JPH0574235B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a large-scale photoelectric conversion device and a method for manufacturing the same, which are manufactured at low temperatures and are therefore inexpensive and can tolerate some circuit errors.

As we increasingly realize that our remaining biofuel resources are finite, and as the need to develop renewable and effective energy resources increases, a significant amount of research has focused on developing solar energy. It is being done against.

A significant problem with the development of photoelectric conversion devices has been the cost of semiconductor materials for the conversion devices. This semiconductor material, usually silicon, uses a PN junction to create a potential when exposed to light. However, for accurate operation, typical systems require large amounts of semiconductor material to cover a relatively small area. Further challenges encountered include the need to ensure that the thickness of the semiconductor material can withstand the tension caused by bending, and that it must be made to have the minimum amount of softness necessary for normal operation or use. The cell needs to be a small unit. The third problem is tolerance to defects in large area cell arrays. That is, when a single shot occurs, the generated electricity may affect all units by escaping through the shot cell.

One solution to these problems is the 1960
This is suggested in a paper titled ``Large-Scale Silicon Solar Cells'' by MB Prince published on page 26 of the 14th Annual Power Sources Conference. He suggests using semiconductor spheres in a plastic matrix. However, problems arose with making electrical connections. For an example, see section G, chapter 9, page 209 of the text "Semiconductors and Metalloids" by Harold Hobel.

It is therefore an object of the present invention to provide a large area photoelectric conversion element array using a minimum amount of semiconductor material.

A second object of the present invention is to provide a flexible array of photoelectric conversion elements that can be bent and deformed without damage even when manufactured in thin film form.

A third object of the present invention is to provide a large area optoelectronic array with tolerance to malfunction due to short circuits, which can handle several shorted cells without degrading the electrical performance. The goal is to develop

A fourth object of the present invention is also to provide a low cost manufacturing process for making large area optoelectronic device arrays in which the maximum temperature required is less than 400°C.

Another object of the invention is to arrange the semiconductor spheres in a continuous internal structure that is connected and coplanar with the array during the manufacturing process, adding very little additional cost to complete the assembly. The goal is to provide a connectivity system.

According to the present invention, a radiant energy conversion system can be provided that includes a matrix support member having a metal foil. The metal foil has first and second layers of polymeric material disposed on opposite sides thereof and has at least a hole through the foil spaced apart in the support member. A substantially spherical semiconductor cell is formed within each hole, each cell having a P-type region and an N-type region. an N-type region contacts the metal foil in each hole;
Conductive means are formed along one side of the support member and connect the P-type regions of each cell. Each connection to the P-type region consists of an electrode with a predetermined resistance.

Further, the plurality of matrix-supported spherical assemblies are interconnected in series and the connection is coplanar with the assembly and has a thickness not substantially greater than the thickness of the assembly. It is set up like this.

A method for making a radiant energy conversion element includes doping the surface of a plurality of semiconductor spheres of P-type material with an N-type dopant, providing a metallic foil between two layers of polymeric material, and the steps of: drilling holes in the foil for placing the spheres; placing the spheres in the holes so as to electrically connect the metallic foil to the N-type surface area of each sphere; and encircling the spheres. removing the first side of the sphere foil to expose the P-type regions on the second surface; and making an ohmic contact to each P-type region with a predetermined resistance. Contains.

The method described above may also include the step of adding another layer of plastic material to the spherical foil assembly to increase the thickness of the matrix-supporting layer to about the average diameter of the spheres.

Each step in the above method is performed at a temperature of 400°C or less.

Additionally, the spherical foil assembly is electrically interconnected in series such that the thickness of each successive interconnect is no greater than the average diameter of the sphere.

The present invention will be explained in detail below with reference to the figures.

