JPS6132831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for generating electrical power from optical radiation, particularly solar radiation.

As older fuels have become increasingly unsuitable for all types of energy generation, efforts have been made to find alternative energy sources. A particularly attractive alternative source is optical radiation, particularly solar radiation, where vast amounts of energy are readily available and largely untapped. Among the most important existing devices for converting solar energy into electricity are those developed in space technology. These devices consist of circuits made of thin single-crystal layers connected in series with a small area. Such devices are relatively efficient in terms of the power generated. However, this view has little effect on ordinary commercial and consumer power generation problems. In this case, the utility criterion is related to economics, such as the amount of electricity generated per unit cost. Based on this efficiency standard,
No useful practicality in space technology.

Devices and manufacturing methods using polycrystalline semiconductor materials have generally been found to be unsuitable due to high production costs. One of the reasons for this high cost is that high temperatures are used in this manufacturing method.
It is necessary to use structural materials with good heat resistance. Additionally, such devices typically utilize metal internal conductors, which further increases cost. Also, the defective rate when manufacturing such equipment is
It is relatively expensive because impurities seep through during manufacturing. Furthermore, control of the deposition of semiconductor material in such processes is also a considerable problem.

Recently, there have been attempts to create a photovoltaic power generation device using a compound semiconductor material having an N-type region and a p-type region and doped with the N-type and p-type regions. In this case, the first semiconductor portion constituting the N type is formed by vapor phase deposition of a metal such as cadmium with the addition of sulfuric acid to form a cadmium sulphide layer.
The material of the p-type second semiconductor part is CuCl.
Formed by immersion in a hot aqueous solution of
This forms Cu _X S. However, the results were poor because cadmium sulfide can be porous, which causes the bond to short. Additionally, deposition requires large amounts of unused cadmium, resulting in photovoltaic power generators that are quite hot and often have low efficiency.

U.S. Pat. No. 3,573,177 discloses supplying sulfur or selenium from a solution containing S ⁼ or Se ⁼ ions,
A conventional method of forming polycrystalline cadmium, zinc sulfide or selenide or cadmium zinc by electrochemical deposition on a Cd or Zn or Cd, Zn anode, making this polycrystalline material usable as a semiconductor material. is listed. The idea of forming thin films of semiconductor materials by electrochemical methods is relatively new and is due in part to this US patent.

The above-mentioned US patent discloses that by an electrochemical method,
It advances the technology of manufacturing semiconductor materials and offers many advantages, including the ability to apply films of semiconductor materials to irregularly shaped substrates that have not been perfectly cleaned. However, in this patent, the final product cannot necessarily act as a PN semiconductor junction material necessary for the operation of a photovoltaic cell or similar diode.
There are various restrictions. This US patent essentially covers electroluminescence. It is intended for the production of non-bonded semiconductor coatings such as those found in panels, electroacoustic transducers, and photosensitive conductors.

The essence of the above-mentioned US patent mainly lies in the anode plating that discharges S ⁼ and Se ⁼ ions. However, it is not known that the method of this US patent can be applied to a more ideal discharge of Te ⁼ ions in the case of photovoltaic cells. However, cadmium telluride has an unrivaled optimum resistance to sunlight.
With a direct bandgap of 1.5 eV, it is these discharges forming CdTe and ZnTe that are of primary importance for the production of solar cells.

Conventionally, a method of electrochemically depositing metal on the cathode has been proposed in order to make a selenium rectifier.
This method is based on Ber.German Che. H. Hon. Bunsengesellschaft 6F (1973), p. 930. Gobrecht, H., D. Reese and A. Tausend in the paper "Electrochemical separation of metal selenides". This paper does not discuss the fabrication of photovoltaic power generation cells. In this conventional method, the deposition of the less noble and more noble components must be very carefully controlled due to the difference in standard precipitation potential. For this method to work, the more noble ingredients must be added in carefully controlled small amounts.

The main object of the invention is therefore to provide a photovoltaic power generation device in the form of a power generation cell constructed of a semiconductor material having an N-type region and a P-type region.

Another object of the present invention is to provide a photovoltaic power generation device of the type described above, which operates at a relatively high efficiency and which can be manufactured at a relatively low cost compared to previous hitherto proposed photovoltaic power generation devices. An object of the present invention is to provide a photovoltaic power generation device.

Another object of the invention is to provide a photovoltaic power generating device that can be manufactured into a relatively flat sheet for placement on a surface arranged to receive solar radiation.

Another object of the invention is to provide a low temperature method for manufacturing photovoltaic power generation devices that eliminates the high temperature operations conventionally used to manufacture power generation devices with semiconductor materials. .

Another object of the invention is to provide a method for cathodically depositing semiconductor-forming materials on the cathode of an electrolytic cell.

Another object of the invention is to provide a photovoltaic power generation device obtained by cathodically depositing a semiconductor-forming material on the cathode of an electrolytic cell to produce a light-responsive semiconductor compound. It is.

Another object of the invention is to provide a method for making a photovoltaic power generation device of the type described above, which has high efficiency and substantially eliminates material wastage.

With these and other objects in mind, the invention resides in novel features employing the form, construction, arrangement and combination of parts as set forth in the claims. Next, the drawings will be explained.

In FIG. 1, a photovoltaic power generation device 20 is shown. It is suitable for commercial and consumer use and takes the form of a sheet or panel 22. The panel 22 is dimensioned to be placed over a surface 24 shown in the figures as the roof of the dwelling. In the illustrated application, a photovoltaic power source 20 generates electrical power from solar radiation incident thereon. Of course, the invention can be used in a wide range of other applications, including large immovable equipment, vehicles, and laboratory applications, and other light sources may be used and other forms of light may be used. Good too.

The power generation device 20 has as its main internal components:
Photovoltaic power generation cell 26 formed of semiconductor material
(Figure 2). Sheet or panel 22 can be constructed from a plurality of cells, such as cell 26, connected in series. In its simplest form, cell 26 has an N-type region 28 and a P-type region 30, which form a junction 32.
separated by. This will be explained in more detail later. Although this invention is effective for heterojunctions, the N-type region 28 with a homojunction between
It is also possible to create a p-type region 30.

