JP2001308357A - Method for manufacturing solar cell and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell of high quality and high efficiency, capable of solving an electric short-circuit problem completely in the assembly process and produced at high yield. SOLUTION: A plurality of spherical diodes 10a are half buried and fixed in a thermoplastic resin 13 and exposed portions of the spherical diodes 10a, are etched to expose the first conductivity diffusion layer regions 11 inside the spherical diodes 10a. A metal film 14 having good wettability to a conductive paste 15 is selectively formed on the whole or the exposed portions of the first conductivity diffusion layer regions 11. The spherical diodes 10a are released from the fixed state and are placed on a conductive substrate 16 coated with the conductive paste 15. The conductive substrate 16 with the spherical diodes 10a placed thereon is bented to melt the conductive paste 15. The spherical diodes 10a are collected and an insulting layer 18 is formed on the spherical diodes 10a. A transparent conductive film 17 is deposited on the spherical diodes 10a so as to cover the second conductivity diffusion layer region 12 and the insulating layer 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a solar cell and a solar cell, and more particularly to a method for manufacturing a solar cell using a spherical diode and a solar cell.

[0002]

2. Description of the Related Art An internal electric field is generated at a pn junction of a semiconductor. When light is applied to the pn junction to generate an electron-hole pair, the generated electrons and holes are separated by the internal electric field.
Electrons are collected on the n side and holes are collected on the p side. When a load is connected to the outside, a current flows from the p side to the n side. Utilizing this effect, solar cells have been put into practical use as elements for converting light energy into electric energy.

In recent years, a technique has been developed in which a semiconductor element is manufactured by forming a circuit pattern on a spherical semiconductor (Ball Semiconductor) having a diameter of 1 mm or less, such as single crystal or polycrystalline silicon.

As one of the methods, a method of manufacturing a solar array in which a large number of semiconductor particles are connected using an aluminum foil has been proposed (Japanese Patent Application Laid-Open No. Hei 6-13633). In this method, as shown in FIG. 10, a semiconductor particle 207 having an n-type skin portion and a p-type interior is placed in an aluminum foil opening through an aluminum foil 201.
209 so that it protrudes from both sides of the
Is removed, and an insulating layer 221 is formed. Next, the p-type interior 21
1 and the insulating layer 221 thereon are removed, and a second aluminum foil 219 is bonded to the removed region 217.
The flat area 217 is the second aluminum foil 2 as a conductive part.
19 to provide a good ohmic contact.

[0005]

However, by etching or grinding the semiconductor particles 207 (spherical diodes), the skin 209 (n-type diffusion region) formed on the surface is partially removed. Then, the p-type interior 211 (p-type diffusion layer region) is exposed and bonded to the second aluminum foil 219 (conductive substrate) as a p-type electrode. At this time, since the semiconductor particles 207 (spherical diodes) rotate on their own, the second aluminum foil 219 (conductive substrate)
In addition, an n-type diffusion region is also joined together, which causes an electrical short circuit, and the output of the solar cell cannot be obtained, which has been a major problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a method of manufacturing a high-quality and high-yield solar cell, which can drastically solve the problem of an electric short circuit in an assembly process. It is intended to provide a solar cell.

[0007]

A first aspect of the present invention is that a pn junction is formed at least on the surface of a spherical substrate which forms a diffusion layer region of the first conductivity type. A plurality of spherical diodes having a diffusion layer region are substantially buried in a thermoplastic resin and fixed, and a portion of the spherical diode that is exposed from the thermoplastic resin is etched, and the spherical diode inside the spherical diode is etched. Exposing a diffusion layer region of one conductivity type; selectively forming a conductive paste and a metal film having good wettability on the entire surface or on an exposed portion of the diffusion layer region of the first conductivity type; Releasing the diode from the fixing, and mounting the spherical diode on a conductive substrate coated with a conductive paste, and reflowing the conductive substrate on which the spherical diode is mounted. A step of melting a conductive paste,
A process of collecting and aggregating the spherical diodes,
A step of forming an insulating layer on the spherical diode; and a step of depositing a transparent conductive film so as to cover the diffusion layer region of the second conductivity type and the insulating layer. According to such a configuration, by performing reflow on the conductive paste, the conductive paste is selectively bonded only to the metal film having good wettability, compared to silicon having poor wettability with the conductive paste. The problem that the conductive type diffusion layer region and the conductive paste are electrically short-circuited does not occur. Also, during reflow, the spherical diodes having a low specific gravity are in a floating state, so that they can be easily assembled without causing an electrical short circuit between the diffusion layer region of the second conductivity type and the conductive paste. In addition, an agglomerated solar cell can be manufactured without causing an electrical short circuit between the pn electrodes.

