Abstract:
A light receiving or light emitting modular sheet having a plurality of spherical elements arranged in matrix. It is constituted only of acceptable spherical elements and photoelectric conversion efficiency therof is enhanced. The light receiving modular sheet ( 1 ) comprises a plurality of spherical solar cell elements ( 2 ) arranged in matrix, a meshed member ( 3 ), and a sheet member ( 4 ). Each solar cell element ( 2 ) comprises a spherical pn junction ( 13 ), and positive and negative electrodes ( 14, 15 ) formed oppositely while sandwiching the center of the solar cell element ( 2 ) and being connected with respective electrodes of the pn junction ( 13 ). The meshed member ( 3 ) has a plurality of conductive wires ( 20, 21 ) arranged in parallel in order to connect the plurality of spherical solar cell elements ( 2 ) in each column electrically in parallel, and insulating tensile wires ( 22 ) arranged between the rows of solar cell elements ( 2 ) to cross the conductive wires ( 20, 21 ) perpendicularly while being woven in a meshed form to secure the plurality of conductive wires ( 20, 21 ).

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a light receiving or emitting module sheet and the production method thereof, and relates particularly to a light receiving or emitting module sheet having conductive wires electrically connected to spherical elements and insulating tension wires for fixing the conductive wires in a woven mesh structure.  
       BACKGROUND OF THE RELATED ART  
       [0002]     Solar batteries in currently practical use comprise a flat pn junction formed by diffusing impurities in a flat semiconductor wafer. The solar batteries having this structure produce maximum output when light enters the light receiving surface at a right angle. Output decreases as light enters the light receiving surface at smaller angles. These solar batteries have a strong directional pattern. It would be difficult to say that they constantly utilize light in an efficient manner. Furthermore, wafers are produced by slicing a semiconductor crystal ingot and, thus, there are significant processing losses including margins to cut, which leads to increased production costs.  
         [0003]     U.S. Pat. No. 4,581,103 discloses a solar battery element that is produced by melting and dropping a highly pure metal silicon material to form p-type crystal particles and diffusing n-type impurities in the p-type crystal to form a spherical pn junction and a solar battery module produced by connecting those solar battery elements using aluminum foil. The spherical solar battery elements of the solar battery module do not have individual electrodes before being assembled into a module, and are mechanically pressed into pores formed in a sheet of aluminum foil, electrically connecting the n-type surface. Then, the part of the n-type layer surface of the solar battery element that protrudes downward from the pore is removed by, for example, etching, to expose the p-type silicon or the core, causing the p-type silicon to make contact with another sheet of aluminum foil to form a positive electrode. A number of solar battery elements having a pn junction are connected in this way to form a module in which multiple solar battery elements are given electrodes and connected in parallel by two sheets of aluminum foil. In producing a solar battery module in this way electrodes are formed and connected in parallel concurrently using two sheets of aluminum foil. However, the p-type region is exposed after the n-type layer is connected to the aluminum foil, making it is difficult to evaluate the properties and quality of individual solar battery elements. Furthermore, this structure only allows for parallel connection. Another solar battery module must be connected in order to increase the output voltage. When the solar battery elements have a smaller diameter, the distance between the two aluminum foil sheets is decreased, making it difficult to insulate the aluminum foil from each other, and complicating the production process. The positive and negative electrodes are formed below the center of the solar battery element; in other words, they are formed at asymmetrical positions. This causes several disadvantages. For example, sufficiently improved photoelectric conversion efficiency is not available because the electric current between the positive and negative electrodes is localized at points where the distance between the electrodes is smaller. The aluminum foil blocks light and, therefore, only the light receiving surface above the aluminum foil is useful. Light from all directions is not received and, therefore, the output is not increased.  
         [0004]     Japanese Laid-Open Patent Publication H09-162434 discloses a solar battery sheet in which multiple spherical solar battery elements are supported by a glass fiber cloth formed by weaving vertically extended conductive wires and horizontally extended glass fibers. In such a solar battery, the solar battery elements are supported by conductive wires, by which they are easily insulated from each other.  
         [0005]     However, also in the solar battery elements used in the solar battery described in Japanese Laid-Open Patent Publication H09-162434, the n-type layer is connected to a negative electrode conductive wire, exposing the p-type region which is entirely surrounded by the n-type layer and connected to a positive electrode wire. Only the n-type layer is externally exposed before the conductive wires and solar battery elements are connected, making it so that the individual solar battery elements cannot be inspected before being connected, with the same problems as exist in the afore-mentioned citations. The positive conductive wire connected to the p-type region is also connected to the n-type layer. Then, the n-type layer is irradiated with light for electrochemical etching to separate the pn junction, by which the positive electrode wire is connected only to the p-type region. Solar battery elements are etched at different rates, making it difficult to reliably separate the pn junction in all the solar battery elements.  
         [0006]     The solar battery element of this publication also has the same problem as the afore-mentioned citations because it is connected to the positive and negative electrode conductors asymmetrically about the center, with the disadvantage that, when the solar battery elements are replaced with spherical light emitting diodes, spherical light emitting diodes cannot be used because they emit light in a limited region between the conductive wires and fail to emit light in all directions.  