As used herein, the term "photovoltaic" refers to a compound semiconductor that is capable of generating electrical power when solar radiation or similar optical radiation is incident on the compound semiconductor. The simplest form of semiconductor is often called a cell. In many cases, the term "cell" is used to include not only the compound semiconductor but also the substrate and terminals or electrodes. In each case, the cell has two regions, eg an N-type region and a p-region, with a junction between them.

N-type region 28 is formed of an N-type material, which may be comprised of any of a number of well-known compositions having N-type semiconductor properties. The p-type region 30 is p
p formed of any known composition with type characteristics.
Made of mold material. In a preferred aspect of the invention, the cation is preferably cadmium or zinc and the anion is sulfur, selenium or tellurium.

FIG. 3 shows a modified photovoltaic power generation cell 34.
this is. It has a substrate 36 preferably formed of a relatively inert, non-conductive material that is transparent to optical radiation. The substrate 36 may be made of relatively low cost materials such as various plastics, particularly plastics sold under the trade name Mylar and Kapton, which have relatively low heat resistance and low cost. It can be formed using cheap materials. However, any other substrate material may be used with the present invention, including fiber reinforced plastic substrates such as epoxy resin impregnated glass fiber substrates. Essentially, the substrate should be relatively inert with respect to electrical conductivity and may not have substantial heat resistance.

A conductive metal electrode 38 is provided on one flat surface of the substrate 36.
are combined. This electrode is made of stainless steel.
It can be constructed from a relatively inert conductive metal such as nickel. In this case, the electrode 38 is a sheet-like thin layer, but the invention contemplates that the electrode 38 may have other shapes or locations.
Electrode 38 can be affixed to substrate 36 by a variety of known methods, such as metal vapor deposition, electrolytic deposition, and the like. Alternatively, the electrodes 38 may be prefabricated as strips and bonded to the substrate 36 by conventional adhesives.

A photovoltaic power cell 40 is secured to the flat exposed surface of the electrode 28 . This cell is substantially similar in construction to power cell 26. In this case, photovoltaic cell 40 is constructed of a compound semiconductor material and has an N-type portion 44, similar to N-type portion 28, and a P-type portion 46, similar to P-type portion 30, with a junction 48 therebetween. A conductive cover on the outer surface of portion 30. sheet 5
0 is fixed.

N-type region 44 and P-type region 44 are formed in substantially the same manner as N-type region 28 and P-type region 30 are formed in cell 26.
A mold region 46 is formed. Additionally, in this case, N-type region 44 and P-type region 46 may have a homogenous junction 48 therebetween, such as if the N-type and P-type regions were formed of substantially the same material. Alternatively, these two regions may be formed of different materials with a heterojunction 48 therebetween. Finally, a conductive connection 52 is connected to the metal electrode 38 and a conductive connection 54 is connected to the sheet 50. Cell 34 operates in substantially the same manner as cell 226, producing a current that flows through a load connected between connections or terminals 52 and 54 when solar radiation is incident on cell 34.

The cells 26 and 34 can be completely enclosed in a leaf container or similar containment means or so-called envelope (not shown). Such a container is made of a material that is transparent to optical radiation. The container means may be formed of any of a variety of known materials capable of transmitting solar radiation as well as all types of optical radiation, such as plastic materials including, for example, polyethylene sheets. Polyptyral sheets and other types of plastics, as well as other non-conductive materials that are transparent, can be used in forming the container.

Like the previously described cells, cell 40 can be made of cadmium sulfide or cadmium selenide, but is preferably made of cadmium telluride. In the illustrated embodiment, the cell 40 is in the form of a laminar layer, but in other applications, the cell 40 and the N-type and P-type regions 44, 46 can have any suitable shape. As will be explained in more detail below, the thickness of the cell 40 can be easily controlled by the method of manufacturing the photovoltaic generator, resulting in considerable savings. In any event, the cell 40, as well as other layers of the cell 40 as described below, may be on the order of 1 to 20 microns thick, although the cell thickness may be approximately 0.1 microns thick.
Preferably, the range is from 40 microns to 40 microns.

Cell 26 or 34 and cover. The upper surface of the container means relative to the sheet 50 is optically transparent and constitutes an element of a light passageway 56, as shown schematically in FIG.
Additional or alternative optical paths (not shown) may be provided on the underside of the cover. At this time, board 3
6 and the electrode 38 have a lattice structure so that light can pass in and out, and are made very thin to minimize internal electrical resistance.

From the foregoing, it is clear that the photovoltaic power generation device of the present invention can be placed in contact with a light-receiving surface, such as the roof of a structure, in the form of a continuous panel that can be fitted to fit the dimensions. Understand that it is possible. This feature, above and among those described further below, constitutes a substantial advantage of the invention in terms of ease of use and economy.

As previously mentioned, the covering means on the photovoltaic cell is made optically transparent and constitutes an element of the passageway 56 through the P-type semiconductor region 46 for entry into the cell 40. Note that although in this case the P-type semiconductor region 46 is the region exposed to the optical radiation, the N-type region 44 may be the outermost region exposed to the optical radiation via the passageway 56.

Conductors 52, 54 connect the cell 40, and thus the power generator, to an external load (not shown). This load may be, for example, the mains power supply for the vehicle or for electrical equipment inside the vehicle. In operation, light through passageway 56 is incident on photovoltaic cell 40 and moves electrons from the semiconductor material in P-type region 46 across junction 48 to N-type region 44 . This is due to the well-known interaction of photons with semiconductor materials. Therefore, electrons move to the positive terminal 52, and current flows through the conductor and the load.

In the example cell shown in FIG. 3, the light path is indicated at 56, and at least the electrode 50 must be transparent. In this case, electrode 38 and substrate 36 do not need to be transparent. In this invention,
As will be explained in more detail below, the cell may have a transparent substrate 36 and transparent electrodes 38 formed of conductive glass or transparent plastic substrates. In this configuration, the cell responds to the light path shown at 56' in FIG. However, it should be noted that all components of cell 34 may be transparent.

