FR2503457A1 - SYSTEM OF SOLAR CELLS CONNECTED IN SERIES ON A SINGLE SUBSTRATE - Google Patents

Abstract

ARRANGEMENT OF SOLAR CELLS 10 INCLUDING A PLURALITY OF ADJACENT SOLAR CELLS, CONNECTED IN SERIES 12 ON A SINGLE INSULATING SUBSTRATE 14, IN WHICH EACH SOLAR CELL 12 IS CHARACTERIZED IN THAT IT INCLUDES: -AN ELECTRODE 16 FORMED ON A 18 OF THE FIRST SUBSTRATE 14; -A SEMI-CONDUCTIVE LAYER 20 CONTAINING AT LEAST ONE INTRINSIC REGION AND ONE TYPE N REGION; -A SUPERIOR ELECTRODE 22; AND - MEANS FOR ELECTRICALLY CONNECTING THE UPPER ELECTRODE 22 OF A SOLAR CELL 12 TO THE LOWER ELECTRODE 16 OF THE FOLLOWING ADJACENT SOLAR CELL 12 WHICH INCLUDE A METAL BAND 22 ON THE SURFACE OF THE SECOND PHOTOCELL AND AN INTER-ELECTRODE LINK 26 BETWEEN METAL BAND 22 AND LOWER ELECTRODE 16 OF THE FOLLOWING ADJACENT SOLAR CELL, THIS INTER-ELECTRODE LINK 26 BEING A TIP METAL CONNECTION.

Description

1 2503457

  This invention relates to solar cells. She

  more particularly applies to silicon solar cells.

  amorphous cium connected in series which are formed on a single substrate. Solar cells are known to convert solar energy into electrical energy. Such cells

  can be made using various semiconductor materials.

  such as amorphous silicon. For solar cells

  available for general use, it is neces-

  that cell arrangements that include a

  of cells, can be achieved at a relatively low price for the consumer. Since a typical amorphous silicon solar cell produces about one volt of electricity

  when exposed to the sun these cells should be

  linked in series to increase their available voltage so that their outputs can be used either directly or by transfer to storage devices, such as batteries, for indirect use. Design and implementation

  of solar cells connected in series can be a

  important. As a result, such a process is generally

very expensive to implement.

  The present invention relates to an automatic method for producing solar cells connected in series, such as

  amorphous silicon solar cells. The cells are pro-

  in the form of serially connected arrangements, in

  sound of the manufacturing process. Such arrangements can be made to have a desired output voltage

without requiring significant effort.

  An arrangement of solar cells according to the present invention

  tion comprises a plurality of adjacent solar cells,

  connected in series on a single insulating substrate, the cells

  adjacent cells being connected in series by implanting a metal

  interelectrode from the electrode on the top of a cell through the amorphous silicon layer, up to

  the electrode located at the bottom of the next adjacent cell.

  Other features and advantages of this invention

  will emerge from the description given below with reference to

  attached drawings which illustrate various embodiments without any limiting character. In the drawings: - Figure 1 illuminates a first embodiment of a solar cell according to the present invention; - Figures 2 to 4 illustrate the manufacturing method of the solar cell according to Figure 1; FIG. 5 represents a second exemplary embodiment of a solar cell according to the invention, and FIGS. 6 and 7 illustrate the manufacturing process of FIG.

  the solar cell according to FIG.

  We first refer to Figure 1 on which we

  sees a solar cell arrangement 10 consisting of a plural

  solar cells. The solar cells 12 are formed on a substrate 14, made of glass, or another similar transparent material according to the present embodiment of the invention. A series of metal electrodes 16, made of molybdenum in the preferred embodiment of the invention, is disposed on a surface 18 of the glass substrate 14. It is within the scope of the invention to use any other metal than molybdenum to make the electrodes 16. Parts 20 of the

  amorphous silicon cells 12 cover the electrodes of

  lybdenum 16 on the glass substrate 14. In the example of

  preferred embodiment of the invention, the semiconductor parts 20

  are made of amorphous silicon. A series of electrodes

  22, which consist of a metal such as aluminum, copper or gold, covers both the amorphous silicon top surface 20 of a cell 12 and at least a portion of the electrode 16 of the next adjacent cell. Above the electrodes 22 is disposed a transparent conductive material, such as tin oxide and indium 24, for reasons which will be

explained below.