         [0007]     In WO98/15983, the inventor of the present application proposed multiple spherical elements that are solar battery elements or light emitting devices and a light receiving or emitting module sheet in which the spherical elements are connected. The spherical element comprises a spherical p-type (or n-type) single crystal semiconductor (such as silicon), an n-type (or p-type) diffused layer formed near the surface of the single crystal semiconductor, a nearly spherical pn junction, and a pair of negative and positive electrodes provided opposite to each other about the center of the spherical single crystal semiconductor. A number of these spherical elements are arranged in a matrix of multiple rows and multiple columns and are connected in series and/or in parallel to constitute a light receiving or emitting module sheet.  
         [0008]     The spherical elements posoition the electrodes at opposite positions to one another about their center. It is easy to connect multiple spherical elements in series by arranging the positive and negative electrodes of adjacent spherical elements to make direct contact with each other. However, it is not easy to connect spherical elements in parallel.  
         [0009]     The inventor of the present application provided a resolution to this problem in WO03/017382 in which two parallel conductive wires are used to flank and connect in parallel the positive and negative electrodes of spherical elements arranged with their electrodes aligned to form a column of spherical elements and, the conductive wires of the adjacent columns of spherical elements then being connected to connect the columns of spherical elements in series.  
         [0010]     The light receiving or emitting module sheet has the problem that its tensile strength is high in the lengthwise direction of the conductive wires, but is significantly lower in a direction orthogonal thereto. Further, it is necessary to simplify the connection between the spherical elements and conductive wires and improve productivity.  
         [0011]     Objects of the present invention include providing a light receiving or emitting module sheet that may be constituted only by good spherical elements, a light receiving or emitting module sheet that has a high tensile strength, a light receiving or emitting module sheet that yields a high photoelectric or electrophoto conversion rate using spherical elements, and a light receiving or emitting module sheet that is easy to produce. Other objects of the present invention will apparent from the description of the embodiments of the present invention.  
       SUMMARY OF THE INVENTION  
       [0012]     The light receiving or emitting module sheet according to present invention comprises plural spherical elements having a light receiving or emitting function, each spherical element having a nearly spherical pn junction, and positive and negative conductive wire connecting parts provided at both ends of the spherical element and connected to both ends of the pn junction; the plural spherical elements being arranged in a matrix with their polarity aligned, plural conductive wires being arranged in parallel to electrically connect in parallel plural spherical elements in each of plural columns via the positive and negative conductive wire connecting parts of the plural spherical elements in each column, and plural insulating tension wires arranged between rows of the spherical elements in a direction orthogonal to the conductive wires and woven into a mesh structure with the plural conductive wires for fixing the multiple conductive wires.  
         [0013]     When used as a light receiving module sheet, light enters the module sheets regardless of incidental directions and reaches plural spherical elements arranged in a matrix with their polarities aligned. The nearly spherical pn junction formed in the spherical element receives light which has been converted to electric energy by the light receiving function of the spherical element. The electric energy is output outside via the positive and negative conductive wire connecting parts provided at either end of the spherical element and connected to both ends of the pn junction. When used as a light emitting module sheet, electric energy supplied to the spherical elements from the conductive wires via the conductive wire connecting parts is converted to optical energy by the pn junction of the spherical elements and the light is emitted to the outside.  
         [0014]     The spherical elements have positive and negative conductive wire connecting parts connected to both ends of the pn junction, making it so the spherical elements may be inspected before they are mounted in a light receiving or emitting module sheet. Consequently, only good spherical elements may be mounted in a light receiving or emitting module sheet, which allows for reliable production of high quality module sheets. Additionally, with the positive and negative conductive wire connecting parts being formed on the spherical elements prior to being mounted, the conductive wire connecting parts and conductive wires are easily connected, simplifying the production process.  
         [0015]     Plural conductive wires extending in the columnar direction and multiple insulating tension wires extending in the row direction are woven into a mesh structure, yielding high strength. The positive and negative conductive wire connecting parts provided at either end of the spherical element are connected to the nearly spherical pn junction and, utilizing the entire region of the pn junction, more efficiently generating electricity or light.  
         [0016]     In addition to the above structure, the following structure may be used as appropriate.  
         [0017]     (1) The positive and negative conductive wire connecting parts of each of the spherical elements are provided opposite to each other about the center of the spherical element.  
         [0018]     (2) A transparent sealing member that houses the plural spherical elements together with plural conductive wires and plural tension wires in an embedded manner is provided.  
         [0019]     (3) Each of the spherical elements is a photodiode or a solar battery element.  
         [0020]     (4) Each of the spherical elements is a light emitting diode element.  
         [0021]     (5) The conductive wires are connected to the positive and negative wire connecting parts by using any one selected from among soldering, conductive synthetic resin, and alloyed metal.  
         [0022]     (6) The conductive wires are embedded in the sealing member so as to be at least partially exposed.  
         [0023]     (7) Insulating tension wires provided and arranged between columns of the spherical elements and woven with the conductive wires in parallel.  