When the cell 34 is configured to respond to the light path 56, the narrow bandgap material can be used as the electrode 38.
The material with a wide bandgap is attached to the electrode 5.
Attach to 0. When cell 34 is configured to respond to light path 56', wide bandgap material is associated with electrode 38 and narrow bandgap material is associated with electrode 50. Essentially, wide bandgap material always points towards the light source.
In this invention, the CDS layer has a wider band gap than the CDSE layer, and the CDSE layer has a wider band gap than the CDTe layer.

In the present invention, the electrode 50 need not be made of metal, but can be made of a conductive transparent oxide as described later. Electrode 38 can also be formed from a conductive transparent oxide. Furthermore, the substrate 36
is conductive and constitutes an electrode, thus electrode 3
8 may be omitted.

A preferred embodiment of the photovoltaic power cell of the present invention is shown in more detail in FIG. In this case, the power cell of the preferred embodiment is designated by the reference numeral 57 and has a non-conductive substrate 5, such as a glass substrate.
Contains 8. Preferably, substrate 58 is relatively thick, such as about 1/8 inch thick. A metal electrode 60 is placed on one flat surface of the substrate 58. The electrode 60 has a grid shape and is composed of a plurality of strips 62 extending in the horizontal direction and spaced apart from each other in parallel, and a plurality of strips 64 extending in the vertical direction and spaced apart from each other in parallel with the width direction. Preferably, the strips 62, 64 are arranged substantially orthogonally.

A conductive coating 66 is applied to the surface of the substrate 58 to which the lattice 60 is applied, which substrate 58 is preferably a conductive coating comprised of antimony-doped stannous oxide or indium oxide. The conductive coating substantially completely covers the entire interior surface of the substrate 58 except for the portions of the grid that contact the substrate, and completely covers the metal grid 60 and is electrically connected thereto while the grid 60 is on the interior surface of the substrate 58. Contact.

This last substrate 58 may be formed of any transparent substrate material, such as polymethyl methacrylate. Furthermore, the substrate 58 may actually form part of a basic cellular building block in the form of a glass roof or wall tile. In any case, when the cell is arranged to allow light to pass through the substrate, it is important that the substrate is sufficiently transparent to allow light to pass through.

A coating 66 facing the source of solar energy is coated onto the substrate 58 as a uniform thin film of electrically conductive material, preferably by vapor coating. Preferably, the conductive material is antimony doped tin oxide or tin doped indium oxide. In this invention, it has been found that there is no need to use metal as an electrode, and that a relatively thick transparent substrate can act as an electrode if made conductive by applying a conductive oxide. Ivy. The conductive oxide is an N-type material, so the conductive oxide must be in contact with the N-type region. Otherwise, another bond will be created.

The grating 60, often referred to as a prism, is placed on the surface of the substrate 58 and between the substrate 58 and the tin oxide coating 66 to reduce ohmic resistance. In this way, the grid 60 becomes a first electrode with a resistivity well below 1 ohm/square inch. Terminal 68 extending from a portion of grid 60
acts as a first terminal electrically connecting to the cell. A flat generatrix bar (not shown) is a grid 60
The terminal may extend along the periphery of the terminal portion of the cell and serve as one of two terminals that make an electrical connection to the cell.

Photovoltaic cell 57 also includes a cell structure of the type shown in FIG. In this case, the cell structure includes an N-type portion 70 corresponding to the N-type portion 44 in FIG.
It includes a P-shaped section 72 corresponding to P-shaped section 46 of FIG. 3, with a joint 74 therebetween. N type part 70
may be constructed of cadmium selenide or cadmium telluride, for example, while the P-type portion may be formed of the same material to provide a homojunction, or may be formed of a different material to provide a heterojunction. A relatively thin metal film 76 is applied to the outer surface of P-type portion 72, as shown in FIG. This outer metal film 76 constitutes the rear electrode assembly, and conductive wire 7
It has 8.

It can be seen that the structure of the cell of FIG. 4 allows light to pass through the substrate 58, thus eliminating the need for a third metal substrate. Furthermore, it can be seen that the grating 60 is also electrically conductive and is also in a conductive relationship with the N-type region 70 via the electrically conductive transparent oxide film 66. The outer metal film may have a reflective surface facing toward the substrate 58 to reflect light entering the cell and increase energy conversion efficiency.

Relatively high efficiencies are achieved in polycrystalline photovoltaic cells through a combination of factors, including the use of a thin layer of cadmium telluride to facilitate maximum transport of photons to the junction region. I can do it. A thin film of another metal, such as vapor-deposited nickel, can be used to provide an anti-reflection coating on the side of the glass facing toward the sun. The structure described above is very effective in reducing ohmic losses in the two electrodes as well as the semiconductor material.

Compared to conventional single-crystalline cell structures, this type of cell structure combines a thin layer of one or more active materials with the high cell structure costs described here on an inexpensive glass or transparent plastic substrate. By depositing on the top, considerable savings can be made.
Very advantageous. The later described embodiments of the invention allow cells with a large total area to be created without interconnecting large numbers of small or independent devices. Additionally, this cell structure may use printed wire type conductors to connect a plurality of individual cells in series or series-parallel on a tile or similar substrate.

FIG. 5 is a schematic diagram of a preferred electrical circuit connecting at least one or more cells of the present invention. It is well known that absorption of photons with wavelengths shorter than the optical bandgap generates electron-hole pairs in the crystal lattice of semiconductor materials. PN junction, e.g. PN junction 32 or junction 48
Alternatively, an internal electric field generated by a Schottky barrier separates the electrons and holes and generates a photovoltaic force that forward biases the junction. Therefore, the solar cell proposed in this invention can be represented by the equivalent circuit shown in FIG.

With further discussion of FIG. 5, each cell is designated by the reference numeral 80. This acts as a current generator per unit area. As shown in FIG. 5, a diode 82 is connected in parallel with the cell. Diode 82 is provided per unit area for a current generator such as photovoltaic cell 80. In this regard, it will be appreciated that cell 80 is connected in parallel with diode 82, but the opposite terminals of diode 82 are connected to positive line 84 and ground line 86. Resistors 88 and 90 represent the sheet resistance of the electrodes and the electrically neutral portion of the semiconductor that borders the internal field region. resistance 8
2,94 represents the contact resistance per unit area between these neutral regions and the electrode, and the resistance per unit area of these neutral regions. Each cell has the fifth
It has similar resistance and diode action as shown in the figure.