  Inter-electrode links 26 are also provided between

  the electrodes 22 on the upper surface of the silicone layers

  amorphous cium 20 and the electrodes 16 on the glass substrate 14.

  The following will describe the method for producing the links 26.

  As can be seen, there is an electrical connection in

  between the tin oxide and indium 24 electrode, the elec-

  upper metal trode 22, the inter-electrode link 26 and the molybdenum electrode 16. Therefore, each electrode with tin oxide and dindium 24, on the top of a cell 12, makes electrical contact with the lower electrode 16 of

  the adjacent cell 12, to the right of the cell 12 on the

  what is the electrode with tin oxide and indium. It will be noted, however, that the amorphous silicon parts 20 must have a low conductivity, so that the connection between the electrodes 16, made by the semiconductor layer

, can be ignored.

  The amorphous silicon portions 20 of each cell 12 are connected in series so that the upper portion of each amorphous silicon layer 20 makes electrical contact with the adjacent lower portion of amorphous silicon 20, to its right.

looking at Figure 1.

  The number of cells connected in series 12 in an arrangement

  particular is determined by the voltage requirements of a

particular application.

  Referring now to FIGS. 2 to 4, the method of manufacturing the cells connected in series according to FIG. 1 is shown. FIG. 2 shows that starting from a substrate 14,

  for example glass, on which is deposited a conductive layer

  trice 16, which in this embodiment is made of molybdenum. The conductive layer 16 may be applied by any desired technique, for example by evaporation. After the deposition of the conductive layer 16 on the substrate 14, the conductive layer

  16 is engraved or cut in such a way as to obtain the discon-

  tinue shown in Figure 3. Engraving or notching

  the conductive layer 16 can be made by any suitable means

  For example, using a laser, in this case the score lines 28 may extend into the glass substrate 14 as shown in the drawing. After notching the conductive layer 16, an amorphous silicon layer 20 is deposited on

  the surface of the notched metal layer 16.

  As is known, the amorphous silicon layer 20 is typically constituted by a three-part structure comprising a P, I and N type semiconductor material.

  In the present invention, the amorphous silicon layer 20 can

  ter only a type I and N semiconductor material and a Schottky barrier. In view of the fact that either the P type material or the N type material can be on the surface of the amorphous silicon layer 20 which is exposed to radiation

  incidentally, the amorphous silicon layer 20 will be referred to simply as

  by the term "layer" in the description of the invention.

  However, those skilled in the art must recognize that the method of

  These structures are well known and are described in US Pat. Nos. 4,064,521, 4,142,195, 4,162,505 and 4,163,677. Reference will be made to these patents to explain how the amorphous silicon layer 20 can be used. to be manufactured

  and to describe the composition of the amorphous silicon layer 20.

  Reference is now made to FIG. 3. Strips 22 of a

  conductor are applied to the surface of the

  amorphous silicon by any suitable technique. Therefore, the metal strips 22 can be evaporated on the surface

  of the amorphous silicon layer 20 by means of a mas-

  than. Alternatively, the strips 22 may be formed using a photolithographic process of the type commonly known in the so-called "paint removal and removal" technique which will be described in detail below. The metal strips 22 are made of a metal such as aluminum, copper or gold which can be

  implanted through the amorphous silicon layer 20 of the

explained below.

  After application of the metal strips 22, a conductive layer 24 is deposited on the surface of the device. The conductive layer 24 must consist of a material chosen so

  to be transparent to incident radiation if the top surface

  of the amorphous silicon layer 20 should receive light

  Mière. Therefore, a material such as tin oxide and indium is typically used to form the layer 24. After application of the conductive layer 24, the structure

  is still subjected to a slitting process, for example in the

  ser, in order to cut the conductive layer 24 to make it discontinuous, as can be seen in Figure 4. Given the fact that tin oxide and indium oxide, used in the manufacture of solar cells to amorphous silicon, have

  typically a thickness of the order of a few hundred Angels

  trbms, a laser etching of the tin oxide and indium layer 24, will typically notch the amorphous silicon layer 20 as shown. However, as will be seen below, it is not necessary for the laser to totally or even partially cut the amorphous silicon layer 20, as long as this laser

  serves to completely cut out the tin oxide and

  dium 24 so that this layer 24 has an electrical discontinuity

cudgel.