[0008] A second aspect of the present invention is a plurality of semiconductor devices having a second conductive type diffusion layer region formed so as to form a pn junction on at least the surface of a spherical substrate constituting a first conductive type diffusion layer region. The spherical diode is substantially buried in a thermoplastic resin and fixed, and the portion of the spherical diode exposed from the thermoplastic resin is etched to form the first conductive type diffusion layer inside the spherical diode. A step of exposing a region, and a metal film having good wettability with a conductive paste on the entire surface in a state of being buried and substantially fixed in the thermoplastic resin and on the exposed portion of the diffusion layer region of the first conductivity type. Selectively forming a spherical diode, releasing the spherical diode from the fixed state, placing the spherical diode on a conductive substrate coated with a conductive paste, and forming the spherical die. Reflowing the conductive substrate on which the circuit board is mounted, melting the conductive paste, forming an insulating layer on the spherical diode, and forming the second conductive type diffusion layer region and the insulating layer. Depositing a transparent conductive film so as to cover it. According to such a configuration, by performing reflow on the conductive paste, the conductive paste is selectively bonded only to the metal film having good wettability, as compared with the conductive paste and silicon having poor wettability. The problem that the conductive type diffusion layer region and the conductive paste are electrically short-circuited does not occur.

According to a third aspect of the present invention, in the method for manufacturing a solar cell according to the first or second aspect, the step of forming the insulating layer comprises: after sprinkling a powdery insulating resin on the spherical diode; A method for manufacturing a solar cell, comprising forming an insulating layer by reflow. According to such a configuration,
Electrical insulation between the second conductive type diffusion layer region and the conductive paste can be easily realized.

According to a fourth aspect of the present invention, in the method of manufacturing a solar cell according to claim 1 or 2, the step of forming the insulating layer includes forming the insulating layer by pouring a liquid insulating resin. A method for manufacturing a solar cell, comprising:
According to such a configuration, electrical insulation between the second conductive type diffusion layer region and the conductive paste can be easily realized.

A fifth aspect of the present invention is a solar cell in which solar cells are laid on a sheet-shaped conductive substrate, wherein the solar cell has a pn junction with a diffusion layer region of a first conductivity type. A second conductivity type diffusion layer region to be formed is formed in a semicircular shape on an upper portion of an outer peripheral portion of the first conductivity type diffusion layer region, and a metal film is formed on a lower portion of an outer peripheral portion of the first conductivity type diffusion layer region. It is formed in an arc shape, is electrically connected to the conductive substrate via the conductive paste, and a transparent conductive film is deposited outside the first conductivity type diffusion layer region. A solar cell, wherein the solar cell is electrically insulated from a conductive substrate by an insulating layer. According to such a configuration, a problem that an electrical short circuit occurs between the diffusion layer region of the second conductivity type and the conductive substrate does not occur, and a high-quality, high-yield solar cell can be provided.

A sixth aspect of the present invention is the solar cell according to the fifth aspect, wherein adjacent solar cells are arranged so as to be aggregated without gaps. According to such a configuration, a problem of an electrical short-circuit between the diffusion layer region of the second conductivity type and the conductive substrate does not occur, and a high-quality, high-yield, and efficient cell-aggregated solar cell is provided. it can.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a solar cell and an embodiment of the solar cell according to the present invention will be described in detail with reference to the drawings. In the following embodiments, the first conductivity type will be described as p-type and the second conductivity type will be described as n-type. However, the first conductivity type can be manufactured as n-type and the second conductivity type can be manufactured as p-type. . Further, in each of the following embodiments, a spherical diode using a p-type polycrystal as a spherical substrate is used, but a p-type single crystal or p-type amorphous silicon may be used.