To optimize conversion efficiency, resistors 88 and 90
and resistors 92, 94 (which constitute parasitic resistance) should be as small as possible. Choosing semiconductor materials to optimize energy conversion is
It effectively converts all solar radiation into electron-hole pairs. In other words, such efficiency is achieved by maximizing the current generator, such as solar cell 80, and maximizing the forward resistance of the various diodes 82. Such maximization is necessary for the solar cell 80 as well as the diode 82, but these conditions are interrelated, so that the bandgap of the semiconductor material chosen is a trade-off; the more radiation it absorbs, the more radiation it absorbs. The band gap becomes smaller. However, the internal resistance of the barrier decreases to convert solar radiation at the surface on cloudy days.
A bandgap of approximately 1.5ev of cadmium telluride is optimal.

The method of making a photovoltaic power cell in accordance with the present invention is shown in more detail in FIGS. The chart is shown in FIG. Essentially, the invention provides controllable electrochemical fabrication of cadmium and zinc type compound semiconductor junctions for use as photovoltaic cells. In this invention, a semiconducting compound material is formed at the cathode from which both the more noble and less noble components discharge.

Referring now to FIG. 6, 100 represents a beaker-like container made of relatively inert material. Disposed within the container 100 is a cathode 102, also made of a relatively inert material, in the illustrated case nickel. However, any other type of metal electrode that is inert to the reaction can be used, for example steel or glass or plastic with a conductive oxide coating. An anode 104 is also disposed within the container 100. The anode 104 may be inert or may be formed of cadmium or zinc or selenium or tellurium, as explained below; in the illustrated case, the anode 104 is made of an inert platinum material. Both electrodes 102, 104 are placed in an electrolyte 106, described below, and both the anode and cathode are electrically connected to a voltage source 108.

The particular configuration of FIG. 6 represents a simplified system for forming a coating on the cathode 102. For example, by using an electrolyte such as SO ₂ in H ₂ O, sulfur can be electrochemically deposited onto the nickel cathode 102 to form a sulfur coating, shown at S in FIG. . This reaction is expressed as follows.

4e ^- +4H ⁺ +H ₂ SO ₃ =3H ₂ O+S This reaction shows that sulfur is reduced when deposited on the cathode. Similarly, TH ₂ SO ₃ at the anode
Oxidized to H ₂ SO ₄ . In this case, the deposition is approximately 10
C. to about 20.degree. C., with about 3 to 6 volts applied between the anode and cathode and a current density of 0.1 ampere/ ^cm.sup.2 . ₁ of SO2 to water
It is optimal to deposit sulfur from mg/solution.

If you want to form cadmium sulfide at the cathode rather than just a layer of sulfur, you can change the electrolyte from SO ₂ in water.
Just change it to SO ₂ +3cdso _{4.4H 2} O. Cadmium becomes positively charged due to cadmium sulfate ion dissociation in water. Ions can be made. This cadmium.
The ions are attracted to the cathode and are discharged there, at the same time sulfur is also deposited on the cathode. Therefore, when cadmium and sulfur are simultaneously discharged at the cathode, they combine to form a layer of cadmium sulfide on the cathode. Thus, depending on the concentration of solute used in the electrolyte, a cadmium sulfide film can be formed in any desired stoichiometric ratio.

FIG. 7 shows a system similar to FIG. 6, except that the cathode used now constitutes the metal on which the coating is to be formed. Cathode 102
is formed of cadmium, and by the above-mentioned reaction, sulfur can be deposited as a film together with cadmium on the cadmium cathode by a cathodic method to obtain, for example, cadmium sulfide.

FIG. 8 shows another embodiment of a method for forming a cadmium sulfide compound film on an inert cathode. In this case, the cathode is shown as manufactured glass with a coating of conductive oxide. Again, the anode is formed from an inert metal such as platinum. in H ₂ O to make a cadmium sulfide coating by the cathodic method.
Introducing sulfur into the electrolyte solution in the form of SO ₂ ,
Sulfur dissolved in the form of 3cdSO ₄ .4H ₂ O is introduced into this solution as described above. In the same way, cadmium telluride, cadmium selenide, etc., zinc sulfide, etc.
It will be appreciated that zinc selenide and zinc telluride can be formed, i.e., the cathode 102.
To form a cadmium telluride coating on the
The electrolyte comprises tellurite as the source of tellurium and cadmium sulfate as the source of cadmium. In this way, cadmium becomes positively charged. Ions are formed and discharged at the cathode. Similarly, tellurium is deposited on the cathode and simultaneously reacts with cadmium to form a cadmium telluride film.

It will be appreciated that it is necessary to deposit the cadmium and tellurium or other components used elsewhere in the desired stoichiometric amounts. However, the standard voltages required to deposit cadmium and tellurium are different. For example, less noble components such as cadmium require more negative voltages than for more noble components such as tellurium and selenium. When semiconductor components are formed, there is some compensation effect with respect to deposition voltage, but it is usually desirable to lower the more noble components. For this reason, when making cadmium telluride, the amount of tellurium in the solution is less than the amount of cadmium.

FIG. 2 shows a nickel anode 1 in the manner previously described to form a telluride, cadmium or similar photovoltaic device as shown in FIG. 3 or FIG.
Plate a first layer of cadmium telluride over the 04. The film thus formed on the cathode is made into an N-type region or a P-type region depending on the ratio of cadmium to tellurium. After forming a first cadmium telluride layer on the cathode, such as the glass cathode with oxide coating shown in FIG. using electrolytes. However, the concentration ratio of cadmium and tellurium in the second solution is P
To form the other of the type region or the N-type region,
Different from the case of the first solution. That is, for example, the initial coating of cadmium telluride is
When provided on the nickel cathode 102 at 50.01%,
This film constitutes the N-type layer 28. When a second coating of cadmium telluride from a second electrolyte is provided over the first coating, this second coating may be formed by e.g.
It can have even lower concentrations of cadmium, such as 49.99%. In this case, the second film is P
It acts as a mold layer 30. To this end, simply by controlling the chemiochemical proportions of ions of metallic components, such as cadmium, and non-metallic components, such as tellurium, or any other metallic and non-metallic components used in this invention, N-type It can be made of either a layer or a P-type layer. In this example, the nickel cathode 1
Homogeneous bond 3 between two films formed on 02
It can be seen that 2 is formed.