         [0024]     (8) The sealing member is a flexible member made of a transparent synthetic resin material.  
         [0025]     (9) A reflecting film that reflects light incidental from a light incident side is composed on the surface of the side opposite to the light incident side of the sealing member.  
         [0026]     (10) The sealing member comprises of a flexible transparent cushion layer that houses plural spherical elements in an embedded manner and transparent surface layers joined to the cushion layer on either side.  
         [0027]     (11) The sealing member has a heat reflecting film made of a polymer material that selectively reflects heat rays that the spherical elements cannot absorb.  
         [0028]     (12) A serial connection means is provided that connects in series plural conductive wires that connect the multiple spherical elements in parallel.  
         [0029]     The method of producing a light receiving or emitting module sheet according to the present invention is a method of producing a light receiving or emitting module sheet comprising plural spherical elements arranged in a matrix and having a light receiving or emitting function, conductive wires that electrically connect the plural spherical elements in each column, and insulating tension wires woven into a mesh structure with the conductive wires for fixing the conductive wires, characterized by comprising a spherical element production step of producing spherical elements having positive and negative conductive wire conneting parts and a connecting step of melting a joining material for connecting the spherical elements and conductive wires by means of Joule heat by passing electric current through the conductive wires to connect the spherical elements and conductive wires by the joining material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]      FIG. 1  is a plane view of a light receiving module sheet according to an embodiment of the present invention.  
         [0031]      FIG. 2  is a partial enlarged plane view of the light receiving module sheet.  
         [0032]      FIG. 3  is an enlarged cross-sectional view of a solar battery element.  
         [0033]      FIG. 4  is a view seen in the arrowed direction IV in  FIG. 2 .  
         [0034]      FIG. 5  is a view seen in the arrowed direction V in  FIG. 2 .  
         [0035]      FIG. 6  is a cross-sectional view at VI-VI in  FIG. 2 .  
         [0036]      FIG. 7  is an equivalent circuit diagram of solar battery modules contained in the light receiving module sheet.  
         [0037]      FIG. 8  is an illustration showing solar battery elements at respective production stages.  
         [0038]      FIG. 9  is an illustration showing a step in which solar battery elements and conductive wires are electrically connected using a positioning jig.  
         [0039]      FIG. 10  is a partial enlarged plane view of a light receiving module sheet according to a modified embodiment.  
         [0040]      FIG. 11  is a vertical cross-sectional view of the core part of a light receiving module sheet having a sealing members according to a modified embodiment.  
         [0041]      FIG. 12  is a vertical cross-sectional view of the core part of a light receiving module sheet having a sealing members according to a modified embodiment.  
         [0042]      FIG. 13  is a partial enlarged plane view of a light receiving module sheet according to a modified embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0043]     The preferred embodiment of the present invention is described hereafter. In this embodiment, the present invention is applied to a light receiving module sheet (a solar battery module sheet) in which spherical solar battery elements are arranged in a matrix of multiple rows and multiple columns.  
         [0044]     As shown in  FIGS. 1 and 2 , a light receiving module sheet  1  has a number of solar battery elements  2  (spherical elements), a mesh member  3  (conductive wire-mixed woven glass cloth), and a sealing member  4 .  
         [0045]     A solar battery element having nearly the same structure as the solar battery element  2  is described in, for example, WO98/15983 and WO03/036731 proposed by the inventor of this application. Therefore, a brief explanation is made hereafter  
         [0046]     As shown in  FIGS. 1 and 2 , a number of solar battery elements  2  have a light receiving function to convert optical energy to electric energy and are arranged in a matrix with their polarities aligned. For example, approximately 2000 solar battery elements 2 per 1 Watt power output are used.  
         [0047]     As shown in  FIG. 3 , each solar battery element  2  is formed by a spherical crystal  10  having a diameter of approximately 0.6 to 2.0 mm and made of p-type silicon single crystal with a resistance of approximately 0.3 to 1 Ωm. A flat surface  11  is formed on the spherical crystal  10  at one end. A n + -type diffused layer  12  (approximately 0.4 to 0.5 μm in thickness) diffused with phosphorus (P) is formed on nearly the entire surface region of the spherical crystal  10  except for the flat surface  11 . A nearly spherical pn junction  13  is formed between the n + -type diffused layer  12  and the p-type region. When the spherical crystal  10  has a diameter of approximately 1.0 mm, the flat surface  11  has a diameter of approximately 0.5 mm. However, the diameter of the flat surface  11  may be smaller than approximately 0.5 mm.  
         [0048]     A positive electrode  14  (a conductive wire connection part) is provided on the flat surface  11  and a negative electrode  15  (a conductive wire connection part) is provided at the position opposite to the positive electrode  14  at about the center of the spherical crystal  10 . The positive electrode  14  is connected to the p-type region of the spherical crystal  10  and the negative electrode  15  is connected to the n + -type diffused layer  12 . The positive electrode  14  is formed by baking aluminum paste and the negative electrode  15  is formed by baking silver paste. An anti-reflection coating  16  (0.6 to 0.7 μm in thickness) consisting of a SiO 2  (or TiO 2 ) insulating film is formed on the entire surface except for the positive and negative electrodes  14  and  15 . The solar battery element  2  has a light receiving function and generates an optical electromotive force of 0.5 to 0.6 V between the electrodes  14  and  15  when it receives the sunlight.  