  Then, the device is subjected to annealing during

  which is heated for a time and at a temperature sufficient for the metal strips 22 to generate spikes

  26 through the amorphous silicon layer 20 to electrically connect

  triply the tin oxide and indium oxide layer 24 to the electrode

  underlying metal 16, as can be seen in FIG.

  The duration and temperature of the annealing are determined by the type

  particular of the material used to make the metal strips

  22-and the thickness of the amorphous silicon layer 20. A

  For example, if copper is used, annealing at a temperature of

  2600C for thirty minutes can be used-. Longer annealing at a lower temperature or shorter annealing at

  a high temperature will of course give the same results.

  After the annealing process, the device 10, as shown in FIG. 1, is finished and there is a serial link

  between amorphous silicon solar cells 12.

  Referring now to FIG. 5, there is shown a second embodiment of a solar cell according to this invention. According to this embodiment, a series

  amorphous silicon solar cells 32, is connected in series with

  The amorphous silicon solar cells 32 connected in series are made on the insulating substrate 34 which may be made of a transparent material, for example glass. On a surface 36 of the substrate 34 is disposed a series of conductive electrodes 38 which may be made of either metal or oxide

  3o tin and indium, depending on whether the incident light should reach

  the solar cells from above the surface 36 or it must cross the substrate 34, one or other of these possibilities not outside the scope of the invention. Each of the solar cells 32 further comprises an amorphous silicon layer 40 which covers the conductive electrodes 38. On the other hand, there are upper electrodes 42, which may be made of either metal or tin oxide and indium as it has been described above. The upper electrodes 42 are electrically connected to the lower electrodes 38 of the

  next adjacent cell 32 via metal strips

  44 and inter-electrode contacts 46 in the same way

  described above with reference to the first example of

10 of the invention.

  In order to manufacture the second exemplary embodiment of the invention, a substrate 34, as shown in FIG. 6, is used. A series of strips 48, for example

  strips of paint or photoresist on a surface 36 of the

  FIG. 34. The paint strips 48, used in the example of

  preferred embodiment of the invention are sprayed onto the

  face 36 of the substrate 34, via a mask provided with strip cutting. Such strips of paint have a relatively large thickness, compared to that of the materials

  typically used in amorphous silicon solar cells

  phe. Then, the material that must include the lower electrodes

  In the case of tin and indium oxide, the material is simply sprayed onto the surface of the strips 48 substrate 34. In the case of a metal, the material will be sputtered or evaporated onto the surfaces. Due to the thickness of the strips 48, the material 38 does not form a continuous layer because of the stepped topology of the strips 48.

  after application of the material 38, the paint strips 48 can

  The result is that, although a photolithographic process can be used to obtain the same result and although such a process does not fall outside the scope of the invention, the fact of using the method described above of "painting and detaching" saves a

  considerable time and effort, and also to

  money, when making arrangement 30 of

solar cells.

  Referring now to FIG. 7. After removal of the strips 48, an amorphous silicon layer 40 is applied to the surface of the structure, according to any suitable method based on

  of the particular structure sought. Reference is made to the

  American vets mentioned above with respect to the

  method of depositing the amorphous silicon layer 40 and its

  sition. Then, the metal strips 44 are applied to the surface of the amorphous silicon layer 40, according to any suitable method, for example by evaporation through a strip mask. Then the inter-electrode links 46 are formed into

  heating the structure as described above in order to

  the metal strips 44 to project in the form of

  points through the underlying electrodes 38.

  Then the upper electrodes 42 are formed.

  upper trodes 42 can be made by implementing the method by painting and detachment according to which one starts by applying a series of strips of paint 49, in the manner

  described above and then the material constituting

  kills the upper electrodes 42, as described above. This material can be either a metal or an oxide of tin and indium and, given the abrupt topology of the paint strips

  49, it is discontinuous for the reasons already mentioned.

  After applying the material constituting the upper electrodes 42, the paint strips 49 and the material 42 on the upper surface are removed by a detachment process.