Optionally, the invention allows the N-type and P-type regions to be made from different materials and to provide a heterojunction therebetween. In this case, a glass cathode 102 with a conductive oxide coating is shown.
It is formed on cadmium selenide or as a first film. Cadmium telluride is then plated onto the first layer of cadmium selenide.
In this way, the concentration of cadmium relative to tellurium and selenium can be stoichiometrically adjusted to create both N-type and P-type regions. The cadmium selenide layer can act as either a P-type region or an N-type region, but is preferably an N-type region, and the same is true for the cadmium telluride layer, which is a P-type layer. It is preferable.

FIG. 9 illustrates an alternative method of making a cathodically formed coating in accordance with the present invention. In this case, the cathode may be made of glass with a conductive oxide coating as shown, for example.
It is still inert. The anode in this case consists of a metal component, for example a solid cadmium or zinc sheet or a cadmium or galvanized sheet. The electrolyte is composed of materials that provide the non-metallic component of the compound. That is, in the case of sulfur, the electrolyte consists of an aqueous solution of _SO2 . In this way, cadmium sulfide is formed at the cathode. Tellurite may be used as the electrolyte, in which case cadmium telluride is formed on the nickel cathode.

When using cadmium sulfide, it has been found that good results are obtained when the cadmium sulfide is formed as a layer approximately 5 microns thick on the cathode. Such a layer is obtained from a 5% solution of SO ₂ at about 45°C.

In the embodiment of FIG. 9 as well as in other embodiments, anodes of cadmium and similar metals containing doping agents can be used, i.e., indium as the donor-doping agent is combined with cadmium and cadmium as the anode. It can be made into an indium alloy. In this case, the electrochemical method of the invention has the advantage of forming a cadmium sulfide film containing indium in solid solution. cadmium·
By appropriately selecting the concentration of indium alloy,
The indium concentration in cadmium sulfide, tellurium cadmium, etc. can be adjusted.

Therefore, it can be seen that the systems shown in FIGS. 6 to 9 are all effective in forming the desired photovoltaic film material on the cathode. Furthermore, in any of these systems, by changing the electrolyte, a second film can be formed in the same manner as described above. That is, the two films are formed of the same material,
If one is N-type and the other is P-type, a homojunction will be formed between them, and if they are made of different materials, a heterojunction will be formed between them.

As mentioned earlier, it is also possible to control the N-type region and the P-type region simply by adjusting the stoichiometric proportions of the components used.
A mold region can be formed. However, any number of doping agents can be used in the two regions. That is, one region can be doped with indium, aluminum, gallium, etc. as a donor, or it may be doped with phosphorus, arsenic, antimony, etc. as an acceptor.

The invention is primarily effective for use in forming coatings by cathodic methods using cadmium and zinc ions and sulfur, tellurium and selenium ions. Furthermore, cd(s.se), cd(s,
Te), cd (se, Te), cd, zn (Te), cd, Hg
(Te) and mixed crystals such as CD, Mg(Te), etc. can be made. To this end, any combination of mixed crystals formed with ions of cadmium, mercury, magnesium, zinc, and any type of mixed crystals, such as those formed with ions of sulfur, selenium, and tellurium, are thus included in the present invention. You can make it by twisting it. These substances may be pure or doped with donors or acceptors as previously mentioned, or with any other type of effective and acceptable donor or acceptor. It's okay.

By electrolytically depositing on a conductive cathode as previously mentioned, ions from both the metallic and non-metallic components in the electrolyte are simultaneously discharged at the cathode, forming a semiconducting compound material on the cathode. I can do it. As mentioned previously, SO ₂ can be used as an electrolyte to form the sulfide layer. Cadmium sulfate is added to form a cadmium sulfide layer.
Use in combination with SO ₂ . When forming various cadmium salt films as semiconductor compounds, H ₂ SeO ₃ ,
Various acids can be used, such as H ₂ SO ₃ or H ₂ TeO ₃ . Alternatively, alkaline salts of these acids can be used with an inert anode. Furthermore, acid solutions of SO ₂ , SeO ₂ or TeO ₂ can be used with inert anodes. The composition of the deposited film is controlled by the composition of the electrolyte, as described above. Instead, cd (cd, Zn), (cd, Hg) or (cd,
An aqueous solution of SO ₂ , SeO ₂ or TeO ₂ can be used as an electrolyte with an anode such as Mg).

Ions formed by metallic components, such as cadmium and zinc ions, and ions formed by non-metallic components, such as yellow sulfur, selenium and tellurium in solution, are not necessarily single cations and anions. That's not possible. In general, cadmium and zinc in solution are generally positively charged;
For example, cd ⁺⁺ and Zn ⁺⁺ , thus forming a single cation. In many cases, non-metallic components give rise to ions, such as S ⁼ and Se ⁼ . For example, tellurium can have several valence states, such as Te ⁼ . However, TeO ₃ ⁼ complex ions can also be formed. Furthermore, TeO ₂ in hydrofluoric acid also produces Te ⁺⁴ ions.
In this case TeF ₄ is formed which dissociates to give Te ⁺⁴ in solution.

The electrochemical principles to explain how both metal and non-metal components are deposited as semiconducting compounds on the cathode are not yet well understood. However, it is certain that these components precipitate at the cathode to form semiconductor compounds. Regarding the ions of the metal components, these ions are normally attracted to the cathode and are discharged at the cathode. The reason why ions of non-metallic components discharge is more complex.

Nonmetallic components generate ions in solution in the presence of hydrogen. For example, non-metal components are introduced in acid form, and in most cases a source of hydrogen is available. The theory is that the presence of hydrogen in close proximity to the cathode helps non-metal ions to be reduced near the cathode. For example, TeO ⁼ +6H ⁺ yields Te ⁺⁴ , which is generated at the cathode and discharged at the cathode. However, although the exact location is not fully known, it is certain that a semiconductor compound material is formed in the cathode.