         [0049]     As shown in  FIGS. 2, 4 , and  5 , the mesh member  3  has positive electrode conductive wires  20 , negative electrode conductive wires  21 , and glass fiber tension wires  22 . The conductive wires  20  and  21  are nickel (42%), iron (52%), and chrome (6%) alloy wires having a diameter of 120 μm and a tin plated layer (2 to 5 μm in thickness) on the surface.  
         [0050]     As shown in  FIG. 2 , the conductive wires  20  and  21  extend in parallel in the columnar direction. The distance between the center lines of the positive and negative conductive wires  20  and  21  of adjacent columns of solar battery elements  2  is approximately 0.75 m. The distance between the centers of adjacent columns of the solar battery elements  2  is approximately 1.75 mm. The positive electrode conductive wire  20  is electrically connected to the positive electrode  14  via a solder paste  23  and the negative electrode conductive wire  21  is electrically connected to the negative electrode  15  via a solder paste  23 . Multiple solar battery elements  2  in each column are electrically connected in parallel by the conductive wires  20  and  21  and the solar battery elements  2  in all columns are electrically connected in series, as is described later.  
         [0051]     Here, the conductive wires are not restricted to the afore-mentioned structure and may be made of iron, iron (58%)/nickel (42%) alloy wires, other iron alloy wires, copper wires, beryllium copper wires, phosphorus bronze wires, other copper alloy wires, silver, silver alloy wires, or nickel, nickel alloy wires or a thread of fine wires of these materials, which are selected in view of their electrical, mechanical, and chemical properties. Among these, beryllium copper or phosphorus bronze wires have spring force and, therefore, ensure contact with the solar battery elements  2 .  
         [0052]     The tension wires  22  are extended between adjacent rows of solar battery elements  2  in the row direction orthogonal to the conductive wires  20  and  21 . Each tension wire  22  is made of a thread of seven glass fibers (9.0 μm in diameter). A set of three tension wires  22  is provided between rows at a pitch of approximately 1.75 mm. In order to fix the conductive wires  20  and  21 , each tension wire  22  is woven in such a manner that they pass above and below the conductive wires  20  and  21 . Multiple conductive wires  20  and  21  and multiple tension wires  22  are woven like a net to form the mesh member  3 .  
         [0053]     As shown in  FIG. 6 , the sealing member  4  is provided to house a number of solar battery elements  2 , conductive wires  20  and  21 , and tension wires  22  in an embedded manner to protect the solar battery elements  2  and mesh member  3 . The sealing member  4  is made of a sheet of transparent insulating polyparaxylene resin having a thickness of approximately 100 μm. Polyparaxylene resin has characteristics such as availability of uniform coating with little pinholes even in minute parts, low gas and vapor permeability, high stability against radiation, high refractive index (approximately 1.64), and low reflection loss on the surface of the solar battery element  2 . Formed as a thin layer to cover the surface of solar battery element  2 , sealing member  4  advantageously allows for the reception of light in a wide range of directions, low reflection loss, flexibility, light-weight, high tensile or bending strength, and a high light collection rate.  
         [0054]     In the light receiving module sheet  1 , light enters the light receiving module sheet  1  regardless of the incident direction and multiple solar battery elements  2  arranged in a matrix with their polarities aligned are irradiated with the light. The light is received by a nearly spherical pn junction  13  formed in the solar battery elements  2  and is converted to electric energy by the light receiving function of the solar battery elements  2 . The electric energy is output outside via the positive and negative electrodes  14  and  15  provided at positions opposite to each other about the center of each solar battery element  2  and connected to both electrodes of the pn junction  13 .  
         [0055]      FIG. 7  shows an equivalent circuit  30  to solar battery modules contained in the light receiving module sheet  1 . In equivalent circuit  30 , for example, each of a number of solar battery elements  2  arranged in a matrix of multiple rows and multiple columns is replaced by a diode  31 . As shown in equivalent circuit  30 , the diodes  31  (the solar battery elements  2 ) in each column are connected in parallel by the positive and negative electrode conductive wires  20  and  21 . Further, the positive electrode conductive wire  20  of each column is connected to the negative electrode conductive wire  21  of an adjacent column in series by a serial connection conductive wire  34 . An optical electromotive force of approximately n×0.6V is generated between the positive and negative terminals  32  and  33  when one solar battery element  2  has an output of 0.6V and there are m rows and n columns. Assuming one solar battery element  2  generates an electric current I, an electric current of m×I is output from the positive electrode  32  to an external load.  
         [0056]     A number of solar battery elements  2  connected in parallel and in series as described above can minimize reduction in output when light does not reach part of the light receiving module sheet and some of the solar battery elements  2  are not available for producing electricity, because the electric current can travel through the other solar battery elements  2 .  
         [0057]     A method of producing the afore-mentioned light receiving module sheet is described hereafter.  