Referring first to FIG. 1, a perspective view of a portion of the completed transducer array is shown, in which several silicon spheres 110 are placed on top of the completed assembly.
is provided. The metal foil 103 is 104
An electrical connection is made to the sphere on the N-type surface region shown. Metal foil 105 is electrically connected to the P-type region shown at 109. The top portion of the sphere 106 is embedded within the matrix assembly with a small portion of the top of the sphere exposed to the air. Plastic layer 102 is comprised of a polyester material and is transparent to and transparent to incident light. The plastic layer 101 is also made of polyester material and is shown at 107 to have a metal foil 105 and a metal foil 103 which are both matrix supports and electrical insulators. This results in a fully conductive sphere 11
1 provides coplanar electrical interconnections between the assembled portions of the matrix, thus allowing series interconnections. Note that after making an ohmic contact in the P-type region, the plastic layer 102 is
can be removed.

In other embodiments, metal wires are placed in place of the spheres 111 to provide electrical interconnection between the upper foil 103 and the lower foil 105.

Referring now to FIG. 2, FIG. 2a shows a cross-sectional view of a thin polymer foil film. 203 is a 2 mil (0.127 mm) thick aluminum foil disposed as a thin film between two layers of polyester sheets 202 and 201, each approximately 2 mil (0.127 mm) thick. Figure 2b shows the membrane after the hole drilling step, and Figure 2c shows the membrane after the semiconductor spheres 204 have been placed in the holes. Prior to insertion, sphere 204 consists essentially of a P-type region and has an N-type dopant region diffused over surface 205. An electrical connection is formed between the N-type surface region 205 and the aluminum foil 203 by insertion into the hole.
The sphere can be centered using a pressure process that applies pressure to the sphere, foil, and plastic assembly between relatively soft surfaces to approximately center the sphere in the hole made in the membrane.

Referring now to FIG. 3, FIG. 3a shows the result of a second pressurization step to create a seal around the sphere 301 with a layer of plastic material. This is done by applying approximately 0.1 pound of pressure to each sphere at a temperature of approximately 250°C. The polyester material thus forms a seal at location 301 and adheres tightly to the bulb.

Figure 3b is a cross-sectional view of the sphere after an etch step in which an N-type selective etch is performed on one side of the matrix of firmly anchored spheres. This removes surface material from the sphere, leaving N-type surface material 302 that connects with the metal foil and P-type region 303 for subsequent processing steps.

Referring to FIG. 4, the assembly of FIG. 4a is turned upside down and a backside connection foil 407 is formed in the exposed P-type area of the surface. Additional polyester material 405 is formed to form N-type surface region 4
06 to form electrical insulation. An electrical connection to P-type region 401 is formed at location 408 by applying pressure across the matrix. An additional polyester sheet is formed over the cells 411, and a pressure-applied sheet 410, such as stainless steel foil with a Teflon coating 409, is provided to maintain symmetry during the compaction process. Teflon coating 409 is
Provided to prevent bonding with the N-type surface area of the sphere,
It is provided for easy removal after the final compression bonding step. In the compression bonding step,
The connecting foil 407 is supported on a desired surface so as not to move at least in the vertical direction.

In FIG. 4b, an electrical connection is formed between the P-type region and the foil by applying approximately 5 pounds of pressure on each sphere at a temperature of approximately 260° C. so that layer 413 forms an essentially continuous matrix support. The sheets of polyester are joined together in such a way that they become the material. When a 14 mil (0.3556 mm) diameter ball is bonded to a 0.5 mil (0.127 mm) aluminum foil, the use of pressure from 0.5 lb to 10 lb for each sphere is effective in this example; however, Sufficient pressure is required to significantly deform the metal to create a repeatable connection. Silicon spheres can also crack if excessive pressure is applied.

Light striking the surface reaches junction 414 and creates an electrical potential between foils 412 and 407. The polyester sheet 413 is essentially transparent to light and further insulates the N-type regions from the P-type connection regions. Also the top foil 412
The ball 4 acts as an optical reflector that causes diffuse reflection.
14 makes it easier to receive light.
This is possible by orienting the dull side of the foil towards the light source.