The method for manufacturing the photovoltaic power generation cell of the present invention is as shown in the configurations of FIGS. 10 and 11.
Even if a plurality of anodes are used, it can work effectively. In this case, the illustrated method uses a beaker-like container 110 that corresponds to container 100. Additionally, in the configuration shown in FIG. 10, a relatively inert cathode 112, e.g., a cathode formed of glass with a conductive oxide coating as shown, may be replaced with an inert material, e.g., platinum, as shown. Neutral anode made from materials 1
Used with 14. Additionally, a second anode 116 made of cadmium is used. two anodes 114, 11
6 is connected to the cathode 112 via a current source 118. Potentiometers 120 and 122 are the tenth
As shown, anodes 114, 116 and source 118
connected to. The cathode 112 is the anode 114, 116
and is placed in a suitable electrolyte 124, such as the electrolytes previously described as well as those described below.

The cadmium anode 116 may be a cadmium plated anode. Similarly, anode 116
may be made of an alloy of cadmium and the desired dove, such as a tellurite composition, which provides tellurium ions in solution. each anode 11
By carefully controlling the currents at both 4,116 and 4,116, cadmium can be introduced into the solution from the anode 116. In this way, tellurium ions contained in tellurite are discharged at the cathode 112, and similarly, cadmium that has entered the solution from the anode 116 is discharged at the cathode 112. To form cadmium sulfide or cadmium selenide, use H ₂ SO ₃ To form cadmium sulfide, use H ₂ SeO ₃
to form cadmium selenide.

Again, a first layer is formed over the cathode 112 or other inert cathode, which forms either an N-type or a P-type region depending on the amount of cadmium introduced into the solution from the anode 116. do. The amount of cadmium introduced from the cadmium anode can be controlled by adjusting two potentiometers 120,122. This is followed by forming a second layer over the first mentioned layer, forming either a P-type region or an N-type region opposite the first deposited layer. When two anodes are used in the configuration shown in FIG. 10 or in the configuration of FIG. 11 described below, the ratio of metal ions to non-metal ions or molecules in the deposited compound is in each case: It is determined by the current flowing through each anode to a single cathode. Moreover, it is equally easy to create homojunctions and heterojunctions in semiconductor films. Heterojunction materials can be created simply by changing the electrolyte used to form the second layer.

FIG. 11 shows that instead of a cadmium anode 116,
A configuration using a non-metallic anode 126 is shown. Furthermore,
Electrolyte 124 contains cadmium. The electrolyte 128 is changed to contain ions. As shown, cadmium can also be introduced into the solution, for example from a solution of cadmium salts. In this configuration,
By adjusting the potentiometers 120, 122, respectively, the amount of tellurium introduced into the solution can be carefully controlled.

The tellurium anode of FIG. 11 may be formed as an alloy with a dopant such as antimony phosphorus or arsenic. In any case, the use of two anodes provides a means of constantly supplying the minority components in order to slowly replenish them in the solution. When the ratio of the concentrations of the majority to minority components in the electrolyte is large, it is common to require supplementation of the minority component, which is generally more noble. If two anodes are not used, but a large ratio exists, the minority component can be added slowly and continuously by dripping into the electrolyte based on the rate at which the minority component is used up. I can do it.

In both the embodiments shown in FIGS. 10 and 11, the P-type region and the N-type region are controlled by stoichiometrically adjusting the amount of cadmium relative to non-metals such as tellurium, selenium, sulfur, etc. You can create an area. In addition, a dopant can also be introduced into the solution. In a more preferred form, the dopant can actually be alloyed into the material of one of the electrodes. For example, cadmium. Indium alloy is used as an anode.

It should be appreciated that when using three or more electrodes, plating may occur on one electrode that does not itself constitute the cathode. By properly adjusting the composition of the electrolyte and adjusting the potential applied to the electrodes, simultaneous anodic and cathodic deposition can actually be carried out. FIG. 12 shows a configuration using three electrodes, one electrode 12
9 is formed of a sulfur-containing material and another electrode 1300
is formed from a cadmium-containing material. A third electrode 132 is also provided, preferably of an inert material. Again, by adjusting two potentiometers, for example potentiometers 120 and 122, the amount of cadmium and sulfur ions introduced into the solution and discharged at electrode 132 to form a cadmium sulfide film is controlled. It can be carefully adjusted.

Although cadmium sulfide is described as an example, any other metal and non-metal component can be used. Furthermore, in this embodiment, the electrodes cannot be defined as cathodes and anodes in the classical sense. By way of example, electrode 129 may be at a potential of, for example, negative 2 volts, electrode 132 may be at a potential of, for example, positive 2 volts,
Electrode 130 can have a positive potential of 4 volts, for example. In this way, cadmium from the electrode 130 is discharged at the electrode 132 by the cathode method, and
The sulfur from the electrode 129 is discharged by the anodic method at the electrode 132 and deposited thereon.

For example, "inert anode" or "inert cathode"
As used in this invention, the term "inert" or "relatively inert" refers to a material that is inert to the reactants used, such as an inert cathode such as a nickel cathode. In this case, the anode is inert and does not react with the electrolyte or with ions introduced therein to form a semiconductor film on the cathode.

This invention is very effective in obtaining relatively thin films using the electrochemical method described above.
In this case, membranes having thicknesses ranging from about 0.1 microns to 40 microns and more can be made as described above. Therefore, when we use the term "thin" or "relatively thin" in reference to a coating thickness, we are referring to a coating thickness in the range of approximately 0.1 microns to 40 microns, or greater, as the case may be. say.

Although the invention is useful for materials such as those described above, and which can be made according to the method of the invention, it is most useful for use in making photovoltaic cells. One material that has been found to be is made of cadmium telluride. The expected energy conversion efficiency of a photovoltaic cell with a PN homogeneous junction is a function of the bandgap of the materials used, with an optimal bandgap of approximately
It was found to be close to 1.5ev. Furthermore, cadmium telluride was found to have a band gap within this range. In addition, cadmium telluride has significantly higher efficiency and is less costly than other materials that can be used. Cadmium telluride is stable in air, non-toxic, and does not decompose even when the temperature fluctuates hundreds of degrees above and below ambient temperature. Additionally, cadmium telluride is preferred because it is neither deliquescent nor hygroscopic, and does not undergo disproportionation under expected land-based operating conditions.