         [0058]     First, a method of producing the solar battery elements  2  is described with reference to  FIG. 8 . However, this method is described in detail by the inventor of the present application in WO98/15983 and WO03/036731 and, therefore, it is also briefly described here.  
         [0059]     First, melted silicon droplets of a fixed quantity are subject to super-cooling for rapid solidification through free-fall, by which a p-type spherical single crystal  10  having a diameter of approximately 1.0 mm is formed. A part of the spherical single crystal  10  is mechanically abraded to form a flat surface  11  (see  FIG. 8 ( a )).  
         [0060]     Then, the spherical single crystal  10  is heated in a vapor-containing oxygen gas at approximately 1000° C. for approximately 40 minutes to form a silicon oxide film  35  having a thickness of approximately 0.3 μm (see  FIG. 8 ( b )). Subsequently, an acid-resistant wax is melted on a glass plate to a uniform thickness to create a mask for thermal diffusing impurities (n-type impurities) only in a desired region of the silicon oxide film  35 . The flat surface  11  is pressed against the wax surface and the wax is solidified. Then, only the part of the silicon oxide film  35  that is exposed from the solidified wax is removed by immersing it in a buffer etching solution (aqueous NH 4 HF 2  solution) for etching. Then, the spherical single crystal  10  is removed from the glass plate and the wax is removed (see  FIG. 8 ( c )).  
         [0061]     Subsequently, the spherical single crystal  10  is heated in nitrogen carrier gas bubbled from a phosphorus oxytrichloride (POCl 3 ) solution at approximately 960° C. for 3 minutes to form a phosphorus silicate glass coating  36  on the surface of the spherical single crystal  10  where the silicon oxide film  35  is absent, and is further heated in an atmospheric gas of dry oxygen at approximately 980° C. for 60 seconds to thermally diffuse n-type impurities (phosphorus) near the surface of the spherical single crystal  10 . With the n-type impurities thermally diffused as described above, an n + -type diffused layer  12  is formed on the surface of the spherical single crystal  10  except for on and around the flat surface  11  covered with the silicon oxide film  35  as a mask, a pn junction  13  being formed on the interface between the n + -type diffused layer  12  and the p-type region of the spherical single crystal  10  (see  FIG. 8 ( d )).  
         [0062]     The silicon oxide film  35  on and around the flat surface  11  is then removed using the buffer etching solution. The spherical single crystal  10  is again heated in dry oxygen gas at approximately 800° C. for 60 seconds to form an anti-reflection coating  16  on the entire surface of the spherical single crystal  10 , made of a silicon oxide film and also serving as a passivation coating (see  FIG. 8 ( e )).  
         [0063]     Then, an aluminum paste  37  is dot printed on the flat surface  11  to form a positive electrode  14 . A silver paste  38  is dot printed on the surface of the n + -type diffused layer  12  at the opposite position to the flat surface  11  about the center of the spherical single crystal  10 , and the whole spherical single crystal  10  is heated in nitrogen gas at approximately 800° C. for 60 minutes so that the aluminum paste  37  and silver paste  38  penetrate the anti-reflection coating  16  to make an ohmic contact with the p-type region and the n + -type diffused layer  12  of the spherical single crystal  10 , respectively, to complete a solar battery element  2  (see  FIG. 8 ( f ),  FIG. 3 ).  
         [0064]     Then, the volt-ampere characteristic of the completed solar battery element  2  is measured under illumination by a solar simulator light source to determine whether the completed solar battery element  2  is good or defective.  
         [0065]     Then, as shown in  FIG. 9 , a jig  41  is prepared having positioning pores  40  at pre-determined intervals for positioning the solar battery elements  2 . Solar battery elements  2  determined to be good are placed on the positioning jig  41  with their electrodes  14  and  15  (the polarities of the electrodes  14  and  15 ) aligned. Solar battery element  2  has a flat surface  11 , making it easy to identify the positive and negative electrodes  14  and  15 , facilitating placement with the electrodes  14  and  15  being aligned.  
         [0066]     The horizontal equator line of the solar battery elements  2  placed on the positioning jig  41  is nearly at the level of the top surface of the positioning jig  41 . Then, the positioning pores  40  are vacuumed to fix the solar battery elements  2  in the positioning pores  40 , preventing the solar battery elements  2  from moving or rolling. The positioning jig  41  has a carbon or boron nitride coating on the top surface, preventing the positioning jig  41  from being joined to a joining material such as solder paste  23 .  
         [0067]     Then, a mesh member  3  formed by weaving conductive wires  20  and  21  and tension wires  22  is prepared. Solder paste  23  is applied by dot printing or by discharging from a dispenser to the points where the positive electrode conductive wires  20  of the mesh member  3  and the positive electrodes  14  are connected and to the points where the negative electrode conductive wires  21  and the negative electrodes  15  are connected. The mesh member  3  is placed on the solar battery elements  2  fixed to the positioning jig  41  from above. Then, an presser jig (not shown) is used to press the mesh member  3  against the top surface of the positioning jig  41  while the solder paste  23  applied to the conductive wires  20  and  21  is pressed against the electrodes  14  and  15 . With a number of solar battery elements  2  and the mesh member  3  sitting on the positioning jig  41 , the solder paste  23  is irradiated with a focused beam from an infrared lamp to melt it, by which the conductive wires  20  and electrodes  14  are electrically connected and the conductive wires  21  and electrodes  15  are electrically connected. Then, the solder paste  23  is rinsed to remove the contained flux and dried.  