  (by peeling them) so that the structure of the

  storage 30, shown in Figure 5.

  According to this embodiment, it is not necessary to perform a notch during the manufacture of the arrangement, given the property of the amorphous silicon according to which

  it has virtually no lateral conduction. By con-

  an interesting aspect of a social cell arrangement

  Figure 30 of the type described with reference to Figure 5 is that it is not necessary for the amorphous silicon layer 40 to be electrically discontinuous. Therefore, although the laser tapping described above with reference to the first embodiment (FIGS. 1 and 4) passes through the amorphous silicon layer 20, such a cutout is not necessary to form

a solar cell arrangement.

  The above description has been made with reference to

  amorphous silicon solar cells, it remains however of course that the invention can be used with other types of solar cells including, without this enumeration being

  limiting, monocrystalline silicon cells, polycrystalline

  flax or microcrystalline or cadmium sulphide solar cells. Similarly, the term "amorphous silicon layer" is used herein to refer to any type of solar cell semiconductor material that can be interconnected by providing

  protruding tips and low lateral conductivity

  for the reasons mentioned above.

Claims (12)

  1.- Arrangement of solar cells (10) comprising a plurality of adjacent solar cells, connected in series   (12) on a single insulating substrate (14), wherein each   solar lule (12) is characterized in that it comprises: - an electrode (16) formed on a first surface (18) of the substrate (14); a semiconductor layer (20) comprising at least one intrinsic region and an N-type region - an upper electrode (22) and   means for electrically connecting the upper electrode   (22) of a solar cell (12) at the lower electrode   (16) of the next adjacent solar cell (12) which   take a metal strip (22) on the surface of the second photocell and an inter-electrode connection (26) between the strip   metal (22) and the lower electrode (16) of the cell   next adjacent layer, this inter-electrode link (26)   being a metal point connection.   2.- solar cell arrangement according to claim 1,   characterized in that the semiconductor layer (20) is constituted killed amorphous silicon.   3. Arrangement of solar cells according to claim 2, characterized in that the inter-electrode connection (26) comprises   a peak-shaped aluminum connection.   4. A solar cell arrangement according to claim 2, characterized in that the inter-electrode connection (26) comprises   a gold connection in the shape of a point.   5.- arrangement of solar cell according to claim 2, characterized in that the inter-electrode connection (.26) comprises   a copper connection in the shape of a point.   6. A method for providing a series connected solar cell arrangement comprising forming a series of conductive lower electrodes on an insulating substrate, forming a semiconductor layer on the surface of the lower electrodes.   conductors and on said substrate and to apply a series of elec-   copper conductive trodes on the surface of the semi-   characterized in that it consists in making an electrical connection between the upper electrode of one cell and the lower electrode of the next adjacent cell by inserting an inter-electrode connection in a point through the semiconductor layer.   7. A method according to claim 6, characterized in that the insertion of the peak connection is effected by heating a series of metal strips on the surface of the semiconductor layer to cause them to protrude according to of the   points through said semiconductor layer.   8. A method according to claim 7, characterized in that the series of conductive lower electrodes is formed by producing a single conductive layer and then by notching   in order to make it electrically discontinuous.   9. A process according to claim 7, characterized in that   the series of upper conductive electrodes is formed in   reading a single conductive layer and then hacking it   in order to make it electrically discontinuous.   10. A process according to one of claims 8 or 9, characterized   in that the notching is performed by laser etching, 11.Procédé according to claim 7, characterized in that   the series of lower conductive electrodes is obtained by   plicating a thick material having a configuration in the form of   strips on the surface of the substrate, applying a layer of   discontinuous duct on the surface of said shaped thick material   strips and removing said material at the same time as the   conductive material on its surface so that a series of electrodes   electrically discontinuous surfaces remain on the surface of   trat. 12. A process according to claim 7, characterized in that the series of upper conductive electrodes is obtained by depositing a thick material having a configuration in the form of   bands on the surface of the amorphous silicon layer,   plucking a discontinuous conductive layer on the surface of said thick material and removing said material at the same time as   the conductive material present on its surface in such a way that   a series of electrically discontinuous electrodes on the   surface of the amorphous silicon layer.