FIG. 13 illustrates the steps used in the method of making a photovoltaic power cell in accordance with the present invention. These steps have been separated in relation to the previous description. However, in Figure 13 it can be seen that the metal cathode is introduced into the electrolyte and the anode is introduced into the electrolyte.
The method includes forming molecules or ions of a non-metal component in an electrolyte as well as forming ions of a metal component in an electrolyte. As previously mentioned, these ions can be introduced into the solution in several ways, and the ions of both components will discharge at the cathode when electrolysis is applied. Both ions and molecules migrate to the cathode and when an electric field is applied they discharge and form a coating in the form of a compound semiconductor as described above. As previously mentioned, the coating is initially formed to have a first region, such as an N-type region or a P-type region. The coating is then provided with a second region opposite the first region.

Finally, conductive terminals can be applied to both the N-type and P-type regions when making photovoltaic power cells. Alternatively, these terminals may be applied to the layers that contact the N-type and P-type regions in the embodiment shown in FIGS. 3 and 4.

One of the unique results obtained with this invention is that both homojunctions and heterojunctions can be created between P-type and N-type regions. Therefore, the problems of material waste and impurities are greatly improved and almost completely solved. Furthermore, all the stringent control procedures traditionally required in making photovoltaic cells and similar semiconductor materials can be fully covered.

Another unique aspect of this invention is that the reactions described thus far can be carried out at or near greenhouse temperatures. Furthermore, as previously mentioned, the method described herein results in very little, if any, material wastage. Furthermore, the method can be practiced with very small concentrations of ions required.

It should be appreciated that each of the photovoltaic power generators described above does not operate as a Galvanic cell and therefore does not require an electrolyte for its operation. Furthermore, in order to further increase the efficiency with which electrons move across the plane of the cell, the generated electrons are
For example, a conductive coating such as a transparent electrolyte coating or any other type of transparent electrolytic gel may be used to select electrical contacts as described in the embodiment shown in FIG.

The type of photovoltaic power generating device of the present invention and its manufacturing method are suitable for continuous manufacturing processes for such power generating devices having considerable length and area. In many applications, the generator can be rolled up on rollers or other storage means, simply unfolded and
It can be a sheet or surface covering areas exposed to light, such as roofs and walls exposed to solar radiation.

What has been described above is a relatively high efficiency photovoltaic power generation device, as well as a method of using and manufacturing the power generation device, which achieves all of the objects and advantages mentioned at the outset. Those skilled in the art will perceive, from the specification and description of the drawings, various modifications, other uses and applications of the power generating apparatus and method herein described. It is intended that all such modifications, uses and adaptations are included within the scope of the invention insofar as they are consistent with the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a simple perspective view of a photovoltaic power generation device according to the present invention, and FIG.
FIG. 3 is a side view of a slightly modified photovoltaic power cell; FIG. 4 is a partially cut-away cross-section of a preferred power cell constructed in accordance with the present invention. 5 is a schematic diagram showing the electrical equivalent circuit of a cell of the invention operated on solar energy; FIG. 6 is a simplified diagram showing one method of forming a photovoltaic power cell in accordance with the invention; FIG. The side view, FIG. 7, is a simplified side view similar to FIG. 6, illustrating another method of making a photovoltaic power cell in accordance with the present invention. FIG. 8 is a simplified side view similar to FIG. 6 illustrating yet another method of forming a photovoltaic power cell in accordance with the present invention. FIG. 9 is a simplified side view similar to FIG. 6 illustrating another method of making a photovoltaic power cell in accordance with the present invention.
FIG. 10 is a simplified side view similar to FIG. 9,
3 shows a variation of the method of making a photovoltaic power cell using multiple anodes in accordance with the present invention. FIG. 11 is a simplified side view similar to FIG.
Figure 3 shows another method of the invention using paired anodes. FIG. 12 is a simplified side view similar to FIG.
3 shows another embodiment of making a photovoltaic power cell in accordance with the present invention. FIG. 13 is a flow chart showing the steps of the method of this invention. Explanation of main symbols, 36... Electrode, 44... N type region, 46... P type region, 102... Cathode, 10
4... Anode, 106... Electrolyte, 108... Power supply.

Claims (1)