         [0068]     In another connection method, an electric current is applied to the conductive wires  20  and  21  to melt the solder paste  23  by means of Joule heat caused by the electric current. Here, the surface tension and flowability of the solder paste  23  is advantageously used for connection. Alternatively, an infrared lamp and Joule heat may be used in combination to melt the solder paste  23  for connection, thereby saving connection time. A conductive epoxy resin may be used to connect the electrodes  14  and  15  and the conductive wires  20  and  21  in place of the solder paste  23 . When a conductive epoxy resin is used for the connection, the epoxy resin is discharged from a dispenser at desired points after the mesh member  3  is placed on top of the solar battery elements  2 . Then, the conductive epoxy resin is heat cured, for example, using an oven.  
         [0069]     Subsequently, a polyparaxylene resin coating is applied as a sealing member  4  over the solar battery elements  2  and mesh member  3  of the light receiving module sheet  1  to a thickness of approximately 100 μm. The sealing member  4  may be formed by, for example, by a chemical vapor deposition (CVD) coating system developed by Union Carbide and Plastic, USA. The sealing member  4  is not restricted to polyparaxylene resin and may be made of a transparent resin such as silicone resin, polyvinyl chloride, and polyester (PET) by spraying or dipping in a solution to form and cure a coating. With the sealing member  4  being formed thereon as described above, the light receiving module sheet  1  is completed.  
         [0070]     The functions and advantages of the afore-mentioned light receiving module sheet  1  are described hereafter.  
         [0071]     In the light receiving module sheet  1 , solar battery elements  2  have the positive electrode  14  connected to the flat surface  11  of the spherical crystal  10  and the negative electrode  15  connected to the n + -type diffused layer  12 . Therefore, the solar battery elements  2  may be inspected using, for example, a solar simulator before they are mounted on the light receiving module sheet  1 . Hence, the light receiving module sheet  1  is allowed to have only good solar battery elements  2  that have passed the inspection, providing a high quality light receiving module sheet  1 . Further, the positive and negative electrodes  14  and  15  are formed on the solar battery elements  2  before being mounted. Therefore, the electrodes  14  and  15  and the conductive wires  20  and  21  are reliably and easily connected, simplifying the production process.  
         [0072]     The mesh member  3  is formed by weaving conductive wires  20  and  21  extending in the columnar direction and tension wires  22  extending in the row direction, enabling the realization of a flexible light receiving module sheet  1  or a highly strong light receiving module sheet  1 . Particularly, when the tension wires  22  consist of lightweight glass fibers, a lightweight light receiving module sheet  1  may be realized while improving strength.  
         [0073]     The solar battery elements  2  are provided with the positive and negative electrodes  14  and  15  being positioned opposite to each other about the center of the solar battery element  2 . Therefore, the current generated within the solar battery element  2  runs symmetrically without being localized, significantly reducing resistance loss and allowing almost all electric power generated at the pn junction of the solar battery element  2  to be output. Further, the solar battery elements  2  are provided with a spherical body, enabling them to receive light in all directions and to output all generated electric power, thereby improving power generation efficiency. The light receiving module sheet  1  is protected by a flexible sealing member  4 , and can therefore be deformed without damaging the solar battery elements  2  and conductive wires  20  and  21 .  
         [0074]     The solar battery elements  2  are primarily formed by a p-type spherical single crystal  10  having an n-type diffused layer on the surface. However, they may be primarily formed by an n-type spherical single crystal having a p-type diffused layer on the surface. The semiconductor used in the solar battery elements  2  is not restricted to silicon. Other semiconductors such as GaAs, GaAlAs, InP, InGaP, Ge, GaSb, InGaAs, and InGaN may be used.  
         [0075]     Modified embodiments in which the afore-mentioned embodiment is partially modified are described hereafter.  
       1) Modified Embodiment 1 (see FIG.  10 )  
       [0076]     In this modified embodiment, solar battery elements having no electrodes are connected to conductive wires by alloy joining to produce a light receiving module sheet  1 , the production process of which is described hereafter.  
         [0077]     First, the solar battery element shown in  FIG. 8 ( d ) is produced. The silicon oxide film  35  is completely removed using the buffer etching solution to produce a solar battery element  2 A, and a mesh member  3 A is then prepared by weaving positive and negative electrode conductive wires  20 A and  21 A extending in the columnar direction and tension wires  22  extending in the row direction. Here, the conductive wires  20 A and  21 A are made of an aluminum line containing 1% to 2% of silicon that is eutectic reactive to silicon and having a diameter of approximately 120 μm. The tension wires  22  are the same as the tension wires in the afore-mentioned embodiment, hence the explanation is omitted.  