(First Embodiment) In a solar cell according to a first embodiment, as shown in an overall view in FIG. 1, solar cells 10 are spread on a sheet-like conductive substrate 16. FIG. 2 shows a schematic cross-sectional view of this.

The solar cell 10 is manufactured from a spherical diode 10a by a manufacturing method described later. As shown in FIG. 2, a p-type diffusion layer region 11 (a first conductivity type diffusion layer region) is formed. The n-type diffusion layer region 12 (the second conductivity type diffusion layer region) forming the pn junction is the p-type diffusion layer region 1.
1 is formed in a semicircular shape on the upper portion of the outer peripheral portion, while a metal film 14 is formed in an arc shape on the lower portion, and a conductive substrate serving as a p-type electrode of a solar cell is formed via a conductive paste 15. 1
6 are electrically connected. Further, n-type diffusion layer region 1
2, a transparent conductive film 17 serving as an n-type electrode is deposited,
The transparent conductive film 17 and the conductive substrate 16 form an insulating layer 18.
Are electrically insulated from each other.

Next, an example of a specific manufacturing method will be described below. First, an example of a method for forming the spherical diode 10a used in the present invention will be described. A p-type polycrystalline silicon particle having a diameter of 1 mm is dropped while being heated in a vacuum to form a p-type polycrystalline silicon sphere (p-type diffusion layer region) 11 having good crystallinity.
Is formed, and an n-type polycrystalline silicon layer (n-type diffusion layer region) 12 is formed on the surface by a CVD method using a mixed gas such as silane containing phosphine. Where CVD
In the process, a thin film is formed by supplying and discharging a gas heated to a desired reaction temperature while conveying a silicon ball in a thin tube.

In this step, the p-type polycrystalline silicon particles are heated in a vacuum and dropped to be spheroidized to form p-type polycrystalline silicon spheres (p-type diffusion layer regions) 11 and to fall while falling. By contacting with the desired gas,
It is also possible to form the n-type polycrystalline silicon layer (n-type diffusion layer region) 12.

Next, a method of manufacturing a solar cell using the spherical diode 10a will be described with reference to FIGS.
3 to 5 are schematic cross-sectional views of each step of manufacturing the solar cell according to the present embodiment.

First, as shown in FIG. 3A, the spherical diode 10a having the n-type diffusion layer region 12 formed on the surface of the p-type diffusion layer region 11 is placed in a thermoplastic resin 13 by about half. Buried and fixed.

Next, as shown in FIG. 3B, the portion of the spherical diode 10a exposed from the thermoplastic resin 13 is etched to remove the n-type diffusion layer region 12.
The p-type diffusion layer region 11 is exposed.

Next, as shown in FIG. 3C, the entire surface fixed to the thermoplastic resin 13 or the exposed portion of the p-type diffusion layer region 11 has good wettability with the conductive paste. A metal film (eg, a metal film of Cu, Au, etc.) 14 is selectively formed by coating using a sputtering method or the like.

Next, as shown in FIG. 4D, the spherical diode 10a is released from the thermoplastic resin 13.

Next, as shown in FIG. 4E, a conductive substrate 1 using a copper substrate coated with a conductive paste 15 or the like is used.
6 on a spherical diode 10 using a mounter or the like.
a is placed.

Next, as shown in FIG. 4F, the conductive paste 15 is melted by reflowing the conductive substrate 16 on which the spherical diode 10a is mounted. At this time, the conductive paste 15 is selectively bonded only to the metal film having better wettability than the silicon having poor wettability with the conductive paste 15. That is, in FIG. 4E, the position of the metal film 14 of the spherical diode 10a is not aligned, but when reflowing, the metal paste 14 is placed on the conductive paste 15 as shown in FIG. The positions are aligned so that only the film 14 is bonded. Therefore, there is no problem that the n-type diffusion layer region 12 and the conductive paste 15 are electrically short-circuited.