[Claims] 1. A method for manufacturing a photovoltaic power generating cell, comprising:
electrochemically depositing a coating of at least one semiconductor formulation on an electrode from an electrolytic cell containing at least two ionic semiconductor formulation components, said formulation capable of producing a semiconductor junction. , which can transmit a light beam and generate electron-hole pairs when illuminated with photons, and the component is at least one of a metal element in group B of the periodic table and a nonmetal element in group A of the periodic table. A method characterized by being unique. 2. In the method described in claim 1,
A method characterized in that said electrode is metal and said junction is made between said metal electrode and said semiconductor compound. 3. In the method described in claim 1,
the electrode is a substrate having a conductive coating of a semiconductor material of a first conductivity type, the semiconductor composition is of an opposite conductivity type, and the junction is between the conductive coating and the semiconductor composition. A method characterized by being made. 4. In the method described in claim 3,
A method characterized in that the conductive film is transparent to light. 5. In the method described in claim 3,
A method characterized in that the conductive coating is of n-type and the semiconductor formulation is of p-type. 6. In the method described in claim 3,
A method characterized in that the conductive coating is of p-type and the semiconductor compound is of n-type. 7. In the method described in claim 1,
further comprising depositing a semiconductor compound material to form a first layer of a first conductivity type and then depositing a second layer of an opposite conductivity type to create the bond between the layers. How to characterize it. 8. In the method described in claim 7,
A method characterized in that the first layer is of n-type and the second layer is of p-type. 9 In the method recited in claim 7,
A method characterized in that the first layer is of p-type and the second layer is of n-type. 10. A method according to claim 1, characterized in that at least a portion of the metal and non-metal components is provided from a material dissolved in the electrolytic cell. 11. A method according to claim 1, characterized in that at least a portion of the metal and non-metal components is provided from an additional electrode immersed in the electrolytic cell. 12. A method according to claim 1, in which a corresponding metallic or non-metallic element is deposited in increased concentration depending on the selected conductivity type, in order to form a semiconductor composition of the selected conductivity type. A method further comprising steps. 13. A method according to claim 1, in which a doping impurity of a donor or acceptor type corresponding to the selected conductivity type is deposited to form a semiconductor compound material of the selected conductivity type. The method further comprises the step of causing. 14. In the method according to claim 1, in order to form a semiconductor compound of a selected conductivity type, a corresponding metallic or non-metallic element is deposited in an increased concentration depending on the selected conductivity type; A method characterized in that it further comprises the step of depositing doping impurities of the appropriate donor or acceptor type at any time. 15. The method of claim 1 for forming a photovoltaic cell on a conductive semiconductor substrate of a first conductivity type, wherein the step of depositing comprises placing the substrate in an electrolytic bath containing a strong acid solution of cadmium sulfate. immersed in an anode having at least a tellurium surface layer, applying a voltage between the anode and the substrate forming the cathode, making this voltage negative between the cathode and a standard reference electrode, and 1 Conductive type 1st
continuing this plating step until depositing a thin polycrystalline cadmium telluride layer of . 16. A method according to claim 15, characterized in that the substrate is of n-type and is made of indium-doped tin oxide, and the first conductivity type is of n-type. 17. The method of claim 16, wherein the electrolytic cell contains an n-type donor impurity for adhesion with the n-type cadmium telluride. 18. The method of claim 17, wherein the n-type donor impurity comprises indium sulfate. 19. The method according to claim 15, wherein the substrate is p-type and made of antimony-doped tin oxide, and the first conductivity type is p-type. 20. The method of claim 19, including a p-type acceptor impurity for adhesion to the electrolytic cell p-type cadmium telluride. 21. The method of claim 15, further comprising the additional step of providing an additional electrolyte containing cadmium sulfate and an active impurity of opposite conductivity type, The cadmium telluride layer is immersed in this additional electrolyte, a negative voltage is applied between the anode and the anode with respect to the standard reference electrode, this applied voltage is applied to the first cadmium telluride, and this applied voltage is applied to the first cadmium telluride layer. different from the voltage used to deposit the first cadmium telluride layer, thereby depositing a second thin polycrystalline cadmium telluride layer of the opposite conductivity type;
A method further comprising forming an n-p junction between the first and second cadmium telluride layers to provide a homogeneous junction device. 22. In the method according to claim 21, the substrate is of n-type and made of indium-doped tin oxide, the first conductivity type is of n-type,
A method characterized in that the additional electrolyte contains a p-type acceptor impurity and the second cadmium telluride layer is p-type. 23. The method according to claim 22, wherein the plating voltage for the first cadmium telluride layer between the cathode and the standard reference electrode is equal to the plating voltage between the cathode and the standard reference electrode for the second cadmium telluride layer. A method characterized in that a second layer is deposited which is more negative than the voltage applied therebetween and has more tellurium and less cadmium than the first layer. 24. The method of claim 22, wherein the p-type acceptor impurity comprises silicon pentoxide. 25. The method according to claim 16, further comprising: removing the n-type cadmium telluride layer from the action of voltage to form a thin p-type layer;
This p-type layer is subjected to the action of a p-type acceptor in an electrolytic cell without applying a voltage, and for a sufficient time to form a tellurium layer of a predetermined thickness with a strong acid.
A method characterized in that it comprises the step of electroplating on said p-type layer a thin tellurium layer from an electrolyte containing sodium sulfate and free of any doping impurities by applying a negative voltage. 26. The method according to claim 25, characterized in that the p-type acceptor for forming the p-type layer consists of arsenic pentoxide. 27. The method of manufacturing a Schottky barrier photovoltaic device according to claim 1, wherein the step of depositing comprises immersing a metal substrate as a cathode in an electrolytic bath containing cadmium sulfate; An anode with a tellurium outer coating is placed in an electrolytic cell, the electrolytic cell is maintained at a certain acidic pH, a voltage is applied between the cathode and the anode, and the voltage is measured between the cathode and a standard reference electrode until the voltage is negative. and the voltage is selected relative to the PH value such that the deposited cadmium telluride deposits a layer of a given conductivity type with a given ratio of cadmium to telluride, and a thin polycrystalline telluride of a given thickness. A method characterized in that it comprises continuing the deposition action until depositing the cadmium layer. 28. A method according to claim 27, characterized in that the cadmium telluride layer is of n-type and is obtained by depositing more cadmium than tellurium. 29. A method according to claim 28, characterized in that the n-type donor impurity is introduced into the vessel for deposition together with the cadmium telluride. 30. The method of claim 29, wherein the n-type donor impurity comprises indium sulfate. 31. The method of claim 27, wherein the deposited cadmium telluride layer is p-type and contains less cadmium than tellurium. 32. The method of claim 22, characterized in that a p-type acceptor impurity is introduced into the electrolytic cell for adhesion in conjunction with the p-type cadmium telluride. 33. The method of claim 32, wherein the p-type acceptor impurity comprises arsenic pentoxide. 34. The method of claim 1 for depositing a photovoltaic cell on a conductive n-type semiconductor comprising indium-doped tin oxide, wherein the deposition step comprises a strong acid solution of cadmium sulfate. A plating voltage is applied between the anode and the substrate forming the cathode, and this voltage is applied between the cathode and a standard reference electrode. is negative,
continuing this plating process until a thin polycrystalline cadmium telluride layer of p-type conductivity has been deposited, and then placing the p-type cadmium telluride layer in an electrolytic bath containing sodium sulfate and a strong acid solution of sodium sulfate. A method comprising the step of dipping and electroplating a thin p-type tellurium layer on the p-type cadmium telluride layer for a predetermined period of time to produce a tellurium layer of a predetermined thickness. 35. A method according to claim 34, characterized in that a p-type acceptor impurity is added to the electrolytic cell for plating the p-type cadmium ptelluride layer. 36. The method of claim 34, wherein the p-type acceptor impurity comprises arsenic pentoxide.