         [0078]     A number of solar battery elements  2 A are placed on a positioning jig similar to the afore-mentioned positioning jig  41  and the mesh member  3 A is placed thereon in the manner in which the conductive wires  20 A and  21 A make contact with the flat surface  11  (a conductive wire connection part) of the solar battery elements  2 A and the opposite point (a conductive wire connection part) to the flat surface  11  about the center of the solar battery element  2 A, respectively. Then, a large, pulsed direct current is applied to the conductive wires  20 A and  21 A in a nitrogen gas atmosphere containing several % of hydrogen gas for several seconds for Joule heating, by which the flat surface  11 A of the solar battery element  2 A and the positive electrode conductive wire  20 A are alloy joined and the n + -type diffused layer  12 A at the opposite point to the flat surface  11 A about the center of the solar battery element  2 A and the negative electrode conductive wire  21 A are alloy joined. The alloyed regions formed between the conductive wires  20 A and  21 A and the solar battery element  2 A by the alloy joining serve as electrodes  14 A and  15 A. Alloy joining may be conducted at approximately 570 to 650° C., by which a pulsed current is used for rapid heating and rapid cooling, thereby realizing excellent ohmic contact without running aluminum or excessively deep alloying. After the silicon oxide film  36  is removed, a silicon oxide or titanium oxide passivation coating is formed on the solar battery element  2 A by, for example, CVD, and the sealing member  4  is formed over the entire surface of the light receiving module sheet to complete a light receiving module sheet  1 A.  
         [0079]     The conductive wires  20 A and  21 A may be made of nickel (42%), iron (52%), and chrome (6%) alloy wires (approximately 120 μm in diameter) in place of aluminum wires. Then, the joining points between the alloy wires and solar battery elements  2 A are coated with aluminum or aluminum alloy containing 1% to 2% silicon. Also in this case, electric current is applied to the alloy wires to produce Joule heat and melt the aluminum or aluminum alloy coating, connecting the conductive wires  20 A and  21 A and the solar battery element  2 A.  
         [0080]     The alloy wires have lower electrical and thermal conductivity in comparison to the aluminum wires. Advantageously, less electric current is required for joining and tensile strength is improved. Alternatively, copper wires may be used as the conductive wires  20 A and  21 A in place of aluminum wires, the joining points to the copper wires are coated with a gold alloy such as gold/silicon alloy, gold/germanium alloy, and gold/tin alloy, and an electric current is applied to the conductive wires  20 A and  21 A to generate Joule heat and melt the gold alloy, thereby connecting the conductive wires  20 A and  21 A and the solar battery element  2 A. Gold alloy allows for alloy joining due to eutectic reaction at lower temperatures than does aluminum.  
         [0081]     In this production method, the solar battery element  2 A and the conductive wires  20 A and  21 A may be easily connected without previously forming positive and negative electrodes, by which productivity is improved and production costs are reduced.  
       2) Modified Embodiment 2 (see FIGS.  11  and  12 )  
       [0082]     A modified embodiment having a modified sealing member is described hereafter. A light receiving module sheet  1 B may be formed with the structure shown in  FIG. 11 . The light receiving module sheet  1 B is provided with a sealing member  4 B comprising a flexible cushion layer  46  that houses the solar battery elements  2  and mesh member  3  in an embedded manner and transparent surface layers  45  joined to the top and bottom surfaces of the cushion layer  46 . The surface layers  45  are made of a transparent enforced glass plate having a thickness of approximately 2 mm.  
         [0083]     In order to produce the light receiving module sheet  1 B, a surface layer  45 , an EVA (ethylene vinyl acetate) sheet, a mesh member  3  to which the solar battery elements  2  are joined, an EVA sheet, a surface layer  45  are superimposed in sequence and are heated in a laminate machine while vacuuming. Then, the EVA sheets melt, the EVA melt between the top and bottom surface layers  45  forms the cushion layer  46 , and the cushion layer  46  fixes the solar battery elements  2  and mesh member  3 .  
         [0084]     The light receiving module sheet  1 B may be reduced in cost and weight by using the surface layers  45  made of a transparent plate member such as polycarbonate and acrylic resins. The cushion layer  46  may be made of a transparent resin such as PBV (polyvinyl butyral), acryl, and silicone.  
         [0085]     The structure in which the solar battery elements  2  and mesh member  3  are placed between two surface layers  45  improves strength relative to mechanical shock, and the see-through light receiving module sheet may be used as a window glass.  
         [0086]     On the other hand, a light receiving module sheet  1 C is provided with the sealing member  4 C shown in  FIG. 12 . The sealing member  4 C of the light receiving module sheet  1 C comprises, from the bottom, a flexible PE (polyester) resin film  50 , an aluminum deposited film  51 , a PE resin reflecting multilayer film  52 , a filler  53  made of an EVA resin and in which the solar battery elements  2  and mesh member  3  are embedded in a manner similar to the above cushion layer, a PE resin layer  54 , a heat ray reflecting film  55 , and an PE resin layer  56 .  
