JPH04223378A - Solar cell - Google Patents

Abstract

PURPOSE:To enable solar cells to be easily connected together by a method wherein both electrodes are provided to one side of the solar cell. CONSTITUTION:A cone-shaped through-hole 11 is provided to a silicon substrate 1 penetrating it through, and a P-N junction 3 is formed on these surfaces. An insulating film 4 is formed on the other side of the silicon substrate 1 around the through-hole 11, and one of electrodes is provided covering the surface of the P-N junction 3 from one side. The other electrode is provided to the other side of the substrate 1 in another part.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure that facilitates connection between solar cells.

0002

2. Description of the Related Art Conventional solar cells have a PN junction in a very shallow portion on the light-receiving surface side of a silicon substrate, and electrodes are provided on the front and back sides. This method makes it easy to form electrodes, but it is inconvenient when connecting to other solar cells because the lead wires must be connected alternately. Therefore, a device in which both electrodes are provided on one side has been devised. There are also examples in which the front electrode is turned to the back side through the side surface of the solar cell or by opening an opening in the silicon substrate using a laser. However, it has been difficult to form a metal film that connects from the front side to the back side.

0003

[Problem to be Solved by the Invention] As mentioned above, when connecting the front side and the back side through the side surface of a solar cell or through a hole opened with a laser, a metal film is formed for the connection. There must be. However, it is very difficult to form a metal film on the sides of a solar cell or inside the opening, and it is difficult to do so by vapor-depositing metal while rotating the solar cell or by vapor-depositing it from an oblique direction. , only a small fraction of the metals used for vapor deposition are available. Further, it requires laborious work. This is because the side surface of the solar cell or the side surface of the opening is perpendicular to the front or back surface of the solar cell.

0004

[Means for Solving the Problems] In the present invention, when providing a through hole reaching from one surface of a silicon substrate to the other surface, the width of the other surface is gradually increased and electrodes are provided on this slope. .

[0005]

[Function] In the present invention, since the through hole from the front side to the back side is sloped, a metal film can be easily formed on the side surface of the through hole by a single vapor deposition.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention.

The silicon substrate 1 used has a crystal axis of (100) and a thickness of 50 to 200 microns. A PN junction 3 is formed on one surface, and a surface electrode 2 of an appropriate shape is formed on the surface. Further, a cover glass 6 is attached to the surface thereof via an adhesive 7. A through hole 11 is provided in a part of the silicon substrate 1 from the front side to the back side, and a PN junction 3 is also extended around this hole. Through hole 11
The back side gradually becomes wider and forms a slope. An insulating film 4 is provided around the through hole 11 on the back side, and the surface electrode 2 is connected to the electrode 5a via the slope of the through hole 11. The insulating film 4 is a silicon oxide film, a nitride film,
Alternatively, a polyimide film or the like is used to electrically insulate the electrode 5a and the silicon substrate 1.

FIGS. 2A to 2H illustrate the manufacturing steps of the present invention. First, as shown in FIG. 2A, a thick silicon substrate 1 is etched in an alkaline solution to a thickness of 50 to 200 mm.
Make it micron.

Next, as shown in FIG. 2B, the silicon substrate 1
An oxide film 9 is formed on the surface. This oxide film 9 is formed by high temperature treatment in water vapor or oxygen.

Next, as shown in FIG. 2C, a portion of the oxide film on the back surface of the silicon substrate 1 is removed to form a window 10.

Next, as shown in FIG. 2D, etching is performed in a weak alkaline solution. At this time, the oxide film 9 on the surface of the silicon substrate 1 serves as a mask, and the window 10 formed in the previous step
etched only from At this time, since the etching rate differs depending on the crystal orientation direction of the silicon substrate, when the crystal orientation direction is (100), the through hole 11 formed in the etched portion is approximately Make an angle of 70 degrees.

Next, as shown in FIG. 2E, the oxide film 9 on the surface is
etched in an acidic solution. Thereafter, N-type impurities are diffused to form a PN junction. A PN junction is formed on the surface and the wall of the through hole 11 by this diffusion. The oxide film 9 on the back side prevents impurities from diffusing to the back side.

Next, as shown in FIG. 2F, the oxide film 9 on the back surface is
are removed except for the area around the through hole 11. As a result, an insulating film 4 made of an oxide film is formed around the through hole 11 on the back side.

Next, as shown in FIG. 2G, the silicon substrate 1
A surface electrode 2 is deposited on the surface of the substrate. Next, as shown in FIG. 2H, from the surface of the insulating film 4 to the surface electrode 2,
An electrode 5a is deposited along the slope of the through hole 11. At this time, since the slope of the through hole 11 is inclined at about 70 degrees with respect to the surface, the electrode material is easily deposited on the side surface of the through hole 11. At this time, by masking portions where electrodes are not needed, the back electrode 5b can be formed at the same time as the electrode 5a is deposited.

[0015]

Effects of the Invention The through-hole 11 having the slope according to the present invention can be easily manufactured by utilizing the anisotropy when etching the silicon substrate 1, and is suitable for mass production. Furthermore, since an electrical connection from the front side to the back side can be made through the through hole, there is no need to make an electrical connection on the outside of the solar cell. Therefore, by bonding the cover glass to the front side of the solar cell with an adhesive or the like, the potential of the solar cell will not leak to the outside of the cover glass. Considering that it is used in outer space, there is no electrical interaction between space plasma and solar cells. Furthermore, by forming the front electrode on the back surface, the area of the front electrode can be reduced and the area onto which light enters increases. As a result, the electrical output of the solar cell increases.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an embodiment of the invention.

FIGS. 2A to 2H are schematic cross-sectional views of each step in an embodiment of the present invention.

[Explanation of symbols]

1 Silicon substrate 2　Surface electrode 3 PN junction 4 Insulating film 5a Electrode 5b Back electrode

Claims (1)

[Claims] 1. A through hole that reaches from one surface of a silicon substrate to the other surface and has a width gradually widened on the other surface side, and a PN junction provided on the one surface and the surface of the through hole;
an insulating film provided on the periphery of the through hole on the other surface of the silicon substrate, one electrode covering the PN junction and reaching the surface of the insulating film, and another electrode provided on the other surface of the silicon substrate. More solar cells.