Next, as shown in FIG. 5 (g), during the above-mentioned reflow for melting the conductive paste 15,
The spherical diodes 10a are gathered together and aggregated in the direction indicated by the arrow. During this reflow, the spherical diode 10a having a low specific gravity is in a floating state.
2 can be easily assembled without causing an electrical short circuit between the conductive paste 2 and the conductive paste 15.

Next, for example, a powdery insulating resin is sprinkled and reflowed to form the insulating layer 18, or a liquid insulating resin is poured by potting to form the insulating layer 18, and thereafter, A thin film of a transparent conductive film (for example, ITO) 17 is deposited by a sputtering method or the like, and this transparent conductive film becomes an n-type electrode of a solar cell.
This state is shown in FIG. The overall view is a solar cell as shown in FIG.

(Second Embodiment) A method for manufacturing a solar cell according to a second embodiment will be described below. In the same manner as in the first embodiment, manufacturing is performed up to the step of FIG. 4F, and thereafter, the process proceeds to a step of forming the next insulating layer without aggregating the spherical diodes 10a. That is, for example, a powdery insulating resin is sprinkled and reflowed to form the insulating layer 18, or a liquid insulating resin is poured by potting to form the insulating layer 18, and the transparent conductive film (for example, , ITO) 17 is deposited as a thin film by a sputtering method or the like, and this transparent conductive film becomes an n-type electrode of a solar cell (see the schematic cross-sectional view of FIG. 6).

This embodiment is an embodiment in which the spherical diodes 10a of the first embodiment are not aggregated. The overall view of the solar cell of this embodiment is such that adjacent solar cells are aggregated as shown in FIG. FIG. 6 is a schematic cross-sectional view thereof.

(Third Embodiment) A method for manufacturing a solar cell according to a third embodiment will be described below. This is an embodiment in which each spherical diode is placed at a predetermined position using a mounter or the like to adjust the arrangement.

In the same manner as in the first embodiment, the steps up to the step shown in FIG. 4D are performed, and then a conductive paste and a copper substrate having good wettability or a metal substrate such as aluminum or SUS are formed. A solder resist 19 is applied on the copper-plated conductive substrate 16. Next, the spherical diode 1
The conductive paste 15 is printed by using a screen printing method or the like in a region corresponding to a place where the substrate 0a is to be mounted, and the spherical diode 10a is mounted thereon by using a mounter or the like. ).

Next, by reflowing the self-alignment, self-alignment by rotation of the spherical diode 10a and self-alignment in the XY axis directions are performed, and the state shown in FIG. 8B is obtained. FIG. 8B shows a state in which only the metal film 14 of the spherical diode 10a is bonded to the conductive paste 15 and the positions are aligned. Therefore, there is no problem that the n-type diffusion layer region 12 and the conductive paste 15 are electrically short-circuited.

Next, for example, a powdery insulating resin is sprinkled and reflowed to form the insulating layer 18, or a liquid insulating resin is poured by potting to form the insulating layer 18, and thereafter, A thin film of a transparent conductive film (for example, ITO) 17 is deposited by a sputtering method or the like, and this transparent conductive film becomes an n-type electrode of a solar cell.
(See the schematic cross-sectional view of FIG. 9). The overall view is a solar cell as shown in FIG.

[0033]

As described above in detail, according to the method for manufacturing a solar cell and the solar cell according to the present invention, the reflow effect on the conductive paste causes an electrical short-circuit with the n-type diffusion layer region. In addition, it is relatively inexpensive and easy to take out the p-type electrode. As a result, a highly reliable electrical connection can be obtained, so that the problem of electrical short-circuit in the solar cell assembly process can be drastically solved.
A high-quality, high-yield, and efficient solar cell can be provided.

[Brief description of the drawings]

FIG. 1 is an overall view of a solar cell according to a first embodiment.

FIG. 2 is a schematic sectional view showing the solar cell according to the first embodiment.

FIG. 3 is a schematic sectional view illustrating manufacturing steps (a) to (c) of a method for manufacturing a solar cell according to the present invention.

FIG. 4 is a schematic sectional view illustrating manufacturing steps (d) to (f) of a method for manufacturing a solar cell according to the present invention.

