# US 5,344,500 A · Thin-film solar cell

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- Number: US 5,344,500 A
- Document ID: US5344500A
- Status: Granted
- Kind: A
- Application number: 08/115,720
- Filed: 1993-09-03
- Granted: 1994-09-06
- Earliest claimed: 1991-03-07
- Assignees: Mitsubishi Denki Kabushiki Kaisha
- Inventors: Hajime Sasaki; Hiroaki Morikawa; Kazuhiko Satoh; Mikio DeGuchi
- Web page: https://patentgrep.com/patent/US5344500A

## CPC

- C30B 29/06: Silicon
- C23C 14/568: {Transferring the substrates through a series of coating stations (C23C14/562 takes precedence)}
- C23C 16/24: Deposition of silicon only
- C23C 16/50: using electric discharges {(generation and control of plasma in discharge tubes for surface treatment H01J37/32, H01J37/34)}
- C23C 16/545: {for coating elongated substrates}
- C30B 25/02: Epitaxial-layer growth
- H10F 19/33: Patterning processes to connect the photovoltaic cells, e.g. laser cutting of conductive or active layers
- H10F 19/80: Encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells
- H10F 19/904: {characterised by the shapes of the structures}
- H10F 71/00: Manufacture or treatment of devices covered by this subclass (patterning processes to connect thin photovoltaic cells in integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/33; manufacture or treatment of encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/80; manufacture or treatment of integrated devices, or assemblies of multiple devices, comprising at least one element in which radiation controls the flow of current H10F39/00)
- H10F 71/128: {Annealing}
- H10F 71/131: {Recrystallisation; Crystallization of amorphous or microcrystalline semiconductors}
- H10F 71/134: {Irradiation with electromagnetic or particle radiation}
- H10F 71/137: {Batch treatment of the devices}
- H10F 71/139: {using temporary substrates}
- H10F 77/1692: {the films including only Group IV materials}
- H10F 77/707: {of the substrates or of layers on substrates, e.g. textured ITO layer on a glass substrate}
- Y02E 10/50: Photovoltaic [PV] energy
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- Y10S 148/122: Polycrystalline
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- 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)
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- 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
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A method for producing a thin-film solar cell having a thin-film active layer on a graphite sheet substrate includes the steps of adhering two sheets of graphite together, forming semiconductor thin films serving as active layers on second main surfaces of the two sheets of graphite, and separating the two sheets of graphite from each other. In this structure, stress caused by a difference in expansion coefficients between the upper sheet and the semiconductor thin film is cancelled by stress caused by a difference in expansion coefficients between the lower sheet and the semiconductor thin film. Therefore, curvature of the substrates is prevented whereby subsequent process steps are easily carried out. In addition, the number of products per unit time is doubled, thereby increasing productivity.

## Claims

### Claim 1

A thin-film solar cell including a polycrystalline silicon thin film serving as an active layer and a flaky graphite sheet substrate having a concavo-convex surface on which the polycrystalline silicon thin film is disposed.

### Claim 2 (depends on 1)

The thin-film solar cell of claim 1 wherein the flaky graphite sheet substrate has two opposed concavo-convex surfaces and the polycrystalline silicon is disposed on one of those surfaces.

### Claim 3

A method for producing a thin-film solar cell comprising:
forming a flaky graphite sheet substrate having a concavo-convex surface; and
forming an active layer comprising polycrystalline silicon on the concavo-convex surface of the substrate.

### Claim 4 (depends on 3)

The method of claim 3 including forming the flaky graphite sheet substrate having concavo-convex configuration by pressing flaky graphite, which is purified and foamed in acid treatment, between rollers having concavo-convex surfaces.

### Claim 5 (depends on 3)

The method of claim 3 including forming the flaky graphite sheet substrate having a concavo-convex configuration by pressing a flat flaky graphite sheet between rollers having concavo-convex surfaces.

### Claim 6 (depends on 3)

The method of claim 3 including forming the flaky graphite sheet substrate with opposed concavo-convex surfaces and forming the active layer on one of the concavo-convex surfaces.