Effective P-N exposed to light by an arrangement that exposes the entire upper hemisphere of the semiconductor cell and brings the spheres into close proximity.
The bonding area will be larger than the planar surface area of the array.

The interconnections of adjacent matrix assemblies are
Using the method of interrupting the foils shown at 107 in the figure and using spheres 111 which are entirely diffused N-type cells or which are entirely conductive, acting as short circuits between the connecting foils. Easily formed. Additionally, shorting balls, such as aluminum or nickel balls, or a length of wire having a diameter approximately the same as the diameter of the balls may be used to form the shorting connection between the foils.

Referring to FIG. 5, a method is shown for interconnecting adjacent assemblies to form a series electrical connection. Foil 51 is shown connected to the N-type region of sphere 53 and connected to the P-type region of sphere 54. A series connection is shown at 52. A polyester insulating and supporting material layer 55 surrounds the continuous interconnects in a substantially continuous manner.

The foil used in the examples herein is intended to be a metal sheet having a thickness of 6 mils (0.1524 mm) or less and having special stretchable properties.
The foil used in this example was wound into commonly available rolls. Usually 0.5 to 2 mil (0.0127 to 0.0508 mm) used for cooking or wrapping things
A variety of common 3 mil foils with a thickness of . Aluminum alloys are also effective.

By manufacturing using the method described above, it is possible to manufacture a large-area solar energy conversion element that converts incident energy into electrical potential. The process of the present invention has the great advantage of being able to produce large area arrays at relatively low temperatures, resulting in low cost and being highly tolerant to short circuits. Therefore, we are confident that we have been able to provide a more economical energy conversion device.

Although the invention has been described and illustrated with respect to particular embodiments thereof, it is believed that variations and modifications may be made without departing from the spirit and spirit of the invention herein.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a portion of the solar energy conversion device. Figures 2a, 2b, and 2c are consecutive process diagrams, of which the second
Figure a is a cross-sectional view of a foil-plastic membrane. Figure 2b is a cross-sectional view of the plastic foil membrane after the holes have been punched. FIG. 2c is a cross-sectional view of the foil-plastic film after doping. Figures 3a and 3b are diagrams showing steps added to the processing steps;
The figure is a cross-sectional view of the foil-plastic membrane and the sphere after sealing the plastic around the sphere. Figure 3b is a cross-sectional view of the sphere with the foil-plastic film and sealed N-type surface material removed. Figure 4a is a cross-sectional view of the completed assembly prior to the installation of the second metal foil and the final hot press step. FIG. 4b is a cross-sectional view of a completed cell with two connected foils formed in a completed solar energy conversion device. FIG. 5 is a diagram illustrating alternative embodiments of the present invention showing alternative ways of interconnecting adjacent matrix assemblies.

Claims (1)

[Scope of Claims] 1 a. Doping a plurality of semiconductor spheres of a first conductivity type with a dopant of a second conductivity type; b. Providing an aluminum foil between the two layers of polymeric material. c. inserting the spheres into holes formed in the aluminum foil such that an electrical connection is made between the surface areas of the first conductivity type of each sphere, and assembling the sphere and foil; d creating a seal around said sphere; e selectively removing a first side of said sphere foil assembly to form a next surface of said sphere from a second conductivity type; A method of manufacturing a radiant energy conversion device, comprising: exposing a region; and f forming an ohmic contact to the next exposed surface of each of the spheres. 2. Inserting each sphere into a hole in the aluminum foil is carried out by bringing the sphere close to the aluminum foil and compressing them between two relatively soft surfaces. A method of manufacturing a radiant energy conversion device. 3 a a plurality of substantially spherical semiconductor cells of a first conductivity type having a doped surface layer of a second conductivity type over a portion of the surface of each cell; b each in the same conductive region; at least one aluminum foil assembly having a hole for making an electrical connection with said cell of; c making an electrical connection for each cell in a region of conductivity type opposite to the region connecting said aluminum foil; d) insulating means for electrically isolating said electrically conductive means from said aluminum foil;