FIG. 5 is a schematic sectional view illustrating manufacturing steps (g) and (h) of a method for manufacturing a solar cell according to the present invention.

FIG. 6 is a schematic sectional view showing a solar cell according to a second embodiment.

FIG. 7 is an overall view of a solar cell according to a second embodiment.

FIGS. 8A and 8B are schematic cross-sectional views partially illustrating manufacturing steps of a method for manufacturing a solar cell according to a third embodiment.

FIG. 9 is a schematic sectional view showing a solar cell according to a third embodiment.

FIG. 10 is a schematic sectional view showing a conventional solar cell.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 solar cell 10 a spherical diode 11 n-type diffusion layer region (first conductivity type diffusion layer region) 12 p-type diffusion layer region (second conductivity type diffusion layer region) 13 thermoplastic resin 14 metal film 15 conductive paste Reference Signs List 16 conductive substrate 17 transparent conductive film 18 insulating layer 19 solder resist

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 5F051 AA02 AA03 AA05 CB04 CB30 DA01 DA03 DA20 FA02 FA06 FA10 FA13 FA15 FA30 GA02 GA05 GA11 GA20

Claims (6)

[Claims] 1. A plurality of spherical diodes having a second conductive type diffusion layer region formed so as to form a pn junction on at least a spherical substrate surface whose surface constitutes a first conductive type diffusion layer region. A step of substantially burying in a thermoplastic resin and fixing the same; etching a portion of the spherical diode exposed from the thermoplastic resin;
Exposing the conductive type diffusion layer region, and exposing the entire surface or the exposed portion of the first conductive type diffusion layer region,
A step of selectively forming a conductive paste and a metal film having good wettability; a step of releasing the spherical diode from the fixed state; and placing the spherical diode on a conductive substrate coated with a conductive paste. A step of reflowing the conductive substrate on which the spherical diode is mounted and melting a conductive paste; a step of collecting and aggregating the spherical diodes; and forming an insulating layer on the spherical diode. A method for manufacturing a solar cell, comprising: a step of depositing a transparent conductive film so as to cover the diffusion layer region of the second conductivity type and the insulating layer. 2. A plurality of spherical diodes having a second conductivity type diffusion layer region formed so as to form a pn junction on a surface of a spherical substrate having at least a surface constituting a first conductivity type diffusion layer region, A step of substantially burying in a thermoplastic resin and fixing the same; etching a portion of the spherical diode exposed from the thermoplastic resin;
A step of exposing a conductive type diffusion layer region; and a step of exposing the conductive paste to the entire surface in a state of being buried substantially in the thermoplastic resin and being fixed or an exposed portion of the first conductive type diffusion layer region. Selectively forming a metal film having good properties; releasing the spherical diode from the fixation; placing the spherical diode on a conductive substrate coated with a conductive paste; A step of reflowing the conductive substrate on which the diode is mounted to melt the conductive paste; a step of forming an insulating layer on the spherical diode; and covering the diffusion layer region of the second conductivity type and the insulating layer Depositing a transparent conductive film as described above. 3. The method for manufacturing a solar cell according to claim 1, wherein the step of forming the insulating layer comprises: after sprinkling a powdery insulating resin on the spherical diode;
A method for manufacturing a solar cell, comprising forming an insulating layer by reflow. 4. The method for manufacturing a solar cell according to claim 1, wherein the step of forming the insulating layer comprises forming the insulating layer by pouring a liquid insulating resin. Battery manufacturing method. 5. A solar cell in which solar cells are laid on a sheet-shaped conductive substrate, wherein the solar cells have a first conductivity type diffusion layer region and a pn layer.
A second conductivity type diffusion layer region forming a junction is formed in a semicircular shape above an outer peripheral portion of the first conductivity type diffusion layer region, and a metal is formed below an outer peripheral portion of the first conductivity type diffusion layer region. A film is formed in an arc shape, is electrically connected to the conductive substrate via the conductive paste, and a transparent conductive film is deposited outside the first conductivity type diffusion layer region. And the conductive substrate is electrically insulated by an insulating layer. 6. The solar cell according to claim 5, wherein adjacent solar cells are arranged so as to be aggregated without gaps.