         [0087]     The reflecting film  52  is formed on the side surface opposite to the light entrance side, and reflects and scatters light entering from the entrance side and passing through between the solar battery elements  2  so that the light reaches the solar battery elements  2 , leading to more efficient light usage and, accordingly, more efficient power generation. The heat ray reflecting film  55  has a multilayer structure consisting of polymer materials having different refractive indices. Because of interference caused by the multilayer structure, the heat ray reflecting film  55  selectively reflects heat rays not absorbed by the solar battery elements  2  (wavelength of 350 nm or larger), preventing the solar battery elements  2  from being heated and leading to more efficient photoelectric conversion. Hence, when light enters from the light receiving surface (the top surface) of the light receiving module sheet  1 C, first, undesired heat ray is partially reflected by the heat ray reflecting film  55  and the remaining light is partially received by the solar battery elements  2  and partially passes between the solar battery elements  2 . Light that has passed through is reflected by the reflecting film  52  and received by the solar battery elements  2 .  
         [0088]     Flexible synthetic resins such as polycarbonate, polyethylene naphtharate, and fluorocarbon resin may be used in place of PE resins, silicone and polyvinyl butyral resin may be used for the filler  53  in place of EVA resin, and the reflecting film  52  and heat ray reflecting film  53  may be eliminated as appropriate. Other layers may be modified as appropriate according to the desired function.  
       3) Modified Embodiment 3  
       [0089]     The light receiving module sheet may be produced by a roll-to-roll technique. When a roll-to-roll technique is used, the mesh member is fixed at both ends in the width-wise direction using heat-resistant resin films such as polyimide films. Sprocket holes are formed in the heat-resistant resin films. The sprockets holes are engaged in sprockets to roll the mesh member in or out.  
       4) Modified Embodiment 4  
       [0090]     In the afore-mentioned embodiment, the spherical elements of the light receiving module sheet are solar battery elements. However, the spherical elements are not restricted to solar battery elements and may be spherical photodiodes or light emitting diodes. These spherical photodiodes or light emitting diodes have nearly the same structure as the solar battery elements  2  described above and are described in detail in WO98/15983 by the inventor of this application and, therefore, their explanation is omitted. In a light emitting module sheet having light emitting diodes, a forward electric current is applied to the light emitting diodes, the electric energy is converted to optical energy by the pn junction, light having a wavelength depending on the crystal and diffused layer material is generated at the pn junction and externally emitted. Light is emitted in all directions from a light emitting module sheet having spherical light emitting diodes. Alternatively, light may be emitted only in a desired direction by providing a reflecting sheet in part. Further, three, R, G, and B, color light emitting diodes are arranged in a matrix and the light emitting diodes are controlled by a controller. Subsequently the light emitting module sheet may be used as a color display. One color light emitting diodes may be used to constitute a single color display. A light receiving module sheet having photodiodes can convert light in all directions to electric signals.  
       5) Modified Embodiment 5  
       [0091]     In the afore-mentioned embodiment, the solar battery elements in all columns are connected in series. However, multiple switches may be provided to change the number of columns to be connected in series, and are turned on/off by a controller depending on light intensity and required electric energy.  
       6) Modified Embodiment 6  
       [0092]     In the afore-mentioned embodiment, a sealing member is provided. However, the sealing member is not necessarily provided and may be omitted as appropriate.  
       7) Modified Embodiment 7  
       [0093]     The number of the tension wires may be changed as appropriated. In the afore-mentioned embodiment, a set of three tension wires  22  is provided between the rows of solar battery elements. The number of tension wires is not restricted to three and a set of one or more wires may be provided.  
         [0094]     The tension wire may be made of highly strong synthetic resins or plastics such as insulating aramide fibers. In this way, a light receiving or emitting module sheet can be provided with improved flexibility and tensile strength and material costs may be reduced.  
         [0095]     The insulating tension wires  22  are not necessarily arranged orthogonally to the conductive wires.  FIG. 13  shows a light receiving module sheet  1 D in which tension wires  22   a  are provided between columns of solar battery elements in parallel to the conductive wires  20 ,  21  and woven with them. With this structure, the tensile strength in the direction that the conductive wires extend may be improved. In  FIG. 13 , the same reference numbers are given to the same components as in the afore-mentioned embodiment and their explanation is omitted.  
       8) Modified Embodiment 8  
       [0096]     In the afore-mentioned embodiment, each column has positive and negative conductive wires. However, one wire may be shared by adjacent positive electrode conductive wire and negative electrode conductive wire. With this structure, the serial connection conductive wires may be omitted for a simple structure and the distance between columns may be reduced, by which a light receiving or emitting module sheet is down-sized.  
       9) Modified Embodiment 9  
       [0097]     In the afore-mentioned embodiment, the spherical solar battery element  2  has the flat surface  11 . However, a solar battery element without the flat surface  11  may be applied. With this structure, it is desirable that positive and negative electrodes be formed in different shapes, by which the positive and negative electrodes are easily identified.  
         [0098]     The present invention is not restricted to the embodiments described above. Various modifications may be made to the afore-mentioned embodiments by one of ordinary skill in the field without departing the scope of the present invention and those modifications incorporated in the present invention.