (1)
100×|(L4−L0)|/L0≤0.037% (2)
where W0 is the width (mm) of the stainless steel foil before being subjected to the coating formation heat treatment, W1 is the width (mm) of the stainless steel foil after being subjected to the coating formation heat treatment, L0 is the length (mm) of the stainless steel foil before being subjected to the coating formation heat treatment, and L1 is the length (mm) of the stainless steel foil after being subjected to coating formation heat treatment.

### Claim 6 (depends on 5)

The solar cell substrate made of stainless steel foil according to claim 5, wherein width and length of the stainless steel foil before and after being subjected to the coating formation heat treatment satisfy the following inequalities (3) and (4):
100×|(W1−W0)|/W0≤0.018% (3)
100×|(L1−L0)|/L0≤0.018% (4).

### Claim 7 (depends on 5)

The solar cell substrate made of stainless steel foil according to claim 5, wherein the temperature of the preparatory heat treatment ranges from 250° C. to 700° C.

### Claim 8 (depends on 5)

The solar cell substrate made of stainless steel foil according to claim 5, wherein the temperature of the coating formation heat treatment ranges from 450° C. to 700° C.

### Claim 9 (depends on 2)

The method for manufacturing a solar cell substrate made of stainless steel foil according to claim 2, wherein the preparatory heat treatment is performed within the range of 250° C. to 700° C.

### Claim 10 (depends on 2)

The method for manufacturing a so cell substrate made of stainless steel foil according to claim 2, wherein the coating formation heat treatment is performed within the range of 450° C. to 700° C.

### Claim 11 (depends on 3)

The method for manufacturing a solar cell substrate made of stainless steel foil according to claim 3, wherein the coating formation heat treatment is performed within the range of 450° C. to 700° C.

### Claim 12 (depends on 6)

The solar cell substrate made of stainless steel foil according to claim 6, wherein the temperature of the preparatory heat treatment ranges from 250° C. to 700° C.

### Claim 13 (depends on 6)

The solar cell substrate made of stainless steel foil according to claim 6, wherein the temperature of the coating formation heat treatment ranges from 450° C. to 700° C.

### Claim 14 (depends on 7)

The solar cell substrate made of stainless steel foil according to claim 7, wherein the temperature of the coating formation heat treatment ranges from 450° C. to 700° C.

### Claim 15 (depends on 9)

The method for manufacturing a solar cell substrate made of stainless steel foil according to claim 9, wherein the coating formation heat treatment is performed within the range of 450° C. to 700° C.

### Claim 16 (depends on 12)

The solar cell substrate made of stainless steel foil according to claim 12, wherein the temperature of the coating formation heat treatment ranges from 450° C. to 700° C.